Car Talk

July 1990

Dear Tom and Ray:
I have a 1987 four-cylinder Toyota pick up truck. It has 42,000 miles on it, and I change the oil every 3,000 miles. The last two times I changed the oil, I noticed that there was very little oil in the filter (there used to be a lot). The oil pressure light seems to be OK. It turns off a few seconds after the engine is started. Do you think the oil filters are bad (I bought them from the same store) or is the oil pump the problem? Please help!
John

Beat up old car

TOM: Hey, John. Did you get these oil filters free with your subscription to Time Magazine? It sounds like they work about as well as that phone they sent me. Your filters are suppose to have "check valves" which prevent the oil from draining back into the crankcase when the engine is turned off. The filters you bought either don't have valves (they may be the wrong filters even if they fit), or they have defective valves.

RAY: As a result, when you start your engine, it takes a few seconds for the filter to fill up with oil and consequently, for the engine to reach full pressure. That's why it takes your oil light a few seconds to go off. That's bad. It should go off (and you should have full pres¬sure) as soon as the car starts.

TOM: This problem would be less noticeable on many other cars. Many cars' oil filters are mounted at the bottom of the engine facing up. That way, gravity ensures that the filter is always full. But the filter on your truck is mounted sideways, on the side of the engine, making the check valve crucial.

RAY: Throw these filters away before they ruin your engine, John. And next time you subscribe to a magazine, take the phone. At least you'll know when that doesn't work.

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