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Automania/Repair & Maintenance
AUTO QUESTIONS AND ANSWERS FOR WEEK 30
by Bob Hagin
Q. I have a 1994 Jeep Grand Cherokee which I purchased new. It has a V8 engine, power steering, automatic transmission and full-time, four-wheel-drive. It has about 82,000 miles on it. When I turn it sharply to the right or left, there is a scrubbing and bumping noise in the front and it feels like the brakes are applying. I was told by the service manager that it could be caused by the power steering pump or trouble in the transfer case. Also there is a roar in the rear of the vehicle that sounds like bad tires but the tires have been changed twice with no change in the noise. I was recently told by another car dealer that this is a common problem with the Grand Cherokee.
A. It's pretty hard to analyze a problem through the mail but if I had to guess on the front-end noise, I'd bet on one or both front universal joints but analyzing it shouldn't be too much of a trick. An automotive stethoscope is built like those used by medicos but with a "wand" on the end instead of a pad. Have the mechanic put the vehicle on a rack and use a stethoscope on the power steering pump with the engine running, the drive train engaged and the steering wheel put to full lock left or right. You might want to drain the transfer case while it's up in the air and check the drained oil for bits of metal or whatever with a mechanic's retriever magnet. While it's up, have him check the differential and the ends of the axle housings for noise too. Sometimes you have to stop guessing and get down to the nitty-gritty.
Q. I own a 1983 Mercury Capri with a 302 HO engine which has about 142 thousand miles. I have owned the car for about a year and depend on it for daily transportation. I am using 20/50 weight oil and have 14 pounds of oil pressure at idle and 30 at 2000 RPM. The problem is that using the recommended spark plugs, I get about 100 miles before the spark plug in cylinder #8 becomes oil fouled. It has relatively new intake manifold gaskets, valve stem seals, fuel pump and water pump. I cannot see any coolant in the oil nor oil in the coolant. I had a dry-and-wet compression test done and the results were 75 dry to 130 wet. The readings on #8 were 90 and 100. The car is reliable and I have read about future collectible potential of this relatively rare car. If the engine does need an overhaul, should I get a new, used or remanufactured engine, or should I have this one rebuilt?.
A. When doing a compression check "dry," ideally the compression
pressure differences shouldn't vary more than 10 percent between the
cylinders. Since they run from a low of 75 psi to a high of 100, you've
got a red flag already. When you squirt oil in the cylinders to seal up
ring leak, Ideally the pressures in each cylinder shouldn't raise more
than 10 percent so you got another red flag there. The problem with the
one fouling spark plug could be rings or worn valve stems so you're
obviously facing a major tear-down. Since you're aware of the possible
collectibility of your Capri, better stick with rebuilding the present
engine. Having everything "original" ads a lot to the value of a
collectible vehicle as time goes by.
Q. I'm an avid amateur auto mechanic and do a lot of work on cars
owned by friends and neighbors. I don't get paid for it and do it as
relief from the boredom of my desk job for the government. I subscribe
to all the auto magazines but I've found that they are more involved
with new car tests and doing hop-up work that technical tips and
information for professional repair mechanics. Is there a publication
for mechanics working in the trade?
A. The only one I know of is "Motor" and it's strictly trade-oriented. Its address is 645 Stewart Avenue, Garden City, Ny 11530.
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