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15th Annual Tech Forum


8/12/2007

This month, Counterman presents the 15th annual Technical Forum, a question-and-answer style section that addresses some of the questions you and your customers need to know.
 

This year, we present technical and sales information on eight important categories:
1. Engine Management
2. Filters
3. Gaskets
4. Oxygen Sensors
5. Refrigerant
6. Spark Plugs
7. Specialty Chemicals
8. Suspension

Engine Management
Question: When an engine doesn’t start, why do people often blame the PCM?

Answer: The Powertrain Control Module (PCM) is often blamed for a variety of starting and driveability problems because that’s the part people understand the least. Actually, PCMs are fairly reliable, and if the engine won’t start, the fault is usually something else that prevents the engine from getting fuel or spark.

The PCM is the brains of the engine management system and it relies on all its sensors for good inputs. So if a sensor is misbehaving and is feeding the PCM bad data, it can affect the output commands from the PCM to the ignition system, fuel system and emission controls.
If an engine cranks but won’t start because it has no spark, the PCM is rarely to blame and replacing it usually won’t fix the car. The underlying cause may be a bad crankshaft position sensor, a bad ignition module, or a bad distributor pickup or ignition coil on an engine with a distributor.

If the engine does not crank, somebody may blame the PCM, thinking it must somehow be responsible. Rarely is that the case because the starter is usually part of a separate power circuit. The most common causes of an engine that won’t crank are things like a bad starter motor, a bad starter relay or solenoid, an open park/neutral safety switch or an open brake pedal safety switch (automatic) or clutch pedal safety switch (manual transmission), or even a bad ignition switch or damaged flywheel. The PCM may be involved if the immobilizer module fails to recognize the ignition key and tells the PCM not to energize the fuel pump or to kill the spark. But you can’t blame the PCM for that. It is just doing what it is told by another module.

If an engine cranks but won’t start because it is not getting any fuel, the PCM may not be energizing the fuel pump relay, or it may be shutting off the relay after a certain period of time because it is not seeing an RPM signal from the engine. On most vehicles, when the ignition key is turned on, the PCM energizes a relay that runs the fuel pump for a few seconds. The PCM will keep the relay energized for a certain period of time, or until it sees an RPM signal. But if the crankshaft position (CKP) sensor is bad and doesn’t send an RPM signal to the PCM, the engine won’t run. The same thing can happen if the engine has a camshaft position (CMP) sensor and it is defective. On some engines, the PCM needs a signal from the camshaft position sensor to figure out where cylinder number one is so it can sync ignition timing in the proper firing order and/or the pulsing of sequential fuel injectors.

The only way to prevent warranty returns of PCMs and sensors is to check the operation of the sensors and PCM with a scan tool. If all of the OBD II monitors have run and no faults are found, chances are the engine management system is doing its job — and any driveability, emissions or performance issues are being caused by something else, or possibly misleading sensor inputs. Oxygen sensors get sluggish with age and EGR differential pressure sensors on Fords have a high failure rate that can upset the operation of the PCM.

Q. Can a faulty PCM be fixed with a reflash?

A. No. If a PCM is not working correctly because of an internal electronic fault in its processor, memory or circuit board, a reflash won’t fix anything. PCM reflashes are only used to update the operating instructions that tell the PCM what to do. Reflashes are typically used to correct glitches in the original factory settings, to correct various driveability or emission problems that are the result of programming issues or to make the PCM less apt to set false trouble codes as the vehicle ages.

Most repair shops and some distributors can reflash PCMs. It does not have to be a new car dealer. But a PCM reflash requires special training and a J2534 pass-through tool or a scan tool with reflash capabilities (such as a factory scan tool or high- end professional grade aftermarket scan tool). Some aftermarket suppliers of reconditioned PCMs flash their PCMs for specific vehicle applications so the PCM is ready to go right out of the box, but others do not, which means the PCM has to be reflashed when it is installed.

Q. If someone is doing an engine swap and replacing one model year engine with another, does the PCM have to be changed?

A. Maybe. It depends on the application and whether or not there are any differences in the PCM and/or programming between the two different model years. If one engine came out of a vehicle with a manual transmission and the other has an automatic, the PCM will have to be replaced or reflashed. If the engine from the donor vehicle is more than a couple of years different from the one receiving it, chances are the sensors and calibrations will be different and the PCM will have to be changed or reflashed to match the donor engine. Even then, it may not work right because of other modules on the vehicle that may communicate with the PCM (like the ABS/traction control/stability control module, transmission module if separate, body controller, HVAC system and other modules). If an older PCM is installed in a newer vehicle, it may not have the hard-wired capability to talk to these other modules.

If a replacement PCM isn’t compatible with the vehicle, it’s hard to tell what kind of problems might result. In many of these instances, the check engine light will come on because the PCM is missing a sensor signal, or is not understanding the data from the sensors. The engine may not start (no spark or no fuel), or the vehicle may not run right. That’s why PCMs have to be carefully matched to the vehicle they are going into.

Filters
Question: How do you replace a cabin air filter?

