Squealing noise

[k3nny]

Hi everyone. My 2006 m3 with 72k miles just recently developed a squealing noise. This only happens upon a cold start and happens for about 10-20 seconds and then it stops. I’ve only heard the squealing noise once while driving. I think it may be related to the pulley and tensioner but not entirely sure. Belts were replaced about 5k miles ago - so don’t think it’s the belts. Sharing a link, please provide some insights! Thanks.

https://drive.google.com/file/d/1fN1TkNriw1x_NzuRAbGk2IPx-tkbghlf/view?usp=sharing

[dl.m3]

Spray some water on the belt while idling to see if it goes away. A slightly misaligned pulley can cause noise, so I would check your tensioners and pulleys. I had a minor squeak on cold starts that went away once the car was warm. It turned out to be the PS pump pulley that had some chips in the plastic. Upgraded to power pulleys and the noise went away.

[yhp2009]

I believe the secondary air pump runs in the first 20-30 seconds of engine starting. Might be the culprit if you can locate it and listen on your next cold start

[JamesSJ1]

I have (likely) the same noise, started ~40k miles ago and has never gone away despite all new tensioners and belts. Probably threw money at a problem that didn't hit the mark, but all new components in there at 12 years old gives some peace of mind (only 90k miles right now). It's hard to re-create or diagnose because it goes away so fast, you barely have time to really source the noise. And once the engine has been running more than 10-15 seconds and the noise is gone, you won't be able to re-create it until everything is *completely* cold again.

[ATB88]

I also have a rare phantom squeal on cold starts. It happens more often in the winter (I'm in SoCal, so, colder temps but still warm overall). It's not belts/pulleys as I replaced them. Possibly the e-box fan?

[k3nny]

I have (likely) the same noise, started ~40k miles ago and has never gone away despite all new tensioners and belts. Probably threw money at a problem that didn't hit the mark, but all new components in there at 12 years old gives some peace of mind (only 90k miles right now). It's hard to re-create or diagnose because it goes away so fast, you barely have time to really source the noise. And once the engine has been running more than 10-15 seconds and the noise is gone, you won't be able to re-create it until everything is *completely* cold again.

Sorry to hear man. It’s always a risk as our cars are getting older, it gets more difficult to diagnose.

[Ob917]

Had that issue, it was the clutch throw out bearing.