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Hi all,
after searching this forum and goggle I didn't find much about replacing just the clutch pulley on alternators, every part store I checked, besides ebay, only carries complete alternator (some without the pulley).

My pulley was frozen, creating visible and audible vibration in the tensioner. Alternator was working fine, so I didn't want to replace it just yet. Ebay has Zen brand pulley for about $40 or original MB for about $80.

So, I had this idea that maybe the pulley is the same as on the VW TDI (I have 2006 jetta), both alternators are Bosch. Since I couldn't find any useful specs, I bought cheap Zen pulley from ebay (claims to fit E300), took off alternator pulley and compared it to VW one. I didn't take pics of zen pulley but it looks just like VW version (right on pics).

Pulleys functionally are in fact the same, 6 grooves, same distance from alternator to belt, same thread and same tools required to pull it off. The only two differences I've found that could affect performance are:

1. VW one has a hump on top where plastic cover attaches (MB version is glued inside the pulley), this puts pulley closer to fan blades but there's still about 1mm gap left and when fan rotates it actually gets pulled in towards radiator due to physics of it
2. The distance between the back of the pulley and the thread is longer on the VW, but you still get about 5 full turns when putting it on MB alternator.

Conclusion, if you want original INA pulley you can buy one for VW which is about $50 and available in most places.

On a side note, I drove my MB in rainy weather for a while without bottom engine cover, which I think shortened pulley life cause when I pulled it off there was a lot of rust between alternator and pulley.

Hopefully this will be useful for others.

Sorry for the long post :)
 

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2001 E430 4matic
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From the last photo its obvious that both pulley will be compatible but that hump on the top maybe troublesome in the future. You mentioned that the distance between that hump and the blades is about 1MM. In the future if waterpump goes a little old and create some play, the blades may hit that hump on the pulley and create noise. This is something to remember...

Thanks for sharing.
 
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