squeaky noise under the bonnet C CLASS C200K 1.8 (pls help)

Page may contain affiliate links. Please see terms for details.

honest g

New Member
Sep 15, 2008
Afternoon Guys,
I just purchased a C CLASS C200K 1.8, unfortunately it’s developed a squeaky noise under the bonnet.

The noise only starts after doing a few miles from start, then when in park/idle, it continues to make the noise, but if you rev the engine over a certain rev, the noise turns off but when you let go of the acc, the noise comes back on again.

Belt / Pully etc????

Please let me apologies if I have just crated a repeat thread, as I wish not to waste anybodies time.

You help is much appreciated.

Could be any of the following --alternator,water pump, power steering pump,air conditioning compressor, or poly V-belt tensioner. All driven by the poly V belt. most likely the tensioner or water pump but could be any of them.
Sometimes if you remove the belt and rotate the various units' pulleys by hand you can feel/hear any roughness/noise in the faulty unit. Sometimes alternators squeal a bit under load =charging-----hows the state of your battery?
Last edited:
The squeak could obviously be a manner of things (as mentioned above).

Coincidentally, I have a squeak coming from my engine but I know what it is but have not got around to fixing it. Reason why I know what it is is because the noise goes away when I rev the engine to about 2000rpm and on my car the magnetic clutch (part of the kompressor (supercharger)) engages at those revs (squeak goes as soon as I hear the kompressor kick in) which means that the front plate of the magnetic clutch needs to be adjusted so it has a slightly larger gap between it and the pulley (needs another shim fitted).

It's something to look at but not knowing what age your car is ( mine is a 1996 C230k) as later models did away with the magnetic clutch but this is one for the record.

Hi Guys,
First of all thanks for the replies guys. My C Class is a 2002 (52 plate), so would that mean that mine does not have a Magnetic Clutch?

I do know that the magnetic clutch was changed on later models but unfortunately I don't exactly know when. Maybe someone else on here could answer that question.

I can say that when I rev my engine slowly to about 2000rpm I can here the Kompressor kick in, it has a very noticeable whine to it. It would obviously be easier to notice this if you rev the engine whilst at the same time looking under the bonnet, the kompressor can make a right din!!:eek: But if you don't have the magnetic clutch then there won't be any difference in noticable change of sound at 2000rpm.

Last edited:

Users who are viewing this thread

Top Bottom