Article > Tech

Antilock Brake System


Antilock brake systems have been around since the mid-1980s and are now offered as standard equipment or as an option on most vehicle makes and models.

There are a lot of ABS-equipped vehicles on the road today that will eventually need ABS replacement parts as they age.

What kind of parts fail? Wheel speed sensors are probably the most often replaced component. Most wheel speed sensors (WSS) are located at the wheels, which makes them vulnerable to road splash, corrosion and road hazards. The WSS wires and connectors are also often a source of trouble.

On many vehicles, each wheel has its own speed sensor. These are called "four channel" ABS systems. On others, a common sensor is used for the rear wheels (which may be mounted in the differential or transmission) but each front wheel still has its own wheel speed sensor. These are called "three-channel" ABS systems.

Another variation is the "single-channel" rear-wheel-only ABS system that is used on many rear-wheel-drive pickups and vans. This includes Ford "Rear Antilock Brakes" (RABS) and GM and Dodge "Rear-Wheel Anti-Lock" (RWAL). The front wheels on these trucks have no speed sensors and only a single speed sensor mounted in the differential or transmission for both rear wheels. Rear-wheel antilock systems are typically used on applications where vehicle loading can affect rear wheel traction, which is why it's used on pickup trucks and vans.

Most ABS systems use magnetic wheel speed sensors that generate a frequency signal as the notches on the sensor ring pass by the tip of the sensor. The sensor ring is usually mounted on the back of the brake rotor or outer CV joint.

On some vehicles (many GM models, for example), the wheel speed sensor is built into the sealed wheel hub assembly - making it very expensive to replace if it fails because the entire hub has to be changed. On most vehicles, though, the wheel speed sensor can be replaced separately if it fails.

The WSS signal is sent to the ABS control module, where the signal pulses are counted so the module can monitor wheel speed. If the tip of the WSS becomes coated with debris, or there's a poor wiring connection between the sensor and module, or the "air gap" between the end of the sensor and the sensor ring is too large, it may prevent the WSS from generating a good signal. An internal short or open in the sensor itself can also render it useless. The ABS control module will detect the problem and set a fault code that identifies the "bad" WSS circuit (a number that corresponds to left front, for example.) This does not mean the sensor itself is bad, only that there is a signal problem in that WSS circuit.

The troublesome WSS circuit can be diagnosed by measuring the resistance of the WSS with an ohmmeter, by checking wiring continuity and inspecting the wiring and connectors, or by spinning the wheel and checking the sensor's output signal.

If a WSS sensor is lost, the ABS system can't monitor wheel speed and can't tell if ABS is needed or not. So it will set a code and disable itself. As long as the warning light remains on, the ABS system will stay "off line." Only when the fault has been fixed and the code cleared will the warning light go out, allowing the ABS system to become active again.

ABS systems are designed to be as "fail-safe" as possible. All ABS systems run their own self-diagnostics and will set codes and deactivate themselves when a serious fault is detected. An illuminated ABS warning light may seem ominous, but most vehicles should still be safe to drive and have normal braking. The only exceptions are some older vehicles with "integral" ABS systems that use the ABS pump and accumulator to provide power-assisted braking. On these vehicles, the brakes should still work, but without the benefit of any power assist if the ABS system goes down.

If the brake warning light is also on, however, it may indicate a more serious problem such as loss of brake fluid or a low fluid level. So if both warning lights are on (ABS and brakes), the vehicle should not be driven until the problem can be investigated.

Another ABS component that often fails is the hydraulic modulator assembly that contains the ABS solenoid valves, or in the case of GM ABS-IV systems, the motor pack and valve assembly. This is the heart of the ABS system that controls the cycling of hydraulic pressure to the wheels. On some systems, the ABS solenoid valves can be replaced separately if one fails.

But on many systems, the entire modulator must be replaced if anything inside fails. Failures may be caused by electrical faults (opens or shorts in solenoids), by internal corrosion or by debris in the brake fluid that jams a solenoid valve or prevents it from fully closing.

Modulators can be tricky to replace because they must be bled after they have been installed to remove all air from the circuits. On some vehicles, they may require using a scan tool to cycle the ABS solenoids. On others, manual bleeder screws may be provided for this purpose. Either way, your customer will also need brake fluid to refill the system. The old fluid should also be flushed out to get rid of any sediment or contamination that may cause future problems.

On systems that use a high-pressure pump and accumulator to provide power-assisted braking or to reapply pressure during an ABS stop, a defective pump or relay can cause a loss of pressure. So can a leaky accumulator. The ABS system monitors these components and will set a code if it detects a problem.

The accumulator can be dangerous to replace because it may contain up to 1,500 or more pounds of pressure. Your customers should be warned to never open up an ABS system that may still be under pressure. The accumulator must first be discharged by pumping the brake pedal 40 times with the ignition key off. Once all pressure has been relieved, it can be safety removed and replaced.

ABS control modules can also fail, though they don't fail that often. Most ABS problems are electrical (bad WSS, pump relay, pump motor, wiring or solenoid) or mechanical (sticking, jammed or leaking ABS valve.) If a module does go bad, it may cause erratic or abnormal operation of the system (such as ABS braking during a normal stop.) ABS should only come into play when traction conditions are marginal or during sudden "panic" stops. The rest of the time, it should have no effect on normal driving or braking.

When ABS comes into play, the module energizes the solenoid valves in the hydraulic modulator to hold, release and reapply hydraulic pressure to the brakes. Sealing off the affected brake circuit prevents any additional pressure from being applied to the brake. The module then energizes a vent solenoid to release pressure from the line. This allows the brake to release momentarily so the tire can regain its grip. The vent valve is then closed and the pressure valve reopened to reapply the brake. This rapid cycling produces a pulsating effect that can usually be felt in the brake pedal during an ABS stop. The driver may also hear a buzzing or chattering noise from the ABS hydraulic unit - which is normal and tells the driver that the ABS system is active.




The battery is a storehouse of electrical energy.

The battery supplies amps to crank the engine, voltage to keep all of the onboard electronics alive even when the ignition is off, and extra juice to meet the vehicle's electrical demands when the alternator can't keep up.

The battery's ability to maintain a certain voltage level is critical in today's vehicles. Low voltage can upset the normal operation of many onboard electronics and cause all kinds of problems from hard starting to stalling to erratic performance. That's why a fully-charged battery in good condition is a must for reliable driving.

A 12-volt battery has six "cells," each of which may contain nine to 20 positive and negative plates (typically the greater the number of plates, the greater the amperage capacity of the battery.) Each cell produces 2.11 volts, so when all six cells are connected together in series, the battery's total output is actually 12.66 volts.

One thing all batteries share in common is that they don't last forever. Four to five years is the average life of most batteries. Life is limited because the chemical processes that make a battery work prove to be its undoing. The chemical reactions that occur between the sulfuric acid in the battery and the lead in the battery's cell plates gradually damages the plates. Over time, some of the sulfate sticks to the plates and doesn't return to solution when the alternator pumps current back through the battery. The plates become "sulfated" and lose some of their ability to hold a charge. As the sulfate builds up, it forms a barrier that further diminishes the battery's ability to produce and store electricity. Eventually the point is reached where the battery will no longer accept a charge and the battery must be replaced.

Battery plates can also become "sulfated" prematurely if the battery is run down repeatedly (leaving the lights on, playing a killer stereo system without the engine running, etc.) or if the battery is chronically undercharged (frequent short-trip driving, especially during cold weather.)

Premature battery failure can also be caused by excessive heat (as in Arizona summers) and vibration. The lead alloys that are used in maintenance-free batteries are fairly brittle and can't take much abuse. Rough handling or a missing hold-down strap that allows the battery to flop around on its tray can result in cracked or shorted cell connections and instant battery failure.

The Battery Manufacturers Association says probably 50 to 60 percent of the batteries that end up in the scrap heap for recycling are still usable but have been discarded because they won't accept a charge. Sometimes a "dead" battery can be revived by applying a long slow trickle charge, by connecting it in parallel (positive to positive, negative to negative) with a good battery and charging both at the same time, or by using a special battery charger that applies a higher-than-normal initial charging voltage to break through the sulfate. But by the time a battery is four or five years old, it's days are numbered, and sooner or later it will have to be replaced.

When a customer needs a new battery, your first job is to figure out the correct "group size" based on the year, make and model of the vehicle. You can also use the group size of the old battery.

A replacement battery must be a compatible group size with similar height, width, length and post configuration as the original. This is necessary so it will fit the battery tray and holddowns. Also, it must have the same or higher cold cranking amp (CCA) capacity as the original. For most vehicles, that means a minimum of 450 to 600 CCAs. The bigger the engine, the more amps it needs for reliable cold weather starting.

The next decision that has to be made is what type of battery best suits your customer's needs: a conventional battery with liquid electrolyte or a gel battery? The acid in gel batteries is held by absorbent glass mats between the cell plates. Gel-type batteries are spill-proof and are well suited for hot climates (less risk of evaporation.) They are also more resistant to vibration-damage.

Some gel batteries have round cells with spiral-wound plates instead of the more conventional flat cell plates. This increases the internal surface area of each cell up to 20 times per amp hour and creates a current path that is 20 to 100 times shorter than conventional flat plate batteries. This allows the battery case to be up to 40 percent smaller and lighter than a traditional battery, to produce up to 25 percent more cranking amps and to recharge four times faster than other batteries.

One thing that should always be checked when replacing a battery is its sate of charge. Most batteries are dry charged (precharged) at the factory for maximum shelf life. Even so, customers should be advised to put a charger on the battery to bring it up to full charge before it is installed in a vehicle. This will reduce the risk of overtaxing the charging system should the battery be low.

The vehicle's charging system should also be checked to make sure it is putting out adequate amperage and voltage to keep the new battery fully charged. The charging voltage is usually about 1-1/2 to 2 volts higher than normal battery voltage.

When batteries are sold, sell the oldest ones first to keep your stock fresh. All batteries have a date code that reveals when the battery was manufactured. The number indicates the year, and the letter corresponds to the month (A = January, B = February, C = March, etc.) The date code can also be used to determine the age of a battery in a vehicle if the age is unknown or unmarked.

Your customer will also have to decide how much warranty he wants to buy. Replacement batteries all come with some type of warranty, be it 24, 36, 48, 60, 72 or more months. As a rule, the longer the warranty, the better the battery - but the higher the price. Most warranties are pro-rated which means a certain amount is deducted for each month the battery has been in service.




All vehicles need replacement belts and hoses at some point in their life. The question is when?

Synthetic rubber provides flexibility for these components, but over time exposure to heat and chemical attack causes the rubber to degenerate, lose strength and become stiff and brittle. That's why all belts and hoses eventually have to be replaced.

Most motorists never even think of replacing their belts or hoses - until one fails, and even then they only replace the one that failed. And so it goes until the next one fails, and the next one and the next one.

Most belt and hose manufacturers recommend replacing belts and hoses every four to five years because they know these parts don't last forever. Sure, many belts and hoses go six, seven or even 10 years without a problem. But many don't, and when a belt or hose fails, it almost always leaves the motorist stranded.

