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11th Annual Tech Forum


8/1/2003
By Larry Carley

 

Your customers are one of the most important aspects of your business. And when they need your help, you need to be ready with the knowledge and the answers that will help them. This month, Counterman presents some of the most pressing issues surrounding the following topics and what customers are asking.

Q: My customer is buying a replacement compressor for an older vehicle with an R12 A/C system. Should he also retrofit it to R134a when he installs the new compressor?

A: Now would be the best time to do a retrofit. If your customer is a do-it-yourselfer, you cant sell him R12 refrigerant unless he has taken and passed a certification course. That means he can only buy R134a or an alternative refrigerant.

Most remanufactured compressors for older vehicles are now engineered to be compatible with either refrigerant. But some original equipment compressors on older vehicles are not compatible with R134a. Compressors with Viton seals include Tecumseh HR980, some Keihin compressors and some Panasonic rotary valve-style compressors (Nissan). These compressors must be replaced if an older vehicle is converted to R134a.

Compressor durability is also a concern with some applications. Because R134a raises compressor discharge pressures and increases the compressors work load, some lightweight compressors may not be rugged enough to tolerate R134a over the long haul. This applies to the Harrison DA6 and Ford FX-15 compressors. The Harrison DA6 can be replaced with a HD-6, HR-6 or HR-6HE compressor. The Ford FX-15 compressor can be replaced with a FS-10 compressor.

Theres really no reason to retrofit a vehicle to R134a as long as the R12 system is cooling properly and contains a normal charge of refrigerant. A/C systems designed to use R12 will cool best when charged with R12 refrigerant. Even if the system leaks, repairing the leaks and recharging it with R12 is usually the least expensive repair alternative.

Retrofit makes the most economic sense when the A/C system needs major repairs such as a new compressor, condenser or evaporator.

Q: What parts are needed to do an R134a retrofit?

A: Most vehicles will require two to three cans of R134a refrigerant, a can of R134a compatible compressor lubricant (POE or PAG oil), a new accumulator or receiver/drier with X-7 desiccant, and the required adapter fittings for the high and low service ports. The A/C system must also be labeled following the retrofit to warn others that it now contains R134a instead of R12.

Converting to R134a typically reduces cooling performance somewhat, and may require some additional modifications to improve cooling performance. This may include installing a larger or more efficient cooling fan for the condenser, installing a larger or more efficient condenser to improve heat transfer and replacing the original fixed orifice tube with a variable orifice tube to improve low-speed cooling performance.

After the changes have been made, the A/C system should be recharged to about 85 to 90 percent of its original capacity with R134a. This will usually give the best cooling performance.

Q: What kind of compressor oil is required for a retrofit?

A: It depends on the application and situation. If the original compressor is not being replaced, the most common procedure is to drain out as much of the old mineral oil as possible and replace it with an equal amount of POE oil. POE oil is the universal choice for this type of retrofit because it is compatible with residual mineral oil in the system and R134a refrigerant.

If the compressor is being replaced with a new or remanufactured unit, follow the lubricant recommendations of the compressor supplier. Some may specify POE oil, while others may specify a particular grade of PAG oil.

Almost all newer vehicles that have factory R134a systems require a specific type of PAG oil. The viscosity of the PAG oil will vary (46, 100 or 150) depending on the type of compressor used.

Q: Should I tell my customer he should also replace his condenser if his compressor has failed?

A: It depends on the application. The condenser is an expensive item to replace, but it may be necessary to prevent a repeat compressor failure.

When a compressor fails, it often throws a lot of debris into the A/C system. The outlet hose from the compressor connects to the condenser, so the condenser becomes a garbage dump for anything the compressor spews out. The condenser also tends to collect sludge that may be in the system, too. If these contaminants are not removed, they can circulate in the A/C system when it is recharged with refrigerant and plug the orifice tube and/or ruin the new compressor.

On some vehicles, the condenser can be flushed instead of replaced. Flushing with a cleaning chemical that has been approved for this purpose may remove most of the debris. But flushing may not remove all of the debris. Flushing does not work very well on parallel flow condensers because the liquid follows the path of least resistance. It may rinse out most of the tubes but leave others plugged with debris (which may dislodge later and ruin the new compressor.)

Flushing may also not work well in condensers with extremely small passages (the type with extruded aluminum flat tubes). Where it does work is on serpentine condensers with large tubes. But even on these it may miss some debris. Whats more, the hoses and other parts must also be flushed to clean the entire A/C system.

If a customer does decide to flush rather than replace, he should install an inline filter in the condenser outlet line for added protection. The filter should trap any debris missed by the flush. Also, installing a protective screen in the compressor inlet hose can protect the compressor from any debris that may be lurking in the suction hose or evaporator.


BRAKES

Q: When doing a brake job, which items must be replaced, and which items should be replaced?

A. The "must" items include anything that is worn out, broken or defective. The "should" items include anything that may be nearing the end of its service life or may affect braking reliability, noise or performance.

The basic purpose of any brake job is to restore safe braking. Ideally, that means restoring the entire brake system to "like-new" condition - but that doesnt always happen.

Professional technicians often base their replacement recommendations on experience and "industry-accepted practices." A more formal set of inspection and replacement guidelines is available from the Motorist Assurance Program (MAP) at www.motorist.org.

The MAP "Uniform Inspection and Communication Standards" cover the brakes as well as every other system on a vehicle. These standards define how certain parts should be inspected and what conditions require replacing the part.

As a rule, parts must be replaced if they are worn beyond minimum service specifications (based on OEM specifications), are inoperative, broken, defective or severely corroded. Parts that typically fall into this category include brake pads and shoes that are worn thin, cracked or contaminated with brake fluid or grease, brake rotors that are worn to minimum thickness, cracked, warped, full of hard spots or severely rusted, drums that are worn to maximum diameter, bell mouthed, cracked or severely rusted, calipers and wheel cylinders that are leaking or sticking, springs and other hardware that are weak, broken or severely rusted, brake backing plates that are badly worn or rusted, brake hoses that are cracked or leaking, and master cylinders that are leaking internally or externally.

Replacing worn out and broken parts is always a "must." But nothing is ever cut and dry in the automotive repair business. Some parts may be in a borderline condition, still good but obviously on their way out. Replacing these parts may not be absolutely necessary just yet, but sooner or later they will have to be replaced.

Labor is often the most expensive part of a brake job, so often it makes sense to go ahead and replace borderline parts that may still be "good" according to the MAP definitions. This includes parts that may still be within acceptable service limits but are reaching the end of the road. Replacing these parts now for "preventive maintenance" increases the parts bill but reduces the risk of a comeback and usually eliminates the need for additional brake work later on - which can save the vehicle owner considerable repair dollars in the long run.

One item that should always be replaced when the brakes are relined is the brake fluid. Old brake fluid is usually contaminated with moisture that promotes rust and corrosion in the calipers, wheel cylinders and brake lines. Moisture also lowers the boiling temperature of the fluid, which may increase the risk of fluid boil and pedal fade under hard use. So always remember to recommend a can of fresh brake fluid to every customer who is buying brake parts.

