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Automania/Repair & Maintenance

AUTO QUESTIONS AND ANSWERS FOR WEEK 48

by Bob Hagin

Q. Our car is a 1995 Oldsmobile 88 model with a 3.8 liter V6 engine and an automatic transmission. It now has 34,442 miles on the odometer. I've always changed the oil and the oil filter every 3000 miles. I've always used one particular brand of filter and 10W30 motor oil. When the engine is cold and the car sits out all night, the engine has a small knock until the engine oil pressure comes up. After that first starting, the rest of the day there is no knocking and it is OK. Why does this happen and is it something that I should be concerned about?
O.S. Fontana, CA

A. Any abnormal or unusual engine noises is cause for concern. You don't mention how long the engine noise has been present but it's possible that it started when you began doing your own servicing. If this is the case, it's possible that the original-type oil filter has a built-in oil pressure restrictor valve that holds the pressure in the system when you shut down the engine. Change to an original-equipment filter as a cheap test to see if the noise is eliminated. It's also possible that the engine's oil pressure relief valve is faulty and is leaking off its residual oil pressure. Hopefully this is the problem since deeper issues could include pistons that are "slapping" before they warm up or hydraulic valve lifters that are bleeding down. Try a can of one of the many internal engine cleaners on the market. It may free up lifters that might be sticking in a slightly open position. If you want to try to pinpoint the exact location and point of origin of the noise, most auto tool makers make an automotive stethoscope that's similar to the ones used in the medical field. But you'll have to be quick and get it identified before the engine warms up.

Q. My 1993 BMW 318i sedan has developed a slight amount of noise and vibration in the front end as well as an equally small amount of play in the steering. I've taken it to the mechanic who usually works on our domestic car but he can't pinpoint the problem. He suspects that the problem is in the suspension ball joints but he says that the wear on the lower ball joints is very small.
K.D. Sparks, NV

A. Your mechanic's diagnosis is no doubt correct, according to the BMW mechanics that I've talked to. They say that if there is any discernible wear in the lower ball joints or even if the rubber boots have separated at their bonding with the metal shroud, the only cure for your shimmy is to replace them. After the job is done, have the front-end alignment checked to make sure that the toe-in, etc., is within specifications. If this isn't done, your BMW might eat up tires at a rapid rate. Suspension systems, both front and rear, don't have to be very far out of alignment to not only produce rapid tire wear but have an effect on how the car handles and how it holds the road.

Q. Since I bought my '87 Chevrolet Camaro IROC-Z as new, I've had to replace the radiator three times. I possibly could have had the original repaired but I want to keep the car in as good condition as possible. I like the car and want to keep it as a collectible vehicle. Why does my car have this problem? It starts by a slight leakage at the seams.
D.D. Cleveland, OH

A. Some of the reasons that radiators fail is that the old antifreeze/ coolant breaks down, the water in the mix has a high mineral content (distilled water would help), or the engine and chassis grounds aren't clean and tight. When these things happen, the cooling system develops a galvanic action caused by the hot water and metal parts of the engine forming a low-voltage battery and the "soft" metals in the system are eaten up. There's a radiator cap on the market that has a built-in "sacrificial" magnesium anode built into it that degrades instead of the solder in the radiator. You can call the manufacturer at 925-689-6214.

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