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Automania/Repair and Maintenance
AUTO QUESTIONS AND ANSWERS FOR WEEK 21
by Bob Hagin
Q. I have a 1993 Pontiac Grand Am that has the Quad 4 four cylinder engine. After a drive of no more than 15 miles, it begins to spit out a small amount of coolant. What could be causing this? I don't see a pressure radiator cap.
A. I haven't come across a car that didn't have a coolant pressure regulating system since I last worked on a friend's Model A Ford so I'm sure that you car has one of these devices somewhere near the coolant reservoir. Usually the coolant pressure is maintained at between 14 and 17 pounds per square inch and this raises the boiling point of the coolant considerably. If the regulator fails and the boiling point of the coolant drops, some of it is boiled out so check the regulator first to see if that's the problem. Some of the other problems could be a slight leak from one of the combustion chambers into the coolant passages in the head or block which would allow burning fuel to superheat the coolant in that area and blow out some of it. If you're not a mechanic yourself, better take it to one (maybe a shop that specializes in radiator repairs) and have it checked out. Those Quad 4 engines are a slick design but somewhat on the fragile side.
Q. I recently purchased a 1979 Class C RV with a Ford 460 CID engine, supposedly with only 60,000 miles on it. After traveling approximately 100 miles, white smoke momentarily spews from the right tail pipe when making left turns. After three or four of these episodes, a quart of oil is burned. I had a shop run a compression test and also checked all the other obvious areas including the heads, pistons, master seal and valves. All were fine. I stopped at an out-of-state Ford dealership recently. They were unable to look into the problem but the mechanic stated that it might be the PCV valve sticking in the manifold. I'm told that it's a big job just to check it out. Is it reasonable to check into the possibility that the PCV valve is sticking? Are there other options to explore?
A. Using a quart of oil every 300 miles or so is a lot and it usually gets worse. You don't mention the method that you mechanic used to check the engine compression but I hope he did a comprehensive cylinder pressure leak-down test too. It's lots more accurate that doing an electronic oscilloscope test. The valve guides or the valve stem seals might be worn and these are hard to analyze short of a cylinder head tear-down. If a vehicle sits around a lot between uses as is often the case with a recreational vehicle, varnishes sometimes build up on cylinder walls and piston rings and excessive oil usage can result. Sometimes an engine flush can help and even just changing to a single viscosity oil can reduce oil consumption. In view of the other things that might be causing your problem and the expenses that could be involved, checking or changing the positive crankcase ventilation (PCV) valve is an cheap job.
Q. My 1996 Dodge Caravan has about 28,000 miles on it and it has a strange feeling to the brakes when I apply them at very low speeds like five or 10 MPH. There's a slight pulsation to the pedal like its being pumped very gently. It's so small that I don't want to take it to a shop and be charged for being told that there's nothing wrong.
A. I recently read a Chrysler factory bulletin that describes your problem as being related to your anti-skid brake system (ABS). The speed sensor on one of your brakes may be misadjusted and reading zero MPH slightly before the others which would trick the ABS into action. Chasing it down is a bit tricky so it might be a good idea to take it to a shop that understands the problem and how to cure it.
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