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  • TDC - Technical Questions & Answers - June 2005

TDC - Technical Questions & Answers - June 2005

Bruce Caldwell
Jun 1, 2005
Flush Or Fleece?
Q: I drive an '00 Chevy S-10 Extended Cab with the big V-6 and automatic transmission. The truck is my daily driver and I've owned it since new. It recently turned over 60,000 miles. About that same time, I had a brake job done on all four corners. While the shop was doing the brake job, the crew there suggested that I have the brake fluid flushed and replaced. I didn't agree to that, because it sounded like bill padding for such a new truck. Also, the brake fluid didn't look rusty or anything.
Now I'm having second thoughts. The brakes work fine, but I wanted to get an impartial opinion. Should I have my brake fluid changed, or is this a variation on having metric air installed in my tires?
Trevor Taylor, Honolulu
A: As fishy as it sounds, replacing brake fluid on a five-year-old truck isn't a bad idea. We think the shop was offering you an optional service that wasn't mandatory but still a good idea. This type of service falls into the difference between owners who religiously follow service recommendations (including all suggested and required procedures) and owners who just fix things when they break.

Flushing and replacing brake fluid used to be the kind of service one would do to an old truck that hadn't been used for many years. The brake service industry (which obviously has a financial interest along with safety concerns) recommends that modern trucks have brake fluid flushed and replaced every three to five years. The industry bases its recommendations on time rather than mileage. The shorter time limits are for trucks with ABS and those used for heavy-duty applications such as towing.

The modest cost of flushing brake fluid can help prevent expensive repairs to the ABS system. Modern brake systems are more likely to experience high temperatures than older trucks. A cycle of heating and cooling can produce condensation.

Water contamination lowers the boiling point of brake fluid. That can increase brake fluid vaporization under emergency braking situations. The various anti-oxidation additives in modern brake fluids can lose some of their effectiveness over time, which is another reason to flush and replace brake fluid. The fact that you live in a very humid region is another reason to flush your brake system.

Brake fluid is designed to absorb water, so any moisture in the system is spread throughout the system. This is a good thing up to the point where too much moisture accumulates. That's when the brake system should be flushed.

A topnotch brake system is one of your best proactive safety features, so we'd go along with the shop and have your truck flushed.
High Speed Anxiety
Q: I'm disappointed in the performance of my '93 GMC Sierra. It seems to be down on power at higher freeway speeds, say 65 mph and above. It doesn't run rough, but it just seems like it used to handle these speeds much more easily. My two-wheel-drive truck has the 5.7L V-8 and automatic transmission. The engine is completely stock and has about 97,000 miles on it. It hasn't ever had any major engine work done to it. I'm hoping you can supply me with some quick fix for my problem. Thank you.
Slade Neuscom, via e-mail
A: It sounds like you have a basic maintenance neglect problem. It should be pretty easy to fix. The most common sources of problems such as yours are either a lack of air or fuel or the ability to get rid of the spent air/fuel mixture (exhaust gases).

The easiest thing to check is the air intake path. An overly dirty or clogged air filter is a common culprit. While you're checking the air filter condition, inspect the path to the filter. Any debris or restriction in the airbox ducting will hamper airflow. If the air filter needs replacing (and it most likely does), consider upgrading with a high-performance filter such as those offered by K&N Filters.

A more likely source of your problem is some type of fuel-delivery problem. This isn't as easy to check as the air filter. An inline fuel filter that's ready for replacement can restrict fuel flow when demand is the highest (e.g. at high speeds).

Fuel filters are inexpensive, so it's a good idea to install a new one. Be careful and follow the instructions on relieving fuel pressure before disconnecting the filter. Be sure the new filter has its arrow pointing in the right direction.

If replacing the two filters doesn't solve your problem, the next place to look would be the internal gas tank fuel pump pre-filter. It can get clogged with sediment. You could also have a fuel pump that is underperforming. You can test the fuel pump at home, but we'd suggest letting a repair shop do the testing.

If the air and fuel components check out, the next place to look is the exhaust system. Do a simple visual check for any crushed or restricted sections of the exhaust pipe. It's possible that your catalytic converter is failing. A basic home test is to tap the converter with a rubber mallet when the converter is cold. If you hear rattling, have the converter thoroughly checked at a muffler shop. A muffler shop can also check the converter with a pressure gauge hooked up to the exhaust system.

