The fan is not designed to go full engine RPM. A bad clutch is a problem.

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Gone to the dark side

- Jeff

wait a second. The clutch for the metal fans is different than the clutch for the plastic fans?

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Yeah I have a plastic.However I've found too a Mustang E Fan is rated at 2800 cfm. So Jegs here I go.

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1999 w140, quit voting to old, and to old to fight, a god damned veteran

that sucks. Anybody want a metal fan?

guess they have different flow rates.

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At least some 240d's had no fan clutch, just a direct drive metal fan.

I once had a fan blade break off at 60 mph on a Toyota FJ55 Cruiser. Hell of a shock. Whole truck was vibrating like crazy. I thought I'd thrown a rod. Blade went up thru the radiator, straight thru the hood and up into the atmosphere. No prior indication of a problem. I now remember to keep my body out of line with the fan.

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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

Its a completely different fan though.

The aluminum clutched fan is designed to never see more than 3500rpm with the clutch locked. If the clutch is seized solid the fan can be spun higher to its failure point.

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Theoretically.

Personally I doubt that they would. I would think that the engineers at benz would design it to stay together in the event that the clutch binds up.

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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.

I have a vague recollection of a tab on the back of the clutch that enable a person to lock the clutch to the water pump and fix it in place should the clutch fail. This allows a person to get full cooling from a failed clutch. Am I just imagining this feature?

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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

I didn't see any such tab on my car. And when the fan clutch failed, the fan basically freewheeled. The good news is my late W126 has two shrouded pusher fans for the air con, and those were able to keep it from overheating (I unplugged the temp sensor to make them come on all the time)

-Jason

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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.

I don't see one.

Here's a post from years ago that I made. That's what I was thinking about.

Locking engine fan "ON"

Looka like that tab is on the van clutch.

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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

In all of the cars that I have owned, 2/3 of them were electric cooling fans. None of them failed. I have had 4 mechanical fan clutches fail, all failing on rather than freewheeling.

The performance and economy of the 3 vehicles that I converted to electric cooling fans from mechanical was noticeable, but in most cases worth it when changing from a BROKEN mechanical fan but maybe not to convert from a working mechanical fan. In all cases, the properly sized and controlled electric cooling fans performed better than the original system.

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Ron Schroeder
'85 300 Turbo Diesel 2 tank WVO
'83 300 Turbo Diesel 2 tank WVO
Some former WVO vehicles since ~1980:
'83 Mercedes 240D
'80 Audi 4000D
'83 ISUZU Pup
'70 SAAB 99 with Kubota diesel
'76 Honda Civic with Kubota diesel
'86 Golf
Several diesel generators
All with 2 tank WVO conversion
LI NY

hopefully you will come to your senses after being on this forum long enough.

Which electric fans were you considering?

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done bought one for a Mustang conversion 3800 cfm,works great.Even wired the Mercedes aux fan in case of failure.16" trouqflex.

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1999 w140, quit voting to old, and to old to fight, a god damned veteran

When the fan clutch on my 300TD went bad, it started freewheeling and wobbling -- definitely non-functional and dangerous. Having worked in an auto parts store and having been on other boards for other marques', I know of damaged radiators from clutch failure, although I'm sure some here will claim it could never happen in an MB.

I was able to get a SPAL 30101516 fan and pulse-width-modulated fan speed controller for less than the price of a new fan clutch, so I went that route.