High-mileage calipers and wheel cylinders are additional items that should often be included on the "should replace" list even if the old parts are not yet leaking or sticking. Why? Because calipers and wheel cylinders eventually succumb to internal corrosion. You cant see it from the outside, but inside the pistons and bores are usually rust, pitting and even sludge. As the piston bore becomes rough, it wears the seal and may cause leaks or piston sticking. Calipers with phenolic pistons are not immune to corrosion either because the caliper housing is usually cast iron.

Noise is another valid reason for replacing some brake parts. If the original equipment brake pads on a particular vehicle are noisy, the pads may need to be replaced to eliminate the noise.

Performance upgrades may also require replacing perfectly good stock brake parts with aftermarket performance parts. Common upgrades include installing premium high-temperature pads and/or drilled and vented rotors. Drilled rotors are especially popular as much for appearance as for performance. Drilled rotors provide better cooling but they also look great behind a set of custom alloy wheels.

Some states such as California have strict rules about replacing brake parts. If parts are not worn to minimum service specifications, are not broken or defective, the rules say replacement is unnecessary and may even be illegal (for a professional technician) - unless the vehicle owner is upgrading his brake system or wants the parts replaced. The purpose of such laws is to protect motorists from being ripped off. But such laws also hinder the ability of professional technicians to make valid judgment calls.

Q: Are all replacement rotors the same?

A: Absolutely not. Though different brands of rotors may all look the same, there can be significant differences in metallurgy and finish that affect friction, braking effectiveness, stopping distance, pad life and noise.

Quality replacement rotors are manufactured to meet certain OEM specifications. The metallurgical properties of a rotor determine its strength, noise, wear and braking characteristics. The casting process must be carefully controlled to produce a high-quality rotor. You cant just dump molten iron into a mold and hope for the best. The rate at which the iron cools in the mold must be closely monitored to achieve the correct tensile strength, hardness and microstructure.

When iron cools, the carbon atoms that are mixed in with it form small flakes of graphite, which help dampen and quiet noise. If the iron cools too quickly, the particles of graphite dont have as much time to form and are much smaller in size, which makes for a noisy rotor.

The rate of cooling also affects the hardness of a rotor. If a rotor is too hard, it will increase pad wear and noise. Hard rotors are also more likely to crack from thermal stress. If a rotor is too soft, it will wear too quickly and may wear unevenly, increasing the risk of pedal pulsation and run-out problems.

The composition of the iron must also be closely controlled during the casting process to keep out impurities that may form "inclusions" and hard spots. One rotor manufacturer says they sample the molten iron every 15 seconds to make sure the composition is correct. The molten metal is also poured through ceramic filters that trap contaminants. Even the sand thats used to make the molds is specially treated to control moisture content. This helps keep the sand in place and prevents core shifts that can affect porosity, dimensional accuracy and balance.

The grade of cast iron thats used in a rotor may even be changed to suit a particular application. One aftermarket rotor manufacturer uses a special grade of "dampened iron" to make replacement rotors for 1997-2002 Chevrolet Malibu and its sister vehicles (Olds Alero, Olds Cutlass and Pontiac Grand Am). In this case, the original OEM rotors turned out to be too noisy, so General Motors switched to a dampened grade of iron to cure the problem.

Another difference thats hard to see is the design of the cooling ribs between the rotor faces. Vehicle manufacturers use a wide variety of different cooling rib configurations in their rotors. They do this to optimize cooling for different vehicle applications. There are currently about 70 different rib configurations in OEM rotors. Some ribs are straight, some are curved and some are even segmented. Some rotors are directional, and some are not. Some rotors have evenly spaced ribs, while others do not. Some ribs radiate outward from the center, and others go every which way.

Some aftermarket rotor manufacturers use the same rib design and configuration as the OEM rotors, while others do not. Some change the rib design to simplify the casting process or to reduce the number of different rotor SKUs in their product lines. But changing the rib design changes the airflow, cooling and noise characteristics of the rotor - which may make things better or worse depending on the application. Thats why some aftermarket rotor manufacturers say the best approach is to use the same basic configuration as the original equipment rotor.

One brake manufacturer showed us a cutaway of an offshore "economy" rotor for a particular vehicle that had 32 ribs. The OEM rotor, by comparison, had 37 ribs and provided up to 8 percent better cooling than the economy rotor when tested in the laboratory. And because the OEM rib design ran cooler, pad life was 28 percent longer than the economy rotor.

Another aftermarket brake manufacturer showed us test results that proved their rib design improves cooling and makes their rotor three times quieter than a competitive rotor. The recorded sound levels showed noise as high as 85 decibels screaming out of the Brand X economy rotor compared to only 40 to 50 decibels from their own "premium" quality rotor.

Q: What are the advantages of "loaded calipers?"

A: Convenience, reliability and ease of installation - these are the main selling points of loaded caliper assemblies. A loaded caliper comes with everything needed to replace a caliper: a new or remanufactured caliper housing, new or reconditioned pistons, new friction pads, plus the shims and related mounting hardware that are needed to install the caliper on the vehicle. All the technician has to do is remove the old caliper and pads, resurface or replace the rotor, bolt on the loaded caliper assembly and bleed the brakes. Its the closest thing you can sell to a brake job in a box.

The demand for loaded calipers continues to grow because they save technicians time and effort. If the calipers on a high-mileage vehicle need attention, its hard to tell what condition they are in internally until the pistons are removed. If the original pistons are steel, they are usually badly corroded and need to be replaced. Whats more, the caliper bores will probably be rough and pitted. This requires careful honing to restore the bore surface so it wont damage the piston seal and hold pressure. Even then, the caliper may leak when reassembled.

Calipers may also be worn or damaged. Wear on the mounting surfaces is common and can allow unwanted vibrations and noise. Cracks represent a potential safety hazard and always require the caliper to be replaced.

Replacing a worn or leaky caliper with a new or remanufactured one eliminates most of the risks associated with rebuilding calipers. And since the pads usually have to be replaced as well, it makes sense to get everything in one box.

Preassembled calipers also help eliminate some of the common mistakes that are often made when replacing calipers, things like leaving off anti-rattle clips and pad insulators that prevent noise, forgetting to bend pad locating tabs that prevent pad vibration and noise, and reusing corroded caliper hardware that can cause a floating caliper to hang up and wear the pads unevenly.

Most aftermarket brake suppliers have loaded calipers in their product lines. Coverage is typically limited to the more popular vehicle applications. Even so, more and more applications are being added every year for a wide range of cars and light trucks.

Q: Are all loaded calipers more or less the same regardless of who supplies them?

A: The calipers themselves will either be new castings or reconditioned OEM castings for the vehicle they fit. So in that respect there may not appear to be much difference from one brand to another. But some suppliers pay more attention to detail than others, and the suppliers may go to greater lengths in the recondition process to assure a top-quality product. Cosmetic differences may also be apparent and are always an important selling factor with the end user.

