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Automania/Repair & Maintenance
AUTO QUESTIONS AND ANSWERS FOR WEEK 26
by Bob Hagin
Q. I have an '89 Mercury Sable station wagon with 51,000 miles on it. It gives off a sulfur smell at various times and it also surges when I have my foot on the brakes at stop lights. This occurs every two or three months. I am the only driver of this car and I have it serviced regularly. I use unleaded 87 octane gasoline.
A. That sulfur or rotten-egg smell you're getting comes from the sulfur content in your gasoline that's turned into hydrogen sulfide in your catalytic converter. This usually occurs because your engine is having a periodic misfire that dumps unburned fuel into the catalytic converter which causes it to overheat (sometimes they glow red-hot) and produce hydrogen sulfide. It's also possible that your engine is running "lean" (slightly less fuel than is needed to support complete combustion) which can usually be rectified through a tune up or the repair of something as simple as a intake system vacuum leak. As an experiment, try changing your brand of gasoline. The fuel you're using may be on the high-side of the legal sulfur limit.
Q. My second car, a 1963 Plymouth Valiant coupe, is really my hobby. It is powered by a slant-six engine and has an automatic transmission that has the push- button system of shifting. I've had it for many years (I bought it from the estate of an old friend who passed away) and have kept it up very well. I don't drive it very much but I like to use it on trips out of town. A couple of months ago, my regular mechanic was on his annual vacation and the back brakes were making noise. I took it to a new car dealer's shop where they replaced the rear brake shoes, one front brake hose and resized all the brake drums. I took a trip of several hundred miles, came home and let the car sit for a week or so. When next I drove it, the brake pedal went to the floor immediately. I nursed it home and had it towed to the shop that did the brakes. The mechanic there told me that one of the rear brake cylinders was leaking and that the charge for replacing it would be $135. Why did the rear wheel cylinder leak after it was just worked on?
A. When new or relined brake shoes are put on drum brakes (especially on an old-timer like your car) the mechanic should always either replace the brake hydraulic cylinders or replace the sealing cups in the originals. The new shoes are thicker and they push the sealing cups deeper into the cylinders and across the rust and debris that accumulates there. This can cause small nicks in them which the fresh brake fluid installed during the bleeding process leaks through, saturating the new shoes. It didn't happen in front because the old thinner shoes were left in place. This problem doesn't occur much on disk brakes because the cylinders (calipers) are built differently. To do the job right on your car, all the cylinders should be rebuilt or replaced, new shoes put on the rear to replace the saturated ones, and maybe a replacement or rebuild on the brake master cylinder. Most brake experts recommend periodic flushing out the old brake fluid to avoid this.
Q. I recently had new tires put on my '90 Ford Taurus V6 at a wholesale discount membership warehouse. The car had 88,000 miles on it. I was later told that the wheels must always be aligned when new tires are installed but the store where I bought them doesn't do alignments. The tires seem OK so is it necessary to get the wheels realigned?
A. An alignment check of the wheels (both front and rear) when new tires are installed is a precautionary measure. If your old tires were wearing evenly, the alignment is probably OK - but it's risky. Check them for six months and if the wear is uneven, have the job done.
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