W124 Pulley chatter/clatter

[isobars]

Hi All,

I've an '89 300E, manual.

There's a chirruping/clatter coming from the front. At its loudest by the water pump.

When I spray water on the belt the noise goes away, so I suspect alignment.

The other part of the mystery is that when driving if I depress the clutch the noise goes, but if I keep it pressed and rev the engine, it comes back.

Is that indicative of anything?

It's a new-ish belt.

Cheers for any info.

Paul

 

[hotrodder]

I take it there's no noises (clutch engaged or disengaged) if the engine is run briefly with the belt removed? All the pulleys turn smoothly without play? Belt tensioner & damper healthy? Harmonic balancer on the crank is healthy?
Depressing the clutch changes thrust loads on the crank... what's the crank end float like [/glass nearly empty]?

 

[isobars]

Thanks very much for the comments.
Not had the tools out yet.
If there was a crank problem would the noise go with the wet belt?

Cheers,

Paul

 

[optimusprime]

May be the damper, it looks like a small shockabsorber . The rubber bushes can wear out over time .And these isolate it from the fixing bolt top and bottom .Then you get the noise as you rev it up.or vice versa ..

 

[isobars]

Hi,

Thanks for the input.

Just been on a half hour drive.

The noise doesn't seem to get louder the more I rev and for a good half of the trip it wasn't there at all.

The plot thickens.

Cheers,

Paul

 

[bolide]

It's usually the water pump that chitters and chatters.

Nick Froome

 

[isobars]

Hi Nick,

Yes, it's certainly that region.

As it goes off immediately when wet, would that lead the chase to the w/p pulley off kilter?

Cheers,

paul

 

[hotrodder]

If the waterpump bearings are on their last knockings it possibly could. Way more likely than my glass nearly empty crank end float guess but dipping the clutch wouldn't quiten a noisy waterpump or tensioner, idler etc
You need to take the belt off to investigate but FWIW when the waterpump on my m104 died of old age it didn't get noticably noisy or develop play (despite the pump feeling rough/gritty when turned by hand), just started leaking and the car started running hotter at low speed/idling.

 

[isobars]

Thanks for the response.
The car runs at never more than medium temp.
I gave it another run this afternoon and now it's happening about 20% of the time.
The enduring puzzle is why it goes on clutch-dip. Today when I dipped the clutch the noise went, but didn't return, which it did previously!
Is it self-healing?!
The car had very little use over the three or four years prior to my purchase.
Cheers,

Paul