This is a famous noise that some of you BMW owners have heard,,,,the check engine light was on,,,,the car had a lean mixture on both banks,,,,I test drove the vehicle and there was no noise,,,I also had the car idling for about 15 minutes,,,,still no noise so I checked fuel pressure was ok,,,I then smoke tested the intake system for any leaks,,,,no leaks were found,,,,I then started the engine again and within 2 minutes it started to whistle,,,,,I then tried to remove the oil cp while the engine was idling,,,,,the oil cap was very hard to remove,,,,but once I opened the oil cap the noise went away tell me what the problem was,,,,the valve cover is bad causing to much vacuum inside the engine,,,,when this happen that whistle noise is coming from the rear engine seal,,,,air is being sucked pasted the rear engine seal.
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bmwtechnician 
Thanks for sharing! Could you please help me to get the crankcase vacuum spec for 2006 525xi E60 N52 engine?I am seeing increased oil consumption and would like to measure crankcase vacuum before doing anything.Thanks
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I believe it 30 mbar,,,,check the oil cap if it easy to open while car is idling,,,,there should be some vacuum,,,,,you should try and smoke test the intake system,,,,there might be a crankcase vent under the intake manifold,,,,there is a vent pipe at the rear of the valve cover that goes to it,,,,,if that crankcase valve is leaking,,,that could be your problem
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Thanks for the info!! Will do that..
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Hi,
Thanks Andreas as always for your very helpful site!
For the last few weeks I’ve noticed a high pitched noise coming from the car… I’m unable to pinpoint from where.
It occurs in two ways.
1- after spirited driving it is a constant whistle when slowing down (brakes not activated) and very low compression.
2 – after the car has been driven for a while, upon shut down the whistle is heard. It is as if there is a release of pressure. See linked video of this happening.
The car is a F10 2011 550i. I had rear main seal changed a few months ago so don’t think it’s that.
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I don’t see any linked video,,,,so besides that it could be your vent hoses on top of your engine might be cracked,,,check out N63tu vent pipe on my blog can help
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https://www.dropbox.com/s/vyqsuxeel6uvcss/IMG_0181.MOV?dl=0
Here’s the link I thought it was added. I will check vent lines.
Thanks
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