Answer: First you have to find it. The cabin air filter is usually located behind the glove box or at the base of the windshield in the cowl area over the HVAC inlet duct. The exact location can be found in the vehicle owner’s manual or a filter reference guide.

On most Fords, the filter is located under the hood in the cowl area. On Chrysler models, it is located under the dash. On GM products, it might be under the hood (Impala, Lumina and Monte Carlo), under the dash (Avalanche, Silverado, Suburban and Tahoe) or behind the glove box (Venture). On Toyota, Lexus, Nissan and most Honda models, you’ll find the filter behind the glove box.

On vehicles where the cabin air filter is mounted under the cowl at the base of the windshield, some disassembly may be required to replace the filter. This may involve removing a plastic cowl cover. The area around the filter usually collects debris, so this area should be cleaned to remove any leaves, bugs or other debris before the old filter is pulled out. This will prevent any contaminants from falling into the HVAC inlet duct.

On vehicles where the filter is located behind the glove box, the glove box may have to be removed to replace the filter. On others, the filter can be accessed from under the dash and pulled out of a slot in the HVAC unit.

Most cabin air filters are flat-panel filters, but some have unusual shapes, so they will fit the HVAC inlet duct. Some filters also come in two sections to make replacement easier.

Q. How often should a cabin air filter be changed?

A. As often as necessary to prevent the filter from clogging, or in the case of cabin air filters that also absorb odors in addition to blocking dust, as often as needed to keep unpleasant odors to a minimum.

Under “normal” driving conditions for a vehicle driven primarily in a city or suburban area, or on paved highways, the average service life of a typical cabin air dust filter is about two to three years, or 25,000 to 30,000 miles. For a vehicle in a rural area that is driven frequently on gravel roads, the service life of the filter may only be six months or less.

Cabin air filters are very efficient and have electrostatically charged fibers that can trap particles smaller than 1 micron in size. Most quality cabin air filters will stop 100 percent of all particles that are 3 microns or larger in size and 95 to 99 percent of particles in the 1 to 3 micron size range. This prevents most pollens, mold spores and bacteria from entering the vehicle. Some cabin air filters are also treated with a chemical biocide to inhibit the growth of odor-causing bacteria, fungi and algae.

When a cabin air dust filer becomes clogged, it restricts airflow into the HVAC unit. This may cause reduced airflow and cooling from the air conditioner and/or lower heater/defroster output during cold weather.

If the cabin air filter is a combination type that has a layer of activated charcoal to absorb exhaust fumes and other unpleasant odors, the service life of the odor filter is only about a year, or 12,000 to 15,000 miles of normal driving. So when odors start to become more noticeable while driving (and isn’t coming from left over pizza or dirty socks in the back seat), it is probably time to replace the filter.

Q. How often should an oil filter be replaced?

A. Every time the oil is changed, which will vary depending on the type of driving and the vehicle manufacturer's recommendations. For the “average” driver, that usually means changing the oil and filter every 3,000 to 5,000 miles or every three to six months.

Many vehicles today have an oil reminder light to indicate when the oil needs to be changed. The mileage at which the oil reminder light comes on (which is not the same thing as the check engine light, by the way) depends on the number of miles driven, the hours of engine operation, ambient temperatures and the average distance of trips driven. Short-trip, stop-and-go driving, especially during cold weather, produces more blowby and condensation in the crankcase. This dilutes the oil and causes it to break down faster, so the oil needs to be changed more often under these conditions.

Some people may try to save on maintenance by postponing oil changes too long, or replacing the oil filter only every other oil change. That’s false economy because the oil filter is the engine’s only protection against abrasion wear. An oil filter is a lot cheaper than an overhaul or a new engine.
If the oil filter becomes clogged, it will restrict oil flow to the engine. Oil filters have a built-in safety device called a bypass valve that allows oil to go around the filter if it becomes plugged. But when the bypass valve is open, no filtration occurs. Any contaminants in the crankcase will go straight to the bearings and cause abrasive wear.

Q. Some vehicles no longer have a recommended replacement interval for the fuel filter. Why?

A. Because the fuel filter on some vehicles is supposed to be a “lifetime” filter — which means it lasts until it plugs up. These lifetime filters are typically located inside the fuel tank and are part of the fuel pump assembly. They are not usually replaced unless the fuel pump is being changed or the filter is plugged and is restricting fuel delivery to the engine.

Realistically, the life of any fuel filter depends on the number of miles driven, the cleanliness of the fuel that goes into the tank and the condition of the fuel system. Most fuel station pumps have filters to catch any sediment or dirt from the underground storage tanks. But if these filters are not maintained, you can pump dirty gas into your tank and clog the fuel filter.

Fuel filters can also become clogged as a result of rust flaking loose inside of a steel fuel tank. The tanks are plated to minimize corrosion, but after years of service and exposure to alcohol and moisture, all tanks eventually develop some rust.

Wear particles from the fuel pump and pieces of rubber that flake off inside aging fuel hoses can also be sources of debris in the fuel.

