[355190E26]

Recently I went through replacing both of the fan clutches on my cars and thought I'd share some helpful information/observations on the process, specifically the 2.6.
I would suspect there are a lot of older Mercedes driving around w/ dead fan clutches right now as it's not always obvious when they're dead.

The way to test is to rev up the engine to about 2500 RPM. You should hear a roar as the fan spins up. If no sound then it's toast. Also, you might noticed the engine will run hotter under load especially up hills or with the AC on.

In terms of brands I decided to do some testing. I refuse to put that Uro/no name garbage on my cars for obvious reasons. For my blue car, I bought an OEM Mercedes one (which turned out to be a regular Behr fan clutch) After replacement, the fan roars up, my AC got much colder and the temp gauge doesn't go above the 90* mark driving uphill w/ the AC on.

Now for my other car, I was able to have FCP Euro source me a Borg Warner fan clutch. I decided to give it a try since they're well known brand and FCP has free lifetime replacement on everything. After installation, I realized the Borg Warner has a higher fan speed and quicker spin up than the OEM Behr. When you accelerate with the windows down you can really hear the fan spin up (like a jet engine). After driving around, I believe the Borg Warner is actually better than the OEM. Driving on the freeway with the AC on, the temp gauge sat slightly below 80*. Even driving up a hill w/ AC on it stayed right at 80*. I'm normally one who recommends OEM parts for things like cooling systems, but in this case, I think the Borg Warner is worth a try since these cars can use all the cooling help they can get.

 

[timgrishkevich]

Very cool write up. Checked autohaus, pelican, and FCP Euro and couldn't find the Borg Warner fan clutch. I am suspecting my fan clutch is on its last legs as it does not roar up as described and looks original with about 110k miles.

 

[dolucasi]

FYI, mine is original at 200K miles. Roars like a lion. No temp issues with the fan. Also passes the spin test.
Needed a new thermostat just last week. Behr one only lasted 3 years.
Tested a no name aftermarket (new) next to the Behr (old) and the problem was obvious. Does not open far enough.

I left the cheapo aftermarket one in there (even though the set temp is 89C instead of 87C) as it is fine.
Went to the dealer and bought a mercedes one for $50 (ouch). Will replace during the next coolant flush coming up.

For the first 13 years of ownership the thermostat never quit on me, so I figured I'll stick with the dealer part going forward.
I though Behr was the supplier to Mercedes. Go figure ....

 

[355190E26]

Dolucasi I'm impressed that your fan clutch is still going strong at 200K miles! Maybe your car got a better batch back in 89?
I've been using Mahle thermostats on the cars, they're dirt cheap $13 on FCP and made in Germany. 7 years on my current one and working perfectly.

Very cool write up. Checked autohaus, pelican, and FCP Euro and couldn't find the Borg Warner fan clutch. I am suspecting my fan clutch is on its last legs as it does not roar up as described and looks original with about 110k miles.

Here's the Fan clutch on FCP. It's actually labeled as ACM Germany, but the box says Borg Warner all over it (ACM is a subsidiary)
Also, if you're planning to tackle this job soon, go find an 8mm stubbby hex key like this. A regular one won't fit in the space between the radiator. The cheaper method would be to get a regular 8mm and just grind it down.

 

[dolucasi]

Me too. I must be fortunate. I keep questioning it and my problems always go back to the thermostat.
The thermostat is the one and only first level of coolant temp regulation device in these systems.
In a clean system and running at highway speeds, it your coolant temp is not straight at the specified coolant temp you should question your thermostat first.

When I got the car back 4 years ago, I noticed the thermostat opened too soon (below 80c) and did not open far enough at temp.
So I replaced it with a Behr unit, and before installing tested the old versus new side by side.

I just noticed that with warmer weather and running down the freeway the temp is higher than should be, more like 90+ C (Behr was a 87C thermostat)
Tested a thermostat I had laying around, side by side with the Behr in the car and sure enough problem found.

The thermostat not opening all the way really clogs up the system at idle speed. With not enough flow, the temp will keep rising and rising with the reduced flow.

 

[plinker17722]

If stuck it is possible to repair these type fan clutches . It means drilling and threading the hole in the clutch ,,then to drain out the old oil , and replacing it with the silicon type oil thats used in electrical servos . .

 

[355190E26]

I was reading about that as well, apparently you can fill it with the same oil that's used in RC vehicles as well. I may experiment with my bad fan clutches and see if it works. Got another friend who's 2.6 also has a dead clutch so I can test it on that.

 

[plinker17722]

Worth a try .🏁

 

[timgrishkevich]

Just replaced my fan clutch with the ACM/Borg Warner unit. I have to say that you were completely right. My old fan clutch must have been near dead because this one really roars when I rev up the motor. My old unit did not do this. Sounds like a different motor now. This one also does not spin freely like my old unit did when the car is off.

One observation: I think the Borg Warner clutch is physically bigger than the old clutch (I am guessing the old clutch was original. It was labeled Behr and had Mercedes logos all over it). I did not compare them side by side, I only noticed something was off when the circular part of the fan shroud did not fit in between the clutch and the radiator. I have removed/replaced the shroud probably 50 times in my life and have never had this issue. It took about 10 minutes of persuasion but I eventually got it in there. Curious if you made a similar observation.