The reason not to wait until a belt or hose fails to replace it is to reduce the risk of a breakdown. Think of new belts and hoses as longevity insurance for the engine's cooling and charging system - and maybe the engine too.

If a belt fails, it can cause the loss of engine cooling, power steering, charging and air conditioning (depending on what it drives.) With single-belt serpentine drive systems, one belt does it all. With V-belts, there may be separate or shared belts for the engine's accessories (water pump, power steering pump, A/C compressor and alternator.)

It's the same story with hoses, but more so. A radiator or heater hose that springs a leak will soon spray the engine's vital supply of coolant on the ground. Depending on how bad the leak is, the first indication of trouble may be a rising temperature gauge, a temperature warning light or a cloud of steam billowing out from under the hood. If the vehicle is not shut off almost immediately, the engine may get too hot and suffer damage to the head gasket, cylinder head, valve guides and/or pistons and cylinders. The price of replacement hoses will seem cheap compared to what it costs to fix this kind of engine damage should it occur.

Heat is the number-one enemy of belts, especially V-belts. If a V-belt isn't tight and slips, friction between the sides of the belt and pulley generate heat and noise (belt squeal.) This can glaze and harden the sides of the V-belt and cause it to lose its grip, which results in more slippage, accelerated belt wear and premature belt failure. Any V-belt that is glazed, cracked or frayed, therefore, should be replaced regardless of its age.

Belt tension is critical with both serpentine belts, flat belts and V-belts, and it must be adjusted properly and maintained for good belt performance, quiet operation and long life. Most engines with serpentine belts have a spring-loaded automatic tensioner that eliminates the need for an initial adjustment as well as readjustments. But on applications that don't have an automatic adjuster, belt tension must be adjusted to specifications, then readjusted after a short break-in period.

Belts should be inspected regularly for obvious signs of wear or damage. Minor surface cracking is normal, but heavy or deep cracking, fraying, missing chunks of rubber or other damage are warning signs the belt has reached the end of its service life and needs to be replaced. Hard, shiny spots (glazing) would also be a reason for replacement as would noise. Glazing and noise can also be caused by pulley misalignment, so pulleys should be inspected to make sure they are properly aligned (especially if an engine is throwing, twisting or eating belts.)


When looking up a replacement belt for a customer, you may need quite a bit of information to find the correct one. In addition to year, make, model and engine size, you may also have to know if the engine is equipped with air conditioning, power steering and/or an air pump. On some applications, you may also need the VIN number to accurately identify the application.

It's always a good idea to compare a replacement belt with the old one to make sure they are the same width and length. A replacement V-belt that's too narrow may bottom out in a pulley and slip, while one that's too wide may not fit the grooves in the pulley. The length of a replacement V-belt or flat belt can vary a little depending on the amount of adjustment that's possible. But on serpentine belts, the replacement belt must be the same as the original because most automatic tensioners have a limited range of travel. A difference of only an inch or so may be too much for some applications.

There is no recommended replacement interval for automatic belt tensioners, but that doesn't mean these units will last forever. Like any mechanical component, they eventually wear out. Replacement becomes necessary when the unit is no longer able to maintain proper belt tension or the unit is making noise. Symptoms of a bad tensioner include clatter, rumble or chirp when the engine is running, visible looseness in the idle pulley bearings, dragging or seized idler pulley bearings (the pulley should rotate freely), physical damage to the idler pulley wheel, arm or base housing, or belt squeal immediately after engine start up or when belt-driven accessories are under load.

As for hoses, any hose that is leaking, cracked, blistered, swelling or shows signs of damage needs to be replaced. Hoses routed near exhaust manifolds or near sharp objects may rub and chaff leading to hose failure. Hoses that have become hard and brittle are also overdue for replacement.

Cooling system hoses often fail from the inside out due to electrolytic corrosion. Some hoses are more vulnerable than others to this type of problem depending on the materials used in their construction. Coolant neglect may be an underlying cause of such hose failures. In some instances, a missing or loose ground strap between the engine and chassis can force electrical current to use the coolant as a path to ground increasing the risk of electrolytic attack on the inside of the radiator hoses.

Replacement radiator hoses may be molded (preshaped the same as the original hose) or universal flex hose (consolidates applications.) The important things to match here are hose diameter and length. (New clamps should also be recommended.) And don't forget to offer your customer a chance to purchase antifreeze.




The calipers on disc brakes squeeze the pads against the rotors when the brakes are applied.

It's a simple job but one that can't tolerate any fluid leaks, sticking or jamming.

If a caliper sticks, it may cause the pads to wear unevenly or the brakes to drag. That's why the calipers must be carefully inspected when the brakes are relined, rebuilt or replaced if there's a problem.

Loaded calipers are a popular replacement alternative to bare calipers. But their popularity varies from one area of the country to another. According to one brake supplier, loaded calipers are much more popular on the West Coast of the U.S. than on the East Coast. The reason? West coast technicians like loaded calipers because everything they need comes in one box; they don't have to worry about mismatched parts from different suppliers, the complete assemblies are quick and easy to install and they see fewer comebacks because of brake noise or other problems. East Coast technicians also like loaded calipers for the same reasons, but do business in a market that is much more sensitive to price. Consequently, the Easterners typically reuse more parts and replace calipers only when necessary.

Regardless of which part of the country you live in, loaded calipers do provide a variety of benefits when doing brake jobs. Most brake suppliers have a loaded caliper program, so availability is seldom an issue. Price, though, remains the main selling hurdle to overcome.

One of the main advantages for the vehicle owner is that loaded caliper assemblies help restore the brakes to like-new condition. Not only do they get new friction, but also a professionally rebuilt caliper and properly matched hardware (shims, bushings, slides, etc.) This significantly reduces the risk of future leaks developing and uneven braking or pad wear caused by calipers hanging up or dragging.

Caliper piston seals don't last forever, and once they start to leak, it's the end of the road for the caliper and the pads. Fluid leaks are dangerous because they can lead to a loss of hydraulic pressure in the brake circuit that may cause the brakes to fail. Brake fluid leaking from a caliper can also contaminate the brake linings and cause them to grab or pull.

A caliper may also have to be replaced if it's sticking. Internal corrosion can cause pistons to jam or freeze preventing the caliper from working normally or releasing completely. External corrosion on the caliper mounts, bushings or slides can cause problems too by preventing a floating caliper from moving normally when the brakes are applied. The result here may be uneven pad wear, uneven braking, dragging or a pull. With a loaded caliper, the caliper is replaced along with the pads.

Attempting to rebuild old calipers is often a waste of time. In many instances, the calipers are so badly corroded or worn, they can't be rebuilt - or they leak when they are put back on the vehicle. Disassembling a caliper to replace the piston seal and dust boot is a messy job, and it may be difficult or impossible if the piston is stuck in place. Steel pistons often can't be reused because they're usually too badly corroded, and scratches or pits in the caliper bore may cause the caliper to leak even after a new piston and seal are installed. That's why most technicians prefer to replace old calipers with remanufactured ones.

Replacing the hardware is also important because old corroded hardware can cause braking problems. We've heard of shims that have worked loose and caused a rotor to fail by rubbing and cutting through the rotor hat! If a technician forgets to install an anti-rattle clip, or installs one that doesn't fit properly, the newly installed pads may be noisy. Loaded calipers reduce these risks by providing the proper hardware and replacing everything that should be replaced.

The type of friction material that's included with a loaded caliper assembly is critical because it should be the same or better than the original. If a vehicle originally had ceramic pads, the loaded caliper should have the same type of friction material. The same goes for semi-metallic pads.

To avoid a mismatch of friction side-to-side, both calipers should be replaced simultaneously if you're installing loaded calipers. If only one caliper is being replaced, be sure to sell the same friction pads for both sides.

When a loaded caliper is installed, the brake system should always be flushed and refilled with clean, fresh fluid that meets the OEM requirements for the application.

Caliper slides and bushings should be lubricated with a high-temperature brake grease, and related brake components such as hoses, lines, rear wheel cylinders and the master cylinder should all be inspected to make sure these components are in good working condition and are leak-free.




Chassis parts carry a lot of weight and play a prominent role in maintaining wheel alignment, handling, steering stability, traction and driving safety.

Chassis parts are out-of-sight, out-of-mind, and are often overlooked as a profit opportunity for your store.

Most chassis parts are kept behind the counter because they are generally a slow-moving product line compared to many other items. Consequently, you won't see many chassis parts on display except maybe some performance suspension parts such as handling kits, brightly colored sway bar bushings or coil-over kits for sport compact cars, or overload springs or lift kits for trucks.

Chassis parts inventories that are in stock are also limited to only the most common parts. Why? Because ball joints, control arm bushings and springs are long lived and may only be replaced once during a vehicle's life - if at all. Many vehicles reach the end of the road with many of their original chassis parts still in place. That doesn't mean those parts went the distance. Many were probably worn out and should have been replaced - but nobody ever noticed or told the vehicle owner that repairs were needed.

Unless a vehicle owner is making changes to the suspension to upgrade handling or towing/hauling capacity, or wants to change the ground clearance of the vehicle (raised for off-roading or lowered for handling and aerodynamics), chassis parts are seldom touched unless they are worn out or damaged and need to be replaced. Many drivers do not notice the gradual deterioration in ride, handling and steering that occurs over time.

Consequently, they may not realize their ball joints or springs or tie rod ends are worn out until things are really bad or something actually fails causing the suspension to collapse or loss of steering control.

Most worn suspension parts and steering components are discovered when a vehicle is in for other types of service work, such as a brake job, oil change or alignment.

A vehicle cannot maintain proper wheel alignment with worn chassis parts. Worn ball joints can upset camber/caster alignment causing uneven tire wear, pulling and suspension noise. Worn control arm bushings can also affect camber/caster alignment and cause unwanted noise. Worn tie rod ends upset toe alignment and cause rapid tire wear. A worn idler arm can cause steering wander and tire wear too. Even spring sag can upset alignment and have an adverse effect on steering, handling, ride quality and tire wear. That's why alignment technicians always inspect the steering and suspension before they do an alignment. If worn or damaged parts are found, they must be replaced before the wheels can be aligned to specifications.

Sometimes a motorist will ask for an alignment if his or her vehicle is wearing tires unusually fast or pulling to one side. Most tire dealers recommend an alignment check when tires are replaced because accurate alignment assures maximum tread life and the best possible handling. But many people don't want to spend the money and put off having their alignment checked - until it is too late and their new set of tires have been ruined because of worn chassis parts.

When parts are needed, you obviously need the year, make and model - and sometimes the VIN - to accurately identify the application. But with chassis parts, you also have to know which ball joint or tie rod a customer wants because parts vary depending on their location.

With ball joints, there are upper and lower ball joints on each side if a vehicle has a short arm/long arm (SLA) suspension, but there are only lower ball joints if the front suspension has struts. Left and right ball joints are usually the same, unless they are part of a control arm assembly. The rear suspension may also be equipped with ball joints. A special tool will be needed to separate the ball joint from the steering knuckle, and some ball joints may have to be pressed out of their control arms.

