300E bad / worn bearing noise ?

Hi
I have a 1987 300E.
I can hear a noise that sounds like a bad bearing in the housing behind the distributor cap.
I took a large long screwdriver and placed the tip on the metal housing that
the distributor attaches to. Just behind the top center of the cap, think the 12 O'clock position. I pressed my ear into the handle end of the screwdriver and I can hear it loud and clear.
I haven't had a chance to look at the manual as I have the manual on cds.
What bearing would this be and what is involved in changing it?
Thanks
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I just looked at it after work.
The Belt tensioner damper is bad, the upper bushing.
So what is involved to change this? I think I might just take it to a shop.
Should I have them also change the belt tensioner while they are at it? They need to remove the tensioner to get the damper out, right?
Thanks

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All you need to do is just change the pulley wheeler on that tensioner... it is replaceble and I have done it... On your car, you loosen up the tensioner...
remove the belt, but before you do that, draw a diagram of how it is routed. You might as well change the belt at this time too.
Then pop off the black cap on the center of that pulley wheel... allen key to remove it... swap, tighten and reinstall new belt and tension it up.
About the tension... feel how tight the tension is now... that is about what you should tighten to when you finish the job.
Pulley wheel is only $21. The belt is only $18... if you get it past $50, free shipping. Autohausaz.com Maybe some oil filters, wiper blade or refill... etc.
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Tiger
Thanks for the reply.
To change just the damper do I have to take the tensioner assembly out?
As for the belt tensioner pulley roller, do these wear? I swung it by a shop and the mechanic took a look at it and said that my tensioner is adjusted almost as far as it can go and the belt isn't really tight. The belt is ok in terms of tension he just mentioned that by looking at a screw and how far in it is that he would think the belt would be tighter. He said the belt was in great shape.
He wants to change the damper and the entire tensioner assembly, 3 hours x $120 = $360 labor, I thought that was a bit much, I was expecting 2 hours. Parts wise was another $350, bill was over $700. I told him I would think about it.
I would like to understand more what I mentioned above. What causes the tensioner to be adjusted near the end of it range to get the belt under the correct tension.
I am learning about this car. I have the manual but it is on cd, I wish I had a book that I could easily browse from time to time, instead of being at a computer and clicking through sections.
Thanks again

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If the damper you are talking about is the shock type... that really doesn't put any tension to the whole belt drive... This tensioner shock is $27.44 and I would change it expecially if yours is original or old.
The wheel does wear out at the bearing... if the bearing is collapsed, it could explain why you can't get it tight enough. The bad tensioner pulley sounds like a rattle... loud one.
The tensioner itself is a solid unit...but it does have the bushings in the middle that wears out over age... due to constant tension and can collapse that leads too belt that cannot be tighten any more. This unit can be had for $99.
You should do all this yourself... I would change out the tensioner assembly (that includes the wheel) and the little shock absorber. Less than $130 worth of parts and maybe 3 hours of your time on a weekend. That's over 70% saving from what that mechanic quoted you.
A pro can change all this out in about an hour. He has all the tools to do it fast.
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