I thank you for this write up! My busted up hands aren't as thankful, courtesy to the one inch of space that the 2.6 motor provides to do this job.

 

[maranelloboy05]

Whats the best way to test? I can spin mine maybe 40 degrees with the engine cold. I definitely don't hear it spin up when getting on the throttle.

 

[dolucasi]

I would say when you spin with your hand if it keeps spinning more than half a turn, it is probably not working that well.

 

[maranelloboy05]

I would say when you spin with your hand if it keeps spinning more than half a turn, it is probably not working that well.

Just tried and I can get it to spin a little more sometimes, I'll add it to my list.

 

[355190E26]

Just replaced my fan clutch with the ACM/Borg Warner unit. I have to say that you were completely right. My old fan clutch must have been near dead because this one really roars when I rev up the motor. My old unit did not do this. Sounds like a different motor now. This one also does not spin freely like my old unit did when the car is off.

One observation: I think the Borg Warner clutch is physically bigger than the old clutch (I am guessing the old clutch was original. It was labeled Behr and had Mercedes logos all over it). I did not compare them side by side, I only noticed something was off when the circular part of the fan shroud did not fit in between the clutch and the radiator. I have removed/replaced the shroud probably 50 times in my life and have never had this issue. It took about 10 minutes of persuasion but I eventually got it in there. Curious if you made a similar observation.

I thank you for this write up! My busted up hands aren't as thankful, courtesy to the one inch of space that the 2.6 motor provides to do this job.

You're welcome, I'm glad you were able to get it installed!
I believe you're correct that the ACM does stick out a little more, I think it's because the bi-metallic strip on the front is bigger. I've developed a habit over the years of installing the fan clutch first, then slipping the circular fan shroud part on, then installing the fan and finally the rest of the fan shroud.

Also, if you have ever have to tackle this job again pull the radiator support! This will allow you to tilt the radiator forward and gain another valuable inch of clearance. Learned that trick from an old MB mechanic.

 

[dolucasi]

Just tried and I can get it to spin a little more sometimes, I'll add it to my list.

My car is by no means the gold standard, not even close, but mine only goes about a 1/4 turn when cold.
Just a reference point.

 

[WaxhawFive]

What's the trick for holding the fan pulley while loosening the 8mm center bolt?

 

[355190E26]

You'll need to create a special tool to lock the pulley in place.
Check out the pelicanparts writeup and you'll see the pictures of how the tool works.
Easiest way to create that tool is to take an allen wrench or find some steel rod and bend it into an L shape.

 

[dolucasi]

My car is by no means the gold standard, not even close, but mine only goes about a 1/4 turn when cold.
Just a reference point.

BTW, mine goes 1/4 turn when cold and 1/2 turn when hot. So hot has more play.

 

[WaxhawFive]

Thanks for the pelican link! That tool looks simple enough to make.
Strange that the clutch spins more when hot. I would think that it should spin pretty freely when cold, when the fluid is in the reservoir, then tighten up only when the bi-metallic strip opens the valve letting the fluid into the shear area of the clutch.

 

[dolucasi]

Thanks for the pelican link! That tool looks simple enough to make.
Strange that the clutch spins more when hot. I would think that it should spin pretty freely when cold, when the fluid is in the reservoir, then tighten up only when the bi-metallic strip opens the valve letting the fluid into the shear area of the clutch.

I also thought the same, that was the intent of the design I thought. Perhaps mine is not working as expected. It should spin more freely when cold. Mine does not.
That does not matter in summer or in hot climates though so I'm ignoring

 

[TheNoobster86]

Recently I went through replacing both of the fan clutches on my cars and thought I'd share some helpful information/observations on the process, specifically the 2.6.
I would suspect there are a lot of older Mercedes driving around w/ dead fan clutches right now as it's not always obvious when they're dead.

The way to test is to rev up the engine to about 2500 RPM. You should hear a roar as the fan spins up. If no sound then it's toast. Also, you might noticed the engine will run hotter under load especially up hills or with the AC on.

In terms of brands I decided to do some testing. I refuse to put that Uro/no name garbage on my cars for obvious reasons. For my blue car, I bought an OEM Mercedes one (which turned out to be a regular Behr fan clutch) After replacement, the fan roars up, my AC got much colder and the temp gauge doesn't go above the 90* mark driving uphill w/ the AC on.

Now for my other car, I was able to have FCP Euro source me a Borg Warner fan clutch. I decided to give it a try since they're well known brand and FCP has free lifetime replacement on everything. After installation, I realized the Borg Warner has a higher fan speed and quicker spin up than the OEM Behr. When you accelerate with the windows down you can really hear the fan spin up (like a jet engine). After driving around, I believe the Borg Warner is actually better than the OEM. Driving on the freeway with the AC on, the temp gauge sat slightly below 80*. Even driving up a hill w/ AC on it stayed right at 80*. I'm normally one who recommends OEM parts for things like cooling systems, but in this case, I think the Borg Warner is worth a try since these cars can use all the cooling help they can get.

Sorry to revive the old thread. But do you know the part # for that Borg clutch fan? I cant seem to locate it anywhere, only aux fans.