With tie rod ends, there are inner and outer tie rods on vehicles that do not have rack and pinion steering. Most recirculating ball steering systems have a parallel steering linkage with an idler arm opposite the pitman arm that's connected to the steering box. A center link ties the two sides together. Those with racks have a simpler arrangement with an outer tie rod end on each side and inner tie rod sockets attached to the rack. The inner sockets are covered by rubber or plastic bellows. Left and right side tie rods are almost always different because one is usually has reverse threads to facilitate toe adjustments.

Replacing a chassis part usually alters steering geometry, so realigning the wheels is almost always necessary after the new parts have been installed.

Springs often have to be replaced because of sag or failure. All springs will sag as they age due to metal creep, but some may sag at a faster rate if a vehicle is heavily overloaded or driven on unusually rough roads. Spring sag changes ride height, which in turn changes wheel alignment. If ride height is at or below minimum specifications, new springs are needed. Springs may also break as a result of corrosion or metal fatigue. Many springs are painted or coated with plastic to protect them from the elements. If the coating is scratched, corrosion can attack and weaken the spring.

Springs are usually replaced in pairs. Upgrade options include replacing standard springs with variable-rate springs or overload springs. Both provide increased load-carrying capacity, but variable-rate springs provide a softer ride. Replacing coil springs often requires a spring compressor. Related parts that may also be needed include spring pads that go under the springs, new bearing plates for the tops of MacPherson struts and new fasteners.




Selling antifreeze these days almost takes a degree in chemistry.

Coolants today come in various colors and formulations. There are "conventional" coolants (the familiar "green" antifreeze that's typically good for two years or 30,000 miles), and a variety of long-life coolants that may be orange, red or even blue and are usually rated for five years or 150,000 miles. The color really doesn't mean much because it's just dye. It's what in the chemistry of the product that counts.

Some types of coolants are formulated for specific vehicle applications or engine types (such as aluminum engines or bimetal engines with iron blocks and aluminum heads.) Some vehicle manufacturers have very specific preferences when it comes to the types of corrosion inhibitors they use. The North American OEMs like one kind of chemistry, the Asian OEMs like another and the Europeans have their own ideas about what works best. That's why there's so much confusion about what kind of antifreeze to use.

The aftermarket, on the other hand, is great at coming up with ways to consolidate the mishmash of OEM requirements. There are now "universal" coolants that can be used in any year, make or model of vehicle. These are single formula long-life coolants that are compatible with both traditional antifreeze and the newer OEM long-life coolants.

Most vehicle manufacturers caution against mixing different types of coolants because of differences in the corrosion inhibitors. The issue is chemical compatibility. Most long-life antifreeze contains "Organic Acid Technology" (OAT) corrosion inhibitors to extend the life of the coolant. OAT inhibitors include a variety of different substances so formulas will vary somewhat from one supplier to another.

Most conventional antifreezes, by comparison, contain silicates to protect aluminum, and also phosphates, nitrates and borates to inhibit rust and corrosion. Over time, these protective additives are gradually consumed. This decreases the reserve alkalinity (pH) of the coolant and eventually increases the risk of corrosion when the coolant turns acidic.

If a cooling system that contains an OAT-based, long-life antifreeze is topped off with ordinary antifreeze, it may shorten the service life of the entire batch of coolant to that of ordinary antifreeze. It's difficult to predict how much of an effect this will actually have on the coolant's longevity because it depends on the condition of the original coolant, the overall capacity of the cooling system and how much ordinary coolant is added to the system.

Intermixing different types of coolants won't make the engine overheat or the cooling system self-destruct, but it may reduce the service life of a long-life coolant.

What happens if the cooling system in an older vehicle when ordinary coolant is topped off with a long-life coolant? Nothing, according to the head chemist with one leading antifreeze supplier. It won't shorten the life of the ordinary coolant because it's not formulated to go more than a couple of years anyway.

Another choice your customer faces is should he buy concentrated antifreeze or a jug of pre-mixed antifreeze that already contains water? The latter is cheaper and easier to use. Antifreeze should always be mixed in equal portions with water when it is added to the coolant reservoir or radiator. A 50/50 mixture will prevent freezing down to -34 degrees F, and prevent boilover during the hottest summer weather.

You should caution your DIY customers to never open a hot radiator cap! It's much safer to add antifreeze and water to the coolant reservoir.

One of the reasons why many OEMs have gone to long-life coolants is to reduce maintenance. The new OAT-based coolants last a long time but not forever. However, many motorists act as if their coolant never needs to be changed - and ultimately suffer the consequences (radiator, heater core and water pump failures.) Another reason for the change is to reduce the risk of contaminating the oxygen sensors on the engine if the engine develops an internal coolant leak due to a failing head gasket or a crack or porosity leak in the cylinder head. Most conventional North American antifreezes contain silicone, which will ruin O2 sensors if it finds its way into the combustion chamber and exhaust. The O2 sensor must go 100,000 miles or more to help the engine control emissions. The same goes for the catalytic converter, which can also be contaminated by silicone from leaking coolant.

Regardless of what type of coolant is in a cooling system, the coolant level, strength and condition all need to be checked regularly. If the system is low, it may indicate a leak that needs to be diagnosed and repaired. Loss of coolant will eventually lead to overheating and possible engine damage. Selling your customer a can of sealer may buy him some time if his cooling system is leaking, but eventually you'll be selling him a new water pump, hoses, radiator or heater core.

If a customer is replacing a hose, thermostat, water pump, radiator or heater core, he will probably need antifreeze - and hose clamps. If the old coolant is dirty or has not been changed in a long time, you should also recommend flushing the system and sell him a can of cooling system cleaner.




The bearings that support the crankshaft and connecting rods inside an engine live in a tough operating environment. They are subjected to constant pounding with every cylinder firing and tremendous loads that multiply in severity as engine rpm goes up.

To withstand this kind of punishment for tens of thousands of miles, the bearings must be extremely durable. They must also be cooled and lubricated with a constant supply of oil. An extremely thin film of oil is all that separates the bearings from the crankshaft journals and prevents metal-to-metal contact that would lead to instant destruction.

With regular oil changes, a set of OE bearings should be capable of going 150,000 miles or more. It's not unusual to see well-maintained engines that have gone a quarter of a million miles on a set of bearings. But many bearings never go the distance for a variety of reasons.

One is neglected maintenance. If the oil and oil filter are not changed often enough, or if the oil level runs low because of a leaky seal or gasket, it can wipe out the bearings very quickly.

Another cause of premature bearing failure is a leaky head gasket that allows coolant to seep into the crankcase and contaminate the oil. Dirt that slips past the air filter and enters the engine can also end up in the crankcase. Even tiny particles can accelerate wear over time.

Aggressive driving can also beat a set of bearings to death. Bearings are engineered to take a lot of abuse, but if they are flogged hard enough and long enough, even the toughest bearings will suffer metal fatigue, crack and flake.

Too much heat can also prove fatal for a set of bearings. If the bearings do not receive enough oil to carry away heat, heat can build up causing the surface temperature of the bearings to soar. If the bearings get up to 620 degrees, it can melt away the lead in tri-metal copper/lead bearings and those with babbitt overlays. Because copper doesn't melt until 1,980 degrees, burned copper/lead bearings will typically have a copper appearance instead of the normal dull gray appearance. Underlying causes that can lead to this type of bearing failure include a worn oil pump, restricted oil pickup screen, internal oil leaks, a low oil level in the crankcase or aerated oil (oil level too high.)

If the rod and main bearings in a high-mileage engine become worn, the increase in clearances will allow more oil to leak out from between the bearings and crank journals. This makes it harder to maintain the protective oil film so wear increases even more. Low oil pressure is a classic symptom of worn main bearings, and deep rapping noises from within the engine are a symptom of worn or damaged rod bearings.


Today's engines are a lot more durable than they used to be. Part of the reason for this is that virtually all late-model engines in this country and from Asia are now built with aluminum bearings. These are bi-metal bearings with a steel shell and a high-strength aluminum alloy overlay. Though aluminum is a relatively soft material, the addition of 3 to 6 percent silicon and some copper give it increased hardness and wear resistance. The addition of 6 to 10 percent tin improves conformability and seizure resistance. As a result, OEM aluminum bearings in most engines experience very little wear - as long as the oil is kept clean, full and changed regularly.

The aluminum alloys that are used for today's rod and main bearings are getting better and better with each new generation of materials. Some alloys still contain a small amount of lead (about 2 percent) but this is being phased out as newer alloys are introduced. According to one major supplier of bearings, several new high-strength aluminum alloys that contain no lead are now in production and will gradually replace the existing alloys over the next several years. The new alloys are even more durable and are even being used in many diesel engine applications.

The current generation of aluminum alloy bearings can easily handle 100 horsepower per liter engine loads, and the next generation alloys are capable of handling even higher loads.

One of the things that allows aluminum alloys to handle high loads is that the bearings can withstand higher temperatures. The melting point of a typical aluminum bearing alloy is over 1,100 degrees F, which is almost three times as high as babbitt. This provides added protection against localized overheating caused by detonation, overloading, misalignment and similar conditions.


Does this mean aluminum bearings will eventually replace tri-metal copper/lead bearings in the aftermarket? They already have for many production engine rebuilders who are doing late-model engines. PERs are installing the same kind of aluminum bearings that were originally in the engine.

Aluminum bearings are now being promoted for many stock engine applications. Even so, tri-metal bearings continue to be popular with performance engine builders. A typical tri-metal bearing has a three-layer construction. The steel backing plate is covered with a layer of copper/lead overlayed with a thin (.0005 to .0008 in.) coating of babbitt. This provides a good combination of strength, surface action and embedability. Copper/lead can carry 12,000 pounds per square inch versus about 7,000 to 8,000 psi for some aluminum alloys, which makes it better suited for the higher-than-normal loads created by racing. Tri-metal copper/lead bearings are also the primary type of bearing for most heavy-duty diesel engines - at least for now. But that too may change with the introduction of new tougher aluminum alloys in the years ahead.


Regardless of what type of bearing a customer wants, it's important to make sure the bearings are the correct size for the application. Standard-sized bearings are for standard-sized crankshaft journals. If the crankshaft has been turned undersize to recondition worn or damaged journals, the bearing IDs (inside diameter) will also have to be smaller to fit the crank. Standard undersizes include 10, 20 and 30 thousandths.

Journal finish is also important, as is journal roundness. For a bearing to last, the journal must be clean, smooth and concentric. One of the advantages of hard alloy aluminum bearings is that the bearing will actually "polish" the journal and help bring it into specifications if it isn't quite perfect. Tri-metal bearings won't do that but will conform to surface irregularities.

Installed bearing clearances should always be checked to make sure they are within specifications. Too much clearance will result in low oil pressure and noise while too little may cause interference problems and wiping.

Bearings must be lubricated with oil or assembly lube when installed, and the engine's oil system should be primed prior to cranking the engine for its initial start-up. These are things you can't control, but you can remind your customers of the importance of adequate lubrication and what they should do to avoid a dry start.

Other related items a customer may need include motor oil, oil filter, pan gaskets, crankshaft end seals (and repair sleeve if the seal surface on the crank is worn), and a new oil pump.




The catalytic converter is one of the most important emission control devices on a vehicle because it reduces the level of pollutants in the exhaust.

