Viscous Fan Clutch
 

My car runs fine on freeway but in stop n go traffic the temp. goes from 90c to 110c until the aux. fans switch on and bring it back down to 100c.
The process is repeated until I hit the highway and she's back to 90-95c.
I changed the cap,thermostate and coolant (50/50)mix and radiator is 1 year old.
My only suggestion from reading the forum is the viscous fan clutch.
A few tests have been done and the results were:

1-on start up in the morning I take it straight to 2000rpm and I can hear a loud howl for 20 secs then it goes away.

2-When turned off cold,the fan spins freely.

3-When turned off hot,fan spins freely(same as cold).

This leads me to believe that it's the VFC (no fluid).Am I right?
If so how much fluid shall I put in?

You cannot add fluid to the VFC. They come sealed from the factory. Once it's gone, it's gone.

Thanx for the quick reply,but do a search and you will find otherwise

There was a thread a while back on someone drilling a small hole in the fan clutch and re-filling it with fluid. It might work, but I'm sure its just a temporary fix.

A new one should cost about $100-$120

First, never take the engine right to 2000 rpm stone cold, you have essentially no oil circulation and you will eventually ruin the bearings and cylinder walls. Wait 30 sec or so, and drive slowly for at least two blocks before exceeding 2000 rpm. The engine will last at least twice as long.

You almost certainly have a dead visco clutch. If it's covered with greasy dirt, it's dead for sure (that's the oil that is supposed to be inside).

The new one is pretty easy to install, you need an 8 mm Allen, a coathanger wire, and a few minutes. Pull the fan shroud clips, insert the allen into the center of the clutch, use the wire to trap the clutch from behind (should be a small slot in the bearing bracket), loosen allen, unscrew it (use both hands, it's tight in there!), remove clutch and fan complete. Unscrew fan from old coulth (10mm screws, I think), screw onto new clutch, install using the coat hanger to tighten. Very easy.

Peter

Psfred,it is covered with greasy dirt.
When engine is hot and I turn the car off the fan just free spins like when cold.Shouldnt it stop within 1 revolution?

I have read on the board that these fans can be filled with new fluid.???

The viscous clutch keys off radiator exit air and this seems to correlate well with a coolant temp of about 100C in warm weather. Once the fan clutch tightens I can hear distinctive "fan roar" begining at about 2000 revs.

This is my "test" for a properly functioning fan clutch. Get it hot enough (100C or a little over) to engage the viscous clutch, but not hot enough (about 105C) to engage the electric fan(s). Then listen for fan roar at about 2000 or above. If you hear it, the clutch is probably okay. If not, the viscous fan clutch is probably dead.

Duke

Great news! It was my VFC and its all done and my car has never been better.The temp barely reaches 95c with ac on in 30c weather.
Thanx to all who responded.
I do have a bit of a howl now,maybe too much fluid?

Did you refill it or buy a new/used one.

Good info here: read the whole thing, great pictures by TomJ.
http://www.peachparts.com/shopforum/diesel-discussion/89145-write-up-fan-clutch-repair.html?highlight=tapped

I keep hearing that it happens, and I have no doubt that it does, but how, and from where does the fluid actually leak out? The Viscous clutch appears to be hermetically sealed.


Phil

The howl is the fan running, and if you dont' get that noise, it's replacement time again.

The oil leaks out the actuating pin seal and the back seal. Silicone fluid "crawls" badly.

Peter

nhodges,I refilled it with approx. 25ml of 10000cst from toyota.

pberku,the fluid leaks out from the seal on the pin hole and you can tell by looking at your fan to see if there is any greasy dirt on the blades(like mine).

psfred,you have been very helpful in this matter (thanx).The howl is there at any temp and is really noticeable between 2500 and 4000rpm.
Is that the way it's supposed to be?Just sounds too loud for a benz.

If it howls all the time, locate the bad bearing and replace it. It will eventually fail and cause big trouble.

Also check for a belt one "row" off on something, as this will make noise and quickly ruin the belt.

The fan should roar only on startup and when "engaged". Some are lower than others, I can barely hear the one on the 280 (will probably be able to tell better when I get the exhaust leak fixed), but the one on the Volvo TD sounds like a jet engine when it locks up!

Peter

It should not sound like that all the time. Either you put in too much fluid or, like Peter said, the bearing is seized. My story of bearing seizure is here.