4.8 is whining/whistling noise

[X5only]

I think I may have fixed the whistling noise! I noticed that it emitted from the passenger side of the cabin and it was in sync with engine RPM. Also it was there when the vehicle is on the move or stationary. So I inspected and cleaned the pressure regulating valves and the cavity where it sits (# 13 in the diagram link below). The diaphragms were not torn but were dirty, especially the passenger side which had creamy stuff. Now no whistling noise!

RealOEM.com - Online BMW Parts Catalog

Take care not to break the tabs on the cover of the valves. I used a small flat-head screw driver to gently unlock the tabs I could reach and then gently pulled the cover off. When installing it back make sure you hear the tabs snapping in as you push the cover in place.

Good luck and hopefully this is also the root cause of your whistling noise.

[X5only]

Originally Posted by X5only

I think I may have fixed the whistling noise! I noticed that it emitted from the passenger side of the cabin and it was in sync with engine RPM. Also it was there when the vehicle is on the move or stationary. So I inspected and cleaned the pressure regulating valves and the cavity where it sits (# 13 in the diagram link below). The diaphragms were not torn but were dirty, especially the passenger side which had creamy stuff. Now no whistling noise!

RealOEM.com - Online BMW Parts Catalog

Take care not to break the tabs on the cover of the valves. I used a small flat-head screw driver to gently unlock the tabs I could reach and then gently pulled the cover off. When installing it back make sure you hear the tabs snapping in as you push the cover in place.

Good luck and hopefully this is also the root cause of your whistling noise.

The whistling noise came back with a vengeance, as if telling me . But I think this time I've nailed it - the noise is clearly and most definitely coming from the speakers. I have a Dynavin N6 head unit. While the noise was there I rebooted the head unit, the sound disappeared. It came back right after the system was ready after reboot I can make the noise stop by simply rebooting the head unit I still have the OEM head unit. Will install it back and see if that makes a difference.

Edit: Also noticing this happens only when Bluetooth is connected to my phone