190E 2.6 fan clutch replacement writeup
 

Had to replace fan clutch due to a constant lockup condition. Of course many of you already know there's basically no room to work, hence the challenge in this otherwise simple job.
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Tools:
MB lock rod tool, improvised steel rod(~5mm dia.), or chopped off sacrificial Allen key
10mm socket & 1/4" ratchet head
10mm GearWrench or similar (low profile)
8mm MB stubby socket, or Allen key cut down to fit (it's tight, real tight)
If using the Allen key, you will need some sort of cheater pipe for leverage
Blue Loctite

Start by pulling the two fan shroud clips on the right & left of the radiator, then pull the shroud up & over the fan.
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Next, remove seven 10mm bolts from the radiator support, so you can pull the radiator forward a couple of inches for some working space. Take note of the threaded plates underneath the sheetmetal on top of the headlights. These plates will go loose after you remove the bolts, so you will need to slip your fingers underneath to line the threaded holes up upon reinstallation. The bottom bolt didn't have the clearance for a socket & ratchet, hence the GearWrench. A normal 10mm boxend wrench will also work.
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Find the hole in the mounting flange behind the fan clutch; line the hole up with the ridges in the bearing bracket. There are several holes, but only two are properly sized and located to fit this piece of rod. You may have to fit your 8mm stubby socket or improvised Allen key tool to spin the fan clutch around until the hole & ridges line up. I got the lock rod tool from Performance Products; the tip was about 2mm too long to fit into the hole in the mounting flange behind the fan clutch. This may be because the fan bearing bracket might not be MB sourced(I had it replaced a while back, did not do it myself), or because exact design had changed a tad. Anyway I ground off enough of the tip to fit the tool. I used a piece of scrap wood wedged between the top of the radiator & the top radiator hose to maintain clearance. Turn 8mm fan clutch bolt anticlockwise & remove. It's a tight space, so just break it free then unscrew it with your fingertips or the socket head will hit the radiator fins.
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Looks like I got to this just in time, what do you think? I was wondering where that mystery shrapnel I spotted on top of the air cleaner came from. Bearing self-destructed and the shrapnel was from the bearing cage, and hence the lockup. And I was driving this car around doing errands all this week! If I had let this go any longer the fan might have come off and annihilated the radiator. Seems I read of something like that happening to someone else.
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New visco fan ready to be installed, note it's a Behr made in Germany. I don't think I would bother with a cheapo, but hey- this one might be bad off the shelf as well. Time will tell. At least it's bearing is new.
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Transfer the plastic fan blade over to the new clutch and install; I used a little bit of blue threadlocker as I think I saw a little bit on the 8mm center bolt. Can't hurt. Torque to 33ft/lbs. Note that the new visco fan clutch may lockup upon installation, but run it in a bit and it will behave as it is supposed to. Mine ran for a few blocks despite a cold engine. Behaves as it should now.
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This job's easy, just take your time & try not to gouge your radiator fins. Your hands will be chopped up & sore no matter what you do however. It would be grand if this writeup helps someone else. Do NOT wait to replace your fan clutch! If it's not working properly or roaring when the engine is cold, it's toast and it needs to be replaced. I have no idea how long I have been driving on a shot visco fan. If it freewheels, the internal fluid's gone. If it's locked as in my case, the bearing's gone. Deal with it before it deals with you.

Thanks for the great write up. How did you go feeding a torque wrench down there?

Tilting the radiator forward made this job possible. I'm also lucky to have had a 3/8" drive torque wrench, the head of which wasn't much thicker than the low-profile ratchet I used to break the bolt free with. I have a 1/2" drive, but the 8mm stubby socket is a 3/8", and that would have necessitated the use of an adapter. No space for that.

You have to thread the bolt in and out with your fingers. With the bolt fully seated with the fingertips, there's only just enough space to use a torque wrench on it.

Would the job have taken much longer if you just removed the radiator?

Would that have been easier?

My goal was to avoid removing the radiator. It's 19 years old. Stuff happens when you disturb 19 year-old radiators. If I had to replace the radiator, which would have been very likely had I messed with the radiator hose connections, I would have also felt like I had to replace the expansion tank and all hoses as well. Thermostat and water pump too since they're both original. I didn't particularly feel like purging the coolant circuit of air and going through all that hassle either. Cooling system works fine and the coolant is in good shape. So a job I had originally wanted to do myself for the express purpose of saving money & time would have suffered a considerable cost & scheduling overrun. Removing the radiator for a thing like this would be a bit like taking the car apart to wash it. More thorough, but not really necessary.

I'm not quite ready to replace the entire cooling system just yet.

Thank you for the write up You got to it sooner than I thought. My fan freewheels so I know I need a new one, but sounds to me that I should be ok driving it still, but if it locks up then its more urgent.

Mine roars nearly all the time even at speed and it's brand new:(. I have a new one waiting. Hope it's okay.

I got this job done in an hour, including the time it took to grind the tip of the lock rod tool. It's about the same level of difficulty as changing the oil.

Cooling efficiency can also be increased by using the newer 9 blade fan. I bolts right on to the later clutches. Just a thought.

And I know what you mean by fiddling with working older systems. Pull one bit apart and it becomes like a definition of history - "Just one damn thing after another."

???

Not sure that's true, but if you have any definitive evidence by all means post it. Stock is 11-blade, and I'm not sure that a 9-blade is even available for my application. M103 engines run best when hot as that's where the best power & fuel economy reside. Running too cool has its pitfalls just as running too hot does.

I wouldn't want this car to run any cooler really. Cooling system has always been strictly maintained i.e. MB coolant & distilled water in 50/50 mix every two years. I'm guessing that's why there's never been any trouble out of it.

The irony of this car is the engine looks terrible, but runs like new. It's just plain ugly under the hood, especially after I fixed the leaky timing cover. It looked a lot better when it was greasy.

My bad. Forgot we're talking 201 here:o. The later fan for the 124 is 9 blade instead of 11. Still the 103 engine though - I wonder why it stays 11 blade. Clutch part numbers are different too.

Close but no cigar.

break off 2 fan blades and test it out :-)

sent this thread to whunter to post under resources tab in diy section. Thanks again for the write up

I tried this and snapped the little cast retainer bit on the pulley bracket. I was using an allen key and turning the ratchet counter clockwise. I was in the process of swapping the air pump and belt and figured I would check the fan clutch because this looked easy but I think I messed it up. It doesn't spin as freely now as it did before I made the attempt. Is it possible I damaged it or am I just being paranoid?

It is also a good idea to protect the radiator with a piece of cardboard when you are wrenching in there.