Z4 3.0i - Whistling Sound
 

Hi guys,

I have this whistling noise when 1,000~2,000 rpm.
I hear no whistle when it's idling, but when i gently press on the gas pedal, it makes the whistle and the engine revs right after.
I hear it the most when I'm driving in the parking lot, rpm around 2,000 it makes the sound and when it revs up, it disappears. Only whistles on low rpms.

I've already changed the oil separator, and i don't know what else to do.

Any ideas?

Alternator pulley?

that or the alternator itself .. I get a small whistle on really cold days.

Very small whistle at those RPM could be related to idle control valve and the vacuum lines around it. It could be making such a noise when the valve is partly closed maybe?

This sounds very interesting. I have noticed a slight but constant movement of the rpm gauge when idling.

Where is this valve/hoses?
If you could identify them from a diagram below, i'd really appreciate it

http://www.realoem.com/bmw/partgrp.d...99&hg=11&fg=05

Part #8 on this diagram.
http://www.realoem.com/bmw/showparts...79&hg=11&fg=40
As far as I know, this valve generally doesn't fail, it gets dirty and you can clean it up with throttle body cleaner.
I would however doubt it and look more towards the vacuum lines that get to/from it.

I tried to identify the location, it seems like the sound is coming from this unit. I'm not sure if it's the unit that's failing or the connections around it. I'll take it apart and clean it up to see if it works.

Thanks again. I'll post an update right after.

BTW. it's not the intake boot.

lol. I was gonna say that's your intake doing its job

It could be the alternator pulley........................cuz the sound seems to come from way front of the bumper.
Easy fix?