there is a suction through oil cap. when it is on the engine makes a high pitch. on 2009 Volvo C70

when the cap is off the sound stops and there is a suction at the opening from hole where oil goes.

by in Ashland, OH on April 16, 2013
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2 answers
ANSWER by , April 16, 2013
The suction is normal. It sounds like the seal in the oil cap is bad. Usually you can replace the O-ring. If you can't just order a new oil cap, shouldn't be more than 10 bucks.
ANSWER by , April 16, 2013
Engine breather is stopped up! Pcv system cant pull in fresh air through it.