Mercedes crank damper

[Belle427]

Just checking my sanity here, work mate has just bought a 2014 Mercedes C220 Cdi and noticed a slight noise from the auxiliary belt.
When you grab the belt with the car off it turns freely clockwise, the outer portion of the crank damper is turning but the inner isnt.
It will turn anticlockwise too but isnt so easy.
I know damper rubber bonding can fail but this is a bit weird or is it a special clutch type pulley similar to the ones used on an alternator?
Not seen this before if it is so just curious.

[GreenV8S]

Never heard of such a thing, and can't see how the crankshaft damper would ever damp if it was free to move in one direction. And if it's able to move in the other direction at all, then clearly it doesn't have a working one way clutch as you'd suppose.

With those symptoms I'd conclude that the damper had separated and the outer part was being held in position by friction, belt tension and so on. So presumably it'll gradually wear itself loose and break free, meanwhile not driving the ancillaries properly and not damping the crankshaft properly.

[Belle427]

Yes its not something ive seen before and would not make any sense really, just thought it was odd that it all rotated as it should with the engine running.
I would have expected to see some slippage if the bonding had failed or some nasty burning smells.

[Belle427]

Apparently it is a thing although i cant find any info on it online.
Must be a 2 piece arrangement where the front section is the freewheel pulley.
Its a new one on me though.

[tapkaJohnD]

See: https://forums.mercedesclub.org.uk/index.php?threa...
Fourth post.

BUT, from the same thread, is this what you see?
https://youtu.be/NrzhFGonscY

[Belle427]

Thanks for that, I have only tried to turn the aux belt from above so cant comment if the damper is the same.
Will be taking a better look next week with belt removed and report back.

[GreenV8S]

So ... is this a three piece front pulley with separate damper and ratcheting pulley components?

[Belle427]

Ive no idea on its construction sorry.