High-pitched whistling sound from engine...ideas?
 

Lads and gents,

Interesting "problem"... But figure it's something that's been encountered before, thus the post here in the forums.

I have a 2009 C63, getting near 100k miles, but still running strong. No mechanical issues... Save for one annoying, piercing whistling sound from the engine that I've yet to pinpoint in a quick once over. The noise ISN'T present for 20-30 seconds after cold start, but then kicks in and doesn't stop thereafter.

All ideas welcome.

Thanks!

Leaking PCV valve at the rear of the engine. Not expensive, but fiddly to replace. Common issue.

I can't hear much on your video but if the PCV valve isn't the problem I would check your idler pulleys. I had two fail at 28K miles and they can screech and squeal before the seize and take out your serpentine belt.