Hey folks. I was taking a look at my '99 E300 today in the engine bay. I just replaced a fan blade that broke at 70MPH that dented my hood and took out my damn radiator hose and shroud, but broke nothing else upon close and detailed inspection. I was extremely shocked that it didn't damage the radiator. I looked at it to find no holes or punctures. Put the new blade in and realized my fan clutch doesn't move clockwise like it should without some heavy elbow grease. Does this explain why the fan blade broke lose and decided to self destruct? I think it just seized up. There's no play in the bearing itself..

You'd think after paying $40K to go to one of the best trade schools in my area for diesel technology, you'd think they go in-depth on cooling systems, but nope.

Should I replace the water pump as well? Since I can imagine they wear at the same rate as the clutch.

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Only diesels in this driveway.
2005 E320 CDI 243k Black/Black
2008 Chevy 3500HD Duramax 340k
2004 Chevy 2500HD Duramax 220k

I had a fan blade come off a 68 Landcruiser at about 60mph. Sliced up thru the radiator, right thru the thick steel hood and up into the stratosphere somewhere. Scared the **** out of me. The sound was deafening and the vibration so bad I thought I'd thrown a rod. Ever since then I've been hesitant to stand in line with an engine fan blade. Was your fan blade metal or plastic? Mine was metal and from looking at the remaining stub I concluded it had been cracked for a while before it let go. I don't remember that vehicle having a fan clutch. It was direct drive I think.

But, back to your problem. I would just replace the existing fan clutch. I think the clutch and the water pump wear independently so unless there's evidence of a bad pump, I would leave it in place. I'd also try to figure out what happened to the existing fan clutch. Don't they typically have a bi-metal spring which opens and closes a hole to let fluid move from one chamber to another? Is that system working?

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Scary story, Kerry!

Mine is a plastic fan blade. Still strong enough to put a small dent in my hood. What would a bad water pump act like? No cooling issues prior to this incident. Not sure also, never had these apart. They're very similar to all the other 60x motors. All I could tell you.

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Only diesels in this driveway.
2005 E320 CDI 243k Black/Black
2008 Chevy 3500HD Duramax 340k
2004 Chevy 2500HD Duramax 220k

I agree with Kerry. Bad WP? overheating or leaking from the pump. not too complicated.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Cool, my water pump is good then. Didn't think there was anything out of the ordinary for the WP.

Looks like I'm going to order the Berg-Werner clutch from our sponsors. They're only $70 and I'm ordering two since the bearing is shot in my w124 and wobbles and squeals like a pig with a match up its ***. I like the fan clutch upgrade I've been reading about for the w124s. I'm still going to keep that hefty metal blade though on my 92. Those were the days before MB started cost cutting on parts like you will find on the next gen body styles..

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Only diesels in this driveway.
2005 E320 CDI 243k Black/Black
2008 Chevy 3500HD Duramax 340k
2004 Chevy 2500HD Duramax 220k

A good clutch has some resistance when sitting cold then loosens after a few seconds of engine operation as fluid circulates. There's a max rpm at which it should disengage regardless of airflow temp. I don't know the cutoff rpm.

Research clutch brands. Cheap ones won't last down your driveway. It might be the case that dealer or OE are worth the price premium for how long they typically last.

Sixto
83 300SD

If the bimetallic spring falls off the front of the clutch that will put it in "lockup" mode all the time. It will still limit overall fan speed, but it'll zap the engine's power and fuel economy.

-J

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1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.

Thanks for the responses everyone.. Great help always around this forum.

I'm gonna go with Berg-Werner. I'm about 90% sure they were what's originally on the car, and they're a reputable brand too. I've heard ACM is good as well. I'll probably buy two BWs and call it a day and put them on both cars.

Compu-85:
I'd like to know that max RPM they cut off at. To be honest with you, I don't pay much attention to the RPMS, but I was crusing at 70MPH when this happened. I would assume it was at 2K-2.5K RPMS at the time. I would assume it was still engaged.. The bearing in there is snug, no play. Just seems seized. But when I start the car the next time I'll see if I can stop it with cardboard.

__________________
Only diesels in this driveway.
2005 E320 CDI 243k Black/Black
2008 Chevy 3500HD Duramax 340k
2004 Chevy 2500HD Duramax 220k

I believe the clutch won't let the fan spin faster than 3000 rpm - that's fan speed not engine speed. The water pump / fan clutch input spins faster than engine RPM.

When I still had the clutch fan on my SDL it would take a bit of driving / higher RPMs for the clutch to unlock. After a cold start it would never unlock at idle.

-J

__________________
1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.