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Automania/Repair and Maintenance
AUTO QUESTIONS AND ANSWERS FOR WEEK 24
by Bob Hagin
Q. Two months ago I bought a 1987 Subaru GL 10 All Time all-wheel-drive turbocharged sedan with the 1.8 liter engine and a five speed transmission. The car belonged to the wife of a friend of mine and she had been the only driver. There was very high mileage on the digital odometer (206,000 miles) but they gave me all the documents that went with a new engine that they had installed. The new engine has only 47,000 miles on it. Everything on this car is like brand new except for an unusual noise that comes from the exhaust system. I took it to a Subaru dealer and the shop changed the turbo gasket which was burned out. The problem was gone for a while but has started again. We don't have an overheating problem on the engine so how is it possible to have to have an overheated turbocharger with a normal engine temperature?
A. Traditionally, turbochargers don't have a very long life expectancy and I'm surprised that the one on your Subaru has lasted 200,000 miles. A turbocharger get very hot since exhaust gas operates its "hot" side and it runs at very high speeds (20,000 RPM in some cases. If they overheat, they usually simply freeze up and/or make a lot of noise. I don't think that the gasket on your turbo burned out so much as it blew out. Next time it's replaced, have the technician check its mating surfaces to make sure that they are perfectly flat and clean and that the securing nuts are tightened correctly. I've always felt that turbocharging a small displacement engine to gain competitive power is "band-aid" technology and I'm personally pleased to see that they have lost favor with the auto makers who are now going to high-technology (multi-valves, variable cam timing, etc.) to produce satisfactory power.
Q. My 1993 Chevrolet S-10 has a five-speed transmission and 54,000 miles on the odometer. Lately it has begun to sound as if I were driving it at 60 MPH in second gear even when I'm in fifth. It idles fast and sometimes continues to do so for 60 to 70 miles or more. The roaring sound can be easily heard inside even with the windows rolled op tightly. Sometimes the roar will idle down after several miles and sometimes it will subside as I drive along. It will also occasionally waver up and down when I'm driving at a constant speed.
A. The cooling fan on an engine uses a lot of power and to avoid excessive loss, the engineers design in a thermostatic control system to shut down the fan (let it free-wheel) when the engine is at normal operating temperatures. It reengage when its temperature goes over a predetermined limit. Most thermostatically controlled fans use a viscous (thick liquid) clutch in their hubs that thickens when things get hot and makes the fan work. When the fan engages, it makes a lot of noise (like an electric house fan - but more so) and I think that's what you're hearing. Have a mechanic check the fan clutch for correct temperature engagement and if it's functioning correctly, your engine underhood temperature may be going too high for whatever reason.
Q. We have a 1993 Plymouth Voyager with the V6 engine and around 50,000 miles. Lately we have noticed that the yellow ABS warning light stays on quite frequently while we are driving it. Although it doesn't seem to have any brake problems, we took it to the mechanic that has always maintained our cars for a brake checkup. He found no problem with our van and is at a loss as to what to do to alleviate the problem.
A. I think that your problem is more electrical than mechanical. Have your mechanic do a diagnostic check on the connections at the ABS wheel speed sensors but you may have to take it to a Plymouth dealer if you want to try for a warranty repair. There was a revision done the wheel sensors and they may need to be replaced to cure the problem.
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