Whining noise in engine. on 1998 BMW 740iL

Can take oil cap off while running and noise stops, could this be a pcv valve. Have checked idlers and all belts.

Asked by for the 1998 BMW 740iL
It appears to be a pressure issue inside the crankcase. Check for vacuum leaks and if it has a pcv valve, replace it.
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I have the same problem , weird., i dont know why? remove the dip stick and the whinning , spaceship sound will end...replace it, whining sound is even loader. Help us , who really need..
I finally took it in and they replaced the intake gaskets and the noise and running rough stopped. Been running great since.