donnylii

2017 C63s - a supercharger like noise happens whenever the car goes over about 3-3500 rpm, only ever when decelerating. I can remake the sound when parked, from the noise alone one mercedes tech from a shop near me is saying it could be a leak. I have no loss in power, mpg, or boost. Car is all stock. No other weird sounds or performance issues, from some posts ive seen with other turbo cars is that it could be totally normal then again it hasnt been making the sound forever

superswiss

Have you searched? There are several threads here about whining sounds. Below are a few. If you post a video with the sound then others could also compare to what theirs sound. Trying to describe a noise in words generally isn't very helpful.

https://mbworld.org/forums/c63-amg-w...ing-sound.html

https://mbworld.org/forums/c63-c63s-...elerating.html

https://mbworld.org/forums/c63-amg-w...ing-sound.html