If a filter is creating a restriction or is plugged, it needs to be changed. Symptoms include a drop in normal fuel pressure, hard starting, loss of power at higher engine speeds or even stalling.
To prevent such problems, the filter should be replaced before it can cause trouble. For most vehicles, this means changing the fuel filter every 30,000 to 50,000 miles.

Gaskets
Question: Is there a cheap fix for a leaky head gasket?

Answer: Not really. Adding a bottle of cooling system sealer to the radiator may slow down or plug a coolant leak in a head gasket, but it’s not a permanent fix. Sooner or later, the head gasket will have to be replaced.

Coolant leaks in head gaskets can be tricky to diagnose. Often, the only symptom is that coolant is disappearing from the radiator but no coolant leaks can be seen. Eventually, the loss of coolant will cause the engine to overheat. Coolant leaking into a cylinder may also hydro-lock the engine. Coolant is incompressible, and if enough coolant leaks into a cylinder while the engine is off, the engine may not crank when the driver attempts to start it.

If a leak is really bad, it will typically produce white smoke in the exhaust. And if the leak allows coolant to seep into the crankcase, the oil level on the dipstick will appear higher than normal and the oil will have a muddy, sludge-like consistency.

Replacing a leaky head gasket is a big job because it requires removing the cylinder head from the engine. In addition to a new head gasket, your customer will need intake and exhaust manifold gaskets and valve cover gasket(s). If the cylinder head is held in place with torque-to-yield (TTY) head bolts, your customer will also need new head bolts because TTY head bolts are one-time use only.

Q. What causes a head gasket to fail?

A. The most common cause is engine overheating. If the engine overheats for any reason (low coolant level, thermostat stuck, electric cooling fan not coming on, bad water pump, clogged radiator, etc.), the cylinder head may get so hot that it crushes and damages the head gasket. This may cause the head gasket to start leaking as soon as the engine cools down and coolant is added, or the damage may only weaken the gasket so that it fails at some point later on.
Detonation can also cause a head gasket to fail. Detonation is an erratic type of combustion that occurs when there’s too much compression and not enough octane. Compression can increase over time as carbon deposits accumulate. Contributing factors include an inoperative EGR system, over-advanced ignition timing and anything that may cause the engine to run hotter than normal.
The other common cause of head gasket failure is a poor OEM head gasket design. In spite of all the testing and certification that auto makers do to assure their engines will be trouble-free (at least through the warranty period), sometimes a weak gasket design gets through and causes problems down the road.

Back in the 1980s and 1990s, GM had head gasket problems with its 2.3L Quad Four engines. In the 1990s, Chrysler had head gasket problems with the first-generation Neon engines. In 1995, Ford had all kinds of problems with the head gaskets failing at low mileage on its 3.8L engines.

As reliable as Hondas are, they have had problems, too, on their older Civic 1.3L and 1.5L engines. Replacing the original gasket with another OEM gasket temporarily solves the problem, but sooner or later the problem returns because the OEM gasket crushes and fails in the same spot again. The cure is to install an aftermarket head gasket that has been re-engineered to handle the hot spot. A reinforcement in this area improves the strength of the gasket and eliminates the premature failure problem.

Some head gasket failures can also be blamed on a hard-to-seal cylinder head. The 1987-96 Mitsubishi 3.0L V6, 1988-95 Toyota 3VZE 3.0L V6 light truck engine, and 1995-98 Toyota 5VZFE 3.4L V6 in T100s, Tacomas and 4Runners are all examples of engines with hard-to-seal heads.
In the case of the Mitsubishi 3.0L V6, the armor around the combustion chambers on the OEM gasket has a tendency to crack. This engine uses aluminum heads and a cast iron cylinder block. Aluminum expands at a much higher rate than cast iron, which causes the head to swell and move around as the engine heats up and cools down. Over time, this leads to the cracking problem that causes the head gasket to fail. The cure for this engine is to install a redesigned aftermarket head gasket with stronger combustion armor and a special anti-friction coating that eliminates the main reasons for gasket failure.

In the case of the Toyota 3.4L engine, the OEM gasket is a graphite head gasket. Graphite is a good high-temperature material, but in some applications it is too weak to withstand a lot of head motion. To address this engine’s motion problems, some aftermarket replacement gaskets are now “Multi-Layer Steel” (MLS). MLS head gaskets are made of several layers of embossed stainless steel. A thin coating of nitrile rubber or Viton is used on the external surfaces as well as between the layers to provide maximum sealing. MLS gaskets are almost bullet-proof, but also much more expensive than conventional soft-faced gaskets.

Oxygen Sensors
Question: How many oxygen sensors are on a typical late-model vehicle?

Answer: There could be as few as two O2 sensors or as many as six. It all depends on the engine, the engine management system and whether the vehicle has single or dual exhaust with one or two catalytic converters.

On four and straight six cylinder engines there is usually a single “upstream” oxygen sensor in the exhaust manifold where the individual runners or pipes come together. This allows a single O2 sensor to monitor the exhaust oxygen content from all of the engine’s cylinders (the PCM uses this information to control the air/fuel mixture). On some engines (typically inline six cylinder engines) there may be two O2 sensors in the exhaust manifold depending on how the runners are configured. This allows better monitoring of the front three and back three cylinders.

