Does anyone know the tool # or name for the device that holds the viscous fan pulley still while tightening the 8mm screw to the pulley? As I'm tightening the fan to the pulley with that shallow 8mm screw, the pulley is turning - even under full tension of the serpentine belt. How do you keep it from turning? The M103 engines had a small hole where you would insert that S-shaped tool into the pulley to hold it still.

R&R of Viscous Coupled Fan, Serpentine Belt Replacement W210 E300D

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A Dalton

That tutorial is for a diesel engine and also (what looks like) a M103 engine. The viscous fan does not attach to the water pump on a M104. There is no provision on the pulley to place that S-shaped tool to lock the pulley to remove the fan and viscous coupling.

Depends on which 104 ....
If you have the late 104, you need tool # 104-589-00-01-00 wrench.
Pull fan cover ring pins and move ring to left side to remove. Hold nut with wrench tool between fan and pulley
Remove attaching screws
Reassemble at 33-37 ft/lbs.

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A Dalton

That is exactly what I need. I have the 104 built in March 1995 - a late model one with the newer tensioner. That link you provided was informative in general (I'm goingt o save it) but useless to me since I have a late 104. That's all I was trying to find out.

Yeah...you can make that wrench out of a 1/8" piece of metal easily enough.

There is also anothewr tool part # 120-589-02-02-00 that works on the 104..
According to my Data CD for that tensioner set-up, the tool holds the assembly right between the pulley and viscous..
I think it is 65mm..the other is 35mm

Allways best to give a year when you post, as there are many production changes thru-out a chassis vintage that determines what procedure you may need to know about.

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A Dalton

If you go to home depot, you will see merchandise hung up on peg boards with display hooks. In the hardware section, buy the one that has a single post that is about 8-10 inches long. Put in a vise and bend the tip (about 3/4 inch) at a right angle.

I have used mine for years and it has never failed me. Even the MB manuals instruct to make this tool yourself.

A word of caution. Be carefull with the fan clutch. The aluminum fins break off very easily...

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93 300D 2.5 Turbo, Black/Palomino 273K
09 E350 Black/Black 41K

That is not the tool he needs .

He needs the large open end counter-turn holding wrench..

http://www.peachparts.com/diy/mb_tools/mb_tools.php?page=25

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A Dalton

Thanks for the input folks!

I just use one of those large rubber band clamp straps they sell at home depot.

Good thinking GeorgeB (I hadn't thought of that), but you can only use one of those strap tools when the serpentine belt is not installed, which means the fan and its coupling are detached from the pulley.
The belt is a hundred times easier to install without the fan in the way. It literally takes five-minutes. Once the fan is off, and the belt is on, that strap wrench does no good-it won't wrap around the pulley because the serpentine belt is now in the way. To put the belt on with the fan attached (and not have to deal with this pulley issue), is an exercise in frustration. Sure it can be done, after twenty-minutes and risking belt damage, I saw the easier route was to remove the fan and its coupling. To correctly tighten that pulley, you need that wrench.

This is a great post, I racked my brains this weekend (doesn't take much) trying to figure out from all the posts why there's no place to put the locking tool... it's because on my m104 (1993 MY) there doesn't seem to be any hole to stick the tool into to lock the pulley from turning...

one member mentioned the same and that there is a special tool for m104 late model years. does the same apply for a 1993 m104? any help would be appreciated! I'm getting quoted $300 labour for changing this when it should totally be a DIY, but i'm getting stuck at getting the fan clutch pulley to not turn! LOL.

Strap wrenches seem to work fine, e.g. - http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=40198

thanks but what would i wrap that around? I can't get it around the pulley due to serpentine belt and there's no space to put it on pulley axle... so I'm still stuck!

here's a few pics of how far I got if someone could take a look and provide guidance on what to do next?


Picture showing the fan pulley and clutch and 2 allen keys I put in as placeholders to show where a couple of the bolts are...


Another pic with a mirror showing fan clutch and center bolt..