Squeaks and rattles

Q--With the ever-increasing use of plastics in instrument panels and dashboards, what can I do to stop those annoying squeaks and rattles? Is there a spray material that can be used? If so, what is the name and where can it be purchased?

A--Squeaks and rattles, officially called NVH (noise, vibration, and harshness) in the industry, are the bane of many a mechanic. The book time usually doesn't cover his actual time. As a result, plenty of cars get the "sunshine treatment." The car is parked on the lot for a day then the customer is called and told it has been fixed. Bunk.

I have had a modicum of success using silicone spray, but the benefits are temporary. In the industry, they use a variety of peel-and-stick products, usually having one felt side. Check out your hardware store for things like green felt dots that protect furniture to thicker felt pads for chair legs. The fuzzy (loop) half of Velcro also works well for some applications.

I suggest using a business card as a wedge or bushing during the down-the-road diagnosis. It doesn't matter if the sun isn't shining.

Airy issues

Q--The dealer told my brother that his tire had a slow leak and the best way to fix it was to put nitrogen in all the tires for $20. My brother got a flyer with all the benefits of nitrogen in tires: Better ride, better gas mileage, etc. Isn't this a scam? Or can you please explain how nitrogen helps to a retired engineer. Would you later top it off with air? Or try to find nitrogen someplace?

A--I keep getting questions like this and feel compelled to keep answering until the word gets to everyone. Yes, there are some benefits to nitrogen, but I think that they are minimal compared to the price. Yes, rubber is less permeable to nitrogen molecules than to oxygen molecules, but you must remember that air is roughly 80 percent nitrogen and less than 20 percent oxygen to begin with.

GM Technical Service Bulletin 05-03-10-020 reads, in part, "General Motors does not oppose the use of purified nitrogen [but] the theoretical benefits to be reduced in practical use due to the lack of an existing infrastructure to continuously facilitate inflating tires…. Given those theoretical benefits…the realized benefits to our customer of inflating their tires with purified nitrogen are expected to be minimal."

It is your call, but if it was my brother, I would suggest checking and adjusting the pressure as necessary and getting the tire repaired.

Tranny changes

Q--I own a 2005 Camry with a four-cylinder engine and automatic transmission. The car has 15,000 miles on it. At what time do I need to change the transmission fluid? The owner's manual says to check it at 30,000 miles. The dealer at the 15,000 mile maintenance check says it is not red any more and it should be flushed.

When checking the transmission dipstick I did notice that the fluid is just a bit darker red, but it is clearly red. The fluid on the dipstick was not black or brown. How red or not red must the transmission fluid be before it must be changed?

A--First off, the color of the fluid isn't much of an indicator anymore. Both oil and transmission fluid darken rather quickly nowadays. I would certainly check the fluid level regularly. I would also sniff it for any signs of scorching, a sure sign that it should be changed. But my rule of thumb is to change it every 50,000 miles. Of course, doing it more often hurts nothing but your budget.

Seeing lights

Q--I've got a problem with my 1992 Dodge Dakota pickup. Whenever I depress the brake pedal the left rear brake light comes on when the lights are off, but it comes on dim when the lights are on. The tail lamps are on but the left rear is dim, not as bright as the right rear.

When you depress the brake pedal while the lights are on the left rear light goes out completely. When you turn the right turn signal on when the lights are on, the left rear light goes out completely. I've replaced the bulb, I've replaced the flasher, and I've checked for continuity in the bulb socket. The rear bulb is a dual-filament type in which one serves as the tail lamp and the other as the turn signal/brake light. This setup seems simple enough but something is going wrong with mine. Any suggestions on this problem?

A--Wow. That sounds crazy and you are probably thinking that this may be a big-bucks repair, huh? There is good news: It isn't. There is simply a bad ground in the brake lights circuit.

When you turn the lights on, the circuit for the tail light filament can't find a convenient ground so the current passes through the filament for the brake light then over to the other side of the truck before completing the circuit. Fix the ground and you'll fix all of the problems, cheap.

A pat on the back

Q--The first new car I bought was a 1978 Honda Accord. The manual stated that the engine oil should be changed every 7500 miles or a least twice a year. Thinking I would keep the car forever, I changed the oil every 5000 miles, using brand-name multi-grade oil. I drove the Accord well over 100,000 miles.

Every new car I have had since: 1989 Honda Accord (over 100,000), 1999 Toyota Camry (at 90,000 - still going), I have always changed the oil at 5000 miles using normal multi-grade oil. I always felt that the 3000-mile mark became popular with the introduction of fast lube shops. What is your take?

A--My take is that you may pat yourself on the back. I also think that 5000 is probably a good number for many drivers. Engines have gotten tighter; there is less blow-by and less contamination of the oil.

Along with other factors, this is why oil-life monitors are now permitting us to drive 10,000 miles or more before oil changes. One caveat, however: If your driving style fits the "severe" category, change it by the book.

New HEPAs

Q--My Dad has an '03 Buick Park Avenue Ultra which needs the HEPA filter replaced or cleaned. He asked me how to do it but I have never attempted it. Can you tell me how to do this or send me to a site that can tell me?

A--The cabin air filter on your father's Buick is located under the dash, to the right of the accelerator pedal. You have to open the trap door, and then take the filter out in three pieces. During installation, be sure to attach each piece by engaging the rails on the filters. It is a bit tricky for someone who has never done it before.

By the way, HEPA stands for high-efficiency particulate air filter and they are found in many devices including some vacuum cleaners.

Due to the large volume, Bob Weber is unable to answer most questions sent to The Car Connection each month. Some may be answered directly, where possible, and others will be included in future columns if the topic is deemed interesting. Be sure to include your real name and full address (city, state, province, country, etc.) when sending your questions.
 
Weber, a self-proclaimed swell guy, is an ASE-Certified Master Automobile Technician, freelance writer and former editor of Super Automotive Service magazine. His column, "Motormouth," appears weekly in the Chicago Tribune. He enjoys good tequila, good cigars, and good times. A chemistry school dropout, he still concocts compounds in the kitchen and makes a mean pot of chili. He and his wife live near the Blue Ridge Mountains of Virginia.

E-mail Bob your questions at Mechanic@thecarconnection.com.