A catalytic converter functions like an afterburner to clean up the undesirable byproducts of combustion. The earliest "two-way" converters, which were used from 1975 to 1980, only burned carbon monoxide (CO) and hydrocarbons (HC) in the exhaust. In 1981, "three-way" and "three-way-plus-oxygen" converters were added to also reduce oxides of nitrogen (NOX) in the exhaust.

In three-way converters, there are two chambers. The first is the "reduction" chamber that breaks down oxides of nitrogen. This releases some oxygen that helps the second "oxidizing" chamber convert carbon monoxide into carbon dioxide (CO2) and burn HC converting it into CO2 and water vapor (H2O).

In three-way-plus-oxygen converters, extra air is routed into the middle of the converter through an air pipe to boost its conversion efficiency. The extra air is supplied by an air pump or aspirator valve.

Some late-model vehicles also have two sets of converters to reduce emissions even more. A small "primary" or "pup" converter is attached directly to the exhaust manifold so it can reach operating temperature quickly to reduce cold start emissions. A "secondary" converter is located further downstream to clean up anything that made it past the primary converter. With Low Emission Vehicles (LEV) and Ultra Low Emission Vehicles (ULEV), the converter(s) must light-off very quickly after a cold start and operate at a very high efficiency.

Converter efficiency depends on the type of catalyst used, how well the catalyst stores oxygen and the surface area exposed to the exhaust. A brand new converter "ages" slightly during its first 5,000 miles of operation, then levels off and operates at a fairly constant level of 95 percent or better efficiency for tens of thousands of miles. The design life of most converters today is 150,000 miles. But over time, a gradual buildup of contaminants can reduce converter efficiency to the point where it may increase tailpipe emissions.

Contaminants include phosphorus from burning oil (worn valve guides or seals, or worn piston rings or cylinders), silicone from internal coolant leaks (bad head gasket or cracks in combustion chamber) and high levels of sulfur in gasoline. Since there's no way to clean a contaminated converter, replacement is the only repair option.

Converters can also be damaged by overheating. Ignition misfire or a compression leak will allow unburned fuel to pass through the engine and into the exhaust. When it reaches the converter, it ignites and sends the converter's temperature soaring. If the converter gets hot enough, the honeycomb that supports the catalyst may melt. This may create a blockage in the exhaust. A plugged converter will cause a big increase in exhaust backpressure, which will hurt engine performance and fuel economy - and may even cause the engine to stall. A plugged converter must be replaced.

On most 1996 and newer vehicles, the Onboard Diagnostics (OBD II) system monitors converter efficiency. The OBD II system does this by watching the signal from the "downstream" oxygen sensor behind the converter. If the OBD II system sees a drop in efficiency that allows emissions to rise more than 1.5 times the legal limit, the computer will set a fault code and turn on the Malfunction Indicator Lamp (MIL). The vehicle may still run fine and show no other symptoms (provided the converter is not plugged), but it will not pass an emissions test.

Original equipment converters are covered by a federal eight-year/80,000-mile emissions warranty. Aftermarket replacement converters must be the same type as the original and EPA-certified as meeting emission standards. Aftermarket converters carry a two-year/24,000-mile warranty.

On 1996 and newer vehicles with OBD II, aftermarket converters must be OBD II certified.

Other exhaust system parts that may be needed when changing a converter include the head pipe and tailpipe, clamps and hangars. Severely corroded clamps must usually be cut or sawed off, so your customer may also need an exhaust cutoff tool and/or pipe chisel to remove the old converter. The entire exhaust system should also be inspected end to end, and any other parts that are leaking, damaged or severely corroded should be replaced.




Flywheels should always be replaced or resurfaced as part of a complete clutch job.

Replacing a clutch is a labor-intensive job because the transmission or transaxle must be separated from the engine. Therefore, it's important to inspect the entire clutch system - including the flywheel - to see if any additional parts also need to be replaced.

In the case of the flywheel, there usually comes a time in its life when it will need to be resurfaced or replaced. That time is usually when your customer is doing clutch work.

Normal clutch operation generates a lot of friction and heat, heat that the mass of the flywheel absorbs and dissipates. If the clutch is starting to slip, even more heat is generated. This added thermal stress can cause heat cracks, warpage and the formation of hard spots in the surface of the flywheel.

If a flywheel is found to be damaged (cracks that are more than surface deep, or cracks around the crankshaft bolt holes), replacement is required. A cracked flywheel can explode with tremendous force, so under no circumstances should anybody take a chance if the flywheel is at all questionable. If the vehicle is equipped with a "dual-mass" flywheel (some Ford pickups as well as some GM trucks and some luxury European imports), a bad flywheel can also cause slipping and/or chattering. Dual-mass flywheels are designed to dampen engine vibrations and shock loading of the drivetrain. They are expensive to replace (around $600 or more!) and because of this, some aftermarket suppliers have come out with conventional one-piece solid flywheels that can be installed in place of an original equipment dual-mass flywheel. A solid flywheel can save your customer some money, but the trade-off may be increased drivetrain harshness and vibration. Some OEMs caution against replacing a dual mass flywheel with a solid flywheel because it may contribute to premature transmission failure (due to increases shock loading of the gears).

Part of the flywheel inspection process should involve measuring the flatness of the flywheel with a straightedge and feeler gauge, and inspecting the surface for cracks, grooving or hard spots, which will look like discolored areas that are slightly raised above the surrounding surface.

Some specifications allow a maximum runout of up to .0005 inch per inch of flywheel diameter. More than .002 inch of runout on a typical passenger car flywheel can cause chatter and vibration problems. More than .005 inch of runout can cause severe vibrations that may cause the clutch to fail. The bottom line: Flatter is always better.

Even if the surface of the flywheel is flat and free from defects, it should be resurfaced or replaced before the replacement clutch is installed.

If a worn flywheel is not resurfaced or replaced, the replacement clutch won't last. Your customer will likely be back with a failed clutch disc demanding warranty satisfaction. Most clutch suppliers will not honor such a warranty claim if the flywheel was not resurfaced (or was resurfaced incorrectly) when the clutch was installed. Installing a new clutch disc on a worn or warped surface is asking for trouble, yet all too often the flywheel isn't resurfaced or replaced to save time or money. It's a big mistake that can end up costing a customer a lot more in the long run.

On many flywheels, the starter ring gear is a separate component that is pressed on -- and can be replaced if any of the teeth are damaged. If the teeth are part of the flywheel itself and are damaged, a new flywheel should be installed to eliminate any possible cranking problems.

If a flywheel needs to be resurfaced or replaced, its index position with respect to the crankshaft should be clearly marked prior to removal to maintain proper engine balance. This step is critical with engines that are "externally" balanced. That is, those engines that have large flywheel counterweights and rely on the balance of the flywheel to minimize vibration.




Friction equals stopping power, but there's a lot more to brake linings than the ability to stop a vehicle on a dime. The brakes also have to be quiet, resist fading, provide a firm predictable pedal feel and withstand wear.

Brake linings are designed to wear. Every time the brakes are applied, the pads rub against the rotors and the shoes rub against the drums. Rubbing creates friction, which transforms the energy of motion into heat bringing the vehicle to a halt.

Eventually the linings wear down to the point where they are too thin to be safe. Or, the linings are so badly worn that the rivet heads or steel backing plate are rubbing against the rotors, which can ruin a set of rotors rather quickly.

Another reason to replace the linings is to cure a noise problem. Many people can't stand noisy brakes; it's like dragging fingernails across a black board. The annoying high-frequency squeals have no effect on brake performance. However, many brake suppliers market linings that are engineered to be quiet. These are usually premium linings that also provide extended life and superior performance.

Most friction materials today are specially formulated for specific vehicle applications. The brake system on a small front-wheel-drive car is not the same as one on a fullsize rear-wheel-drive pickup or SUV. Consequently, different types of friction materials are used by the same supplier for different vehicle applications.

"Application-engineered" friction materials more closely match the performance, feel and life of the OE pads than "generic" friction materials. Some are even certified as meeting or exceeding OEM requirements.

Actually, there are no federal performance standards for aftermarket brake linings. The brakes on all new vehicles must comply with federal motor vehicle safety standard 105 or 135 (FMVSS 105 or 135), which specifies maximum stopping distances according to vehicle weight, loading, pedal effort (with and without power assistance) and brake condition (green and burnished linings.) Though these standards aren't required for aftermarket linings, most brake suppliers rigorously test their products to make sure they're safe.

The friction characteristics of replacement linings should closely match the OE linings to maintain like-new stopping performance, feel and safety. Linings that are more aggressive than the original may make the brakes feel grabby or upset front/rear brake balance, which can increase the risk of rear wheel lockup and skidding on wet or slick roads.

The risk of a mismatch in friction material increases even more when different brands of aftermarket replacement linings are installed on the front and rear brakes. One manufacturer's replacement linings may be a close match to the OEM linings, but another manufacturer's linings might not. If the front brakes are relined with Brand A linings, and the rear brakes are relined at a later time with Brand B linings, the vehicle may end up with mismatched brakes.

For this reason, sell both the front and rear brakes at the same time with linings from the same supplier. You should also recommend using linings that are based on similar friction materials. In other words, replace ceramic with ceramic, semi-metallic with semi-metallic and nonasbestos organic (NAO) with NAO.

Ceramic-based friction materials have become very popular in recent years for a number of reasons. Over half of all new vehicles come equipped with these type of linings because ceramics have stable and predictable friction characteristics, more so than most semi-metallic materials. Ceramics provide a consistent pedal feel that is the same whether the pads are hot or cold because the coefficient of friction doesn't drop off as quickly as semi-metallics. NVH (noise, vibration and harshness) is also less with ceramics, so the brakes are significantly quieter.

Ceramic compounds can be very complex and may have 18 to 20 different ingredients in a formula, including various fillers and lubricants that are added to help dampen vibrations and noise. A typical semi-metallic compound, by comparison, might contain only eight or nine ingredients.

Though semi-metallic linings generally provide better wear at higher temperatures, ceramics do just as well if not better at lower temperatures for the average driver. Consequently pad life is often improved.

Low dust is another desirable characteristic of the material. The color of most ceramic materials is a light gray, so it is less visible on wheels.

One very important point to keep in mind about ceramic-based friction materials is that they are not all the same. In other words, ceramic is not a generic term for a type of friction material. It's a marketing buzzword that covers a wide spectrum of different friction products. Most brake suppliers have their own special ceramic-based formulas. The type of ceramics used, the particle size, distribution, hardness and other ingredients that make up the total friction package can all vary - even from one vehicle to another. The point here is to recommend a quality name-brand supplier that stands behind their products and has a proven track record.

A customer who is buying brake linings should also be advised to thoroughly inspect the entire brake system and to replace any parts that are worn, damaged or badly corroded.

Though it may not always be necessary, especially if this is the first time the linings are being replaced, a complete brake job may include rebuilding or replacing calipers and wheel cylinders, replacing disc and drum brake hardware, resurfacing or replacing drums and rotors, changing the brake fluid and bleeding all the lines, checking and adjusting the parking brake, and even checking the ABS system. Overlooking such items can lead to problems later.

