Clutch Fan on 300D 124

[francis]

Any other way to check if fan is busted? I noticed that when I turn off the engine, the fan still spins quite a few turns and when I turn it by had (engine newly turned off) I feel no resistance.

How is the fan suppose to work? Does it get harder to turn when engine is hot?

Thanks!

Francis

[jeffsr]

Francis, your fan clutch has gone south. If it is still spinning after you shut down the engine, it has lost it's ability to "clutch". This device operates on a viscous coupling which, when it reaches a preset temp engages the fan blades to the fan pully, thereby increasing air flow thru the radiator. the clutch is there to prevent wasting horsepower driving the fan when the extra load (heat) is not there. This is a precision device (why they are soo $$$). When the coupling loses its' silicone oil (most frequent cause of failure) it is no longer able to engage when the ambient temp rises. It should get harder to turn as it gets hotter.

[Benzmac]

I believe that Jeff is correct in his analysis. We sell them in the partsshop if needed.

------------------
Benzmac:
Donnie Drummonds
1992 500E (very soon I hope
1981 280GE SWB
ASE CERTIFIED MASTER AUTO TECHNICIAN
SERVICE MANAGER FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM

[be459]

Per my document, when the engine is cold, the fan couples at 2100 rmp until the fluid move from the working area to the resevor. When it is at normal operating temp., the fan should not run faster than 2100 rpm. When it is between 90 to 95 degrees, fan coupling starts. The fan rpm will increase up to 3500 rmp as engine rpm goes up.

When you turn the fan by hand and feel "no resistance". How much resistance is said to have "no resistance"? It is obvious that the fan has resistance since the fan turns only a few turns after the engine is off. If there were no resistance, the fan would keep going for a while (like turning off a household electric fan).

Speed up your engine to about 4000 rpm when the engine is at operating temp and then speed it up again when when it is about 90 to 95 degree. If the fan clutch is working you should be able to tell (by the noise) the difference of the fan speed (2100 rpm vs. 3500 rpm) between the two occasions. Also, if the fluid is leaking or the shaft has too much play, you will need a new clutch.

Here is my problem. My diesels never operate over 85 degrees during idling. I have to drive it up hill for a while on a hot day with A/C on in order to got the engine up to 90+ degrees.

David

[francis]

got a point here David. Thanks! Will I be able to hear the fan at this temp? coz' the AUX fan would be on this time and this makes a pretty loud hum. Should I disconnect the AUX fan first?


Thanks guys! Will let you know.


Francis

[be459]

Francis,

When you know what a 3500 rpm fan should sound, it does not matter if the aux is on or off. I don't know how to explain the fan noise to you.

You may want to try it on a MB having a good fan clutch (of the same type as yours) listen to the noise of the fan at different rpm and different engine temp.

Maybe, someone else can you you a better suggestion.

Have fun with it and just be careful with the fan blades, keeping things away from the blades, no loose sleeves, etc. I think yours is metal fan which may chip when it is running. Auto repair is a dangerous occupation.

David

[francis]

Tested the fan again and here's what happened:

Run the engine til' 95 degress for about 30 mins parked, my max temp went up very near 100 without AC on. IS this normal?

When I turned the engine off, the fan kept on spinning like a house fan when you turn it off. Definitely "no" resistance at all. When I spin it by hand it would just go on spining for about 4-6 seconds.


Francis

[jeffsr]

Francis, your fan clutch is kaput!! If you don't replace it, you will eventually wind up with an over heat condition (not good). The temp is rising b/c the fan is not working. Get a new clutch ASAP. I dont't know how warm it is in the Phillipines right now, but this problem (fan) will not go away without your help..

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Jeff L
1987 300e
1989 300e
1987 BMW 325

[francis]

Thanks Jeff!

Will be getting a new fan today. Just want to add one more thing - When the engine is cold, the fan "has" resistance. I try to spin it with my hand and it goes about a quarter turn and that's it, but when the engine is hot it goes for about10-15 turns. Weird - is'nt it suppose to be the opposite?


Thanks!

Francis

[jeffsr]

Nope, not weird. When the oil and housing are cold, the oil is somewhat more viscous and will produce slight resistance to turning at low speed (read turning by hand). As it warms up and is under more of a load the oil will flow into the rotor stator vanes and clutch the fan.

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Jeff L
1987 300e
1989 300e
1987 BMW 325

[This message has been edited by jeffsr (edited 04-28-2000).]

[francis]

So is is safe to say that a good working clutch fan should have more resistance when engine is hot?


Francis

[jeffsr]

Yes, that's generally true. But,remember, when the fan is turning at speed >2000 RPM, there is a lot more dynamic force in play than when you try to turn it by hand. Centrifugal force also plays a big part in the operation of the clutch. You don't get that component when it's not moving or you're turning it by hand.

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Jeff L
1987 300e
1989 300e
1987 BMW 325

[This message has been edited by jeffsr (edited 04-28-2000).]

[francis]

My car is an 1985 (W124) 300D Euro - 603 engine.

Got a new Clutch fan (603 200 00 22) but it still keeps on spinning after I shut engine off. About 10-15 turns. It has no resistance. I also tried to stick in a rubber hose while the engine was running at 95 degrees = The hose eventually got the fan to stop in about 3-4 seconds. I tried this in an E280 (W124) at 85 degress and the rubber hose could not stop the fan.

I also shut down a friends 250D (W124) and the fan stopped as soon as the engine was shut down.

Does anyone know if the clutch fan for 300D is really like this? I am afraid that the new one I got is a factory defect.


Francis


[This message has been edited by francis (edited 05-03-2000).]

[This message has been edited by francis (edited 05-03-2000).]

[be459]

Francis,

Actually, testing the clutch is very simple. Based on the clutch specifications I provided in my previous post, you can come up with some sort of test method to test it.

Here is what I would do,

(1) Idle the engine to normal temp. Then speed up the engine rpm from idle to about 3500. If the clutch is working at that temp., you should only notice a little increase in the fan speed because the specification is calling for maximum of 2100 rpm fan speed even if you increase the engine rpm.

(2) Next step, idle the engine to 95 degrees. Many diesel cars have hard time to reach that temp during idling, you may have to put newspaper in front of the radiator to get to 95 degrees. When you use the newspaper, watch the engine temp. I don't want you to overheat the engine. When the engine gets to 95 degrees, increase the rpm from idle to 4000. If the clutch is working, you should hear the loud noise from fan and feel the high volume of air flow (compare to the test performed during normal operating temp.)as you increase the engine rpm to 4000.

Your new clutch should pass these two tests.

David



[This message has been edited by be459 (edited 05-03-2000).]

[jeffsr]

Francis, Is the engine overheating? Is the fan doing the job. I wouldn't be trying to stall the blades with a rubber hose, or anything for that matter. Dangerous and really stresses the inside of the mechanism. If it's not keeping the engine temp in an acceptable range, bring it back and demand another replacement.

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Jeff L
1987 300e
1989 300e
1987 BMW 325