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Old 12-21-2003, 12:53 AM
The Warden's Avatar
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Location: Pacifica (SF Bay Area), CA
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Question Any reason to leave a fan with a dead clutch installed?


As I've mentioned before, I've got a dead fan clutch on my '85 300D. The clutch doesn't engage at all, letting the fan freewheel, and as a result, AFAIK, isn't making a real difference either way regarding cooling.

So, my question is, is there any reason anyone can think of to not remove the fan and clutch assembly and put the bolts back in (to keep the pulley from coming off the water pump) and just leave the fan and clutch off until I can afford to get a new fan clutch?

I've already got the fan removed (wanted to see if cleaning the clutch face would help, but it was already pretty clean, as I found out after getting it out of the car), so it's more of a matter of "should I put it back in or not?"...


2001 VW Jetta TDI, 5 speed, daily driver
1991 Ford F-350, work in progress
1984 Ford F-250 4x4, 6.9l turbo diesel, 5 speed manual
Previous oilburners: 1980 IH Scout, 1984 E-350, 1985 M-B 300D, 1979 M-B 300SD, 1983 M-B 300D
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Old 12-21-2003, 01:15 AM
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I think it's worth a $15 investment in a bottle of Toyota clutch fan silicone fluid. Cooling in the SDL improved with the 6000 centistoke variety. It's all in the archives.

I guess you'll be okay without the clutch fan if you don't idle for long and don't run the AC while idling and your electric fan is working.

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Old 12-21-2003, 02:12 AM
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In the long run; your'e right; adding fluid would be nice..although I thought I remember reading that, for some reason, that won't work on a 123.

And regarding leaving the fan off, I mean this as a short-term thing and as an alternative to the fan sitting there basically as dead weight, since the clutch is letting the fan freewheel...I'm guessing that nothing else will be damaged if I leave the fan off, but wanted to double-check. And I already keep a very close eye on my coolant temp gauge...
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Old 12-21-2003, 02:18 AM
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The factory shop manual claims that the viscous fan clutch is not serviceable. But maybe someone has figured out how to do that in the time since the manual was written...
It also says the fan clutch is NEVER to be placed with the front down.. and that it is supposed to be stored ( like at the dealer, on the way home to install, etc ) in the upright, working position...
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Old 12-21-2003, 04:20 AM
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I think most of us will never need the fan clutch as it only engages at very high coolant temps, something like 110C. But I think the fan is very important even when it's just free-wheeling and you should put it back. Now when it's cold you can probably get by without it, but in the summer you'll definitely see higher coolant temps if you run without it.
2004 VW Jetta TDI (manual)

Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL
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Old 12-21-2003, 07:32 AM
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Originally posted by DieselAddict
But I think the fan is very important even when it's just free-wheeling and you should put it back.
Why's the fan important when it's just free-wheeling? What exactly is it doing? I don't think it's really drawing any air in through the radiator...maybe I'm wrong?
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Old 12-21-2003, 12:00 PM
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The Warden,

The clutch fluid is available and so are illustrated instructions by doing a search. If you have the clutch out the process is mostly done, as the next step is to remove the bimetallic spring (a rectangular piece of sheetmetal) held in place by a screw and some slots. Then you remove a pin in a hole and, using some kind of a small nozzle you force the new fluid in the hole the pin came out of. Then you reassemble and put the clutch back in the car. It should work fine until the fluid leaks out again. I am not clear on how the fluid leaks out, or if the repair will last if the reason it leaked is not addressed. But it sounds like it is easy to fix, once the clutch is out of the car.

Removing the fan entirely will probably make you more susceptible to overheating while standing still. Once running at any speed the freewheeling fan is probably a flow blockage more than a flow inducer. Check to see if the fan turns at all while standing still. If it does turn, it is probably better to leave it in place. If not, it is really of no benefit and may be a hindrance at speed where the engine load is higher than at idle. Good luck, Jim
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)
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Old 12-21-2003, 12:08 PM
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"Why's the fan important when it's just free-wheeling?"

It is not SUPPOSED to be freewheeling except when the air coming through the radiator is below a certain temperature...

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Old 12-21-2003, 12:19 PM
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When I bought my 409d it had no fan or clutch on it since the clutch had been damaged. It was cooled by a manually switched electric fan. When I reinstalled a clutch and fan, it ran cooler and at a more consistent temperature even without the fan clutch being engaged. For what it's worth. By the way, I paid $5 for a fan clutch at the local pick and pull. The clutch on a 230 gasser was the same (?) as the clutch on the 617 in my 409d. The repair looks pretty simple depending on whether the pick and pull is closer than a Toyota dealer who sells the fluid.
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
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Old 12-21-2003, 01:11 PM
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The visco clutch never freewheels completely -- it should be somewhat stiff when the engine has been sitting a while, as the fluid will be in the bottom.

The fluid normally leaks out the pin, I think, as it runs down with the engine stopped.

Get the Toyota fluid and refill it, at least. If the fan isn't doing anything at all, you run the risk of overheating in traffic.

1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!
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Old 12-21-2003, 02:14 PM
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"The visco clutch never freewheels completely"--Psfred
Peter, have you read the description of the vicous clutch in the FSM ? What is your definition of free wheeling ? Want to reconsider/restate/modify the above sentence ?
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Old 12-21-2003, 06:12 PM
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I got the bimetallic spring off and got to the pin you guys mentioned (at least I think it's the pin; it's dead-center on the clutch), so you're right that it's not that difficult to get to once the clutch's off the car.

The bad news is, I don't think there's a Toyota parts store that's open on Sunday around here, so I'm thinking on the lines of leaving the fan off the car for the trip down there and finding a Toyota dealer down there that'll (hopefully) have the fluid...
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Old 12-21-2003, 07:32 PM
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I don't think you're gonna hurt anything running without the fan as long as you are not stuck in traffic and keep moving. Just keep a close eye on the temp gauge. Freewheeling is a funny definition. Most of the dead fan clutches I have seen still spin the fan and move some air they just don't engage when things heat up like when towing, etc. If its really dead and not spinning then pulling it off like JimSmith suggested can't hurt since its already not doing anything. I would opt for the boneyard replacement myself. RT
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Old 12-21-2003, 07:43 PM
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If you're worried about it overheating just "rewire" the electric fan to stay on all the time that it's running... that should keep it cool enough at least during the winter.... probably most of the summer over there in SF.
1985 300D Turbo ~225k
2000 F350 (Powerstroke) 4X4, SWB, CC, SRW, 6spd ~148k
1999 International 4900, DT466e (250hp/660 ft/lbs), Allison MD3060 ~73k
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Old 12-22-2003, 03:13 AM
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Or... wire your factory fan with one of the adjustable thermostatic controls. They usually have these for sale in the streetrod mags, etc.

My '81 VW Jetta diesel ,w/factory electric fan, stays cool and the fan rarely comes on even in the summer !

I have a '83 6.2 Diesel Chevy van. Removed the engine driven fan and shroud and replaced w/thermo controlled aftermarket electric...been running it for years like this...the temp is just right and the fan rarely runs. Gets great fuel mileage and it's MUCH easier to work on !

I have an '81 Gas van - Ditto.

I have yet to have a good enough reason to modify a Benz this way, but I think it is doable. The alternator output is the only ??? I know of, but that should be solveable with a higher output alt. No fan should work also, if you can avoid long, thin parking lots.

Whatever you do, don't let that beautiful and expensive chunk of cast iron get overheated

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