How to Replace an Overrunning Alternator Pulley - Mercedes C/CLK/E Class

In this video, I show you how to replace the alternator pulley, on a Mercedes. The car in the video is a Mercedes CLK (W209 2002-2009), but the process is the same for all Mercedes vehicles that have an OM646 diesel engine (200/220 CDI). This includes the C Class (W203), E-Class (W211), CLC Class (W203), and any car that has a clutched/overrunning alternator pulley. The alternator pulley can fail, causing the tensioner to bounce around due to increased resistance.
Tools used:
- 17mm 12 point deep/swan neck spanner
- 1/2 inch drive breaker bar or 1/2 inch drive ratchet
- Blue Print ADG05506 Freewheel pulley tool - this is an M10 spline bit, with a 33 tooth bit around the outside. You can purchase the 33 tooth bit separately and use an M10 spline bit that you already own.
- 17mm spanner to hold the alternator tool
- Small pick or flat head screwdriver, to remove the cap from the alternator pulley
- 1/2 inch drive torque wrench
- Laser Tools 7017 Wrench Extender, to attach a torque wrench/ratchet onto a spanner
- Philips/cross head screwdriver
Note: In the video, I should have reduced the setting on the torque wrench, as the wrench extender moves the head of the torque wrench away from the pivot point - meaning the applied torque was higher than indicated. If I re-did it, I would reduce the setting to around 75-80Nm.
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*This video is for entertainment purposes only*
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[@Propriis.automotive]

I have a om646.811 and I belive it's the pully also was it clicking slightly at idle but as soon as you hold revs slightly higher it goes away ??

[@konstantin-big]

What is the difference between OAP and OAD??? Can we see the difference with eyes??? Can we replace an OAP pulley with an OAD pulley????

[@williamkennedy5492]

Thats a very good video, I have a W212 E220 and Mr Mercedes gave little thought to maintenance access.. I have a problem following the cars auto box service by Mercedes at 148k, you now feel the car jump as drive is selected, its ok in reverse, Also slowing down through 40 and 20 you feel the car change down. Its very noticeable. The car has been back to Mercedes and fluid levels are correct, BUT the service manager did mention this over run pulley, I cannot see the connection between that pulley and my gearbox can you ?

[@toufikhaddad1094]

MerCi

[@vincemarshall8550]

hoping to do this on my fiat doblo ,taking the alternator off involves all kind of mental gymnastics ,great vid ,thanks

[@mrsinghsgarage]

Glad you found it useful:) I can imagine it was a tight squeeze to get the alternator out! Good luck for the pulley replacement.

[@vincemarshall8550]

@@mrsinghsgarage thanks mr singh x

[@erdoganog]

do these pulleys make any noises before they go out or some bearing noise normal ? 70k on e300

[@mrsinghsgarage]

The idler pulleys are more common to produce noises when they're failing. The only noise that the alternator pulley will produce is a squeak when you shut off the engine.