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December 20, 2007

Email|Print| Text size + By John Paul, AAA Car Doctor
December 21, 2007

Q. I received an e-mail from a local dealer promoting the benefits of filling my tires with nitrogen. I had heard about this years ago, but I thought it applied to race cars only. They charge $40 and, according to the e-mail, the tires will last longer and fuel economy will be better. What is your take on nitrogen? I have read that Jay Leno has his fleet of cars and motorcycle tires filled with nitrogen. Would you put nitrogen in the tires of your car?

A. Lets start with the air that is in your tires right now. Air is primarily made up of two elements, nitrogen and oxygen. Nitrogen makes up 78.05 percent of air and oxygen another 20.95 percent. The remaining less than 1 percent is argon and other inert gases. Nitrogen molecules are "fatter" than the molecules in air so they don't tend to seep out of the tires. Since the tires will remain at the correct inflation longer, the tires should last longer and fuel economy will be improved. That said, this would not make mileage and economy any better than if you kept your tires properly inflated with plain old air. Would I put nitrogen in my vehicle tires? No, but I'm cheap and don't host a late night talk show.

Q. I have a 1999 Jeep Grand Cherokee, and this weekend the key did not turn in the ignition. What could cause this to happen?

A. If you couldn't turn the key, it could be due to excessive pressure on the ignition lock. This can happen if you shut the vehicle off with the wheels turned on an angle. This causes a great deal of pressure on the ignition switch. Whenever possible, shut off your truck with the wheel in a straight-ahead position.

Q. I just had my brakes fixed three months ago. Now, when I step on the brake it sounds like a plate dropping. When I finish stepping on the brake, the sound stops as if the plate had stopped spinning and landed. Could this be something other than the brakes?

A. The noise could be something other than the brakes, but at this point I would bring your car back to the garage that serviced the brakes. If the noise varies with the vehicle speed and quickens the faster you drive, the problem could be the brakes, an axle or wheel bearing. When you bring the car back, road test it with a technician so they can hear the same noise you hear.

Q. My 10-month-old Toyota FJ Cruiser, with only 7,000 miles on it, is starting to chip paint in a few spots on the forward pillars. The dealer said this was caused by pebble strikes. He gave me a vile of matching blue touch-up paint. I'll read the directions carefully before applying, but are there any tips you can give me about applying touch-up paint?

A. Like all painting projects, the key to doing a good job is in the preparation. Start with cleaning the surface to remove any wax buildup. If the chip is down to bare metal, sand the area lightly and apply a primer. When using touch-up paint, apply several light coats until the chip is filled in. After the surface has dried, some light sanding with very fine sandpaper may be necessary. Finish the repair with a little coat of factory-style clear paint. After about a month (or as recommended by the paint manufacturer), buff and wax the repaired surface.

Q. Recently I purchased a 2002 Chevy Venture van. The other day I noticed a front parking and turn-signal bulb just went out. I bought a new bulb, thinking it would be no big deal. This is the first van I have owned and I'm dumbfounded as to how I can put in the new bulb. I opened the hood and thought I would just have to remove the coolant reservoir to get at it. After unbolting and moving this to the side, it looks like a bunch of other stuff has to be removed to get at this bulb. Is this the only way that bulb can be replaced? If it is, this will be my last van, or least one that is designed like this.

A. To replace the turn-signal bulb, you need to remove the headlight bracket. This is done by removing the wing nuts that hold the bracket. Once you have done this, you should be able to access the bulb.

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