W203 C280 help identify my noise?

[Tailoutcharlie]

Hi all
I have a w203 c280 on 96k miles. I have a slight noise I've noticed since taking delivery of the car and I'm not sure if it's anything to worry about.

It's a very slight knock that can be heard on idle from within the car and under the bonnet but only after the car has fully warmed up. I generally only notice it after returning from a drive. Definitely seems to be coming from the engine bay. It rises with revs until the engine is too loud to hear it. Shifting from drive to park does not change it at all.

Upon shoving my head under the bonnet I noticed my crankshaft pulley seems to have more movement than the other pulleys and tensioners in the serpentine belt arrangement. A slight wobble.

Could this be the source of the noise? It seems odd that it only appears when warm as I know the damper pulleys usually squeal like hell when they go and tend to make noise on cold start.

Im flummoxed, I did think it could be the dreaded balancer gear as I think my m272 engine falls in the range but I honestly don't know how that sounds.

I honestly only noticed it as the car is so damn quiet.
Sorry for the essay but any help would be appreciated.


Edit: no fault codes showing and car drives faultlessly.

 

[LostKiwi]

Crank pulleys can delaminate and should be replaced if they wobble.
Start with that then re-evaluate if the noise is still there.

 

[Tailoutcharlie]

Thanks for the reply, I know they were a problem on one of smaller engines, wasn't sure if it was a known issue on the m272?
Lets hope its not a huge job.