Another difference youll find in loaded caliper assemblies is the type of friction linings included by the supplier. Some suppliers increase their product coverage and/or minimize the number of different part numbers by offering loaded assemblies with "generic" semi-metallic or NAO linings. Other suppliers are more selective and use "application-specific" friction materials that are more closely matched to the OEM friction material for a given vehicle application. The advantage with this approach is that it more closely matches OEM brake performance and stopping power, which reduces the risk of a dissatisfied customer and a comeback. But it also increases the number of SKUs needed in their product line.

As a rule, loaded calipers should be sold and installed in pairs. This will eliminate any mismatch of friction materials side to side that might otherwise cause a brake pull.

Q: Are all "ceramic" disc brake pads the same?

A: Are all pizzas the same? Of course theyre not, and the same goes for disc brake pads that contain ceramic-based friction materials.

Each brake supplier has their own definition of what "ceramic" means. Ceramic has become a hot buzzword for marketing brake pads. How much ceramic content is actually in the pads and what type of ceramic materials are used can vary greatly from one brand of pads to another.

Linings containing ceramic fibers were first introduced back in 1985 on some OEM applications, and are now found on nearly a third of all new vehicles including many Japanese models that are made in the U.S. In recent years, ceramic pads have also been introduced into the aftermarket by brake suppliers.

As a rule, ceramic pads contain no steel wool or fibers. Instead, ceramic and copper fibers are used to handle the heat. Annoying brake squeal is virtually nonexistent because the ceramic content helps dampen noise and moves vibrations to a frequency beyond our range of hearing. Whats more, the dust produced by some ceramic pads is a lighter color and is less visible on alloy wheels.

Friction materials contain many different ingredients including various types of reinforcing fibers for strength (ceramic, fiberglass, aramid and other mineral fibers), metallic strands (steel, brass, titanium, copper, etc.) for dissipating heat, fillers and other substances for modifying the friction characteristics of the material, and binders and phenolic resins to hold it all together.

Most semi-metallic friction materials contain at least 60 percent steel by weight. Low-metallic materials are ones with less than 30 percent ferrous content. Nonasbestos organic (NAO) materials contains little or no iron or steel, and usually have several times as many ingredients as semi-metallic compounds. As a result, NAO compounds are more complex to develop and manufacture.

As for ceramic-based friction materials, ceramic is only one of up to 20 or more ingredients in the formula. The type of ceramic used and the percentage content will vary from one brand to another depending what the manufacturer is trying to achieve. Most aim for the best combination of low noise, good braking performance, good fade resistance and long life. Most ceramics do an excellent job of meeting all of these criteria.

Q: With so many different brands and types of brake pads available today, how do I select the "right" replacement linings for a given vehicle application?

A: The "right" set of brake pads are those that provide safe braking, low noise, long life and good value for the money.

According to a recent Babcox survey, over 90 percent of brake technicians say they prefer to install "application specific" brake linings.

"Application-specific" is a marketing term that means a set of replacement linings are engineered to closely match the friction requirements of different vehicle types and platforms. It may be an "off-the-shelf" compound, a modified compound or a brand new compound that provides the best combination of noise, braking performance and wear for a particular car or truck. In many instances, application-specific aftermarket brake linings are very similar to, if not identical to, OEM brake linings.

One aftermarket brake supplier said they now use about 40 different friction compounds in their various product lines to achieve application-specific coverage. Another supplier said they currently have 25 different compounds in their line, and will be adding more as needed to keep pace with new models and changes at the OE level.

The braking requirements of a Lincoln Navigator are obviously different than those of a Kia Rio. Vehicle size, weight, brake type (disc or drum), the design of the calipers and rotors, front-to-rear brake balance and how the vehicle is driven are all factors that influence the selection and development of a particular friction compound. Consequently, a friction formula that works well on one application might not be the best choice for another. So aftermarket brake suppliers use a variety of different friction compounds to cover the diverse mix of vehicles that are on the road today. There are probably several hundred different compounds being produced by friction suppliers worldwide.

The "right" replacement linings, therefore, are any brand or type of lining that makes your customers happy.

Q: Whats the difference between "premium" pads and "standard" pads?

A: The price and performance of pads differ. In recent years, aftermarket brake suppliers have introduced new lines of premium pads and even "ultra-premium" brake linings. Most of these pads are "application specific" and may include a mixture of ceramic, semi-metallic and/or NAO formulas in the product line. The only thing they all share in common is the best all-round braking performance the supplier can provide - and a higher profit margin for jobbers and installers.

Compared to standard pads, premium pads generally provide better stopping power, increased fade resistance, longer life and quieter operation. Most premium grade pads incorporate such features as chamfers and slots. Some have built-in shims to control noise and vibrations. Some premium pads are also "preburnished" to eliminate many of the problems that can occur if the pads are not broken in properly.

When brake linings are manufactured, the resins that bind the ingredients together are not fully cured. When the linings are later installed on a vehicle, the heat produced by normal braking bakes the linings and cooks out the residual chemicals from the resins to improve the friction characteristics of the lining. But if the brakes get too hot before the linings are fully cured, it can "glaze" the linings causing noise and performance problems. So to eliminate the need for a break-in period, some brake suppliers fully heat-cure (burnish) the linings.


CHASSIS

Q: What kind of replacement shocks are best for Sport Utility Vehicles (SUVs)?

 

A. It depends on the how the SUV is driven. Different types of driving require different types of shock valving and construction.

For a smooth ride, a low-pressure gas shock with relatively soft valving works well. For extra control when towing or driving on rough terrain, a stiffer shock or a high-pressure monotube shock would be better. If the suspension has been raised to increase ground clearance for off-roading, shocks with longer travel are required to keep the dampers from bottoming out.

One type of shock that works well in a wide variety of situations is an adjustable shock. Manually adjustable shocks typically offer a range of settings from soft to extra firm. Electronic adjustable shocks are also available for adjustments on the go. Adjustable shocks are available in gas-charged twin-tube and monotube designs for most SUVs including many of the new "mini-SUVs" such as Honda CRV, Toyota RAV4, Kia Sportage and others.

Q: Do shock absorbers affect driving safety?

A. Absolutely. They are part of the "safety triangle" which includes stability, steering and braking.

Stability is of particular concern to SUV owners because of the high center of gravity on many of these vehicles. Stability can be lost in an instant if the shocks are weak and something happens that causes a sudden shift in weight or direction (a tire blow out at 75 mph, swerving to avoid an obstacle in the road, etc.).

For a vehicle to maintain steering control and stability in emergency situations, the shocks must be in good condition. Safe driving also requires tires that are in good condition, properly matched to the application (load rating, temperature, traction, etc.) and properly inflated for load and speed conditions. It also requires a steering system and linkage that is not worn, wheels that are properly aligned and brakes that can stop the same as when the vehicle was new.

A problem in any one of these areas can undermine the safety triangle and increase the risk of losing control in certain driving situations. Thats why the shocks, steering, tires and brakes should all be inspected regularly. And if repairs are needed, they should be done ASAP to restore the safety triangles foundation to a firm footing.

Q: How long do OEM-sealed wheel bearings typically last?