On V6, V8 and V10 engines there is an oxygen sensor in each exhaust manifold. This allows the computer to monitor the exhaust oxygen from each bank of cylinders separately.
On all vehicles built since 1996 with Onboard Diagnostics II (OBD II), there is also one “downstream” O2 sensor for each of the main catalytic converters in the exhaust system. The downstream O2 sensor(s) are used to monitor the operating efficiency of the converter(s).

Q. How can the operation of the O2 sensors be checked?

A. By using a scan tool that can read the status of the OBD II readiness monitors and/or display O2 sensor outputs. If the O2 sensor monitor and catalyst monitors have both run (completed) and the check engine light is not on (no fault codes), the assumption is the oxygen sensors are functioning normally and all is well — maybe.

As O2 sensors age they can become sluggish and slower to respond to subtle changes in the air/fuel mixture. As a result, the PCM does not receive accurate information and may not maintain the air/fuel mixture at the best ratio. Old O2 sensors tend to read lean, which makes the fuel mixture run richer than normal, causing a loss of fuel economy and higher emissions.

With a scan tool that can display actual O2 sensor output voltages, a technician can see how the sensors are performing. He can also look at fuel trim on the scan tool to see if the engine is running richer or leaner than normal.

On a scan tool, the output signal from the two upstream sensors is usually referred to as Bank 1 Sensor 1 and Bank 2 Sensor. Bank 1 is usually the front bank on a transverse mounted engine. But on a longitudinal V6, V8 or V10 it could be either the right or left bank. It may be necessary to refer to the vehicle service literature to determine how the cylinder banks and oxygen sensors are labeled.

Q. How often should O2 sensors be replaced?

A. Most vehicle manufacturers no longer have a recommended replacement interval for O2 sensors, though some do on older vehicles. As a rule, most late-model O2 sensors should last 100,000 to 150,000 miles or more — assuming there are no other problems such as a leaky head gasket that allows coolant to leak into the cylinders and contaminate the O2 sensors, or oil burning that can also contaminate the sensors.

The OBD II system does a pretty good job monitoring the O2 sensors and if it detects a fault it will set an O2 sensor code and turn on the check engine light. If the code is a O2 heater circuit code, in most cases the heater element inside the O2 sensor has burned out and the sensor has to be replaced. For other O2 sensor codes, additional diagnosis may be needed to confirm what exactly is causing the problem because it might only be a loose or corroded wiring connector in the oxygen sensor circuit.

Q. Do all oxygen sensors function the same way?

A. No. The most common type of O2 sensor (zirconia) all work the same way, but there are others, namely titania O2 sensors and “wide-band” O2 sensors.
Unheated zirconia O2 sensors are the oldest type. They have one or two wires and take up to several minutes to generate a signal after a cold start because they rely solely on the heat from the exhaust to reach normal operating temperature. Consequently, an unheated sensor may cool off at idle and stop producing a signal causing the engine control system to revert back to “open loop” operation (fixed air/fuel ratio setting).

In 1982, heated zirconia O2 sensors appeared that added a special heater circuit inside the sensor to bring it up to operating temperature more quickly (in 30 to 60 seconds). This allows the engine to go into closed loop sooner, which reduces cold-start emissions. It also prevents the sensor from cooling off at idle. The heater requires a separate electrical circuit to supply voltage, so heated sensors usually have three or four wires.

Titania O2 sensors use a different type of ceramic and produce a different kind of signal than zirconia type O2 sensors. Instead of generating a voltage signal that changes with the air/fuel ratio, the sensor’s resistance changes and goes from low (less than 1,000 ohms) when the air/fuel ratio is rich to high (over 20,000 ohms) when the air/fuel ratio is lean. The switching point occurs right at the ideal or stoichiometric air/fuel ratio. The engine computer supplies a base reference voltage (one volt or five volts, depending on the application), and then reads the change in the sensor return voltage as the sensor's resistance changes. Titania O2 sensors are only used on a few applications, including some older Nissans and 1987-1990 Jeep Cherokee, Wrangler and Eagle Summit.

In 1997, some vehicle manufacturers began using a new type of O2 sensor: the heated planar O2 sensor. This type of O2 sensor has a flat, ceramic zirconia element rather than a thimble. The electrodes, conductive layer of ceramic, insulation and heater are all laminated together on a single strip. The new design works the same as the thimble-type zirconia sensors, but the “thick-film” construction makes it smaller, lighter and more resistant to contamination. The new heater element also requires less electrical power and brings the sensor up to operating temperature in only 10 seconds.

Some newer vehicles are also using a wide-band O2 sensor that is similar to the planar design but produces a higher voltage signal that changes in direct proportion to the air/fuel ratio (instead of switching back and forth like the other types of O2 sensors). This allows the engine computer to use an entirely different operating strategy to control the air/fuel ratio. Instead of switching the air/fuel ratio back and forth from rich to lean to create an average balanced mixture, it can simply add or subtract fuel as needed to maintain a steady ratio of 14.7:1.

