Belt judder and low revs on C220 CDI coupe

[Pumas25]

hi,

Looking for a little advice on my 2002 C220 CDI COUPE;

A few weeks ago my revs dropped a little, didn't think much of it as it was cold weather - ended up the belt snapped.
Fitted a new belt and noticed it was flapping around a bit when the engine was running so i changed the tensioner which didn't help.
I checked all the pulleys last night for play and found a little play in the alternator pulley and the power steering pump pulley - COULD THESE BE THE CAUSE OF THE POOR RUNNING?
The belt also keeps trying to run off the tensioner, I suspect that if one or more of the pulleys are running wrong it would do this...

HELP PLEASE!!

thanks.

 

[panason1c]

Check the alternator pulley, this pulley has a free-wheel clutch built in, they commonly seize up which effectively turns them into a 'fixed' pulley, this is then what causes the drive belt to flap about as the inertia of the alternator tries to drive the belt at engine idle speed.

Sometimes, an audible sign of a seized pulley is a short 'squeal' sound every time you stop the engine.

Is the coolant at the right strength?..........maybe it was cold enough that the the water pump has frozen which caused the belt to get hot (thru friction) and snapped, usually accompanied by a burning smell.

 

[Pumas25]

Thanks for the reply, I've heard that it could be the alternator belt a few times before but nobody explained it as clearly as that before, makes perfect sense and matches the way the alternator pulley that's on there is working.
Oh and the belt didn't "snap" (though that's what I said), it more stripped and shreaded, strimmed through a vacuum hose on itx way out and threw the car into limp mode. I've been picking fluff out of the engine bay ever since! I think the belt flapped into the fuel pump thing on the front of the cylinder head and started to come apart. Wasn't a very new belt.

I'll update when the new pulley is fitted.

Will I definitely need the freewheel pulley removal kit?

Thanks