Other items that may also be needed include brake grease, calipers, wheel cylinders, brake hoses, brake lines, a master cylinder and brake fluid.




Fuel injection has been used on almost all vehicles since the mid-1980s.

Some of the older fuel injection applications are Throttle Body Injection (TBI) systems with one or two injectors mounted in a single throttle body. Most, though, are Multiport Fuel Injection (MFI) systems with individual injectors for each of the engine's cylinders. One other variation is General Motors Central Point Injection (CPI) that uses a single centrally-located master injector to route fuel to mechanical injectors at each cylinder.

All electronic fuel injectors work essentially the same. An electrically-operated solenoid in the top of the injector pulls open a pintle or ball valve that allows pressurized fuel to spray out of the injector nozzle. The amount of fuel that's delivered by the injector is regulated by the engine computer (which varies the injector's "dwell" or "on time" according to inputs from its various sensors), and the fuel pressure regulator (which increases or decreases fuel pressure according to changes in intake vacuum.)

On some engines, all the injectors are fired simultaneously once every engine revolution. On others, each injector is fired individually in a sequence that corresponds to the firing order of the spark plugs (Sequential Fuel Injection or SFI.) This allows more rapid changes in the fuel mixture for improved throttle response, performance and emissions.

The flow characteristics, spray pattern and calibration of a particular set of injectors is matched to a specific engine application and has an important affect on engine performance and emissions. Replacement injectors must have the same flow characteristics as the original.

Fuel injectors are relatively trouble-free, but as the miles add up they may become clogged with fuel varnish deposits. Dirty injectors can't deliver their normal dose of fuel with each squirt, which leans out the fuel mixture causing hesitation, lean misfire, rough idle and similar driveability symptoms.

Dirty injectors can often be cleaned with fuel additives, or by on-car or off-car cleaning. But if they fail to respond to cleaning, replacement is the only option to restore performance.

Injector replacement is also necessary if an injector is worn, leaking or is dead electrically. A working injector will make a buzzing noise as it cycles open and shut, but a dead injector will remain silent. A single shorted injector may even prevent the engine from running depending on how the injector driver circuits are wired with the PCM.

Accurate diagnosis of injector problems is essential before any parts are replaced to rule out other possibilities. A bad wiring connector or computer circuit can render an injector inoperative. Air leaks past the rubber O-ring seal at the base of an injector can also mimic the symptoms of a clogged injector.

For fuel pressure, EFI systems rely on a high-pressure electric pump that is usually mounted inside the fuel tank. Power to the pump is usually routed through a relay. Pump pressure and flow ratings can vary from about 35 to 85 psi depending on the application. There are also different styles of pumps including single or double-vane, roller vane, turbine or gerotor-style pumps.

If a fuel pump does not develop full pressure, it may make the engine hard to start or run poorly. If the fuel pump fails, the engine will not run at all. Some pump noise is normal but increased noise is often a sign that a pump is failing.

Pump failures may be due to wear, or an electrical problem in the pump motor, relay or wiring voltage supply. Rust or sediment inside the fuel tank can also cause a pump to jam or fail, or plug up the pump's inlet filter.

Most pumps can be replaced without having to also replace the fuel tank sending unit. But on some applications the pump is part of the sending unit assembly so everything must be replaced. The pump's filter sock or strainer should also be replaced when the pump is changed.

Sales Tip: If the pump or injectors are being replaced, you should also recommend replacing the fuel filter. The filter protects the fuel system against dirt and debris. It is located in the fuel line in the engine compartment or under the vehicle. Some filters are held in place with quick-lock spring couplings, which require a special tool to release.

Another important component in the EFI system is the fuel pressure regulator. The regulator controls the pressure within the fuel injection system and routes excess fuel back to the fuel tank. It is usually mounted on the fuel rail on the engine, the regulator has a spring-loaded diaphragm attached to a source of intake vacuum. As engine load (vacuum) changes, pressure is adjusted up or down as needed to maintain proper fuel delivery. A problem here can result in lower-than-normal fuel pressure and poor performance. Some newer vehicles (Chrysler) have "returnless" systems with the regulator mounted in the fuel tank with the pump.




Ever see a car that quit running and refuses to start? If the engine cranks normally and has spark but is not getting any fuel, it might be a bad fuel pump.

A bad fuel pump will certainly kill an engine and prevent it from running. But sometimes the lack of fuel may not be the pump's fault. The real problem might be a bad relay, wiring or ground connection that is preventing the electric pump from running. Or, the fuel filter might be plugged, or the vehicle may have simply run out of gas.

Fuel-injected engines require a lot of pressure to operate the fuel injectors. The pump has to push fuel from the tank to the injector supply rail on the engine and then force it through each injector when the injector opens to spray fuel into the engine. The amount of pressure is critical and must be within specifications for the injectors to deliver their normal dose of fuel. The amount of pressure required may vary from 35 to 85 pounds of pressure depending on the system, application and load on the engine.

On older carbureted engines with mechanical fuel pumps, much less pressure (two to six lbs.) is needed because all the pump has to do is keep the carburetor bowl filled with gasoline. The intake vacuum sucks the fuel through the carburetor.

What happens if fuel pressure is not within specifications? Too much fuel pressure in a fuel-injected engine will create a rich fuel condition, which will cause an increase in fuel consumption and carbon monoxide (CO) emissions. An engine that's running really rich may also experience a rough idle, surging and possibly even carbon-fouled spark plugs.

Not enough fuel pressure can starve the engine of fuel, creating a lean fuel condition. This can cause hard starting, misfiring, rough idle and loss of power. If there's no pressure because the pump has failed or is not running, the engine will crank normally but it won't start.

Fuel pumps run constantly, so over a number of years they can experience wear not only in the armature bushings and vanes but also the brushes and commutator. Electric fuel pumps rely on the fuel passing through them for lubrication and cooling. Any "junk" that's in the gasoline will therefore accelerate wear and shorten the life of the pump.

Most outright pump failures are due to fuel contamination such as dirt, rust or hose debris from deteriorating braided fuel lines. The pump pickup inside the fuel tank has a filter sock or screen to keep large pieces of debris out of the pump and fuel line, but smaller pieces can pass right through. Pump failure can also occur if the sock becomes clogged and starves the pump for fuel. With no lubrication, the pump can run hot and self-destruct.

Testing a fuel pump involves measuring fuel pressure while the engine is running. Many fuel-injected engines have a pressure test fitting on the injector supply rail for this purpose. Another method is to disable the ignition, disconnect the fuel supply hose from the injector rail and energize the pump to see how much fuel it delivers. A "good" pump will deliver at least 750 ml of fuel in 30 seconds.

If a pump fails to run, a check should be made to see if it is receiving normal battery voltage. The pump motor itself can be checked with an ohmmeter. As a rule, most pumps should read two to 50 ohms if good. If the pump is open (reads infinity) or shows zero resistance (shorted), the motor is bad and the pump needs to be replaced.

If a pump motor runs but system pressure is low, the problem might be a faulty fuel pressure regulator. The regulator is usually mounted on the injector supply rail. Its job is to vent pressure and route excess fuel back to the tank when system pressure exceeds specifications. The regulator is connected by a vacuum hose to the intake manifold so it can balance pressure according to engine load.

A plugged fuel filter can also obstruct the flow of fuel and cause a drop in pressure.

Replacement fuel pumps must have the same pressure and flow ratings as the original. The style of pump may differ from the original as long as it performs the same as the original.

Sales Tip: The pump is usually mounted inside the tank and is part of the fuel gauge sending unit. The pump can usually be replaced separately but on some vehicles, the whole assembly must be replaced. Complete assemblies are also available for many applications where the pump alone can be changed because a complete assembly is faster and easier to install, and it reduces the risk of a comeback due to improper installation.

When a tank-mounted pump is replaced, the inside of the tank should always be inspected and cleaned if there's evidence of rust or debris in the pump or filter - otherwise you may doom the new pump to premature failure. When the pump is changed, a new pickup sock should also be installed along with a new inline fuel filter.

Warn your customers not to "test" a new pump before it has been installed by jumping it. Running a pump in a dry condition with no fuel to lubricate it may damage the pump.




In the good ol' days, all vehicles had wheel bearings that needed to be cleaned, inspected, repacked with grease and adjusted about every 30,000 miles. That generated a lot of grease, seal and wheel bearing sales.

Today most vehicles have sealed wheel bearing assemblies that require no maintenance.

Hub assemblies, as they are often called, are unitized, maintenance free and non-serviceable units that are preset, pre-greased and pre-sealed. Most hub assemblies are designed with a unitized bearing or flange that is intricate to the hub and/or bearing housing, which are not replaceable.

Since they are sold as a single part, hub units allow for easier installation for the technician and increased product reliability for enhanced performance. These hubs require no maintenance or handling, which eliminates the need for preventive maintenance, grease and/or future adjustments.

They also last a long time. The bearing and hub assemblies are engineered to go 150,000 miles or more - and most do, so there are far less unit sales. Even so, the price of these parts tends to be high (some cost over a hundred dollars depending on the application), so the total annual sales for wheel bearing and hub assemblies is estimated to be over $120 million a year.

According to a recent Babcox Research survey, 51 percent of bad wheel bearings are identified and replaced as a result of a vehicle owner complaining about noise, 24 percent are found during a brake job and 19 percent are discovered during an alignment.


A classic symptom of a bad wheel bearing is noise, so if a vehicle is making "funny" noises when driving (squeaks, chirps, squeals, moans, etc.), it may indicate a bad wheel bearing. Other symptoms include steering wander or possibly a pull to one side when braking.

Wheel bearings can be checked by grasping the tire at the 12 and six o'clock positions and rocking the tire. If there is any play, the bearings may be loose and need to be replaced. Also, if any roughness or noise is heard while rotating the tire, it would indicate bearing trouble.

If one wheel bearing has failed, all of the other hubs on the vehicle should be inspected too, especially if the vehicle has a lot of miles on it or has been driven in hub-deep water or mud. Chances are some of the other bearings may also be nearing the end of their journey.

On some vehicles (many GM models, for example), the sealed wheel bearing and hub assembly also contains a built-in wheel speed sensor for the antilock brake system (See pages 28-29 for more information on wheel speed sensors and the antilock brake system). If this sensor fails, it will turn on the ABS warning light and disable the ABS system until the sensor is replaced. But the sensor can't be replaced separately on these applications. The entire hub assembly must be changed.

A wheel bearing failure can be dangerous because it may cause the wheel to separate from the vehicle and/or cause a loss of steering control. A wheel bearing that's making noise or is loose is not something that should be ignored. There's no way to know how many miles the bearings will go before the unit fails completely.

Replacing a sealed wheel bearing and hub assembly involves removing the wheel, hub nut and brakes to replace the unit. Special tools that may be needed include a socket large enough to fit the hub nut, a replacement hub nut (if not included with the hub assembly), a torque wrench and possibly a hub puller depending on the application. Related items that may also need attention at the same time include the outer CV joints and/or boots on the halfshafts of FWD cars, the brake linings, and the rotors and drums.

