[mira4581]

Hey guys, I need some help. I have a 2011 c300 and about 5 month ago it developed squeaky kind of a noise. I took it to the mercedes dealer as my car was still under warranty and they been trying to fix it ever since. It has been back at the shop 4 times already and it seems like they replaced everything that you can imagine but the noise is not going away. Yesterday I picked up my car yet again after they had it for 3 weeks and this morning it started doing it again but much louder this time. So clearly whatever it is they can't figure it out. It seems like its especially clear and loud when the car is cold. Would any of you perhaps know what it is or personally experienced the same issue, I would appreciate any feedback.

I updated some vides on youtube.

This one from October 2014: C300 noise 10/21/14 - YouTube

This one from today: http://youtu.be/fXqRcTRlf90

 

[C300fan]

Sounds like a belt or something spinning by the belt. High pitch irregular noise. Might the the alternator, or a pump driven by the belt. I would start by spraying wd40 everywhere I could around where the accessories connect to the belt. You can take off the plastic cover with the Mercedes logo very easily to take a look at the serpentine belt. That's my guess !


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[mira4581]

I think the alternator is the only part they didn't replace. According to the dealer, they thought that some of the pulleys might be miss aligned so they took the entire front apart and replaced everything but looks like i will be going back to them on monday as that didn't work. I just don't get it how they can't fix it after 4 tries.

 

[C300fan]

Alternator was my first guess since you said it was worse in the mornings, that's when the alternator works the most. Once it quiets down a bit try loading it up with radio heated seats, max heat, all lights etc see if it gets worse


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[C300fan]

Please update when you figure it out


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[Mikefan]

Looks like drive belt tensioner getting weak,