I was told that my fan clutch could be malfunctioning- meaning the fan is spinning all the time and sapping power.

After reading about testing methods, I let the car sit for a few hours and tried to spin the fan. It moved but with significant resistance. Does this mean the hypothesis is correct... the clutch is stuck engaged, causing the fan to spin when the engine is cold?

This is opposed to what seems like the more common problem of the clutch freewheeling when the engine is hot, causing overheating. Proper function would be to freewheel until the engine gets hot, then the clutch engages and the fan spins with it, correct?

So if this is the case, do I need to replace it or should I try cleaning the spring- I only saw cleaning the spring as a solution to the clutch not engaging. If my clutch is stuck engaged, spinning the fan all the time, whats my next move?

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1984 300CD

Rare, but possibly the operating pin behind the thermo-sensing plate is stuck out in the on position . In this condition the fan makes a loud whooshing noise due to air flow all the time.
you may like to check if the pin is free to move in out as the plates flexes out l ,ideally under hot operating conditions.

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mark

Static tests of the fan clutch aren't very meaningful. Instead, watch the fan when you shut the engine down when hot and when cold.

Mine recently failed in the engaged position also. It rattled and squeaked for a while and then practically locked up requiring lots of force to turn it. New ones are expensive but I was able to purchase one from a forum member at considerable savings. Seems like I read that they should be stored and shipped on edge whenever possible, not flat.

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1983 M-B 240D-Gone too.
1976 M-B 300D-Departed.

"Good" is the worst enemy of "Great".

tango, elaborate?

When the engine is hot, the fan should stop in one or two turns?

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1984 300CD

nevermind, if mine is stuck it will always behave as if the engine is hot...

so what is the proper procedure for me to check this?

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1984 300CD

Cold engine: engine stops, fan spins (freewheels) multiple times.
Hot engine: engine stops, fan stops almost immediately.

Use the manual shut-down lever so you have a good view.

That's true. Getting UPS to cooperate is another matter, entirely.

Did this test this morning-

dead cold, fan stops immediately.

Guide me, o great bogwon!

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1984 300CD

with a stuck clutch, you are wasting hp, I'd source a new one, or a good used one.

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

TRUE... either you read it in the FSM... or somebody quoting the FSM...

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1980 240d ,

chain elongation, cam marks reference:
http://www.peachparts.com/shopforum/showthread.php?threadid=10414

http://www.peachparts.com/shopforum/diesel-discussion/305365-9-degrees-chain-stretch.html

evap fin cleaning:

http://www.peachparts.com/shopforum/showthread.php?t=156207&highlight=evaporator

A/C thread

http://www.peachparts.com/shopforum/diesel-discussion/297462-c-recommendations-mb-vehicles.html

Shutting the engine down immediately after start-up will give a false indication, since the clutch will normally be engaged initially. Since the clutch depends on centrifugal force to operate, you might want to try running the engine for a couple of minutes at 2000 rpm before you draw a conclusion.

TF007 is correct. When you first start cold, the fan will be engaged and roar when you rev the engine until the fluid is distributed and the fan disengages.

It should not be engaged and roar with engine revs after that, with the hood up you should not get a lot of wind and noise from the fan when revving.

Once the coolant is up around 195F (check the FSM for the exact number) the fan should again engage, which will turn it up to around 3000rpm and then the clutch will partially disengage to limit max. fan RPM.

The fan should turn with some resistance when the engine is shut off, hot or cold. Without the engine running the clutch can't operate, the hub needs to be spinning. If it spins freely it has probably lost its fluid. If locked up, it's probably seized. If it has ANY perceivable play, find where the play is (loose bolt, bad bearing, etc.) and replace the offending part(s) before you lose a radiator and fan. Clutches are expensive, but when you add the fan, radiator, belt, shroud, and anything else that could be damaged the clutch will seem cheap.

Also, as mentioned, the clutch is a speed-limiting device for the fan. If it is somehow locked up you run the risk of the fan coming apart at high RPMs like a BMW fan, which can also get expensive.

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Gone to the dark side

- Jeff

so, just to get this down for anyone else who attempts it in the future-

start up the car cold, run for a few minutes at 2000rpm, then shut it off and the fan should spin multiple times. after the fan slows, should i try to spin it and feel for resistance, or is this purely visual?

because the clutch is meant to engage at 90-95c, if the engine is above this temperature the fan will stop almost immediately after shutoff.

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1984 300CD

Just look (visually) for the fan to freewheel when the engine is shut down cold.

pretty certain it's seized. seems pretty common to have problems with these fan clutches, should I replace new or is working used generally okay?

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1984 300CD