For older vehicles with serviceable wheel bearings, your customer will need wheel bearing grease such as a #2 NLGI lithium-based grease or a synthetic wheel bearing grease. Wheel bearing grease is designed for high-temperature, high-load conditions. Warning: Ordinary chassis grease should never be used in wheel bearings.

Other parts your customer will need include new grease seals (old seals should never be reused) and cotter pins. If an inner or outer wheel bearing needs to be replaced, the complete package (inner race, outer race and ball or rollers) must be replaced as a matched set. Special tools that may be needed include a bearing removal tool and bearing and seal drivers.


With trailer wheel bearings, the bearings should be inspected annually and serviced as needed if the bearings are not sealed for life. Boat trailers, in particular, are very hard on bearings because the hubs are usually submerged in water when unloading and loading the boat. With serviceable boat trailer bearings, annual cleaning, inspection and re-greasing is highly recommended (usually at the end of the season.)




The Heating Ventilation and Air Conditioning (HVAC) system provides year-round climate control in today's vehicles.

Most late-model cars and trucks are A/C equipped, and on those with automatic temperature control (ATC) systems, the A/C is combined with the heater in such a way that the driver selects a temperature, and the system figures out how much heating or cooling is needed to maintain that setting.

The major components in HVAC systems include the A/C compressor, condenser, evaporator, orifice tube or expansion valve, high- and low-pressure hoses, an accumulator or receiver drier, plus the heater core, blower motor, motor relay and door motors (vacuum or electric.) With ATC systems, you can add in various temperature sensors, a sunload sensor and the control head (which may incorporate the ATC module if it is not a separate component.) And don't forget the refrigerant that charges the A/C system, and the all-important compressor oil that keeps the compressor pumping smoothly.

The HVAC system's job is to keep the vehicle's occupants in their comfort zone. Now there are "dual-zone" HVAC systems that provide separate controls for the driver and the front seat passenger.

On cold days, the HVAC system provides heat and defrost. On hot days, it supplies cool air and dehumidification. And on in-between days, it lets in fresh air via an external vent. Actually, most HVAC systems provide fresh air all of the time unless the controls are set to the "RECIRC" mode, in which case the outside vent is closed and the air inside the passenger compartment is recirculated.

The RECIRC mode is good for two things: for speeding up the warming or cooling process when a vehicle is first started, and for shutting out obnoxious fumes in heavy traffic or odors such as dead skunks. The RECIRC mode is not so good on rainy days because it tends to fog up the windows.

HVAC problems are usually related to heating or cooling complaints, but may also include coolant or refrigerant leaks. Hot coolant from the engine circulates through the heater core to provide heat, and refrigerant vapor circulates through the evaporator inside the HVAC unit to provide cooling. Blend air doors route incoming air through the heater or evaporator to provide the desired amount of heating or cooling. On vans and SUVs with rear A/C, a second heater core, evaporator, blower motor and controls are located in the rear area of the vehicle to provide heating and cooling for the back seat passengers.

Heating problems can be caused by low engine coolant, a cooling thermostat that is stuck open, obstructions in the heater core (internal or external), or blend air doors that are mispositioned or broken. Heater cores sometimes fail, too, usually because of internal corrosion or sediment circulating in the coolant (dirty coolant.) Replacing a heater core is a labor-intensive undertaking because the core is buried deep inside the HVAC assembly. Replacement usually requires tearing the dash apart so the HVAC assembly can be opened up.

Cooling problems may be caused by low refrigerant (often due to a refrigerant leak), a compressor failure, a compressor clutch that is not cycling on and off, a plugged orifice tube or various control problems. ATC systems can be very complicated and may relay compressor on/off commands through the Powertrain Control Module (PCM). Problems with ATC sensors, the control head, the PCM or the wiring can prevent the system from operating normally.

Diagnosis usually involves two things: checking the refrigeration circuit (the amount of refrigerant in the system, the operation of the compressor clutch, etc.), and scanning the control electronics for fault codes. ATC systems have their own self-diagnostic capability and will set fault codes when problems are detected. A scan tool can then be used to retrieve the information and to check the operation of the various components in the system.

Most automotive A/C systems hold only a couple pounds of refrigerant. The amount is critical because any loss of refrigerant reduces cooling performance. Leak detection dye is often added to the refrigerant to reveal leaks. The dye is visible under ultraviolet light. An electronic leak detector may also be used to sniff suspicious connections and seals for leaks.

Leaks most often occur at hose connections and at the compressor shaft seal. But leaks can also occur if internal corrosion eats holes through the evaporator. The condenser, which is mounted ahead of the radiator, is mostly vulnerable to collision damage and road hazards.

If refrigerant is needed, it must be the correct type for the system. Newer vehicles (most 1994 and up) require R-134a. Older vehicles use R-12, but can be retrofitted to R-134a, - which makes sense if the A/C system requires major repairs such as replacing a compressor, condenser or evaporator. Don't forget that only EPA-certified professionals can buy R-12.

Compressor failures also happen with some frequency. Compressor failure often occurs after a refrigerant leak has allowed compressor oil to seep out of the system. The oil circulates with the refrigerant, so if the refrigerant leaks out, so will the oil. A plugged orifice tube can also block the flow of lubricant to the compressor causing it to fail.

The amount of oil in the system is critical for two reasons. One is that it takes a certain amount of oil to keep the compressor lubricated. The second is that too much oil can interfere with cooling.

R-134a A/C systems require PAG oils, with different types of compressors requiring different viscosity PAG oils. R-12 systems require mineral oil. R-12 systems that have been converted to R-134a may use PAG oil or POE oil. Make sure your customer gets the type of oil specified by the compressor supplier or vehicle manufacturer. Also, some compressors are shipped dry, others are filled with a temporary oil that must be drained before the compressor is installed, and others are shipped with the correct type of oil. Bottom line: Read the installation instructions!

Several things should be done prior to replacing a failed compressor. One is that the A/C system should be flushed to clean out any debris or sludge that may have caused the original compressor to fail. Flushing requires special equipment and should only be done using an approved flushing chemical or liquid refrigerant. Parallel flow condensers and those with very small passageways are very difficult to clean and should be replaced if the system contains sludge or debris. An inline filter should also be installed in the liquid line to trap debris in the system, and the orifice tube and accumulator or receiver drier should also be replaced.

Some compressor manufacturers may void their warranty if the system is not flushed when the compressor is replaced.




When a headlamp fails, what does the typical customer look for? A replacement headlamp that will fit their vehicle. Instead, this should be an opportunity for a lighting upgrade sale.

The sales process involves figuring out which headlamp or bulb fits the car, truck or SUV, and then deciding whether to buy a standard replacement bulb or headlamp, or some type of upgrade product that offers more light output and/or better visibility.

Finding the right bulb or headlamp that fits the application should be fairly easy, provided the customer knows which bulb is burned out. Is it a high beam, a low beam or a combination high/low beam? Turn on the lights and flick the dimmer switch to see which one doesn't work.

Once the bad bulb has been identified and removed, it can be compared to the replacement bulb to make sure both have the same socket configuration. This is very important because the wrong bulb usually won't fit the receptacle and/or wiring connector.

Next comes the "numbers" decision. If a customer is buying a standard replacement bulb, the new bulb will have the same wattage rating as the original. Low beams are typically rated at 45 to 60 watts, while high beams are usually 50 to 72 watts. But the customer may also notice that some replacement bulbs offer a higher wattage rating than the original, and/or a higher "lumen" rating (a measure of light output.)

As a rule, the higher the wattage rating, the more light a bulb produces. More light increases the reach of the headlights and allows the driver to see further down the road for safer nighttime driving.

Lighting efficiency depends on how many lumens per watt a bulb gives off when it is illuminated. Halogen bulbs are up to 40 percent more efficient than ordinary incandescent bulbs because the filament burns hotter and brighter. This requires a special mixture of bromine, krypton and argon gases inside the bulb to cool the filament, and a special kind of high-temperature quartz glass that can withstand the heat.

Note: Halogen bulbs must be handled with care. Advise customers to never touch the glass with bare fingers because the oils left by a fingerprint can lead to premature bulb failure. A telltale symptom of this kind of failure is a large brown spot on the bulb glass.

When choosing an upgrade lighting product, the wattage and lumens numbers alone don't tell the whole story because lighting performance and visibility also depend on the color (temperature) of the light and how it reflects and scatters (glare).

The new "High Energy Discharge" HID lighting systems that are on many late-model luxury cars and SUVs produce a bluish colored light. Though HID headlights do provide improved visibility for the vehicle's occupants, many drivers who face these vehicles in oncoming traffic at night say the harsh blue headlights are distracting and the glare produced by these lights hinders their own visibility.

The color of light produced by a light source is measured in degrees "Kelvin." Natural daylight is rated at 4,500K, which is where the human eye sees most clearly. By comparison, the original equipment halogen headlamps on most cars and trucks produces light with a color temperature rating of about 3,200K, which gives it a duller, yellowish appearance. HID lighting typically produces light in the 4,200K range, which is closer to natural daylight but has a bluish tint at night.

For those who want more light but not the bluish tint or glare of HID lighting, there are high-output, xenon-filled bulbs that produce a whiter light than ordinary halogen headlights. The "super-white" bulbs have a special coating that filters out the yellow rays produced by the high-temperature filament. The result is a temperature rating of around 3,800 degrees K, which is much whiter than standard halogen bulbs but without the bluish tint.

Another benefit of upgrading to whiter, brighter headlamps is reduced glare. This is an important selling feature for older drivers who may not see as well at night.

The whiter, brighter headlamps are a direct-fit replacement for standard headlamp bulbs and require no modifications. Just remove the old bulb and replace it with a better bulb. It's that simple - and your customer doesn't have to wait until a bulb fails to make such an upgrade. They can do it anytime. But many customers may not be aware of their upgrade options and may simply choose to buy a standard replacement headlamp because that's the part listed for their vehicle. If you're helping a customer find a replacement headlamp, be sure to mention the upgrade options that are available and how whiter, brighter headlamps can improve nighttime driving visibility and safety. And if a customer has already selected a standard headlamp, ask him if he'd like to upgrade to a whiter, brighter headlamp. You might be surprised by how many customers take you up on your offer.

Sales Tip: Finally, don't forget to ask about other visibility related items such as wiper blades and windshield washer premix.




Ever see the inside of a used oil filter?

If you were to cut open a used filter, remove the oozing filter element and examine it under a microscope, you'd see the all the crud and debris that accumulates during several thousand miles of driving.

Trapped in the filter media would be metallic debris that flaked off engine bearings and other wear surfaces inside the engine. You'd also find rust particles, chunks of soot and little shards of silicone from dust and dirt that found its way into the crankcase. Some of this debris might be visible to the naked eye, but most of it is extremely small: five to 40 microns (millionths of an inch) in size. A human hair, by comparison, is about 60 microns in diameter.

The filter's job is to catch all of this junk before it can circulate through the oil system and reach the engine's vital parts (main bearings, rod bearings, camshaft journals, lifters, etc.) The more efficient the filter, the better job it does trapping all of these impurities. The filter is the engine's only means of protection against abrasion and premature wear.