Q. Is an air/fuel (AF) sensor the same thing as an oxygen sensor?

A. Yes and no. An air/fuel sensor performs the same basic function as an O2 sensor by monitoring oxygen levels in the exhaust, but it does it better and works differently than an ordinary O2 sensor.
A conventional zirconium O2 sensor is really a rich/lean indicator. It tells the PCM when the exhaust contains little oxygen (a rich signal) and when it contains more oxygen (a lean signal). The sensor generates a small output voltage that goes from about 0.2 volts (lean) to 0.8 volts (rich). So it can tell the computer when the engine is running rich or lean, but not by how much. In other words, it can’t tell the computer the exact air/fuel ratio. The PCM has to figure it out by alternating and averaging the fuel mixture until fuel trim is within the desired range.

An AF sensor, by comparison, reads the exact amount of oxygen in the exhaust. The sensor, which is also referred to as a “wideband O2 sensor,” contains extra circuitry (called an “oxygen pump”) that enables it to determine the exact air/fuel ratio for the PCM. This allows the PCM to control the air/fuel mixture more precisely for lower emissions and better fuel economy.

AF sensors run much hotter than conventional oxygen sensors (1,200 to 1,400 degrees Fahrenheit) and reach operating temperature very quickly (within 20 seconds or less to reduce cold start emissions). They also respond much more quickly to changes in the air/fuel mixture. And they are typically much more expensive to replace than conventional O2 sensors.

Refrigerant
Question: A vehicle is low on refrigerants and needs a recharge. Where did the refrigerant go?

Answer: Refrigerant is never used up. It’s recycled continuously inside the sealed A/C system. So, the only place it can go is out through a leak. The A/C systems in late-model vehicles are much tighter in terms of leakage than they were years ago thanks to better hoses and seals. Today, most vehicles leak less than a few tenths of an ounce of refrigerant a year. This doesn’t sound like much, but the total refrigerant capacity of some late-model cars is only 12 to 14 ounces — much less than the charges that were commonly used in older systems.

According to a recent industry repair survey conducted by the Mobile Air Conditioning Society, the A/C system parts replaced most often are:
• Compressor (17 percent)
Cause: case leakage;
• Compressor (14 percent)
Cause: internal failure;
• Hoses (10 percent)
Cause: leaks;
• O-Rings or Seals
Cause: leaks;
• Compressor Clutch (6 percent)
Cause: failure;
• Condenser (5 percent)
Cause: leaks or damage; and
• Evaporator (4 percent)
Cause: leaks.

Based on these findings, it’s easy to see that refrigerant leaks not only generate the sales of refrigerant, but also the sales of A/C component parts. In fact, loss of refrigerant is one of the leading causes of compressor failure because the refrigerant carries the lubricating oil that keeps the compressor lubricated.

Q. How can you find A/C leaks?

A. There are several ways to find refrigerant leaks. One of the most popular methods for finding leaks is to charge the A/C system with refrigerant that contains a fluorescent leak detection dye. When the dye starts to leak out, it leaves telltale stains that can easily be seen when illuminated by an ultraviolet light.

OEMs that currently use dyes or endorse dye use include Ford (since 1995 in some and 1998 in all), GM (since 2002 in cars and 2003 in trucks), Chrysler (since 1993) and Nissan (since 1999). Those that do not use or endorse dyes include Honda, Mazda, Toyota, Hyundai and Mercedes.
The risk of using refrigerant dye is overdosing the system. Too much dye may dilute the compressor lubricant and increase the risk of compressor noise and failure. The standard recommended dose is only one quarter ounce! A second dose won’t usually cause problems, but multiple doses over a period of time may allow too much dye to accumulate inside the system requiring it to be flushed out to remove the contaminants.

Leaks can also be found with electronic leak detection equipment. There are three basic types:
1. Electromechanical corona discharge detectors. This type of detector pulls air through an electrical field around a wire. The presence of refrigerant or other gases in the air changes the current in the wire to trigger an alarm. The tool may beep or flash when a leak is detected. The level of sensitivity for this type of tool is not as high as the next two technologies, but it can still find leaks as small as 0.3 ounces to 0.6 ounces per year.

2. Solid-state heated diode detectors. The sensing element in this type of detector is a heated ceramic diode. When air containing a halogen gas is drawn across the diode, it generates an electrical signal that triggers the alarm. This type of equipment is much more sensitive than the corona discharge detectors and is capable of finding leaks as small as 0.1 ounce a year with R-134a. The sensor element has a limited service life, though, and must be replaced every few years.

3. Nondispersive infrared detectors. This is the newest leak detection technology and will be used in more new leak detectors. This type of equipment uses an “optical bench” that shines an infrared light of a specific wavelength through air passing across the bench. If the air contains any halogen gas, the gas disrupts the light beam and triggers the alarm. It’s the same basic technology that is used in many refrigerant identifiers to find out what kind of gases are inside an A/C system. It can detect leaks as small as 0.1 ounce per year.

