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2003 C240 broken pulley

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Old 01-10-2018, 07:37 PM
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2003 C240 Wagon
2003 C240 broken pulley

I found these inside the engine compartment of my 2003 C240 Wagon a while ago. I assumed they were relics of a breakdown before I owned the car, and thought it was peculiar that they had stayed with the car so long. I kept them to show to my neighbor. Tonight I showed that neighbor, and he started feeling the various pulleys on the front of the engine, and discovered that these pieces come from the back side of a current pulley. The pulley is pictured. My friend thinks this looks like the water pump, but serpentine diagrams I find on line make it seem as if this is the idler pulley. Any information is appreciated.

It is amazing that the belt has stayed on, and I have no idea how long this condition has existed. Does anyone have a DIY on this repair? Sincere thanks in advance!

Old 01-12-2018, 03:54 AM
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Pretty basic stuff, remove the belt, replace the pulley.
You'll need an inverted torx to put on the front of the tensioner to move it to ease the tension to remove the
belt, and not sure what's holding the idler pulley. Can't see if thats the bolt on the front, or a plastic cover.
Torx? Everything on these cars is torx, Inverted torx or metric Allen,
well and good old metric bolts too.
Old 01-12-2018, 08:05 AM
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It was an easy fix. Behind the plastic cover on the idler pulley was a simple torx. The only issue was the tensioner - I had watched a video on this specific repair, and he did what @C230 Sport Coup suggests...inverted torx. On mine is actually this bolt, requiring a more specialized tool, pictured. This center bolt, however, does not move the tensioner, but removes it. To move the tensioner, there is an 11mm bolt under the belt, which is difficult to see.

Hopefully this information saves someone some time on this repair.








Old 01-12-2018, 09:45 AM
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One would generally change the entire tension pulley assembly. Then you dont need a special tool. Also if the pulley itself is bad you can bet that the spring in the arm is getting weak.
Old 01-12-2018, 10:02 AM
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Originally Posted by insame1
One would generally change the entire tension pulley assembly. Then you dont need a special tool. Also if the pulley itself is bad you can bet that the spring in the arm is getting weak.
I was replacing a disintegrated idler pulley. What would this have to do with the tension pulley being bad?
Old 01-12-2018, 10:19 AM
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just replace the bad idler pulley. This has nothing to do with the tensioner or its pulley unless that is also worn or damaged. Just make sure the broken pulley didn't also damage the ribs of the belt.
Old 01-12-2018, 10:24 AM
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Originally Posted by Racin_fool
just replace the bad idler pulley. This has nothing to do with the tensioner or its pulley unless that is also worn or damaged. Just make sure the broken pulley didn't also damage the ribs of the belt.
Done and done. The middle-most rib was the only one damaged, and it seems to have just been sheered off or flattened out. The belt is still in excellent structural condition, and is seated well everywhere.
Old 01-12-2018, 12:47 PM
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Originally Posted by Brianbanion


I was replacing a disintegrated idler pulley. What would this have to do with the tension pulley being bad?
The only issue was the tensioner - I had watched a video on this specific repair, and he did what @C230 Sport Coup suggests...inverted torx. On mine is actually this bolt, requiring a more specialized tool, pictured. This center bolt, however, does not move the tensioner, but removes it. To move the tensioner, there is an 11mm bolt under the belt, which is difficult to see.
I was responding to this comment
Old 01-21-2018, 11:39 AM
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Update: Two days ago, not long after the replacement of the idler pulley, the belt tensioner assembly needed to be replaced. The rubber holding in the grease for the bearings was broken, and the grease was completely dry and solid. The plastic wheel broke off. I assume that this was related to the idler pulley breaking. I feel fortunate to have gotten out of this without major damage.
Old 02-12-2018, 08:52 AM
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It must be the season. My wife texted me to say that our C320 Coupe gave a lurch, warning lights came on and the car was hard to steer. She got it home ok and when I checked it that evening, the belt was lying on the belly pan, and the tensioner pulley was frozen. The plastic wheel was completely sheared off. I replaced both the tensioner and the idler pulley, as the idler pulley also felt a little rough when I turned it by hand. I replaced the belt and put the old one in the trunk as a spare.

The coupe had a strut connected to the tensioner. The strut did not show up for our VIN at the dealer, which was strange. The parts guy checked several times to make sure he had the manual transmission V6 C320. I had him confirm that the version with a strut, uses the same tensioner part. It took longer to transplant the strut than it did to replace the tensioner. You have to remove the top bolt of the strut and then remove the bottom bolt of the strut after you remove the tensioner. The strut is attached to the tensioner with a self-tapping bolt. It took a bit of muscle to get it screwed into the new tensioner, and some finagling to get the top bolt realigned with it's mounting hole.



Remnants of tensioner pulley wheel


Strut connected to tensioner
.

Last edited by kokketiel; 02-12-2018 at 08:58 AM.

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