A. The design life is 150,000 miles, but many end up having to be replaced at 85,000 to 100,000 miles.

According to a recent Babcox Research survey, 51 percent of bad wheel bearings are found because the vehicle owner noticed an unusual noise coming from the wheel, 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 wheel is squeaking, chirping, squealing or moaning, the bearing should be inspected without delay. Other symptoms include steering wander or sometimes a pull to one side when braking.

Wheel bearings can be checked by grasping the tire at the 12 and 6 oclock positions and rocking the tire. If you feel any play, the bearings are loose and need to be replaced. The tire should also be rotated by hand to check for roughness or noise.

If one wheel bearing has failed, the bearings on the other wheels should be checked because all of the wheels have the same mileage.

On vehicles equipped with antilock brakes and hub assemblies with an integral ABS sensor or tone ring, the ABS warning light will come on if a wheel speed sensor is reading erratically or the signal is lost. The ABS system will set a fault code that corresponds to the sensor location (left front, right front, right rear or left rear) and disable the ABS system until the fault is fixed. On these vehicles, the only way to get the ABS light to go out is to replace the hub assembly (assuming the problem isnt a simple wiring fault or loose connector).

There is no way to disassemble and repair a sealed hub assembly. If the internal ABS sensor has failed or if the external ABS tone ring on the hub is damaged or badly corroded, the whole unit must be replaced.

Q: What causes CV joints to fail?

A. Like U-joints, CV joints eventually wear out from the accumulated effects of normal wear. Normally this doesnt occur until the joint has 80,000 to 130,000 miles on it. But CV joints can be ruined at any point in their life if the protective boot around the joint fails and allows the grease inside to leak out or be contaminated by road splash and dirt.

The rubber or hard plastic boot around a CV joint serves two purposes: it keeps grease in and contaminants out. If the boot cracks, tears or is punctured, the seal is broken and anything can happen. By the time the bad boot is discovered, its often too late to save the joint by replacing the boot.

Most CV joints give ample warning when they are failing, so by the time theyre making noise, they almost always need to be replaced. The classic symptom of a worn outer CV joint is a popping or clicking noise when turning. A worn inner CV joint on a FWD car will typically make a "clunk" when putting the transaxle into Drive, and it may create a vibration when accelerating or decelerating.

Replacement options include a new or remanufactured CV joint, or a complete halfshaft assembly. Many technicians prefer to install a complete halfshaft because its faster and easier.

Make sure the replacement CV joint or shaft has the same number of splines as the original, and that the overall length of the shaft is the same. Also, if the vehicle is equipped with ABS and has a wheel speed sensor ring on the CV housing, make sure the replacement joint or shaft has the same ring (the ring is often press fit on the joint housing).

Q: When should steering components be replaced?

A. When they are worn or damaged. Most steering parts are replaced when a vehicle goes in for an alignment and worn parts are discovered during the prealignment inspection, or when a tire wear problem or looseness in the steering prompts someone to inspect the steering gear and linkage.

The parts most likely to need replacing are the tie rod ends, idler arms (on rear-wheel drive vehicles with parallelogram steering), center links and sometimes even the steering gear itself (usually power rack and pinion steering).

Any looseness or play in a tie rod end is grounds for replacement because a tie rod failure may cause loss of steering control. The condition of the protective rubber boot on the tie rod end is also important. If the boot is split, leaking grease or missing, the tie rod is doomed and will succumb - if it isnt wobbling already.

When looking up replacement tie rod ends, you should know that left and right tie rods are threaded differently. Also, the inner and outer tie rods on vehicles that dont have rack and pinion steering are different. So if only one tie rod end is being replaced, make sure you get the correct one.

Most professionals recommend replacing all the tie rods at the same time even if only one or two are bad because all have the same mileage, so the others will probably fail soon as well.

Other items that may also have to be replaced include the tie rods and tie rod adjustment sleeves. Replacing these items can make toe adjustments a lot easier, especially if the old parts are badly rusted or frozen.

The inner tie rod sockets on a rack and pinion steering system usually holdup better than the outer tie rod ends because theyre protected from the elements by the rubber bellows on the ends of the rack. But over time, they can also wear and loosen up. Though the inner tie rod sockets can be replaced separately just like the tie rod ends, many professional will replace the whole rack if the sockets are loose and the rack has a lot of miles on it.

Steering racks can develop leaks and center wear as the miles add up. If the inner tie rod sockets are also worn (or even if they are not), replacing the rack with a new or remanufactured unit will be necessary to eliminate these problems.

Another item that can be replaced separately on a steering rack is the bellows that surrounds the inner joint. Made of rubber or hard plastic, the bellows may split or crack with age allowing contaminants to enter the joint.

Most replacement racks come with new mounts. But if mounts are not included, be sure to recommend new ones. The mounts help secure the rack in the chassis and prevent unwanted motions that could make the steering feel loose or harsh.

Other items to suggest if someone is replacing a rack are new power steering hoses and power steering fluid. Leaky hoses can be a real annoyance and may even cause the power steering pump to fail if the system loses all of its fluid. As for fluid, it should always be changed if the rack is being replaced. Make sure the fluid meets OEM requirements. Some OEMS specify a special type of power steering fluid that contains unique additives for the pump and seals.

Another steering part which is frequently replaced is the idler arm on rear-wheel drive vehicles without rack and pinion steering. The idler arm is a pivot point that helps maintain proper toe alignment as the wheels are steered. A center link connects the idler arm to the pitman arm on the steering box, and tie rods on both sides tie the linkage to the arms on the steering knuckles. A worn idler arm will usually cause toe wear on the tires, as well as contribute to looseness in the steering.

A point worth noting here is that some original equipment idler arms have a reputation for not holding up very well. For these applications, more robust aftermarket idler arms that feature special bushings and a heavier design are a good choice.

Q: What is "toe" wear?

A. Toe wear is a feathered wear pattern across both front tires. It may also appear as shoulder wear on the inner or outer edge of both tires. Toe wear is usually caused by worn tie rod ends, but may also result from worn or loose inner tie rod sockets on rack and pinion steering gears. Other causes include bent steering arms or misalignment in the rear wheels.

If toe wear is discovered, toe alignment should be checked and reset to specifications as needed. It may also be necessary to replace the tires if they show heavy wear.

If toe wear is accompanied by steering looseness or steering wander, theres a very good chance the tie rod ends are worn. The steering linkage and suspension should be inspected for loose or worn parts.

If toe wear is accompanied by a steering pull or off-center steering, rear wheel toe alignment or axle alignment may be out of specifications.

Q: How do I identify the correct ball joint for a 1996 GMC G3500 Van?

A. Looking up a ball joint for a 1996 GMC G3500 or G30 van can be confusing because GM introduced a new body style with a new suspension midyear. The early 96 vans


CHEMICALS

Q: What does "OEM Specified" (Original Equipment Manufacturer Specified) mean?

A: "OEM Specified" means a particular brand and grade of threadlocker has been specified by an original equipment manufacturer for use on a specific application. The OEM might be BMW, Caterpillar, Ford, General Motors, DaimlerChrysler, John Deere, Nissan, Toyota or any of the other major vehicle manufacturers. Or, it might be a manufacturer who makes small engines for lawn mowers, boats or toy airplanes. The term "OEM" covers a lot of territory and may be stretched to include companies that make almost any kind of product from washing machines to ping pong paddles.

