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Old 02-26-2008, 10:53 PM
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slk230red slk230red is offline
WECO Installer
Join Date: Jul 2006
Location: Tampa, FL
Posts: 820
Originally Posted by supersportwagon View Post

I'm new to the forum. I have an awful vibration at idle that the shop told me is due to the need of a new belt tensioner and belt. Is this a PITA job, or feasibly do-able for a person with average mechanical know-how and a Haynes manual.

FYI, shop wants just under $500 = $270 Tensioner, $70 belt, balance = labor.

Thanks in advance,

Hi Johnny,

First, make sure your belt tensioner is defective. It's either good or need to check to see if the belt is tight, if it is then push down on the belt and the tensioner should move and return to the original position when you release the belt. If is defective, the belt will stay slack due to the rubber bushing being torn.
OK, if the tensioner is shot, then you will need to replace it. If the tensioner is good, then I would check the small tensioner shock that goes from the tensioner to the alternator. This is one source of vibration/rattle that I have had to fix in the past.

If your tensioner and tensioner shock are ok, then check your engine mounts for another source of vibration at idle. I replaced my original ones on my '93 2.3 last August when I replaced the head gasket and what a difference. The engine idle is now extremely smooth like it was when I bought the car new.

Below is a reply I posted on another forum:

Don't be's not a hard job. I just replaced my belt tensioner when I installed a new A/C compressor.

This is from memory:

Remove fan, 1 bolt
Remove shroud, 2 clips and it pulls straight up..this allows for more access room.
Loosen the large lockdown bolt on the tensioner.
Loosen and remove the tension adjusting rod nut.
Remove belt.
Remove small tensioner shock bolt at alternator location.
Remove bolt from tensioner bracket.
Remove large lockdown bolt and the tensioner assembly should pull out.
Be sure to look at how the adjusting rod and bracket is attached on rear of tensioner so you can match up the new one.

You will have to remove the belt pulley from the new tensioner to transfer the tensioner shock. The black plastic cover pulls off to gain access to bolt.

Now, install new tensioner by sliding the shock thru first, then push the adjusting rod up thru the hole and install the front bracket and Large lockdown bolt. Install the other bracket bolt, install tensioner adjusting nut, attach alternator end of the tensioner shock, install belt and tighten adjusting nut enough to take up slack. Reposition tensioner plastic tab to the left side starting point, install shroud and fan.
I like to adjust the shroud and install the retaining clips after I install the fan so it is centered.
At this point every thing should be tight EXCEPT for the large lockdown bolt and the tensioner adjusting nut. If so, then tighten the adjusting nut until the plastic pointer reaches the maximum mark, (I usually stop short of the mark....belt is tight and doesn't slip).

Last, don't forget to tighten the large lockdown bolt.

If you ever need to tighten the belt, always remember to loosen the large lockdown bolt first before attempting to tighten the adjusting nut.

Good luck,




1993 190E 2.3
2001 SLK230
1971 LS5 (454) Corvette Convertible
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