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The Car Doctor - January 10, 2008

Email|Print| Text size + By John Paul, AAA Car Doctor
January 10, 2008

Q. I have a 1989 Ford Escort, which I purchased new. I recently had it serviced at a local Chrysler dealer, where the oil and filter were changed along with the transmission fluid. Would it cause a problem if "Mopar" transmission fluid was used?

A. The Ford Escort uses Mercon fluid, and the later model Chryslers use Mopar ATF type 4; these two fluids have different characteristics and should not be substituted for one another. Check with your dealer to see what kind of fluid was used. If the Mopar fluid was used, I would ask the dealer to flush out the transmission and have it refilled with the proper Ford Mercon fluid.

Q. I have a 2000 Honda Accord with a six-cylinder engine. The car has about 85,000 miles on it. During a recent trip to the dealer the service manager told me I should bring the car back at about 90,000 miles to have the timing belt, water pump, drive belts, and the valves adjusted. I'm using more gasoline now than when the car was new; do you think all this work will help improve my car's fuel mileage?

A. According to AllData, the information database that I use, the timing belt should be replaced at 105,000 miles and the water pump inspected at that time. The valves should be adjusted every 30,000 miles and the drive belts inspected at that time. With the exception of the valve adjustment, the other work is preventive maintenance; although quite necessary it won't affect fuel economy.

Q. I have a 1990 Ford Thunderbird with anti-lock brakes. I recently lost the power assist to the power brake system. This happened with no warning and no warning lights. Can you point me in the right direction as to what to look for?

A. Your Thunderbird, unlike most cars on the road today, uses a hydraulic power booster rather than a vacuum brake booster. Testing this system requires the use of a "scan" tool. The booster contains a control valve, located in a parallel bore above the master cylinder. Under normal braking, the control valve modulates pressure of brake fluid from accumulator to rear brakes. The control valve also modulates boost pressure to master cylinder pistons. Since this is potentially a safety issue, I would have the car towed to a repair shop.

Q. I have a 1996 Jeep Grand Cherokee, and for the past 8,000 miles the coolant light has been coming on. Although the dealer has tried to fix the problem a second issue has started: The check engine light comes on and the Jeep bucks. Recently the crank shaft sensor was replaced but the Jeep still bucks for the first five minutes of driving. The mechanic is stumped; do you have any ideas?

A. Your repair shop needs to start with diagnosing the "check engine" light. This light is indicating a failure of one or more of the computer sensors. The two common issues are faulty oxygen sensors and a faulty crankshaft position sensor. Although this was replaced once, in this case I would suggest only a factory part.

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