I've been noticing some sounds that I can't pin down in my wife's 2011 BMW 535 ix with 107k miles. The best way that I can describe it is that it's kindof a whirring sound that follows the RPM band.

I listened to the alternator with a stethoscope with a rod on the end (backyard mechanics oscilloscope) and it does sound like the bearing in the alternator may be dragging a bit. There are also a few rattles at low RPMs between 1,000 and 1,800rpms.

I uploaded a video of the sound through different rev ranges. Has anyone here had a similar problem?


Thanks for reading/helping.

 

Sounds like a bearing on the alternator.

 

Is that replaceable separately from the alternator or do I have to buy a new alternator?

 

It's replaceable only if you know how to rebuild an alternator if not then you will have to buy one.