The point is different OEMs have different requirements and different specifications for threadlockers. The threadlocker specified by Detroit Diesel for a critical engine component that has to go hundreds of thousands of miles may be a lot different from the threadlocker specified by a manufacturer of light-duty lawn mower engines. So just because a threadlocker supplier claims its product is "OEM Specified" doesnt mean it meets the requirements of all of the major vehicle manufacturers.

When an OEM "approves" a specific threadlocker product, they do so after extensively testing that product to make sure it holds up under normal operating conditions. The last thing anybody wants is a critical fastener working lose because the threadlocker wasnt strong enough, heat resistant enough or oil resistant enough for the job. Thats why the OEMs issue specifications for their applications, and thats why you have to help your customers select the right products for their applications.

If you remember nothing else from this article, remember this: All threadlockers are not the same. There are different products for different applications, and specific products are required to meet OEM specifications.

To select the products that meet OEM Specifications, refer to the OEM Repair Manuals or contact the OEM directly to verify what manufacturer(s) have been listed on the specification.

Q: What are Thread Treatment Chemicals?

A: These are specially formulated chemical products that include threadlocking adhesives, thread sealers and anti-seize coatings.

When a threaded fastener is used to hold something together, there is actually a lot of empty space between the threads on the fastener and the threads in the hole or nut to which it is mated. The areas that do make contact create friction, which affects the loading on the fastener and the amount of torque needed to tighten it.

Threadlockers are a chemical alternative to mechanical locking devices such as lock washers, lock nuts, set screws and cotter pins. Threadlockers work by filling the spaces between the threads. This creates a solid, secure bond that wont allow the fastener to loosen up or lose torque as a result of vibration or stress. The threadlocker chemical is usually applied directly to the threads on the fastener, or the threads in the hole or nut. It can also be used to hold studs, bearing assemblies, pulleys, sleeves and other parts in place.

The threadlocker chemical may be a liquid from a tube or bottle, or in a wax-like stick. Most are "anaerobic" adhesives that dont set as long as air is present. When the parts are assembled, the absence of air causes the chemical to cure and lock the threads in place. Most take an initial set in 10 to 30 minutes and reach full cure within 24 hours.

"Wicking" threadlocker is also available for parts that have already been assembled. This type of product wicks along the threads of pre-assembled fasteners to secure them in place.

There are different grades of threadlockers, so its important to use the right product for each type of application. Medium-strength threadlocker is for applications that may have to be disassembled later with ordinary hand tools. High-strength threadlocker is for permanent assemblies that usually do not require disassembly (removal is possible, but it requires the application of heat to loosen the adhesive).

Some threadlockers are also formulated to be highly resistant to oil. Applications for this type of product include valvetrain fasteners, bolts on timing covers, valve covers and oil pans, oil pump bolts, intake manifolds and disc brake calipers.

High-temperature threadlockers are designed for high-heat applications and can withstand operating temperatures of up to 450 degrees F. High-temperature applications include camshaft and crankshaft bolts, idler bearings, press-fit filler tubes, transmission shaft threads, ring-gear bolts and shock bolts.

Thread sealants serve a different purpose. Their job is to fill the void between threads to prevent leaks. They also make assembly easier and protect the threads from rust and corrosion, which makes disassembly easier, too. Also available in stick or liquid form, thread sealants are often required for water pump bolts, certain head bolts, intake manifold bolts and threaded pipe connections.

Anti-seize compounds are used for threaded fasteners and other assemblies that are subject to high heat and corrosion but may require removal or disassembly at some point. This includes the threads on spark plugs installed in aluminum cylinder heads, oxygen sensors, coolant sensors, knock sensors and other screw-in sensors, exhaust manifold bolts, thermostat housing bolts, head bolts and even battery cable connectors. Anti-seize compounds do not harden and also act as a lubricant to prevent galling, rust and corrosion. Graphite is typically used as an ingredient, and tiny flakes of copper may be added for increased heat resistance.


COOLING SYSTEM

Q: With so many different types of coolants in vehicles today, how do I know which color is the right one to use?

A. First of all, forget color as a means of identifying the type of coolant. Its too confusing. Vehicle manufacturers who use similar coolants may dye their coolants differently to distinguish their own brand of coolant from other brands. The color of the dye means nothing. What matters is the type of corrosion-inhibiting additives that are in the coolant.

If an aftermarket coolant meets the OEM specifications for a particular vehicle application, it should be okay to use the coolant whether the color matches or not. In other words, as long as the corrosion-inhibitors are chemically compatible, the coolants should intermix just fine without any problems.

Choosing the "right" coolant means reading the owners manual to find out what kind of coolant is specified, and reading the label on the coolant package to see if it meets the OEM specifications. On newer vehicles, the radiator cap or coolant reservoir will usually tell you which type of coolant is required.

As a rule, aftermarket coolants today fall into one of four basic categories:

  • Organic Acid Technology (OAT), which contains no phosphates or silicates. It is used in late-model GM (1996 and up) and many late-model European and Japanese makes. It is compatible with Dex-Cool (orange), Audi/VW (pink), Toyota (red), 1999 and up Ford Cougar (orange) and other makes (some of which may be blue or yellow in color). Typically, its an extended-life, five-year, 150,000-mile product.
  • "Hybrid" OAT coolant contains a little silicate and is used in late-model Ford (2000 and up), Chrysler (2001 and up) and Mercedes. It may be orange, green or blue. Typically, Its a five-year, 150,000-mile product.

  • A traditional silicate package is usually green or yellow and is used in most older domestic vehicles. Typically, its a two-year, 30,000-mile product, but some versions offer extended life. It can also be used in older Asian and European makes.

  • Diesel coolant contains special nitrate inhibitors and is required for heavy-duty diesels such as Caterpillar and Cummins to prevent liner pitting and scale deposits. Typically, it is a six-year, 600,000-mile product, and it is usually red in color.

One thing to keep in mind is that no single product on the market today meets all of these requirements. A product that is compatible with OAT coolants will not be compatible with traditional silicate coolants.

Intermixing noncompatible coolants can lead to trouble. The different additives may react causing silicates to gel and gum up the cooling system or cause a reduction in corrosion protection that shortens the service life of the coolant.

The bottom line is dont intermix OAT coolants with those that contain silicates and vice versa.

If a standard two-year, 30,000-mile type of coolant is used to refill or top off a system that contains an extended-life, five-year, 150,000-mile coolant, the service life of the mix will be reduced to that of the lesser product. It only takes about a pint of the wrong coolant to cause this change.

Contaminated coolant will not make an engine overheat (provided theres no silicate gel formation). But as the miles add up, the contaminated coolant wont provide the extended corrosion protection that would normally be there. Consequently, if the coolant isnt changed regularly, the cooling system may experience internal corrosion and damage once the inhibitors are used up.

Q: How can I tell if coolant has been cross-contaminated?

