w203 c280 can you help find 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.

 

[slade1]

If you suspect its idler and tension pulley and are original, change them along with the belt. only use OEM parts.
They give no warning when they let go and on my CLK (M272) the belt caused more problems by wrapping it's self round the crankshaft between pulley and engine block. Should be a time serve service item.

 

[Tailoutcharlie]

If you suspect its idler and tension pulley and are original, change them along with the belt. only use OEM parts.
They give no warning when they let go and on my CLK (M272) the belt caused more problems by wrapping it's self round the crankshaft between pulley and engine block. Should be a time serve service item.

Thanks for the reply. I think i'll change the lot then just to be sure. I agree that it should be a service item. Do you think it could account for the noise?