Overactive belt tensioner?

[glenlloyd]

Replaced belt tensioner and shock yesterday, today I was fussing with some new pulley bolt covers, mine were all apparently discarded by some idiot mechanic, and I noticed that the tensioner had come loose.

I tightened it back up, probably overtightened it a bit but I do not want another freeway catastrophe like last year with the belt sliding off the edge of the tensioner pulley.

At any rate, I have no reference point but at idle this thing vibrates a lot, more than I would expect. I've run it with the fan removed, same thing. Off idle it's not bad but it does vibrate a good deal at idle.

Comments....things to check...someone give me some feedback on this thing.

Thanks
Steve A

[whunter]

Originally Posted by glenlloyd

Replaced belt tensioner and shock yesterday, today I was fussing with some new pulley bolt covers, mine were all apparently discarded by some idiot mechanic, and I noticed that the tensioner had come loose.

I tightened it back up, probably overtightened it a bit but I do not want another freeway catastrophe like last year with the belt sliding off the edge of the tensioner pulley.

At any rate, I have no reference point but at idle this thing vibrates a lot, more than I would expect. I've run it with the fan removed, same thing. Off idle it's not bad but it does vibrate a good deal at idle.

Comments....things to check...someone give me some feedback on this thing.

Thanks
Steve A

OK, you have a
Model: 300SD
Chassis: W140.134
Years: 1992-1993
Engine: OM603.971

* Is the shock old/damaged/chattering? NOTE: This part has been superseded four times due to chatter, MB# 6042000214

* Is the spacer washer in place?

Use Loctite 24205 Threadlocker Medium on the bolt threads..



.

[patr1707]

I just had a huge problem with mine on an '87 OM603.

Make sure that the tensioner is straight and aligned with the other pulleys. If not the belt will tend to pull off and hit the fan causing your "highway" catastrophe. It will only get worse and you will have to replace the tensioner again because the bushing is shot. It may also mess up the alternator bearings, so it is very important to make sure that it is square to the other pulleys.

What had happened on mine was that the timing chain cover where the tensioner bolts to was stripped, someone before me over tightened it and stripped the casting and I had to replace the entire timing chain cover.

I would maybe pull it out and clean the threads and definitely use some loc tite when you put it back in. The torque on the tensioner is 74 ft/lbs.

[glenlloyd]

Originally Posted by whunter

OK, you have a
Model: 300SD
Chassis: W140.134
Years: 1992-1993
Engine: OM603.971

* Is the shock old/damaged/chattering? NOTE: This part has been superseded four times due to chatter, MB# 6042000214

* Is the spacer washer in place?

Use Loctite 24205 Threadlocker Medium on the bolt threads..

.

The shock was definitely old and was chattering not because the shock was bad but because the shock bushings were hardened and worn. They could be pushed out easily.

Unfortunately the spacer washer was not there when I removed the old one, and I didn't know this beforehand otherwise I would have ordered it and had it on hand. The tensioner has never completely come off before but it did loosen last summer causing the belt to slide off the end of the pulley and wreak havoc.

I noticed the spacer in EPC the other day and jotted down the number just in case I needed it and it looks like I will need to order that now.

I did use some locktite but it shouldn't be a problem getting it undone, I just wish whoever had taken it off before would have remembered to reinstall the spacer washer . There's nothing like having to cleanup after someone who didn't do what they should have.

Thanks guys

Steve A

[whunter]

Originally Posted by glenlloyd

The shock was definitely old and was chattering not because the shock was bad but because the shock bushings were hardened and worn. They could be pushed out easily.

Unfortunately the spacer washer was not there when I removed the old one, and I didn't know this beforehand otherwise I would have ordered it and had it on hand. The tensioner has never completely come off before but it did loosen last summer causing the belt to slide off the end of the pulley and wreak havoc.

I noticed the spacer in EPC the other day and jotted down the number just in case I needed it and it looks like I will need to order that now.

I did use some locktite but it shouldn't be a problem getting it undone, I just wish whoever had taken it off before would have remembered to reinstall the spacer washer . There's nothing like having to cleanup after someone who didn't do what they should have.

Thanks guys

Steve A

The shock is trash, the shock bushings are the reason it was superseded.

Call Phil for the parts.


.

[agood]

Did the bushing fix the chatter? I have the same issue, just looking for the resolve, I've already replaced the shock and the belt. Didn't help.

[compu_85]

I had this problem with an aftermarket belt tensioner, the washer between the tensioner and timing cover was rubbing on the tensioner body... the friction built up and eventually the tensioner snapped

Be sure the tensioner arm can move freely when the bolt is tightened down.

-J

[agood]

Mine moves freely, that's the problem....it moves so easy, the belt wobbling makes it chatter.

[compu_85]

Is the bearing still good? The shock should prevent it from moving too much. If there is play in the bearing it will make a ton of noise.

-J

[agood]

Bearing? In the tensioner itself?

[compu_85]

Yes. There is a needle bearing which the tensioner arm swings on. If the bearing wears out (or a bunch of the rollers fall out like mine did) the arm will flop around.

-J