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SLK320 Belt Tensioner Replacement

5337 Views 5 Replies 3 Participants Last post by  Firm
So replaced my serpentine belt a few months ago - pretty easy job. But my belt still makes a bit of a squeal for the first 30 seconds or so of run time in the mornings. I figure it's probably because my tensioner is getting weak?

Does anyone have instructions on how to replace this? I am trying to guage whether it's something I should attempt myself, or if I should just wait till my next service and let my indie do it.


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None of the All-data stuff point 1 is relevant for the SLK320. Start at point 2.
If you have the old-style tensioner, it is way overdue for a replacement. The new style has a 'bolt' head cast into the lower corner to release the tension with, while on the old style you had to use the torx in the center. Also the old style had a 2-part metal pulley and were prone to sudden disintegration.
While you at it, also check the plastic idler wheel (top left looking at the engine). It develops cracks at the rear where you cannot see it. Remove the idler wheel and inspect. It's quite a cheap part so it may be wise to replace it if you have more than 80,000 miles on the car.
You can also check the W210 forum for writeups on replacing the tensioner and the idler wheel.
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