AUTO GURU - QUESTIONS AND ANSWERS

By Bob Hagin

Q.   This question still comes into my mind a year after my wife passed
away. How did she manage to blow up our Buick Skylark by just backing 
it out of our driveway? The engine caught on fire and exploded a hole 
in the pavement. The car was just serviced. - J.B. Sacramento, CA

A.   I've only come across a situation like yours once and it was about
25 years ago. One of my students had a '55 Chevrolet V8 that he'd 
hopped up but he didn't really understand what he was doing. He hadn't 
tuned it out very well and it was subject to periodic backfires through 
the carburetor when he accelerated hard. His car also suffered from a 
leaking fuel pump that trickled gasoline into the engine's crankcase. 
Eventually, the engine backfired into the crankcase through its funky 
restricted-orifice crankcase ventilation valve and the gasoline fumes 
it contained blew the oil pan down onto the asphalt and burned a hole 
in it. The explosion blew off the valve covers as well and set fire to 
the area under the hood. It would take a detailed and exhaustive 
examination of your Buick to determine the cause of its explosion but 
it sounds a lot like the one I saw happen.

Q.   I own a 1998 Chevrolet Camaro with a V8 engine and an automatic
transmission. I bought it second-hand from a used car lot that 
specializes in high performance sports cars. It only had around 12,000 
miles on it when I bought it and I was told that the former owner had 
sold it in order to get a Corvette. I drive it a lot in my business and 
it now has almost 51,000 miles on it. It works fine and gets great 
mileage for a car of this type but it has one minor but annoying 
problem. When I back up and step on the brakes, I hear a chirping 
noise. I think it comes from the rear brakes but when I took it to my 
regular mechanic, he said that there was nothing wrong with either the 
front or back brakes. I can live with the noise if I have to, but I'd 
like to get it eliminated.                          P.O. Phoenix, AZ

A.   I've perused the internet and found a reference to you problem. It
also affects some Camaros up to 2000 and Pontiac Firebirds of the same 
years. The problem is in the rear brake pads and it's apparently caused 
by friction material being incompatible with the brake rotor material. 
General Motors says that just replacing the pads with its own modified 
pads will cure the problem, but I don't know if an aftermarket pad will 
cure it or not. Although the GM information sheet doesn't mention it, I 
think it would be a good idea to have the rear brake rotors resurfaced 
at the same time. Sometimes they develop a glaze that can make 
replacement pads squeak when they're applied at around-town speeds.

Q.   My 1995 Ford F-250 is used in my business and it gets a lot of
stop-and-go driving around town. The brakes have never been what I 
consider great for a truck this size but I don't drive it very much 
myself. It has always had a lot of brake pedal travel before the brakes 
take hold. Our mechanic assures me that all the adjustments are correct 
and that the pedal travel is within the factory limits. A.B. Seattle,WA
                           

A.   Apparently Ford put an undersized brake master cylinder on some of
its F-250 trucks. The problem is that the internal size of the master 
cylinder is too small which requires a longer stroke on the pedal to 
fill up the wheel brake cylinders and calipers with hydraulic brake 
fluid. The repair is to replace the master cylinder with one that has a 
bigger bore but if you buy an aftermarket master cylinder, make sure it 
isn't internally identical to the one your mechanic is pulling out.