Originally Posted by elp_jc
Sounds just like a main bearing man; sorry for the bad news. You should be able to easily reproduce it by revving the engine between idle and 1,500 rpm, as reported on other threads. Here are other 2 YouTube videos so you can hear how to reproduce it:
That's definitely not good news for '08 and early '09 owners (before main bearings were upgraded). Time to take it in. I know this is not a widespread problem, but it's scary to think it could happen after warranty expires, especially for those of us who don't put much mileage on our cars. Will have to seriously think about keeping mine beyond warranty. Good luck, and please keep us posted.
I have a 2011 M3 which suffers from this same noise on these two videos as well as the noise upon start up. The clacking noise from the bottom of the engine is only noticeable when the engine has been on for a while and it has fully reached its normal running temperature. I'm taking it back to the dealer next week but I'm expecting one of those typical replies "we could not duplicate the noise, so blah blah blah". These Miami service advisors are use to everyone trying to fool the system and are always predisposed; when an honest customer with an honest problem comes along, they treat it as unimportant. We'll see.