Q. Can refrigerant leaks be stopped by adding sealer to the A/C system?

A. Yes, but it depends on the type of sealer and the type of leak. Some refrigerants that are marketed for “high-mileage” vehicles may contain a sealer additive that causes aging seals and o-rings to swell slightly. In theory, the sealer causes the parts to swell and tighten, and hopefully prevent or stop any leaks. But this type of sealer can’t stop a leak in metal tubing, or a pinhole in the evaporator or condenser.

There are other sealer products that activate when exposed to moisture. These are designed to seal leaks in metal tubes, the evaporator or condenser. But many technicians are leery of these products because the residue can gum up A/C service equipment. Do-it-yourselfers, on the other hand, don’t have refrigerant recycling or recharging machines and are mostly unaware of the possible side-effects of using this type of product.

The best and longest lasting repair for any leak is to replace the leaky component.

Spark Plugs
Question: What’s the latest technology in spark plugs today?

Answer: Long-life spark plugs have become the norm in most new vehicles. Platinum plugs have been around for years and do an excellent job of reducing electrode wear for extended plug life. There now seems to be a shift in the marketplace to iridium for the center electrode in spark plugs, or alloying iridium with platinum to increase wear-resistance while reducing cost.

Iridium plugs have also been around for a number of years, but until recently were used primarily in Asian engines as original equipment. Now iridium is finding its way into domestic engines as well as the aftermarket for a wide-range of applications.

Iridium actually has a higher melting point than platinum, making it a very wear-resistant material. The center electrode can also be made very fine, which helps concentrate the spark for more reliable ignition.

Plug life can be shortened if a vehicle is burning oil, is used mostly for short trip, stop-and-go driving or spends a lot of time idling. This kind of use increases the risk of spark plug fouling and misfires. The OBD II system can detect misfires and will turn on the check engine light and set a misfire code if the plugs are bad and need to be replaced.

Long-life plugs are more expensive than standard spark plugs but actually save the vehicle owner money over the long run because they last more than twice as long as standard plugs. On engines where the spark plugs are hard to reach, it also means the plugs don’t have to be replaced as often. Consequently, long-life plugs maintain fuel economy and emissions longer.

Q. How can I make sure my customers get the right replacement spark plugs for their engines?

A. Just follow the spark plug supplier application charts and you usually can’t go wrong. Spark plugs come in many different sizes, styles and electrode configurations. So follow the application guide and compare thread diameters, the length of the threads, plug reach and the plug seat (flat with a gasket, or tapered) on the old and new plugs to make sure they match.

Warning: Installing the wrong spark plugs in an engine may damage the plug threads in the cylinder head, or the engine itself if the plugs protrude too far into the combustion chamber.

Spark plugs are pre-gapped at the factory. Even so, due to consolidation, the electrode gap should also be checked before the plugs are installed — unless the plugs have a special type of electrode that is non-adjustable (follow the spark plug manufacturer’s recommendations).

Q. A customer said his Ford pickup truck blew out a spark plug. Why did this happen?

A. Ford has had problems with spark plugs blowing out of the cylinder heads on some of its Triton V8 truck engines. Though the spark plugs are deeply set in the heads and have a long reach to the combustion chamber, the spark plug hole is only threaded part-way up the hole.

If the spark plugs are not installed with the proper amount of torque, they can loosen up over time. After 30,000 to 50,000 miles, a loose plug can unscrew itself down to the last couple of threads in the hole. When this happens, pressure often blows the spark plug right out of the head and destroys the threads in the spark plug hole. The repair requires drilling out the spark plug hole and installing a thread repair insert, or replacing the damaged cylinder head.

To prevent this from happening, the plugs must be properly tightened when installed and rechecked every 20,000 to 30,000 miles to make sure they haven’t loosened up.

Q. What does “reading” the spark plugs mean?

A. “Reading” is visually inspecting the spark plugs after they have been removed to look for signs of trouble. This should always be done when spark plugs are changed.

All spark plugs get dirty with use. Combustion by-products stick to the electrodes and typically cause the white ceramic insulator around the center electrode to discolor. Normal deposits are a light gray or tan color.

You can tell a lot by “reading” plugs. If the electrodes are coated with black fluffy carbon deposits, the engine is running too rich — or is not being driven long enough or fast enough for the plugs to get hot and burn off the deposits. If the electrodes are coated with black, oily deposits, the engine is burning oil. Switching to a spark plug with a slightly hotter heat range may help keep the plugs cleaner longer.

Spark plugs with a yellow or blistered center electrode means either the spark plug or the engine is running too hot. The plugs may be the wrong heat range for the engine, or the engine may have a cooling problem (bad thermostat, water pump, plugged radiator, low coolant or inoperative cooling fan).

Specialty Chemicals
What’s the best way to loosen rusty fasteners?

Answer: Old, rusty fasteners are always a challenge to remove, both for professional technicians and do-it-yourselfers. After years of exposure to moisture and oxidation, old fasteners can be very difficult to loosen and remove. Spraying fasteners with penetrating oil and allowing the oil to soak in for several hours, or overnight, will often make the difference between successfully removing a fastener and breaking it. Penetrating oil has a capillary action that pulls it into cracks and pores. The solvent action of the oil loosens corrosion while lubricating the threads at the same time. The reduction in friction makes it easier to break the fastener loose without damaging it. But sometimes even penetrating oil isn’t enough.