A. You cant. The color may appear slightly different depending on how much of the wrong coolant was added to the system. But for small amounts, theres almost no noticeable difference in color. Even so, theres no way to tell to what degree the different additives have affected each other.

Coolant test strips are available to test different types of coolants. The test strips reveal the condition of the corrosion inhibitors. If the test strip indicates that little or no protection is left, the coolant needs to be changed.

Q. Can standard coolant be used in newer vehicles?

A. Yes, but only if all of the original coolant is drained out and the cooling system is flushed before it is refilled with standard coolant. Up to a third of the coolant will remain in the engine block if only the radiator is drained. Thats why the cooling system must also be flushed to remove the remaining coolant. If the system is then refilled with standard coolant, it should work fine - provided the coolant is inspected and replaced regularly for preventive maintenance.

Thats one reason why the vehicle manufacturers and coolant suppliers have switched to long-life products. By improving or changing the additive package, the vehicle owner doesnt have to change the coolant as often. The downside is that the vehicle owner may totally neglect the cooling system and never change the coolant - which may result in corrosion damage once the coolant wears out.

Q. If a customer is replacing a water pump, should he also change the coolant?

A. It is a good idea for several reasons. One is that coolant also contains additives that help lubricate the water pump seal. Over time, the lubricant is used up. Changing the coolant will replace the lubricants. Changing the coolant will also restore its ability to prevent corrosion, which can attack the water pump, radiator and other parts in the cooling system.

Replacing the water pump requires draining the cooling system anyway, so why not go ahead and change the coolant, too? Its no extra work, and it will help ensure trouble-free operation for years to come.

Use a 50/50 mix of antifreeze and distilled water, or a premixed coolant.


BATTERIES

Q: Should batteries be replaced for preventative maintenance?

A. Its probably a good idea, but most people wont buy a new battery unless their old battery has quit on them. In some instances, people will upgrade to a more powerful battery if their old battery is obviously inadequate and cant provide enough amps for easy starting. Or, they might buy a new or more powerful battery if theyre installing electrical accessories such as auxiliary lights, a high-wattage audio system or other such goodies.

As long as a battery can accept and hold a charge, provide adequate cranking amps for reliable starting and supply the reserve needs of the vehicles electrical accessories, theres no reason to replace it. But after four or five years of service, most batteries are reaching the end of their service life. In extremely hot climates, battery life might only be three or four years. Consequently, if the vehicles owner knows this and is concerned about reliable starting, replacing the battery before it fails might be wise. It would certainly reduce the risk of a no start, being stranded and having to call for assistance.

Q: How can the batterys condition be determined?

A. By testing it - the condition of the battery depends on the condition of the cell plates inside the battery. Current is produced when sulfuric acid in the electrolyte reacts with lead in the cell plates. As the battery discharges, sulfate accumulates on the plates and reduces the batterys ability to make current. The sulfate is returned to solution when the alternator recharges the battery by forcing current to flow in the opposite direction.

Over time, some of the sulfate becomes permanently attached to the plates. The sulfate forms a barrier that diminishes the batterys ability to produce and store electricity. This process can be accelerated if the battery is run down frequently or is allowed to remain in a discharged state for more than a few days. If the plates have become sulfated, the battery wont accept a charge and will have to be replaced.

In conventional lead-acid batteries that have liquid inside (as opposed to "gel" batteries), the plates can dry out and be damaged if the water level gets too low. This can be caused by high ambient and/or underhood temperatures as well as overcharging. In "gel" batteries there is no liquid to evaporate or spill. The acid is in the gel between the plates, which makes this type of battery more durable.

The batterys condition can be determined with a carbon pile "load test" that applies a calibrated load to the battery, or by using electronic test equipment that measures the batterys conductance.

Equipment that uses a carbon pile for load testing requires the battery to be at least 75 percent charged for reliable test results. If the battery is low, it must be recharged prior to load testing for accurate results. If an electronic conductance tester is used, battery charge doesnt matter.

The batterys state of charge can be measured with a voltmeter.

A fully charged battery should read 12.6 volts. A reading of 12.4 volts equals about a 75 percent charge and is good enough for load testing. Anything less means the battery is low and needs to be recharged.

If a battery is being replaced, the Cold Cranking Amp (CCA) rating should be the same or higher than the original. For many years, the rule of thumb was to recommend a battery with a rating of at least one CCA per cubic inch of engine displacement. But twice that is probably a better recommendation for reliable cold weather starting.

For most small four-cylinder engines, this would be a 450 CCA or larger battery, for a six-cylinder application, a 550 CCA or larger battery, and for a V8 a 650 CCA or larger battery. For diesels, 750 to 850 CCA might be required.

Also important is a batterys "reserve capacity" (RC) rating. This is how many minutes of juice the battery can provide on its own without the benefit of input from the charging system.

Q: Ive heard a lot about aftermarket "high-output" alternators lately. What are they for?

A. High-output alternators are designed for vehicles that have higher-than-normal electrical loads. Most of these alternators are modified OEM alternators that have been beefed up to produce more amperage - up to 40 percent or 50 percent more current than the stock alternator they replace.

The electrical load on the charging system is typically highest at idle because thats when the alternator is turning at the lowest rpm. Turning on the lights, heater or A/C, electrical defrosters, radio or other accessories while the engine is idling can sap all the amps the alternator can produce, leaving none to keep the battery charged. Over time this can run down the battery and shorten battery life, and it may even overtax the alternator to the point where it fails from being overworked.

Original equipment alternators are usually adequate to handle normal electrical loads and operating conditions. But if someone has installed auxiliary lights, emergency lights, special communications equipment, a killer audio system or other electrical accessories, the power demand may be more than the OEM alternator can handle. Thats when a high-output replacement alternator may be needed.

A high-output alternator puts out more amps at idle than a stock alternator, and it also has a significantly higher maximum amp rating. The rewound stator and rotor have more turns of wire which allow the unit to produce more current at the same rpm than a stock alternator. Heavy-duty diodes are also used to handle the extra power.

Most high-output alternators are direct bolt-on replacements for the stock alternator, but some may require wiring adapters or other modifications to install.

One modification that is recommended with all high-output alternators is to upgrade the alternator/battery cable connections with heavier gauge cables. Thicker cables are needed to safely handle the increased current loads.

The battery should also be tested and replaced as needed to make sure it can handle the higher demands on the electrical system.


EXHAUST

Q: Whats hot in aftermarket exhaust products today?

A. Big bore mufflers, oversize tailpipe extensions and complete converter-back bolt-on exhaust systems - especially for sports compact cars. The "tuner" street market is hot, and anything the owners of these vehicles can find that can be bolted on their Honda Civics and Preludes, Acura Integras, Mitsubishi Eclipses and Lancers, Ford Focuses, Dodge Neons and Chevy Cavaliers theyll buy.

Exhaust products that are in high demand include polished stainless steel performance mufflers with huge outlets and styled dual outlets. These products typically retail for $90 to $140 and are available in universal-fit designs or direct fit for specific vehicle applications. And yes, size does matter. The bigger the outlet pipe(s) the better.

