pen22

2010 E63. When first started when cold (in the morning or after sitting 5-6 hours) it has ALWAYS made a high pitched whinning sound for a few seconds. Very noticeable. Sounds like a little turbine engine winding up & down.
Just had it serviced (40k miles). The only thing that should have been done to the engine was oil change & air filter.
No more sound in the morning!
Dealer has no idea whats going on.
Any ideas?

R-N

Air filter noise perhaps, caused by restricted airflow through the old filter material, or the way the filter was situated.

pen22

It was not a defect or problem. It is supposed to do it.
Sounds like a separate vacuum or air pump winding up & down.
Lasts about 5 seconds.

grantwoodtx

It's the secondary air injection pump and from a cold start that is absolutely normal especially in colder weather.

Shellbmb

It sounds exactly like my home depot shop vac!