PCV valves (archive)

Just bought a beautiful '90 750il, 125k miles but it burns a quart every 400-500 miles. Am I looking at a complete rebuild or valve/valve stem seal job? The only time I notice oil burning/smoke is during hard accel. after idleing for a few minutes. No puddles under the car, although the underside appears moist, only visible significant amount of oil is in the hollow in front of the oil filler cap. The car does exibit some "blow by", when the oil filler cap is removed while running, air does blow out of the filler. What is a repair going to cost? Otherwise the car is in excellent cond. I paid $6800 should I fix or bail out?

Usually excessive oil consumption is caused by the PCV valves being clogged/worn. You could of course try to clean them but they're very cheap so it's pointless to clean them.

What they do is regulate pressure in the valve chambers. When they're clogged there's pressure buildup and oil leaks to cylinders and burns plus leaks out through gaskets.

Search the database for PCV valves or scroll down, think there was something about it on this page as well.

Mine burns next to nothing at low rpm but when I beat the car it sucks incredible abounts of oil. Just bought the valves and gonna see how much changing them helps as soon as I get the car out of the shop.

Hope this helps,

Henkka

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