Does anyone know with certainty how to tell if the viscous fan clutch is faulty? I have a 1995 C280 with 130k miles. I have heard several different views on this. Some say the fan should have a good bit of resistance when turned by hand and the engine is cold. Others say it does not begin to lock up until quite hot. I can keep mine from turning when the engine is started easily (not using my hand, BTW).
The temp continues to creep up in hot weather where it did not before. Water pump and thermo are new. Radiator clear and fins unobstructed. I use distilled water, Water Wetter, and the DIY Cool Harness mod. All of this has served me well until this summer. BTW, the aux fans are also new and kick in and out to specs. Any help on the fan clutch is appreciated.
RG
Last edited by 95280GUY : 07-24-2008 at 01:46 PM.
Reason: misspelling
The Fan Clutch should be EASY to spin when COLD and HARDER to SPIN when the engine and Clutch are HOT! Think about it... When the engine is cold you don't need the mechanical, or the electric fans so no need to waste horsepower on them right? When the engine is HOT that is when the Bi-Metal Clutch does its job and becomes MORE resistive engaging the Fan. Make sure the front of it is clean! This does affect how it operates. If you have an original one you may want to consider replacing it since you have done everything else already. I'm big on staying ahead of trouble... I'll even bet YOUR money on it!
I posted this somewhere else, but FWIW, one of the MB mechanics on another forum uses a test where he lets the engine warm up and then puts it in park to idle. He then carefully takes a thick shop rag to protect his hand and tries to stop/slow down the fan by friction from the rag as it rubs against the blades of the fan. If he can stop it, he knows it is time to replace it.
It's probably time to replace it. Mine spun freely and was creeping up in temp around 110k. I replaced mine not long ago. Once I replaced it there was an obvious difference. The part is cheap and the job is so-so. More of a PITA than anything. Be careful NOT TO poke a hole in your radiator. Do a search on the job. I think I even posted pictures on it.
Mods should really sticky this, or put it in the common problems thread (which honestly got hijacked and doesn't seem to be as useful as it could be, but I digress.)
Thanks for all the feedback guys. I think I'll replace it. As noted here, it's cheap and now I have some good pics for removing the radiator. Ordering one today along with a new serp belt.
BTW, any thoughts on where to get the clutch holding tool?
EL PASO Ebay store has it. I just ordered it and don't have first hand experience with the tool yet. There are other tool stores which sell top quality tools with higher price.
FWIW, I had good luck with El Paso when I ordered a transmission dipstick. Fast shipping and quality was decent (considering the price). Let us know how your purchase works out.
Fan Clutch 
Linear Mode
