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1990 Benz 300E 2.6 (mine) ; 1994 E320 Wagon (wife's) ; 1993 300CE Cabrio, needs some TLC
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Can one see the condition of the tensioner rubber when it's on the car? I noticed that my M103 belt is rather new but not sure about the condition of the tensioner..

no, youo can't. its quite buried, and you really wont know its condition til you release the tension via the golden hollow tube-nut, and remove the whole assembly.


see the flats on the shaft? draw an imaginary line through the center of that shaft, parallel with those flats. if that points to the pulley, like the one on the left, its good. if it points off to the side like the one on the right, its toast.

VERY late model M104.99x have an entirely different spring loaded tensioner that doesn't have the piston damper, or the adjustment bolt, these last forever and are cheap. catch-22, you need to replace the power steering or tandem pump mount in order to switch to the new style.
 

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There’s a star bolt in the center of the pulley that i tried to show in this pic, do I just need to loosen that?
 

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1990 Benz 300E 2.6 (mine) ; 1994 E320 Wagon (wife's) ; 1993 300CE Cabrio, needs some TLC
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7,164 Posts

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1992 W124 260E
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65 Posts
no, youo can't. its quite buried, and you really wont know its condition til you release the tension via the golden hollow tube-nut, and remove the whole assembly.


see the flats on the shaft? draw an imaginary line through the center of that shaft, parallel with those flats. if that points to the pulley, like the one on the left, its good. if it points off to the side like the one on the right, its toast.

VERY late model M104.99x have an entirely different spring loaded tensioner that doesn't have the piston damper, or the adjustment bolt, these last forever and are cheap. catch-22, you need to replace the power steering or tandem pump mount in order to switch to the new style.
Thanks LCG. I'll try to imagine what you have said and make sense of it . I'm a bit concerned about the tensioner because when I replaced my rear flex disc last week I noticed that there were cracks in it. And it's the original MB flex disc, possibly 28+ yrs old already.. So, maybe the tensioner is that old, too.
 

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1992 W124 260E
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65 Posts
So, which route should one take?
1. Remove, inspect, replace if needed or,
2. Purchase, replace
 

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W124
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You can see the belt condition from a few vantage points along its length. The important view is the grooved side. Look for cracks. If you see them, its time for replacement.

As for moving the tensioner, that star headed bolt is the one you fit an appropriate socket over (star not conventional) and use a breaker bar for leverage. The tensioner WILL move. You are working against a strong spring.
 

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Yeah mine looks like the 3rd version so I'll give it a try....If I understand right, I just need to crank the star bolt in the middle of the pulley counterclockwise which will move the pulley enough against the spring tension to be able to slip the belt off and the new one on.....What's that special tensioning devise tool they show there though for the 3rd version? Hopefully I don't need that.
 

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1992 W124 260E
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65 Posts
You can see the belt condition from a few vantage points along its length. The important view is the grooved side. Look for cracks. If you see them, its time for replacement.

As for moving the tensioner, that star headed bolt is the one you fit an appropriate socket over (star not conventional) and use a breaker bar for leverage. The tensioner WILL move. You are working against a strong spring.
Thanks tuttebenne. I'll point my usb endoscope camera at it...
 

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I replaced my belt finally on the 400E. Thanks for all the help and sorry golfboy to hijack your thread. To replace the belt on mine, I didn't have to remove the fan shroud or anything at all, just cranked the tensioner with the proper torx socket and ratchet, slipped the old one off the tensioner and slid it around the fan and off all the pulleys and out and then put the new one on reversing the process and using the tensioner pulley as the last one to slip the belt on (definitely draw a picture first of the pulleys old belt routing). It was a little tricky and my socket got stuck on the tensioner but I wedged a socket extension on the tensioner for a second after cranking it up a little so I could pull off my ratched to get the new belt around it but overall it wasn't too bad. Oreilly's Automotive had two belts for my car surprisingly, a cheaper brand and then the Gates belt that I went with....thanks again for the info!
 

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1989 W124 260E
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So is the 2nd and 3rd gen tensioner are better than gen 1 . I see nothing to say that gen 2 and 3 tensioner is better than the gen 1 unless the gen 2 and 3 tensioners are self tensioning .Am i right to think this .
 

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W124
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Yes you have the later and much better spring loaded tensioner. Glad you did the replacement yourself and noticed how easy it is. Nothing has to come off as the manual would have you do. Good for you. And Gates was a great choice. Enjoy your 400e - they are truly wonderful W124 variants!
 
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