Heating stubborn fasteners with a propane torch is another trick that often works. Heat causes the metal to expand. This creates movement that often helps loosen the threads. It also improves the effectiveness of penetrating oil by allowing the oil to penetrate more deeply between the threads.
But heat has some drawbacks. You should never use an open flame near any part of the fuel system (rusty clamps on fuel lines, or fuel filters, fasteners that hold the fuel tank in place, or fasteners on a carburetor or throttle body). Heat can also damage nearby rubber boots and seals, and plastic intake manifolds and valve covers. You may also have to wait a bit for the fastener to cool down after applying a torch (don’t want to burn your fingers, right?).

Too much heat can also cause additional problems. Excessive heat, even from a propane torch, can soften aluminum. And using anything hotter than a propane torch (such as an acetylene torch) to loosen parts is not recommended because excessive heat will cause heat-treated steel to lose temper (strength and hardness). So if someone is trying to remove a stuck wheel bearing on a spindle, too much heat can ruin the spindle and the bearing.

Another way to create thermal movement between the threads on fasteners or other parts is to use cold instead of heat. Some new aerosol penetrating products use a propellant that chills the parts when it is sprayed on them. The liquid propellant inside the can is under pressure. When it exits the can, it rapidly expands creating a sudden chilling effect. The cold causes the part to shrink a bit, creating movement between the threads or surfaces that allows the penetrating oil to penetrate more easily and deeply between the surfaces. There is no risk of damaging heat-sensitive parts, no open flame to cause a potential fire hazard and no waiting for hot parts to cool off before loosening them. However, the propellant in these products is extremely flammable so it must be used with caution. Also, the user should avoid eye or direct skin contact with the spray because of the danger of frostbite.

Q. What kind of product should I recommend for lubricating fasteners?

A. There are a variety of products that can be used to lubricate a fastener, depending on the application. Penetrating oil, silicone spray, graphite or products that contain teflon, wax or any combination of these ingredients are all good lubricants and can be used to make assembly easier and to keep threaded fasteners and other parts from rusting or corroding.

The threads on cylinder head bolts and other internal engine fasteners, however, are typically lubricated with ordinary engine oil. Motor oil has a much heavier viscosity than penetrating oils and other aerosol products. But is is usually specified to lubricate the threads on cylinder head bolts, main caps and connecting rods. Oil reduces friction between the threads and allows the bolts to clamp with greater force than dry fasteners with dry threads when the bolts are torqued to specifications. Using a lubricant that is too slippery (such as engine assembly lube or an aerosol penetrating oil, for example) may actually reduce friction too much, and increase overloading and breakage when the bolts are tightened.

Most of the torque that is applied to a fastener when it is tightened is used to overcome friction between the threads rather than to apply clamping force. The torque specifications for cylinder head bolts and other critical fasteners are based on a certain amount of friction and a particular type of lubricant (motor oil in the case of most engine fasteners, for example).


Q. What type of additive should be used to remove carbon deposits from pistons and combustion
chambers?

A. A “top cleaner” usually works well for most applications. A top cleaner typically uses a strong solvent to loosen and remove stubborn carbon deposits inside the combustion chamber. The product is usually poured into the engine through the throttle body, or fed into the intake manifold with a vacuum siphon bottle. The engine is then shut off so the product can soak on the deposits for 10 to 15 minutes. When the engine is started again, the loosened deposits are blown out the tailpipe.

Q. Why do fuel injectors get dirty and what can customers to about it?

A. Fuel injectors can become clogged with fuel varnish deposits. This can sometimes happen when gasoline contains inadequate levels of detergents that are added to keep the injectors clean.
To keep fuel injectors clean, it takes about 1,000 parts per million of dispersant detergent in the fuel. Yet as much as 85 percent of the gasoline sold in the US contains only about one-tenth of the required additives. Consequently, fuel injectors, intake valves and combustion chambers all get dirty and require cleaning by adding some type of aftermarket fuel additive to the fuel tank.

Over the counter types of fuel system cleaners come in various formulations. The best advice you can give your customers is to recommend a product that is designed for a particular application. Some additives are more for preventive maintenance purposes and to help supplement the low levels of detergent that are in some gasoline. Other products are formulated to remove deposits that have already formed and may be causing driveability problems.

As always, advise your customers to follow the directions on the product. Typically, a 12 oz. bottle of fuel system cleaner can be used to treat 10 to 20 gallons of gas.

Suspension
Question: When should tie rod ends be replaced?

Answer: Like other steering and suspension parts, tie rod ends have no recommended replacement intervals and are not replaced until they are worn out — which is when play exceeds specifications. For most tie rod ends, that means no visible movement when the steering is rocked back and forth with the full weight of the vehicle on the wheels.

The design life of most steering and suspension parts today is upwards of 150,000 miles. Many parts go the distance, but others do not. Washboard roads that give the suspension a pounding, wet weather and exposure to road salt are much harder on steering and suspension parts than smooth roads and a dry climate.

