OM603 Tensioner Shock - burnt me!
 

Cold engine. Only turned the car on to pull it in the driveway from the street and up on some ramps. So maybe a minute of operation?

Was idling the car to look at the vibrating tensioner spring. See here:

<iframe width="560" height="315" src="https://www.youtube.com/embed/ChA8CLAv6OM" frameborder="0" allowfullscreen></iframe>

I accidentally touched the shock and burned my finger. Like a real first degree burn. Even with ice, an hour later the fingertip still tingles. No blisters but red and very painful.

So a minimal amount of operation makes this thing literally burning hot.

Wonder if that’s related to the vibration I feel under speed? Beyond a point the engine is high enough rpm that the whole thing is unstable and shakes the engine (which is smooth as glass even on cold idle).

Thoughts??

Isn't friction fun? Time for a new tensioner shock and spring at a minimum. Check for play in the pivot lever and tensioner pulley too. You might consider upgrading the alternator pulley to a clutched pulley, it really reduces the amount of flutter in the belt, even with a good tensioner shock/spring.

Clutched pulley? Source? One thing at a time with this, but nice idea.

I bought a spring, didn’t think it should vibrate like that. Now I have to wonder if it’s actually OK and the shock is the culprit (obviously)...

Get an OAP pulley on that alternator.

Have a link and/or source? Definitely up to getting that if it helps and is a straightforward/ bolt on mod.

Does the alternator even need to come out?

https://www.pelicanparts.com/More_Info/022903119C.htm?pn=022-903-119-C-M40

This is the one I have in my '87 300D. It works with the stock belt. I'd take the alternator out, it's not hard to drop from the bottom. If I had switched the pulley out, I would have not had my only breakdown so far -- a shredded belt from an alternator pulley coming loose.

I have the same INA pulley on my SDL, put an end to the belt flutter right now.

The spring and shock should be replaced together as a pair. When the shock goes, the spring can fail sometime later on from stress. The spring keeps tension on the belt, the shock dampens the oscillation. When the shock fails, you get the rapid fluttering and rough rattle that you show in your video.

Makes sense. I was under the impression that the spring is under tension and just breaks at some point. I thought the shock might be ok. Boy did I learn my lesson! It still hurts!

Wonder if the vibration I feel at 65 is actually due to this somehow?

I doubt the 65mph vibration is due to the tensioner rattle. If it was, you'd get the same vibration any time you were operating at the same RPM. Since the vibration is vehicle speed dependent and not engine RPM dependent, it's in suspension or driveline.

If you're in there, replace the rocker and idler pulley as well. They're not expensive, but cause a lot of trouble if they go. The rocker bearing tends to develop false brinelling, uneven wear, because of it's limited range of motion. And the pulley tends to wear to a slight conical shape because of the architecture of the hub and the tension of the belt.

I’m generally in agreement, but I’m not usually at 2500-3000 rpm anyplace but on the highway. The confusing thing is how good my driveline looks (to me).

EDIT, this is not directed at JHZR2 ,

First degree burn, Ha.

Try and be a mechanic in a shop where cuts , burns , scrapes are part of the daily routine. But hey, the general public thinks they are stupid a holes that rip everyone off and deserve to be harmed.

Certainly don’t put words in my mouth.

There are imbeciles in every profession. And folks who shine.

“Service advisors” and underbid behaviors of corporate shops give the industry a bad name.

It was more the unexpectedness of this part to get so hot so fast....

Yep, I get it. My words are not directed at you, I should have been more clear. It was directed to others. Sorry. I've add some words to my post.

It has to come out to get an impact gun on the nut holding the solid pulley in place. Once you have an OAP in place you don't even need the shock absorber anymore. The spring alone can do the job and it doesn't vibrate.