The filter should always be replaced when the oil is changed. Yet some owners manuals still say it's only necessary to replace the oil filter every other oil change. The logic is that it reduces maintenance costs - at least for awhile. Such a budget-minded approach may get the engine through the initial three-year, 36,000-mile warranty period, but what will the long-term effects be? It makes a lot more sense to replace the filer with every oil change.

Most technicians still recommend changing the oil and filter every 3,000 miles or six months (or three months during cold weather or if a vehicle is only used for short trips of 10 miles or less.)

Many OEM maintenance schedules allow much longer intervals (up to 10,000 miles on some vehicles), or rely on an "oil reminder" light to signal the driver when the oil needs to be changed. Even so, most technicians say the more conservative approach works best over the long haul.

If a motorist waits too long to change the filter, there's a danger that it might become plugged. To prevent a plugged filter from starving the engine for lubrication, oil filters have a built-in safety device called a "bypass valve." When the differential pressure across the filter element exceeds a predetermined value (five to 40 psi depending on the application), the bypass valve opens so oil can continue to flow to the engine. But when the bypass valve is open, no filtration occurs. Any abrasive contaminants that are in the crankcase will circulate through the engine accelerating wear. That's why regular filter (and oil) changes are so important.

Another reason for replacing the oil filter when the oil is changed is that the old filter contains anywhere from a pint up to a quart of dirty oil depending on its size. The oil in the filter accounts for 10 percent to 20 percent of the total crankcase capacity, so why contaminate the new oil with this much dirty oil? Someone might say the filter could always be removed and drained to get rid of the dirty oil, but if they are going to go to that much work, why not just replace the filter with a new one and start fresh?

Spin-on oil filters come in a wide variety of lengths, diameters and thread sizes. Because of consolidation, some replacement filters may be slightly taller or shorter than the original, or slightly larger or smaller in diameter. But as long as the hole size, pipe threads (SAE or metric), seal position and bypass valving are the same, there should be no mismatch. Always follow the filter listings in your supplier catalog or cross-reference index.

If a customer gets the wrong oil filter for his vehicle, it may not fit properly, damage the threads on the filter pipe or leak. Or worse yet, it may come loose causing a loss of oil pressure and expensive engine damage. So if a customer has any doubts about which filter to buy, help him find the correct one.

As for brand preference, that's the customer's choice. Some filters feature finer filtration than others, or are designed for "extended life." Others may have a easy-to-grip, rubber-like coating on the outside of the can that makes installation easier in tight quarters.

Sales Tip: In addition to a filter, your customer will also need oil (four or five quarts for a typical oil change), plus an oil filter wrench of some kind to remove a stubborn filter (there are many different sizes and styles to choose from), and a catch pan to catch the used oil. He may also need a repair plug for the oil pan if the original plug or hole has been damaged.

Sales Tip: Finally, if your store accepts used oil for recycling, don't forget to mention this to your customers. Used oil disposal should be disposed of properly to protect the environment.




The radiator is one of the main components in the cooling system.

Internal combustion engines produce a lot of waste heat when they are running. Almost one third of the heat energy that's produced by combustion is absorbed by the block, pistons and cylinder heads. To keep these engine parts from getting too hot, the cooling system's job is to manage heat. It does this by circulating coolant through the block and heads, and then routing it to the radiator. Air flowing through the radiator cools the liquid, lowering its temperature by a hundred degrees or more. The coolant is then recirculated back through the engine by the water pump to provide continuous cooling as long as the engine is running.

To cool efficiently, the radiator must be clean, in good condition and receive adequate airflow. The radiator's front-mounted location ensures good airflow when the vehicle is in motion, but at low speeds and when the vehicle is stopped a cooling fan must be used to boost airflow.

If a vehicle has air conditioning, a second heat exchanger called a "condenser" is usually mounted in front of the radiator. The condenser cools the refrigerant after it leaves the A/C compressor. The heat given off by the condenser when the A/C is on makes it harder for the radiator to do its job, so the cooling fan usually remains on all the time while the A/C is running.

Radiators can usually go eight to 10 years or more without requiring any repairs. But their frontal location makes them vulnerable to damage by stones and other road hazards. They can also become clogged with dirt and debris. In cold climates, road salt can also attack the metal causing corrosion that may eventually cause the radiator to leak. But the most common cause of radiator failure is internal corrosion caused by coolant neglect. If the coolant isn't changed at the recommended service intervals, it may become acidic and attack the radiator.

The plastic end tanks on late-model vehicles can sometimes be damaged by steam erosion. The underlying cause is usually a low coolant level, which may be due to coolant leaks or a bad radiator cap that doesn't hold its rated pressure.

Too much pressure inside the cooling system can also damage a radiator by blowing out the seam along an end tank. The cause is often a leaky head gasket that allows combustion gases to escape into the cooling system. The wrong radiator cap (too high a pressure rating) can do the same thing.

And did we mention freezing as yet another possible cause of radiator failure? If the concentration of the antifreeze in the coolant isn't strong enough during cold weather to prevent freezing, the coolant may turn to ice, expand and rupture the radiator.

If a radiator is leaking, it must be repaired or replaced to stop the loss of coolant. Even a tiny leak that seeps only a few drops a day will eventually allow enough coolant loss to make the engine run dangerously hot. The capacity of many cooling systems today is only a couple of gallons, so any loss of coolant greatly increases the risk of overheating, boilover and possible engine damage.

Cooling system sealer products can be added to a leaky system and will usually stop small leaks temporarily. But the only permanent fix for a leaky radiator is to repair it or replace it. Many radiator repair shops have closed their doors because of environmental concerns and market changes. Many customers don't want to wait for a radiator to be repaired - and often the cost of the repairs is more than what a brand new radiator costs.

Replacing an old leaky radiator with a brand new one restores the cooling system to like-new condition. A brand new radiator also has zero miles on it and has not been subjected to any internal or external corrosion. A new radiator also comes with a far better warranty than most radiator shops can offer on a repaired radiator.

When selling a radiator, the most important considerations are sizing the radiator correctly and making sure the inlet and outlet fittings are in the right locations so the hoses will line up the same as before. The height and width and the most critical dimensions so the radiator will fit properly. Some replacement radiators may be somewhat thicker or thinner than the original, but as long as it provides the same degree of cooling (or better) than the original, it would work fine.

It's extremely important to give every new radiator a clean start in its service life. That means flushing the cooling system and replacing all the old dirty, contaminated coolant with new coolant.

Other items your customer will probably need include a new radiator cap (make sure the pressure rating is the same as the original), antifreeze (long life or standard), and new upper and lower radiator hoses (and clamps). If the vehicle is more than six years old and/or has overheated, you should also recommend replacing the thermostat.




If engine parts could be machined perfectly smooth and flat, and would remain in perfect alignment regardless of temperature and loading, there would be no need for gaskets.

Engine parts need a variety of different types of gaskets to keep oil, coolant, combustion gases and vacuum where they belong.

Oil pan and valve cover gaskets seal the top and bottom engine covers to keep the oil where it belongs and to keep dirt and other contaminants out. On most older engines, these gaskets are cork/rubber, but on most newer engines the oil pan and valve cover gaskets are molded rubber or silicone for improved durability and sealing.

Cork/rubber is a good gasket material but takes a compression set and hardens with age. The loss of elasticity reduces sealing pressure between parts and may eventually allow a leak to develop. Once a cork/rubber gasket starts to leak, it must be replaced.

Replacement oil pan and valve cover gaskets may be the same material as the original (such as cork/rubber), or you may be able to offer your customer an upgrade if a molded rubber gasket is available. Molded rubber gaskets are more expensive but are much long-lived.

Some cork/rubber oil pan and valve cover gaskets have metal grommets in the bolt holes to prevent overtightening. Others may have a metal reinforcing carrier to improve strength, rigidity and torque retention, and to make installation easier. Cork-rubber gaskets can be installed dry or with sealer, or with adhesive to make installation easier. Molded rubber gaskets must always be installed dry (no sealer or RTV silicone.)

Intake manifold gaskets seal the junction between the intake manifold and cylinder head to keep the air/fuel mixture flowing to the engine's cylinders. A leak here can reduce engine intake vacuum and allow air to lean out the fuel mixture causing driveability, performance and emission problems.

Intake manifold gaskets on older engines are often made of die cut material, while those on many newer engines are molded plastic with O-rings or synthetic rubber sealing beads. The plastic gaskets are often reusable, but cut gaskets and O-rings should always be replaced if the manifold comes off for any reason.

Another important gasket is the one under or behind the throttle body, and on older vehicles it's under the carburetor. This gasket seals the throttle body or carburetor to the intake manifold. Leaks here can also reduce intake vacuum and allow air to lean out the fuel mixture.

Exhaust manifold gaskets have one of the toughest sealing jobs because of the searing heat they must withstand. Temperature changes that occur as the engine warms up and when it is under load causes a lot of thermal expansion in the exhaust manifold. This, in turn, creates a lot of movement between the manifold and head. The exhaust manifold gasket must be able to handle this without tearing apart or blowing through. Many exhaust manifold gaskets are made of graphite or Multi-Layer Steel (MLS) because these high-temperature materials can withstand both the heat and the motion.

Head gaskets seal the cylinder head to the block. The gasket seals combustion pressure, coolant and oil. Head gaskets may have a composition construction with a solid or perforated steel core faced with a soft nonasbestos material or graphite. The soft facing material provides compressibility needed to seal the head to the block, while the steel core provides rigidity and strength. The elasticity of the facing, its overall thickness and the design of the gasket itself all play a role in a gasket's ability to retain torque.

Many such gaskets also have a Teflon, synthetic rubber or silicone surface coating that aids cold sealability. "Slick" coatings are typically used in bimetal engine applications where an aluminum head is mated to a cast iron block. Aluminum expands at a faster rate than iron when it gets hot, so the head gasket must allow some movement without tearing itself apart.

Many late-model engines have Multi-Layer Steel (MLS) head gaskets. These gaskets typically have three to five layers of steel with a thin surface coating of synthetic rubber to provide cold sealability. MLS gaskets are extremely tough - but also require a very smooth surface finish to seal properly. Some aftermarket MLS gaskets now have a thicker surface coating so they will seal properly on a less-than-perfect finish.

Engines with MLS head gaskets use special torque-to-yield (TTY) head bolts that should not be reused. TTY bolts stretch when tightened to provide more uniform clamping pressure on the head gasket. If reused, they may break.

Head gaskets also cannot be reused and must always be replaced once they have been installed. Coated gaskets are ready to install as-is and do not require any additional sealers or chemicals. In fact, no sealer should be used as it may damage the factory-applied coating.




Spark plugs are the business end of the ignition system, but not all are the same.

The electrodes at the tip of the spark plug are located inside the combustion chamber of each cylinder. When the ignition system sends a jolt of high-voltage current to the plug, a spark jumps across the gap. This ignites the air/fuel mixture to produce power and keep the engine running.

The spark plugs are working hard all the time the engine is running. From the first moment the engine is cranked until it is turned off, the plugs are firing away like crazy. On most applications, each spark plug fires once every other revolution of the crankshaft. At idle, each spark plug in a four-cylinder engine will fire five times a second. At 60 mph, those same spark plugs will be zapping away at a rate of 25 to 30 times a second.