People who buy these kind of mufflers want two things: the look and the sound. The bright polished stainless steel finish provides the "notice me" appearance while the low-restriction, straight-through muffler provides the roar. Stainless steel also provides much-needed durability, which is important for any rear-mounted muffler thats plainly visible from the rear of the car.

Chrome and polished stainless steel tailpipe extensions, on the other hand, are the first step up for vehicle owners who would like to buy a performance muffler but dont have the bucks just yet to fulfill their dreams. Tailpipe extensions are easy to install and create the same visual effect as a big bore muffler, but obviously have little (if any) impact on exhaust backpressure and performance.

For those who want a real attention getter, there are even illuminated tailpipe extensions that have LEDs to create an afterburner glow. A range of colors are available so the exhaust glow can be color coordinated with the seat covers, floor mats, steering wheel cover, wiper blades and rear spoiler.

For those who are serious about real performance, bolt-on, free-flow exhaust systems can provide a much-needed improvement in horsepower, especially at higher rpm. There are cat-back systems and bolt-on four-into-one tubular exhaust headers. Installing a complete high-performance exhaust system can often add 10 to 25 horsepower over the stock exhaust system - and even more if the engine is also modified with a hotter camshaft, big bore throttle body and turbocharger or supercharger.

Q: If a vehicle fails an OBD II emissions test because of a converter code, does the converter have to be replaced?

A. Yes - its an expensive fix, but if the problem has been correctly diagnosed, the only fix for a worn-out or contaminated converter is to replace it.

On 1996 and newer vehicles with OBD II, the vehicle computer monitors converter efficiency. It does this with the help of a second oxygen sensor located in or behind the converter. The computer compares the main "upstream" O2 sensor readings to those of the second "downstream" O2 sensor signals to see if the converter is doing its job. If the converter is working efficiently, the downstream O2 sensor should show little activity and few "crosscounts." Crosscounts occur when the O2 sensor switches from rich to lean or lean to rich. If the computer notices increased activity in the downstream O2 sensor, it sets a trouble code when the number of crosscounts exceeds a certain threshold and turns on the "Check Engine" lamp.

If a vehicle is inspected in a state that requires an OBD II system check as part of the emissions inspection or in lieu of a conventional tailpipe test, and a converter trouble code is found, the vehicle will fail the test. In some states, the vehicle owner may be given the option of taking a conventional tailpipe test if they fail the OBD II check. Either way, if the car fails the emissions test because of a bad converter, it will need a new converter.

On new vehicles, the converter is covered by a federal eight-year, 80,000-mile emissions warranty. That means the vehicle owner can take his vehicle back to the new car dealer for a free converter if the converter needs to be replaced. Thats bad news for the aftermarket, but the 1997 and older vehicles as well as those with more than 80,000 miles on the odometer are now out of warranty. The 8/80 warranty is from the factory build date not the model year.

Aftermarket replacement converters must be EPA certified for the newer OBD II applications and carry a two-year, 24,000-mile warranty. The replacement converter must be the same type as the original and installed on the vehicle in the same location.

The converter is an expensive item to replace, so its important to find out why the old converter died before the new converter is installed. If the engine is misfiring because of a fouled spark plug, bad plug wire or weak coil, running rich because of a leaky fuel injector or dead oxygen sensor, or leaking coolant into the combustion chamber past a leaky head gasket or cracked cylinder head, such problems must be diagnosed and repaired before the new converter is installed.


FUEL PUMPS

Q: Why does Electronic Fuel Injection (EFI) require an electric fuel pump?

A: It requires an electric fuel pump because a mechanical pump cant deliver enough pressure to meet the needs of an EFI system. Mechanical fuel pumps on older carbureted engines operate at low pressure (4 to 10 psi), which is enough to keep a carburetor supplied with fuel. But fuel injectors require much higher pressures to spray fuel into the engine. The high-pressure spray creates a finely atomized mist of fuel vapor that mixes easily with air to improve power, fuel economy and emissions.

Engines with electronic fuel injection (EFI) use a high-pressure electric pump mounted inside or near the fuel tank. Most EFI pumps operate continuously and generate 35 to 85 psi depending on the application. The fuel is pushed from the pump to an inline filter, then to the fuel rail on the engine that supplies the injectors. A pressure regulator then routes the excess fuel back to the tank through a return line.

On some newer vehicles (Chrysler, for example), a "returnless" constant pressure EFI system is used. There is no return line from the engine to the fuel tank because the pressure regulator is mounted on top of the fuel module assembly inside the fuel tank, and fuel is returned directly in the tank.

On some engines like General Motors 4.3L V6 Vortec engines with Central Point Injection (CPI), a somewhat different setup is used. A single "Maxi" injector mounted on the engine routes fuel pressure from the tank-mounted pump to six individual mechanical poppet injectors. The amount of fuel pressure is especially critical here because it takes 58 to 60 psi to overcome spring tension inside the poppet injectors. If the fuel pump is weak or the filter is obstructed, the engine may run poorly or not at all.

Q. How can you tell if a fuel pump needs to be replaced?

A: If an engine cranks normally but wont start or run because theres no fuel at the carburetor or injectors, it has a fuel delivery problem. But it may or may not be a bad fuel pump. Other possible causes include a plugged fuel filter, a blocked fuel line, a bad fuel pump relay, a poor electrical connection at the pump motor or relay, or no fuel in the tank (the fuel gauge might be wrong).

On older vehicles with carburetors and mechanical fuel pumps, the pump needs to be replaced if the diaphragm has ruptured, the internal check valves are leaking or the pump itself is leaking. A new pump is also needed if the diaphragm spring is broken or weak, or if the pump lever arm is worn or broken.

Some older carbureted engines have a low-pressure electric fuel pump instead of mechanical pump. Some have both and use a "pusher" electric pump mounted in or near the fuel tank to push fuel to the engine-mounted mechanical pump. Failures here can be due to leaks in the pump bellows or check valves, an electric motor failure, a bad pressure switch, relay or wiring. On these applications, the OEM low-pressure electric pump or mechanical pump can often be replaced with a "universal" electric pump. The pressure rating of the replacement pump should be the same range as the original pump.

On fuel-injected engines, high-pressure electric single- or double-vane, roller-vane, turbine or gerotor-style pumps are used. Some even use two pumps, a "transfer" or "feeder" pump inside the tank and a main pump or "pusher" pump outside the tank. Most high-pressure electric pumps are mounted inside the fuel tank and are part of a modular assembly that also includes the fuel level sending unit, pickup tube and filter sock or strainer. On most, the pump can be replaced separately, but on some the whole assembly must be replaced as a unit.

High-pressure electric pumps contain a one-way check valve that holds system pressure when the engine is shut off. Leaks in the check valve can contribute to hard starting but will not cause the engine to stall. If the pump is bad, usually the motor doesnt spin, or it spins too slowly to generate enough pressure and/or volume. This can be due to wear in the pump, low voltage to the pump, or high resistance or opens in the pump motor, wiring or relay. Many good pumps are replaced needlessly because of electrical problems elsewhere in the pump circuit.

