I have a 190e 2.6 with a bird-like squeak coming from the belt drive system - I believe. Here's the history:

Original water pump failed at 86k. Replaced with a Graf unit. Also replaced the thermostat and rib belt (Conti).
Filled with some genuine MB coolant. Followed the factory service manual steps.

At 90k, it developed a random 'squeak' coming from the water pump area. Got my stethoscope out and searched for the noise. It was not clear. Suspected the tensioner pulley. Sprayed a little lube on it and it seemed to quiet down for a short period. Heard some noise around the bracket, so I pulled everything off to replace the pulley. It was worn, so I replaced it and the idler as well. After pulling it off, I turned the water pump a couple of times and heard a slight noise, like a squeaky rubber bushing - so, I replace the Graf with a genuine MB pump, and put it all back together.

After a short trip (1000 miles) the squeak is now back in full force. Stopped into a Benz dealer in KY and had a mechanic look at it with his scope. Did not hear anything in the water pump - heard some noise in the tensioner area. After explaining my replacement story, thought that it could be the tensioner failing. Belt tension was okay.
He suggested replacing the shock and the tensioner - both could fail and cause this type of noise.

Car runs excellent with perfect temp in hot weather.

Any experience with this type of failure? I am trying to nail this before a replacing another part.


Chris

'93 190E 2.6 92k
'81 240D 209k
'89 Range Rover 140k

Usually it is the belt. I have replaced many AFTER coolant has hit them. Is it possible that coolant was on the pulleys when the belt was installed.

__________________
Benzmac:
Donnie Drummonds
ASE CERTIFIED MASTER AUTO TECHNICIAN
MERCEDES SPECIALIST 11 YRS

Yes, it is possible. Would this cause a belt to squeak loud, even if it is new?

Do you recommend replacement with a genuine MB belt?

Maybe the belt but 99 of 100 times the rubber insert in the belt tentioner is broken. Try and tighten the belt if it won't tighten replace the tentioner.

Found some other posts using the search function. Seems like it is indeed a tensioner problem - so I will replace and repost with the results for future use.

I ended up replacing the tensioner assembly and the shock. The lower bushing on the shock was worn badly and squeaking - probably contributed to the noise.

It was tough to tell if the tensioner assembly was bad - although the belt had lost all tension - so I assumed it was time for a replacement.

In terms of procedure for those of you who attempt this in the future, I would recommend the following:

1. Purchase the MB tools to remove the fan - device to hold the fan clutch and the hex socket. Get them from your dealer, or Performance, less than $20 and well worth the money.

2. You do NOT have to remove the radiator on a 201 to get the job done. Just be patient, work slow, and it will come out. Here is what I did.

Removed radiator support.
Remove fan shroud.
Remove fan and clutch (the socket is required for this. I could not get a round head ratchet in there, had to use my oblong head Craftsman to get it out)
Loosen the belt pulley bolts on the WP and PS.
Loosen the main tensioner bolt and relase the belt tension.
Remove the belt and the pulleys.
Remove the two bolts on the tensioner support bracket that are attached to the PS pump. Remove the main tensioner bolt. Leave the left-most bolt attached and swing the bracket upwards to let the tensioner come out.
Remove the top bolt from the tensioner shock.
Work the tensioner out - it will come.

Re-assembly tips:
Make sure that the tensioner support is fitted correctly over the center section of the tensioner. Should be able to move the tensioner enough to slip the belt on.

If replacing the shock, don't bolt the top down until you get the belt on. The new shock will be stiff and it is easier to get the belt on first, then compress the shock and bolt in the top.

Hope this helps. Good luck!

__________________
Chris
93 190e 2.6 147k
81 240D 265k
89 Range Rover 165k