If your catalytic converter is going bad, you may have noticed some other symptoms. A loss of high-speed power is the most noticeable sign of a bad converter, but you may also experience fouled spark plugs or engine pinging. Tapping the converter as mentioned previously can yield a rattling sound. The Check Engine light should come on when the catalytic converter has failed.
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The Leaky Wheel
Q: I bought a '95 Dodge Dakota pickup from a used-car lot. It came with some decent-looking mags, but I don't know what kind they are. I'm not sure if they're aftermarket or factory ones. That doesn't matter, because I'm saving my money for some 18s, or maybe even a set of 20s. Until that time, these wheels will have to do.
My problem is that two of them seem to have a problem holding air. One loses about 10 psi a week, and the other is more like 5 psi. I had the tires checked at a tire store and the guys there said the tires were fine and that the problem was probably the wheels. The store wanted to sell me new wheels, but I still need to wait.
I keep close tabs on the air pressures, but I'd like to fix the problem if it isn't too difficult or too expensive. The tire shop guys didn't offer any repairs, because they seemed more interested in selling me some new rims. Would a can of instant tire sealer fix the problem?
Darrell Yee, Ottumwa, Iowa
A: It sounds like you have a pair of overly porous alloy wheels. This is a common problem with many older factory and aftermarket alloy wheels. The instant tire sealer won't help, because it's designed to coat the inside of the rubber to stop leaks in the tire.

The first thing you need to determine is where the air is escaping. You'll need a cooperative tire repair shop to find the leak, unless you live on a farm with big water troughs.

Remove the wheel/tire combo and inflate it to 40-45 psi. Immerse the unit in a big tub of water and watch for bubbles. Use a grease pencil to mark sections of the wheel where air is escaping.

Dismount the rim. Look at the inside of the rim near the grease marks. It's likely that you won't be able to see any obvious holes. Without removing the grease reference marks, clean the inside of the rim with soap and water. Dry the wheel and then use an aerosol cleaner such as brake or carb cleaner (lacquer thinner on a rag will also work) to super-clean the area.

Cover the suspected porous area with a high-quality silicone sealer. Apply a layer of silicone approximately 1/8-inch thick. Let it cure according to the instructions. Then have the tire remounted on the rim. If the tire and rim were indexed before being separated, you probably won't need to rebalance. Check the wheel/tire combo in the water tank and hopefully there won't be any bubbles. Then work overtime so you can get the new rims.
Milky Way
Q: We had a lot of rain recently and some minor flooding. My '00 Dodge Durango ended up in a situation for a couple hours with standing water up to the axles, and possibly a little higher. I don't think the axles were submerged for any length of time, if at all.
I have access to a hoist, so just to be safe, I put the Durango up and checked the gear lube. I was dismayed to see a milky-looking lube. I changed the lube.
My concern is that I should do something to super-seal the axle. I do my best to avoid deep water, but since we live in a flood plain by a river that overflows its banks almost every year, I need to be prepared. Can you offer suggestions for waterproofing my Durango? I appreciate your help.
Ted Moultray, Carnation, Washington
A: We don't think you had water in your axles. Milky-appearing axle lube has appeared in enough '99-'00 Dodge Ram pickups, Dakota pickups, and Durangos that a technical service bulletin (TSB 03-02-00) was issued on the problem.

What happened is that some axles were assembled with a white gear-marking compound. The compound is used to check for proper alignment of the ring gear with the pinion. The white compound mixes with the normal gear lube, giving the appearance of water contamination. It isn't anything to worry about, but we'd still suggest moving to higher ground when the river rises.
Carbon Copy
Q: Is there an easy way to paint metal surfaces to look like carbon fiber? I built a custom metal console and some big speaker boxes for my tricked-out '02 Chevy Astro van. I'd like to make these items look like they're made out of carbon fiber. I've seen this on other trucks at shows, but I couldn't find anyone to tell me how it's done. Can you tell me? Thanks.
Jeremy Tretheway, San Jose, California
A: We've seen a pretty realistic rendition of faux carbon fiber done using drywall seam tape. This woven tape (usually plastic-based) is available at hardware stores and home-improvement centers. Be sure to get the woven type, not the solid-paper "tape."

Start by spraying a base color. You might want to use a color that complements the rest of the interior. Or, you could use silver for a traditional carbon-fiber look. After the base color has dried, cover the area with the drywall tape. Then spray the top or primary color. This top color can also complement the interior or it could be a dark gray or black for a standard carbon-fiber look.

When the tape is removed, you will see a "grid" or "fibers" from the base color. You can make the surface look more three-dimensional by shading the edges with the darker of the two colors. An airbrush works well for shading. You should protect the "carbon fiber" with a clearcoat. If you notice, the carbon-fiber trim in late-model cars has a glossy look to it. The clear will have to be color-sanded and buffed.

Painting faux carbon fiber is more art than science, so you might want to practice on an inexpensive blank metal sign. Any clean and prepped sheetmetal will work. Besides mastering the general technique, this is also a good way to experiment with different color combinations.
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