W212 Belt Squeal

[xrm88]

Hi guys,

I have a 2011 2.1 E Class and have recently started to hear a high pitched squeal coming from engine. I’m guessing it’s the serpentine belt?
The squeal seems to speed up as the revs increase but does go away completely once the engine is up to temp.
I have poured a small amount of water on the belt whilst idling and the squeal stops straight away but comes back after a few seconds.
I did take a video but can’t seem to upload it?

Any help or advice would be very much appreciated.

Thanks!

 

[Ted]

If the squeal starts again with headlights, heated window etc on then the belt is slipping. Try tightening it

 

[xrm88]

I’ve used the car with lights and heating on and still had the noise.
Forgot to mention that in the vid I took, the tensioner pulley looks to be moving left and right slightly

 

[Bellow]

I’ve used the car with lights and heating on and still had the noise.

I think what Ted is saying is switch as much electrical off hopefully to the point of silence then switch as much on as possible simultaneously (inc AC) and if the noise suddenly appears/increases then belt slippage is the problem. I'll add that it should be most noticeable at cold start when the battery immediately wants replenishing after operating the starter motor (unless a control strategy prevents this) and the belt is cold and hard and thus more slip prone.

Forgot to mention that in the vid I took, the tensioner pulley looks to be moving left and right slightly

That may point to something in the belt drive creating a problem. Removal of the belt and turning by hand and feeling for anything untoward at the pulleys can identify such an issue. Check also the harmonic damper/pulley on the nose of the crank for being out-of-round/wobbling.

 

[m80]

When removing the belt you should find out if the tensioner is tight in its travel.

 

[Trickythemerc]

Idler pulley bearings seizing up would cause belt squeal.

 

[xrm88]

So there should be NO movement in the tensioner puller when idling?

 

[ALFAitalia]

Often there is slight movement on these belt tensioners....caused by the belt having varying amounts of stretch along it's length...or very slightly out of round pulleys. My old ALFA and our A Class both wobble very slightly at idle.

 

[Trickythemerc]

That is why the tensioner is spring loaded, to allow slight movement in much the same way as the alternator clutch pulley stops the belt snatching on the overrun.

 

[xrm88]

Thanks guys.

The movement from side to side looks very rhythmic. It’s doesn’t look out of shape or loose.
Wish I could upload the video to show you

 

[Oleks1992]

Could also be cause by a seized alternator clutch pulley (if yours has one)

 

[pcthrillrider2]

If the squeal starts again with headlights, heated window etc on then the belt is slipping. Try tightening it

you cant tighten it, it's automatic

 

[xrm88]

I’ve uploaded the vid to YouTube so you can see/hear

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[xrm88]

What do you guys think my first port of call should be with this?
Just change the belt?

 

[xrm88]

Took this just now. Idler pulley tensioner looks to be abit crusty back there so going to change that and belt and see how we go…
£105 incl VAT for the tensioner from Merc and £49 incl VAT for the belt… didn’t think that was too bad

 

[xrm88]

Please guys, is it worth me replacing the belt and tensioner as a first port of call?

Many thanks

 

[oldguy57]

Please guys, is it worth me replacing the belt and tensioner as a first port of call?

Many thanks

That's what i would be doing any way. It's worth having a good look at all the other pullies while you're at it.

 

[xrm88]

That's what i would be doing any way. It's worth having a good look at all the other pullies while you're at it.

Thanks!