Could this happen? the fan clutch in my car seems to be stuck enganed, or at least it is engaged stronger than required and more frequent. Could this happen if the oil leaked from it? i thought it will be less engaged. Or, could the oil inside "gel" and loose its elasticity and stick stronger? should i replace the silicone oil? The fan clutch was new, about 2 years now without much driving. It is "Sachs" with the plastic fan. What is the danger of too much engagment? please help!
Thanks

With the engine off, how hard is it to spin the fan by hand? There should be moderate resistance unless the engine is super hot.

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2004 VW Jetta TDI (manual)

Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL

When you say 'stuck engaged', do you mean that you cannot turn it when the engine is cold, or what are the physical symptoms?

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1987 Mercedes 300D

here is what is happening:
When the car is cold, you can spin the fan by hand and it seems less resistance than when hot. After the engine starts ( 1 -2 minutes) and temp showing 40 or so, I turned the engine off from the handle and the fan has 2 -3 free revolutions before stop. Shortly after, I can hear the fan speed roaring when I raise the rpm. When the engine is hot enough (80-90), the fan still roaring. when I stop the engine, there will be no free revolutions in the fan, it will stop directly with the engine (stuck?). I can rotate the fan by hand when engine hot and off, with harder resistance. When I drive on the highway, I can hear the fan roaring (more noise than it suppose to be, I guess). I cannot see/feel when the fan is disengaged - very rare?!! I read in one website that the oil inside the fan clutch can be bad and gel causing it to stck engaged, here is the website:
http://zhome.com/ZCMnL/tech/FanClutch/FanClutch.htm
But I am not convinced. On the fan clutch, i can see traces of leaking oil, but I am not sure if it is from it or the engine (the oil is old and dried there).
Thank you for help
P.S. this fan clutch with fan is very expensive ($300), I am surprised now to know that the newer ones 9for engine 606 cost only $90. Will these fit in my car?

You might want to check out this thread:
Proper behavior of fan clutch

The consensus was that the fan should never really freewheel, even right after shutting off the engine. My fan clutch is brand new and there's always some resistance. The fan definitely makes more noise now but that's because my old fan clutch was always freewheeling.

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2004 VW Jetta TDI (manual)

Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL

I just read an article in popular mechanic that there is a valve in the fan clutch can be stuck either open or close, or opens fast etc. If it opens fast, the clutch will grip faster than normal and will be like this for longer time. They said that due to defective bimetal element (or could be dirt, or sluggish mechanism, I guess). The point here is the power that i lose due to this. Besides the danger of overloading the water pump and the fan etc. And ofcourse, less mileage.
what to do now?

From the information that you provided in post #4, it sounds like doing nothing is your best alternative.