lol - I just did exactly the same thing. Wanted to replace the viscous coupling but ended up stripping the tensioner adjuster nut and so the job was made much longer.
For those of you wanting to replace the fan clutch you can make the tool to do this job (on the M103 at least) from some 4mm diameter metal, e.g. a strong nail.

The 19mm bolt goes through the tensioner. The bolt head is kind of under the water pump pulley. Reach in there with your hand and feel for it.

Steve

Thanks! Need I remove any other components for access?

I must say this so please don't take offense.

You just need to get in there and figure it out.
Imagine the time it would take to get step by minute step
instructions for something like this. One e-mail at a time.

Also search the archives. There are numerous posts on this various
subject.

If you can't get to something then remove or move whatever is in the way.

Solving mechanical problems is like that. At least it always was for me since about age 16. Took a long vacation from wrench twirling during those company car years. Now I only do those tasks that are not too challenging.

Belt tensioner R&R is a pain in the you know what. It's just so crowded in there. I have had tensioner problems on two different 300E's. The belt tensioner and it's adjuster are tricky. I just pay to have it done. Much easier that way. You are probably talking about max. $150 in labor probably less. I remember having one done at an indy MB shop. He was done in 30 minutes.

Oh, one other thing. Be sure to replace the belt tensioner shock absorber while you are in there.

Steve

I hear ya, the difference is that with another make or model I'd have a Haynes manual or something with pictures which would tell the story rather quickly. I'm thinking with all the tensioner horror stories it would be quicker to have a shop do the work.

I agree, just have it done.

Steve

You guys are lucky. My 19mm center bold just broke inside the bracket. total nightmare now. Easy-out ain't working.