Hello Everyone,

I recently purchased a used 2009 BMW E60 528i xDrive when my previous vehicles engine died. I've had BMW's in the past and I'm glad to be back into one for my daily driver but my vehicle needs some TLC.

This is the second time this has happened to me so far - If I turn off the engine and restart the sound stops and doesn't come back. The first time it occurred was a month ago.

Quick Information:
Engine is the N52
Coming up on 120,000 miles on vehicle
My Guess - Belt Tensioner Bearings?

Whats your guess?

 

Does the pitch change when you speed up the idle?

 

who's high pitch?

 

It sounds like the oil separator. Try to take the oil filler cap off while running if its hard to take off then its is the oil separator.

 

If it's on the right side down low it is probably a belt pully bearing near the air conditioner compressor
Take off the belts and start the engine again to see if the noise goes away