Can somebody confirm this? Is it possible that a fan clutch will fail or slip at 3000 RPM engine speeds? I was driving at the freeway this afternoon at 70-80 MPH and RPM around 3000-3500 and the Engine Water Temp would creepp to 100 deg. C but if I slow down to 50 or 60 MPH at RPMs around 2500 or lower the Water Temp gauge drops like a rock at 85 0r 87 deg. C. The fan will immediately stop when the engine is stopped. It started acting up and behaved this way this afternoon. BTW, I dont think this type of fan clutch is rebuildable/servicable with viscous oil, it is one of those sealed type with MB PN: 116 200 0122 with a 9 blade Aluminum MB PN: 116 205 1906.

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'85 300D Turbo - CA Version

There is an old shade tree method of testing a fan clutch. When the engine is cold, give the fan a good spin by hand and if it spins more than five times it is time for a new one.

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Dave
1983 300D Daily Driver

I doubt the fan clutch is your problem if it's heating up at 75-80 mph, the fan is doing very little cooling compared to the road speed.

I would have thought the same thing until I started driving my Wanderlodge. It has a themostatically controlled electric fan clutch. It's very obvious when it engages. Even at 60mph, the effect of the engagement of the fan clutch is substantial. The temperature guage immediately starts to drop. Prior to this experience I would have thought a 60mph 'breeze' was much stronger than 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

I was just going by my 617 experience. When my clutch failed last year (you could hold it still with your hand with the engine hot), the temperature was close to normal on the highway (maybe 5C high), but it really shot up as soon as I got into stop and go traffic. Even at 40 mph the motion of the car was adequate to keep it reasonable (below 100C, or so). I agree that the fan helps at highway speed, but the primary symptom of a bad clutch should be high temperatures at low speeds, not on the highway.

If his engine is too hot at 70-80mph, but OK at 50-60mph it sounds more like a cooling system issue (radiator maybe) than a fan issue.

I tried revving the engine with the hood up and the fan would roar from 2000 to 3000 RPM but will quit roaring beyond that, as if the clutch is disengaging. And when I tried revving the engine via the throttle linkages, at higher engine speeds, i'm not sure what RPM, the fan is still spinning but the air speed is slower and weaker.

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'85 300D Turbo - CA Version

What do you all think? Looks like 20+ something years old? Do you think it's tired? or just lazy?

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'85 300D Turbo - CA Version

Looks just like mine.... The problem is likely something else. The fan clutch does not allow the fan to spin as fast as the engine. It begins to slip in the upper rpms on purpose so the fan doesn't go 4000+ rpm. (thats crazy fast for an engine fan) It'd also draw off a TON of power from the engine.

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-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

If I'm not mistaken, that fan clutch will have a small metal tab that can be bent into a slot to lock the fan and clutch making it a single unit with the fan spinning all the time. It's designed so that a failing fan clutch can be used as a solid fan until the clutch is replaced. (I've read this in one of the shop manuals). If yours has this, bend the tab, get the fan to turn all the time and see if it solves your problem.
Most 240d's (I believe) don't have a fan clutch so the fan spins at engine rpm all the time so I wouldn't be too concerned about overrevving 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

I was thinking about that but this type of fan clutch is sealed, and if I'm going to to that I want to use it with a more flexible plastic fan blade and not with an aluminum, but i don't have any luck finding a 9 blade plastic fan blade that will mount on this fan clutch. The 606's 11 blade fan upgrade would be perfect but it only has 3 holes for the bolt and I need a 4 hole type.

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'85 300D Turbo - CA Version

Your clutch is defective, probably low on oil. It should spin at engine speed up to 2500 rpm or so, and then slip and go no faster, but not slow down.

I suspect all the oil spins into the reservoir at high rpm and the fan slows down instead of staying at the correct rpm.

However, you need to check the radiator for cold spots -- I'd suspect your highway overheating is due to a bad radiator or water pump instead of the engine fan, it's not doing that much on the highway.

Do you have the under body panel installed?

Peter

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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!

You can trying to fill in the three holes with a plastic epoxy and then drilling the four holes that will make the fan line up with the clutch. As long as you let the epoxy cure and the sand off and excess, you should be able to keep its balance.

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Dave
1983 300D Daily Driver

I don't think this fan clutch is servicable with viscous oil. It is the sealed type and the metal strip in front is not visible, I can't even see the thermal coiled spring and I can't find any screw or holes that can be filled with oil.

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'85 300D Turbo - CA Version

The 606 11-blade fan that I saw has 3 tabs with a hole on each tab, so there's no way that I can rig w/ epoxy. I think the best option is to find a water pump for 617 engine with a that has the same fan clutch attaching point with a 606. You know what I'm talking about? The water pump that don't have the 4 bolt holes for the fan clutch, and only has a single bolt at the center instead to hold the fan clutch? ...and I don't think it exists...?

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'85 300D Turbo - CA Version