When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Hello, I have a 2019 W205 C300 4-Matic. When starting the car from a cold start, the car doesn't squeak or squeal until it drops RPMS. After dropping rpms, it will SOMETIMES squeak and squeal. Example being in the first video, it is squeaking and squealing, and in the second video, which is after driving the car from work to home (10 min car ride), it has stopped and is idling at the same rate as it was in the first video. Thank you in advance, and I apologize if it seems like I'm being paranoid or stupid, but I'm just a little confused.
First thing I would assume causing the sound at low rpm idling is related to the belt ( A6269930096 ) or the pulley. As it drops RPM the frequency of the noise would be easier to hear.
Last edited by RomeoS; Jan 9, 2026 at 05:43 AM.
Reason: Added M274 poly belt diagram
First thing I would assume causing the sound at low rpm idling is related to the belt ( A6269930096 ) or the pulley. As it drops RPM the frequency of the noise would be easier to hear.
Nope, they are VERY easy to access and replace with even the most basic skill set. Just be careful putting the belt back on.
Experianced person....well, it would take me (and has) under 20 minutes start to finish to replace the two pullies. Novice? Hour tops. It is a very easy job. If you have a metric ratchet wrench set you have everything you need.
with the belt off, inspect the waterpump shaft. any roughness in rotation, high drag or wobble in that shaft will necessitate pump replacement in the future.
Mercedes SLR McLaren 722 S Is Extremely Rare Example Modified by McLaren
Slideshow: A one-of-one U.S.-spec Mercedes-Benz SLR McLaren Roadster became even rarer after a factory-backed transformation at McLaren's headquarters.
Squeaky Idling
Belt or Pulley issue?