If an electric pump has died, it wont make any noise when the ignition is first turned on. A pump thats working (or at least attempting to pump fuel) should buzz momentarily (about two seconds) when the ignition is turned on. The pump receives voltage through a relay when the ignition is turned on or when the PCM receives a cranking signal from the distributor pickup or crankshaft sensor. On GM vehicles, the relay circuit may also be wired in parallel to the oil pressure switch or sending unit to allow starting should the primary sensor (distributor or crank sensor) fail. These circuits should all be checked first before condemning the pump.

If the pump runs, it should be tested to see if it delivers the required fuel pressure and volume. Low fuel pressure can cause hard starting, stalling and misfiring. Measuring the pumps output pressure and delivery volume will confirm if the pump is good or bad. Sometimes a pump will generate good fuel pressure at idle, but not enough pressure or volume at higher engine rpms or loads.

When a tank-mounted electric fuel pump is replaced, the fuel filter should be removed and inspected to see if it contains rust or sediment. A new inline filter as well as pump pickup screen should also be installed. The inside of the fuel tank should also be inspected when the pump is removed to check for rust or sediment. If the tank is dirty, it must be steam cleaned before the new pump is installed. If the tank is rusty, it should be replaced to prevent repeat pump failures.


GASKETS

Q: Why do head gaskets sometimes fail?

A: Head gaskets are one of the hardest working gaskets on an engine. It has to provide a leak-free seal from the moment it is first installed, and maintain that seal for the life of the engine.

If the head gasket doesnt go the distance, it may have failed for any of the following reasons:

  • Poor OEM design - Some engines are difficult to seal because of cylinder head design. Thermal stress created by a bimetal engine can also tear a gasket apart if it is not properly designed for the application. Ford, GM and Chrysler have all had such problems over the years (Ford 3.8L engines, GM 2.3L Quad Four engines and Dodge/Plymouth 2.2L Neon engines). Even Toyota and Honda have had problems. The Toyota 3.0L and 3.4L V6 engines as well as Hondas 1.3L and 1.5L engines have all had a high incidence of failures.

  • Installer error - Sometimes techs screw up when installing a head gasket. Old head gaskets must never be reused. Once the head bolts have been tightened down, the gasket is permanently deformed and must be replaced if the head comes off the engine. The head gasket must also be installed on a clean, smooth and flat surface. This is really critical with late-model engines that have multi-layer steel (MLS) head gaskets. MLS gaskets require an extremely smooth surface finish. Other screw-ups may include reusing old, dirty, damaged or stretched head bolts, reusing torque-to-yield head bolts, failing to tighten the head bolts in the proper sequence or to the proper torque, or applying sealer to a coated gasket.

  • Operating conditions that overstress the gasket - This includes engine overheating, preignition or detonation. Common causes of overheating include coolant leaks, low coolant level, a plugged radiator, a defective cooling fan, air in the cooling system, a defective thermostat, exhaust restrictions and overworking the engine. Common causes of preignition and detonation include engine overheating, inoperative EGR valve, carbon buildup in the combustion chambers, over-advanced ignition timing, wrong spark plugs (too hot for the application), lean air/fuel ratio (vacuum leaks, dirty injectors, etc.) or low-octane fuel.

  • Performance modifications - Stock head gaskets are engineered to handle stock compression ratios, stock combustion pressures and stock operating temperatures. If an engine has been modified to boost its power output, the stock head gasket may not hold up. With V8 engines, reliability may be an issue when horsepower starts to exceed 400 to 450 hp. With smaller engines, adding a turbocharger, bolt-on supercharger or nitrous oxide may push compression past the limits of the stock head gasket. Especially important here is adequate engine cooling. An engine that creates more horsepower also creates more waste heat, which may require a larger radiator and cooling fan.

Preventing repeat failures means eliminating the underlying cause of the head gasket failure and/or installing a better replacement gasket that can take the abuse.

For many "troublesome" applications, aftermarket gaskets are available that have been reengineered with stronger materials and reinforcements to improve over the OEM gasket design. Hot spots often form in areas where exhaust ports are located next to each other. Heat buildup in these areas makes the head swell. This can crush the gasket between the cylinder bores causing the gasket to leak and fail. To prevent this from happening, gasket manufacturers may use a gasket material such as graphite to dissipate heat away from the hot spot and/or reinforce the most highly stressed areas of the gasket with a shim so it wont crush. Durability can also be improved by using stronger or reinforced combustion armor, tougher, high-temperature fibers such as aramid and Kevlar in composition gaskets, and adding extra reinforcements to critical oil hole grommets.


BELTS

Q: What are the differences between V-belts and "serpentine" belts?

A: Belts come in two basic varieties: V-belts and flat V-ribbed or "serpentine" belts. Older engines that use V-belts may have as many as three or four separate belts to drive its accessories. Most newer engines, though, have a single serpentine belt to drive all of the accessories. But many also use a combination of belt types (V-belt, serpentine and/or flat) to drive their accessories.

Even though both types of belts perform the same basic function, they work differently. A V-belt drives by gripping a pulley with its sides, while a serpentine belt grips a pulley with either its flat back or v-ribbed surface (depending on which side of the belt faces the pulley). A V-belt is much thicker than a serpentine belt and generates more heat because of internal friction as it bends and flexes with every revolution of its pulleys. To improve cooling, some V-belts have notches in the top or bottom of the belt.

Notches on the underside of a V-belt also provide added grip against the grooves in the pulleys.

Because serpentine belts are flat, they are more flexible and can handle smaller diameter pulleys. The increased flexibility means they also generate much less heat which allows them to run cooler and enjoy a significantly longer service life.

Heat is the number-one enemy of all belts, but especially V-belts. If a V-belt isnt tight and it 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 resulting 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 types of belts and 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 dont have an automatic adjuster, belt tension must be adjusted to specifications, then readjusted after a short break-in period.

Q: How can you tell if a belt needs to be replaced?

A: Both types of belts should be inspected regularly for obvious signs of wear or damage. Minor surface cracking is normal for both V-belts and serpentine belts, 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. But glazing and noise can also be caused by pulley misalignment, so the pulleys should also be inspected to make sure they are properly aligned (especially if an engine is throwing, twisting or "eating" belts).

Often times, a high-mileage belt that is dangerously weak on the inside may appear to be as good as new on the outside. Unfortunately, theres no way to see inside a belt to determine if the cords are failing. Thats why belt manufacturers recommend periodic belt replacement for preventive maintenance. Replacing a belt BEFORE it snaps can save your customer the inconvenience and expense of a breakdown. Replacing V-belts every three to four years or 40,000 to 50,000 miles, and serpentine belts every five years or 50,000 to 60,000 miles, can minimize the risk of sudden belt failure.

Q: What kind of information do I need when looking up a belt?

A: When looking up replacement belts in your catalog, you may need quite a bit of information to find the correct belt. 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.

Its 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 thats too narrow may "bottom out" in a pulley and slip, while one thats too wide may not fit the grooves in the pulley. The length of a replacement V-belt can vary a little depending on the amount of adjustment thats 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.















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