How to tell if belt tensioner shock damper is bad? - PeachParts Mercedes-Benz Forum

glenlloyd · #1 03-10-2011, 08:42 PM

Hey all
I'm replacing the belt tensioner, I think the bearing has had it. The pulley appears to be fine but I'm also questioning the shock damper. I think all of these items are original to the car.

The question I have is how to really tell if your tensioner shock damper is going and whether or not these are gas charged or just fluid damping shocks? If it doesn't need replacement I won't bother but there's a tendency for it to chatter somewhat at startup although when the tensioner is relaxed it seems very solid and moves stiffly.

Comments appreciated.

86-300sdl · #2 03-10-2011, 09:02 PM

It is kind of hard to tell unless it is shot. On my 603 I was getting the chatter so I just replaced the shock. Later I find that the opposing spring can break at the hook which if it goes you will be to peeling wound strips of your belt out from behind the harmonic balancer, possibly wreck the front main seal, and also in my case the belt ripped through the trans cooling lines at the radiator. Ugly! The damage cost me much more than the spring. "Would have-should have-could have" Just not thinking.

vstech · #3 03-10-2011, 09:02 PM

when it's in your hand, push it closed, then open it up. if it's smooth, and easy to move, it's bad.
it should be difficult to push closed, and pull open. almost stiff.
it's fluid, not gas charged.

glenlloyd · #4 03-10-2011, 09:14 PM

Quote:

Originally Posted by robcarsonjr

It is kind of hard to tell unless it is shot. On my 603 I was getting the chatter so I just replaced the shock. Later I find that the opposing spring can break at the hook which if it goes you will be to peeling wound strips of your belt out from behind the harmonic balancer, possibly wreck the front main seal, and also in my case the belt ripped through the trans cooling lines at the radiator. Ugly! The damage cost me much more than the spring. "Would have-should have-could have" Just not thinking.

Well last year while on the freeway the belt 'slipped' off the tensioner pulley and did exactly what you said, it flapped around the disconnect the vacuum lines (couldn't shut down) and resulted in a lot of time spent pulling strips of ruined belt out of the harmonic balancer. Fortunately it didn't do any other damage.

Problem was that the tensioner bolt loosened up a little and allowed the tensioner pulley to pivot out and the belt to work its way off. after the ordeal I tightened up the tensioner but found that the bearing had some slop in it, hence replacement now, but maybe I will replace the shock and the spring as well, that way I don't have to worry about any of it.

Thanks for the comments!

compu_85 · #5 03-10-2011, 09:26 PM

If you are already replacing the tensioner arm I would just do the shock too and be done with it. It's not expensive.

-J

glenlloyd · #6 03-11-2011, 07:58 PM

Quote:

Originally Posted by compu_85

If you are already replacing the tensioner arm I would just do the shock too and be done with it. It's not expensive.

-J

I looked at it today while I fussed with the glow controller, there's some wetness on the lower mounting point courtesy of damper itself, I think it needs to be replaced as well.

Next question, what's the frequency that we see the springs break on these?

thx

steve a

jonbobshinigin · #7 03-11-2011, 09:21 PM

Interesting you ask because I replaced mine about two years ago, along with tensioner arm, pulley, and spring. I recently replaced my front crank seal and hub and upon reassembly, mine it rattling. This occurs when the bushing that bolts on either side gets worn out. For some reason, my bushing is worn out, although I suspect the shock itself is fine. My guess it that it was like this before, but I simply did not notice it until my head was in the bay checking everything after the last job I completed.

glenlloyd · #8 03-19-2011, 05:05 PM

Quote:

Originally Posted by jonbobshinigin

Interesting you ask because I replaced mine about two years ago, along with tensioner arm, pulley, and spring. I recently replaced my front crank seal and hub and upon reassembly, mine it rattling. This occurs when the bushing that bolts on either side gets worn out. For some reason, my bushing is worn out, although I suspect the shock itself is fine. My guess it that it was like this before, but I simply did not notice it until my head was in the bay checking everything after the last job I completed.

After I got mine off the engine I found the same thing you did, that the bushings on either end were bad but the shock itself wasn't worn out. The bushings were so bad I could push them out with relative ease. I replaced it anyway but I thought it odd that the shock outlived the bushings.