The plugs have to keep this up mile after mile and year after year. But all spark plugs eventually wear out - even long-life plugs.

Electrode wear is just one of the factors that determines the service life of a spark plug. Every time the plug fires, a tiny bit of metal erodes away from the electrodes. Over time, this widens the gap between the electrodes and increases the voltage the ignition system must produce to create a spark. If the electrode gap gets too wide, the plug may misfire causing a loss of performance and fuel economy and a big increase in emissions.

Under normal driving conditions, a set of standard spark plugs will usually go 35,000 to 45,000 miles. Refer to the vehicle owners manual for the recommended replacement interval.

Long-life plugs, which have center electrodes made of wear-resistant metals such as platinum or iridium, can typically go up to 100,000 miles before replacement is recommended. Plugs with platinum on both the center and ground electrodes ("double" platinum plugs) or those with multiple ground electrodes experience even less wear than plugs with a single platinum or platinum-tipped electrode.

One thing all types of spark plugs must do is resist fouling. The trick here is to keep the electrodes hot enough to burn off fouling deposits but not so hot that they cause preignition. To burn off carbon deposits, the center electrode needs to reach about 700 degrees F quickly. But if it gets too hot (above 1,500 degrees F), it may ignite the fuel before the spark occurs, causing preignition and detonation. For most plugs, the ideal operating temperature is around 1,200 degrees F.

The temperature of the electrodes is controlled by the length of the ceramic insulator that surrounds the center electrode and the design of the electrode itself. Ceramics do not conduct heat very well, so an insulator with a relatively long nose will conduct heat away from the electrode more slowly than one with a relatively short nose. The longer the path between the electrode and the surrounding plug shell, the slower the rate of cooling and the hotter the plug.

A spark plug's heat range, or heat rating, depends on the length of the ceramic insulator and the design of the center electrode. The heat range must be carefully matched to the engine application, otherwise the plugs may experience fouling problems at idle or run too hot under load causing preignition and detonation. Most plugs today have a relatively broad heat range thanks to the copper core center electrode described earlier. This allows the plugs to reach a self-cleaning temperature quickly and also prevents them from overheating.

If one or more spark plugs are fouled and misfiring, the engine needs a new set of spark plugs. New plugs will restore reliable ignition performance, make starting easier and improve fuel economy and emissions. But if the engine is burning oil because of worn valve guides/seals and/or rings/cylinders, fouling may continue to be a problem. Frequent short-trip driving where the engine never runs long enough to keep the plugs clean can also cause plug fouling. The cure here is easier: just make an occasional trip at highway speeds to burn the plugs clean.

Sales Tip: Replacement plugs must have the same threads (metric or SAE), same diameter and seat configuration as the original. The "reach" or distance the electrodes protrude into the combustion chamber must also be compatible with the engine to prevent physical damage to the plugs or pistons. The configuration of the electrodes or electrode materials can be different - and will probably be different than the original plugs if another brand or style of spark plugs are used.

Long-life plugs don't cost much more than standard plugs, and they extend plug life. They should be recommended for any engine that has hard-to-reach plugs (which is most transverse mounted V6 engines in FWD cars and minivans, as well as V6 and V8 engines in tightly-packed engine compartments.)

The spark plug wires (ignition cables) should also be carefully inspected when the spark plugs are changed - and replaced if the insulation is damaged, if resistance exceeds factory specifications or the boots are loose. The spark plugs need good ignition wires to deliver a hot reliable spark. The wires can deteriorate over time, and in many high-mileage engines the wires must be replaced to restore ignition performance.




Rotating electrical parts are electrical components that spin. The two main items in this category are starters and alternators.

As vehicle electronics become more demanding, the parts integral to running those systems become more critical too.

In fact, today's typical alternator puts out nearly twice the amperage that was commonly required only a decade ago. The popularity of high-powered aftermarket sound systems, for example, has also created a booming market for high-output alternators. Several aftermarket suppliers now offer special replacement alternators for these extreme audio applications. Some units are rated up to 200 amps - nearly double that of the typical stock alternator. These high-output alternators are bolstered by a greater number if windings and by the reduction of the air gap between the stator and rotor.

Even in "normal" applications, the combination of higher engine temperatures and higher loads often proves lethal to the alternator, which also happen to have a higher than average return rate. But in the end, the tough life of an alternator means good news for alternator sales.


In very basic terms, the alternator is the rotating electrical component in a vehicle's charging system. The alternator is belt driven by the engine. It generates current to maintain the battery at full charge and to provide all or most of the amperage needed by the ignition system, fuel injectors, fuel pump, lights and electrical accessories.

Alternators produce alternating current (AC), which is converted to direct current (DC) by a diode trio (rectifier) on the back of the unit. The alternator's output increases in proportion to the electrical loads placed on the charging system. Charging output is controlled by a regulator, which may be mounted inside or on the back of the alternator (internally regulated), or somewhere else under the hood (externally regulated.) On many newer vehicles, the powertrain control module (PCM) controls the alternator's output. On General Motors vehicles with Delco "CS" series alternators, for example, the PCM varies the alternator's output by cycling the digital voltage regulator on and off (a process called "pulse width modulation.") This allows the PCM to modify the charging rate at idle or when the engine is accelerating hard to reduce the load on the engine.

Alternators have different amperage ratings, so an alternator should be replaced if its charging output is less than specifications. Replacement is a must if the alternator has quit altogether.


Alternator failures are most often caused by overloading and overheating. Either condition can damage the rotor, stator or electronics inside the unit.

The underlying cause of such failures may be short-trip driving with heavy electrical loads (the lights, heater, defroster or A/C on) and not driving far enough to keep the battery fully charged. This taxes the alternator to the limit every time the vehicle is driven and eventually causes it to fail. Idling for long period of times with high electrical loads can also fry an alternator. This is why work vehicles such as police cruisers tend to kill alternators. The emergency lights alone can require as much as 85 amps from the alternator. For these applications, recommend an alternator specifically designed for police or emergency vehicles.

Symptoms of a bad alternator include a run down or dead battery, a charging or alternator warning lamp, or dim headlights. On 1996 and newer OBD II vehicles, low charging output may set a fault code (P0560, P0561 or P0562) and turn on the Malfunction Indicator Lamp (MIL.)


Alternators can be bench tested to simulate electrical loads and to determine if they are working properly or not. Testing is recommended to confirm the need for replacement and to reduce warranty returns.

A replacement alternator (new or reman) should have the same or higher amp rating as the original. If the replacement comes with a pulley (some do not), make sure it matches the original (same diameter, width and belt type.) Exchange units must be the correct one for the application and complete to receive full core credit.

Related items that may also need to be replaced include the regulator (externally regulated applications only), drive belt, battery cables and/or battery.



Starter motors are generally much longer-lived than alternators these days because they are only used to start the engine. Thanks to fuel injection, it doesn't take much cranking to start most engines so starter failures are less common.

There are several different types of starters:


  • Direct-drive starter motors
  • Gear-reduction starter motors
  • Permanent magnet starter motors. These motors are smaller and have permanent magnets inside instead of wire coils.

When the engine is cranked, the starter drive engages the flywheel. When the engine starts and the driver releases the ignition key, the starter drive should retract. A one-way overrunning clutch is used to protect most starters against damage should the starter remain engaged after the engine starts.

The most common cause of starter failure is prolonged cranking. If an engine is hard to start, the starter should not be cranked for more than 30 seconds at a time. It should then be allowed to cool down for a minute or two before the engine is cranked again.

Starters also wear out as the miles add up. Brushes and bushings take a beating as does the starter drive, solenoid, armature and field coils. Starter drives (which can be replaced separately on many starters) can also fail, preventing the motor from engaging the flywheel. A bad solenoid or relay will prevent the starter motor from cranking at all.

Accurate diagnosis of a starter problem is important to make sure a starting problem is due to the starter and not something else. Like alternators, starters should be bench tested to confirm the need for replacement and to reduce warranty returns. Related items that may be causing a cranking problem and may have to be replaced include the ignition switch, park/neutral safety switch, starter relay, battery, battery cables and ground strap.

A replacement starter (new or reman) should have the same bolt pattern and electrical connections as the original, and the same number of teeth on the drive gear. Exchange units must be the correct one for the application and complete to receive full core credit. Permanent magnet starters must be handled with care because the magnets are brittle and can be easily cracked.




The importance of being able to see the road ahead clearly when driving in wet weather is the reason windshield wipers were invented in the first place.

In 1916, a motorist struck a man on a bike during a rain storm because water on his windshield blurred his view. Soon thereafter the first hand-operated windshield wipers appeared, followed by one innovation after another as time went on: automatic vacuum-powered wipers, multi-ply wiper blades, dual wiper blades, windshield washers, winter blades, electric wipers, variable speed and intermittent wipers, airfoils on blades to resist wind lift and so on.

The proliferation of wiper systems with different arm styles and blade designs has created a lot of confusion when it comes to replacing wiper blades today. Not only does a customer have to match the length of the blade, but also the mounting system. And if he only wants a refill, it's even more confusing because of the different blade widths, blade designs and blade holder assemblies. Many OEM and even some aftermarket blades won't even accept a refill.

Many aftermarket replacement blades come with a mounting adapter that allows the blade to be installed on almost any mounting configuration. This reduces the number of SKUs that have to be stocked to provide good coverage, and makes it much easier for customers to find a blade that will fit their vehicle.

There are also "exact fit" replacement blades that are designed for a particular mounting system. These blades typically look and fit exactly the same as the original equipment blades. This eliminates the need for adapters and simplifies installation but requires more SKUs in the product line than universal blades to provide the same vehicle coverage.

Premium blades cost only a couple of bucks more than standard blades and are a good upgrade for improving wet weather visibility. Premium blades typically have more suspension points built into the blade holder to reduce skipping and streaking, and the holder may have slots or airfoils to improve the blade's aerodynamics. This prevents wind lift at highway speeds. The blade itself is usually made of higher grade materials which may include special synthetic rubbers, silicone or teflon. Some have a natural rubber wiping edge backed by other synthetic materials to improve cold weather flexibility and blade durability.

For cold weather driving, standard wipers can be replaced with special "winter" blades. Ordinary wiper blades can become packed with ice and snow, causing them to streak and wipe poorly. But winter blades don't have that problem because they have a rubber boot to keep ice and snow out of the blade holder. This prevents the blade from freezing up. The result is consistent wiper performance regardless of weather conditions for safer winter driving.

For optimum visibility and driving safety, wiper blades should be replaced at the first sign of trouble. Streaking, chattering and noisy operation are all clues that the wipers are nearing the end of their useful service life.

Motorists shouldn't wait until they can barely see where they're going to think about changing the blades - but unfortunately that's what many people do. Wiper blades don't last forever because dirt, road splash and bug splatter wear away the wiping edge of the blades during normal use. Sunlight and ozone also age the rubber, causing it to harden and lose its natural elasticity. This reduces their ability to wipe cleanly and quietly and eventually causes the rubber to split and crack. Old blades can also develop a permanent set (called "parked" rubber) or curvature, which prevents full contact with the windshield.

For all of these reasons, wiper blades should be replaced at least once a year to maintain good wiping performance, visibility and driving safety.

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