belt tensioner 300e 2.8 M104

[radunegru]

I suspect a belt tensioner problem, because of the noise in the water pump area. Also when the car is in drive I can hear a rattle noise towards the front of the engine that is increasing in intensity when the a/c is on.
What is your opinion?
Thanks

[deanyel]

Get a cheap stethoscope and see if you can tell where it's coming from. They are quite good at isolating the noise. But watch out for the belt.

[Arthur Dalton]

Common belt tensioner shock bushings.
Hold screwdriver blade at bushing and apply tension by twisting blade to tighten bushing mount to verify..
...may also be comp. clutch rattle.

http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1D00YU6RY1ID1CTLJN&year=1993&make=MB&model=300-E-003&category=G&part=Acc.+Belt+Tension+Damper

[hudsmore]

I agree. dollars to doughnuts its the top bushing on the little shock absorber on the belt tensioner. It attaches right behind the thermostat. A bit of a job to get out as the fan, three pulleys and the tensioner has to come out to get to it. I know as I just did this repair 2 weeks ago on my 300sl. (104). If you need more info let me know and I'll walk you through it. You'll need a torque wrench, something to hold the pulleys (strap wrench works) and some high-temp sealer for the one "wet" hole that you need to extract a bolt from. I couldn't be bothered to chase down a bushing so I just replaced the whole shock (accessory belt tension damper) 31.94 @ importpartsonline.com

[Arthur Dalton]

...there is an easy, low cost fix if the shock is rattling back and forth on the top bushing pin. [ which is common].
You can take the one lone mounting bolt that goes through the
the shock top eyelet and sandwich an "O" ring between the
shock eye and the washer. That takes up the side play [which
is the Rattle] dimension of the shock. The bushing itself
is still good. it is just sloppy on the side and this shimming works fine and last long. [And gets rid of the Rattle !! }
What actually has happened is the bushing eyelet glue has dried up and the shock is sliding back and forth on the bushing. The sandwiched O ring stops the sideway movement.

[radunegru]

Thanks for your prompt imput guys but I am afraid it is not the little strut or bushings. It seams to be very tight. I think is the tensioner because the belt is kind of loose and I can't make it tight using the tensioner adjuster.
Now sience the belt is kind of old maybe 60k I am going to change the belt and the tensioner.What other thinks shoud I pay attention to while I am there?

[nglitz]

Check the bearings in the idler pulleys for wear & looseness. My fan bearing was wobbling around so much, the bottom edge of the fan pulley was rubbing on the block. Ugly noises. The smaller idler above the alternator is also worth looking at. Might as well check out the tensioner itself. I understand they get hard & take a set. Much discussion in the archives.

After reading all the books on how to sneak in behind the radiator, I just decided to pull the rad. Much more room to work. Three hoses, the two AT fluid lines and a couple of clips and it's out. Fifteen minutes to pull it the first time ever, and ten to stick it back in. Well worth the scraped knuckles and the chance of sticking a wrench into the core. It also gave me a chance to look into the health of the radiator hose necks and try to look at the inside.

HTH,

[radunegru]

Thanks for your great info.I am going to order the parts and change the belt, tensioner, adjuster, and the puley above the alternator, I will keep you poste as the work progresses.

[hudsmore]

The tension adjusting nut is reverse threaded and really soft metal. If you extend it past its throw you will strip it. Checking the pulley on the tensioner for play is a good suggestion. As far a shimming the bushing goes, the rubber gromet that insulates the bushing preventing metal to metal contact does so both laterally and vertically. Even if lateral play is nil, you might be getting the rattle from vertical movement which would be tough to detect by moving the piece manually. Aside from using a mechanic's stethascope, a short piece of broom handle or dowel pressed to the bone behind you ear and then touched to various parts of your engine will help narrow down rattles.

Order the adjusting bolt and nut while you're at it. It is cheap and I'll bet you will need it if you've been trying to adjust it without success. Also make sure you get the right size belt. The difference between the two that I show for the 104 engine (2440 and 2445) is tiny but makes all the difference.

Good luck

[radunegru]

I just come back from the garage taking a closer look at the engine belt. This is the simptom:
Start the engine from cold, air pump is making a noise like a drum.If I am covering the air intake from the pump with a finger I feel the vacum suction, and the noise goes away.By taking off the finger from the air pump intake the noise comes back.
After engine warms up I am starting the a/c and no noise yet. But I have asked a friend of mine to sit in the car with the foot on the brake and the shifter in D position.
Now, whenever the cicle of the a/c compresor begins(after the a/c clutch engages) i can get a noise coming from the air pump like a rumble. I was trying to locate the noise but I was not able to do it.
What it puzzles me is, if the engine is warm, why the pump is making noise. Or could be something else.
Please help me with the diagnostic.

[radunegru]

Still no result yet. What do you think?