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Automania/Repair & Maintenance
AUTO QUESTIONS AND ANSWERS FOR WEEK 38
by Bob Hagin
Q. I have a 1989 Toyota pickup truck that I bought second hand. It has the four cylinder engine and the speedometer has 167,000 miles on it. I'm pretty sure that it has the original engine. Since I got it eight months ago, it has used about a quart of oil every 1000 miles or so. I watch it very closely to make sure that it doesn't run out of oil. There isn't any oil drippings under the engine and there isn't any oil on its underside so I'm pretty sure that there isn't a leak. The only thing I see wrong is that in the morning, a lot of blue smoke comes out of the tailpipe. I've talked to mechanics and some of them say that the engine needs to be rebuilt but others say that the engine just needs seals on the valves. Is there a way to figure out what's causing the oil to go away without taking the engine apart?
A. You may not be up to doing the job yourself but there's a home- mechanic procedure that can pretty well pinpoint the problem. With all the spark plugs removed, the throttle blocked open and the secondary side of the ignition system disabled, take a compression check of each cylinder. Get the readings and jot them down. The lowest should be no less than 10 pounds per square inch lower that the highest. If these are within specs, squirt no more that a teaspoon motor oil into cylinder number one and get a second compression reading. Then do the rest of the cylinders and if any of the second readings raise more than 10 pounds, the piston rings are suspect. But the most likely cause of the oil usage is worn valve stem seals which are causing the blue smoke before the engine and the catalytic converter warm up. The seals can be replaced without removing the head but it's very tricky and you should hire out the job. If the head has to come off, replace the timing chain too.
Q. My '89 Nissan Sentra two-door sedan has over 150,000 miles on it. Gasoline is getting into the oil. Can you tell me how it's getting there and what is wrong? The problem is driving me crazy.
A. I assume that you've been checking the oil level and are assured that the level on the stick is raising. There's always a small amount of fuel that bypasses the piston rings and contaminates the oil but the positive crankcase ventilation system is designed to pull those fumes back into the intake manifold. From there they're reintroduce into the combustion chambers where they're burned. If your oil dip stick just smells like gas as opposed to recording a raise in the oil level, I'd check out the PCV system to make sure it was clear and operating correctly. You could also have a problem with leaking fuel injectors or a cold-start valve that's sticking. On a vehicle that uses a mechanical fuel pump I'd suspect a ruptured diaphragm which would push a small amount of fuel into the engine through the operating lever hole. If you're in doubt, it's possible to have an oil sample tested for gasoline contamination and there's usually a testing lab close to major airports.
Q. I've always done a lot of my own services on my cars for many years and this includes changing the antifreeze. The antifreeze I've always used is green. I was looking over the new car of one of my neighbors and found that his antifreeze is orange. According to his owners manual, it doesn't ever have to be changed. Can I use this stuff in my car?
A. All antifreezes contain chemicals that inhibit the corrosion of the various metallic engine parts (cylinder head, engine block, radiator, water pump, etc.). In "regular" antifreeze, these additives become inactive over time and replacing the coolant is the fix. It's not a good idea to mix the two but according to its makers, it's OK to use after a complete change of coolant which would include the heater core. Long- life antifreeze has the added advantage of extending water pump life.
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