Cold start noise

[alxy]

Hi bros,I just noticed a knocking/ticking sound (appears to be from engine bay) whenever I start engine from cold. Noise seems to get worse when I engage gear. After warming up a while, noise goes away, or at least, is not so audible. Any idea what it could be? I have to wind down window to hear the noise. If windows are up, then sound is muffled. Problem might have been there a while already. Just that the other day I wound down windows (was a cold morning after rains) before I started engine and then heard it as I engaged reverse gear. Obviously since I am aware of the noise now, I hear it even with windows up and noice muffled. But probably before that it might have been there also, just that being muffled I didn't really notice as usually my windows are up all the time during engin startups.

 

[Nick335i]

It could be wastegate rattle. Ask a bmw workshop to comfirm that

 

[alxy]

Turned out to be alternator bearings....