Many motorists don’t realize they have worn steering or suspension parts until they notice the tires are wearing unevenly. Worn tie rods will change toe alignment and cause the front tires to wear rapidly. Toe wear typically causes a feathered wear pattern across both front tires and sometimes shoulder wear on the inner edges of both front tires. The tie rod ends connect the steering gear and tie rods to the arms on the steering knuckles. All vehicles have two “outer” tie rod ends (a left and a right) that attach to the steering knuckles. On vehicles without rack and pinion steering, there are also two “inner” tie rods (a left and a right) that connect to a “center link.” On vehicles with rack and pinion steering, the rack is connected to the tie rods with “sockets” that are surrounded with flexible rubber bellows.

Most tie rod ends are a ball and socket design, but some late-model Ford pickup trucks have “rubber bonded socket” (RBS) tie rod ends. Some replacement tie rod ends for the Ford RBS applications have a conventional ball and socket tie rod end.

The steering and suspension should be inspected regularly (at least once a year) for potential problems and any time a steering, handling or ride problem is noticed. As a rule, any measurable looseness or visible play in a tie rod end calls for replacement. The condition of the rubber boot on the tie rod end is also important because if it is torn, leaking grease or missing, the joint’s lubricant will be lose or contaminated. Tie rod ends are often replaced in pairs, even if only one is bad, because both have the same mileage. Left and right tie rod ends are usually threaded opposite of one another to allow for alignment adjustments. Special tools such as a tie rod separator or fork may be needed to separate the tie rod ends.Anyone replacing tie rods may also need new tie rods and/or tie rod adjusting sleeves, especially if the old ones are badly rusted or frozen.

Q. What causes “shock fade?”

A. When the piston inside a shock absorber pumps rapidly back and forth (as when driving on a rough road), it creates an area of low pressure directly behind the piston. This allows tiny air bubbles to form in the oil — a process called “cavitation.” The faster the piston pumps up and down, the more rapidly cavitation aerates the oil on both sides of the piston and churns it into foam. The result is a “foam zone” around the piston that offers little resistance and causes the shock's dampening ability to fade.

Most shocks and struts today are pressurized with nitrogen gas to minimize foaming and shock fade. This also provides a firmer, more stable ride. In a twin-tube shock, 100 to 150 psi is typically used though some performance twin-tube shocks that may contain as much as 250 psi inside.
With monotube shocks and struts, a floating piston separates the gas from the oil. Because of the larger surface area, a much higher gas charge is normally used: typically 360 to 400 psi.

Q. Are worn ball joints dangerous?

A. Yes. If a worn ball joint fails and pulls apart, the suspension will collapse, causing a loss of steering control. Worn ball joints often make a clunking noise when the suspension encounters bumps. They can also change camber alignment and cause the tires to lean and wear unevenly.
Ball joints should be replaced if wear exceeds specifications. Acceptable play varies depending on the type of joint and vehicle. There are no standard rules of thumb. Technicians should always refer to the wear specifications in a manual and check ball joint play using the recommended procedure. Jamming a large crowbar between the control arm and knuckle, prying with all your might is not the way to check for wear. Pry hard enough and even a new joint may show excessive wear.

Some ball joints have built-in wear indicators. This type of joint must be checked with the joint loaded (the weight of the vehicle on it). The weight of the vehicle must remain on the tire. Raising the vehicle and allowing the suspension to hang free will not allow the wear indicator to read properly. Placing a jack under the control arm also does not fully load the joint because the weight has to go through the wheel and tire.

On ball joints that do not have a built-in wear indicator, the joints must be unloaded by raising the suspension. If the vehicle has an SLA suspension with the spring over the upper control arm, the upper arm must be supported to take the weight off the joints. A dial indicator can then be used to check radial and axial play in the joints when the wheels and tires are rocked up and down (to check axial play) and back and forth (to check radial play).

Many experts recommend replacing joints on high-mileage vehicles in pairs. Some vehicles also seem to wear out their original-equipment ball joints faster than others, such as Jeep Liberty and Ford and Dodge pickup trucks. More durable aftermarket replacement ball joints with steel bushings and grease fittings are available for most of these applications.

Q. What does an idler arm do?

A. The idler arm is a steering component used on rear-wheel drive cars and trucks that do not have rack and pinion steering. The idler arm is mounted on the opposite side of the chassis as the pitman arm (which is attached to the steering box). The idle arm and pitman arm move in tandem to allow the steering linkage to steer the front wheels.

The idler arm is held in a sleeve bearing that allows the arm to rotate. The bearing wears over time, causing the steering to feel loose. The vehicle may also experience steering wander as it travels down the road. A worn idler arm can also accelerate wear on the front tires.

The arm is usually inspected for looseness by pulling down on it and measuring how much the arm deflects. If play exceeds specifications, the idler arm needs to be replaced.

Idler arm lengths and bolt patterns can vary from one model application to the next, so it may help to compare old and new arms to make sure your customers get the correct replacement part.















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