Is there a way I can test whether my fan clutch is working properly? I am worried that the clutch may not be engaging and so while I am in gear a red light the fan spins at a low speed, and thus not suffuciently cooling the car. I am ready to buy a radiator but I dont want to just start replacing parts, hoping one of them may stop my overheating problem.

What car?

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'95 E300 Diesel, 264,000 Miles. [Sold it]

Start with the simple things. Put in a new radiator cap. If the cooling system is losing pressure through the cap it will overheat. with the car running and hot take a towel and hold taught between your hands and try to stop the fan from turning. If the fan clutch is working it'll take some effort to get it to stop. Search for fan clutch.

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89 300te 222,222
92 300e 190,000

While doing some major work on my car, I thought I would replace the overflow tank cap. The new one was really tight. So tight, it loosed the crimped metal top of my overflow tank. This is now bubbling and seeping when the car is hot and it's running 5 degrees hotter than it did before. This is a sneaky problem, and I don't see any practical, permanent way to fix it short of getting a new bottle (which I did, $60).

Maybe I should have left well enough alone!

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86 560SL
With homebrew first gear start!
85 380SL
Daily Driver Project

http://juliepalooza.8m.com/sl/mercedes.htm

A mechanic told me this trick. Get an old radiator hose (I used a rolled up towel). Start your car. Let it warm up. At idle, stick the hose gently into the fan. If it stops easily, it's bad. BE CAREFUL if you ty this.
Mine stopped VERY EASILY & took about 30 seconds to come back up to speed. I put a new one on (4 bolts) and my problem is solved (temp was creeping up when I stopped at 3 or 4 red lights in a row).

The clutch in my vehicle is really goofy. When cold, it stiffens up fairly well. When hot, it free-wheels very easily. I just received a new fan clutch yesterday from Phil at Fastlane (best price around). I'm going to put it in this weekend. The V12 ran VERY hot last summer. I swear you could melt lead on the intake manifold. This should bring it down to acceptable levels.

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1995 S600, 1 of 618 (sold)

"Speed is just a question of money...how fast you wanna go?"

LONG LIVE THE W140!
Visit my Web Page at www.v12uberalles.com

I think that your car has the newer type viscous fan clutch. If that's the case, it will WILL NOT ROAR when it engages. The best way to test it is as follows:

Next time your engine temperature rises above 100C, do the following:

a) With the engine idling, look closely at the rotating fan.
b) While you are looking at the Fan, get a helper to shut-off the engine.

If the fan stops turning within 1-2 revolutions than its OK. If it free spins for a long time than it needs to be replaced.

Phil

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'95 E300 Diesel, 264,000 Miles. [Sold it]

Guys all this information is very very helpful, I will try all of these suggestions in the morning.

Thank you so much.

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190e 2.6 1990. 300,000 KM
C230 K 2000, 130,000 KM

Whoops, slight error in my post - it should have read that I've replaced the fluid twice, not the actual clutch. That's my next job!

Duke2.6 and pberku's testing suggestions are correct but you definitely have the elder clutch - it has no electronic governing system as so will react as suggested.

Just a couple of points to correct some of the previous posts; the fan doesn't need to be cold but simply left standing for around 15minutes. This is usually long enough for the fluid to change from chamber 2 to 1 under gravity and it's in chamber 1 which the fluid grips the fan.

According to MB data the fan will rotate at half engine speed until 90-105degC (air exit temp) which translates to around 85-95degC water temp -due to losses, thermal relief in engine block etc.

I used to own the same exact car and yes it should 'roar'.

You will also note the design is such that it will also disengage at >=4500rpm for efficiency reasons - MB assume that there is plenty of air traveling through the rad at this high rpm and you're not still and simply just reving.

Your symptoms do seem to indicate that it is indeed cutting in when hot, but I wonder if you have lost fluid and so the fan isn't attaining the correct rpm. I have exactly this with my current 500SL and have to top up every 6 months as gradually the fan rpm slows (the clutch progressively slips) and engine temperature slowly increases.

Lea

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'93 R129 500SL-32
'89 190E 2.6 - sold in 2002

http://antron.pwp.blueyonder.co.uk/i...nature/Sig.jpg

. . different models but my vfc starts to cutin around 100C because that's where the bimetallic switch (bms) bends enough to allow the 'juice' to flow into the proper chamber.

If you look at MENU#21 where I tested the bms, you can see that it around 100C there is enough bending to engage the vfc. So you can see that to get 100C EXIT temp, the engine coolant has to be MORE than 100C, thus the complaint against the vfc operation. "AIR" is the coupling medium that causes the bms to bend. So for the bms to bend enough, the engine temp has risen way over 100C probably 110C+ to get 100C air temp. That's why the vfc mod described in MENU#20.

I tried to get some companies interested in making a lower temp version bms. But after some initial interest, nothing ever came of it. The target was 90 -95 coolant temperature.

The other point is the cut-out point is around 3000-3200 prm. That represents about 85 - 90 mph.

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Regards . . . . JimF
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'94 S500 Cpe

Visit my Mercedes Web Page

I have to chirp in here about the suggestion one stick a towel or rubber hose in the fan while it is turning. I am a paramedic and attended to an incident a number of years ago where a mechanic was doing exactly that. I piece of the fan broke loose and struck him in the neck, taking out the carotid artery, internal and external jugulars. Needless to say, such an injury is not compatible with life. He bled out almost instantly.

The idea of heating the car up and shutting it down and testing if the fan has stiffened up seems way more sensible.

Play safe everyone

What kind of fluid can I use to replenish the clutch??

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190e 2.6 1990. 300,000 KM
C230 K 2000, 130,000 KM

Jim, Could not resist, I am back,

Here is the relevant extract from the W124 "Mercedes Maintenance Manual". Procedure No: 20-310. This is also applicable to all other Mercedes models that use this type of Viscous Fan Clutch. If you like I can E-mail it to you.

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"The Viscous fan coupling is a maintenance-free hydraulic coupling which operates steplessly dependent on temperature.

If the coolant temperature rises because of higher engine load or high outside temperatures, the air which flows through the radiator and impinges on the bimetal strip, becomes warmer. The bimetal strip alters its shape as it heats up and opens a valve at approx. 71C by means of a pin and thus also the passage of oil from the storage chamber into the working chamber, which causes the fan to cut in.

The coolant temperature during this switching operation is between approx. 90 - 95C
--------------------------------------------------------------

Jim, The above states that the Viscous Fan Clutch has been designed to engage at an air temperature of 71C, which is approximately equivalent to a coolant temperature of 90 - 95C. The Auxiliary fans on the other hand trigger at 100-105C. So by design, the Viscous Fan Clutch will engage BEFORE the auxiliary fans.

Phil

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'95 E300 Diesel, 264,000 Miles. [Sold it]

i just read this thread and i was wondering if i have a viscous clutch?how do i fill the cluch and with what fluid?
car is '95 s500

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'95 s500 (bought for wife but can't bear to share!!!) 125kms
'92 legend 180kms
'88 tbirdturbo(fantastic car-only regular maint.)120kms
'87 mustang gt(gone)
'86 tbirdturbo(gone)
'85 mustang gt(gone-but not forgotten)

Hi Rory

Sorry for the name confusion thing . My name is often mispronounced as Leah (Lee-ah) but anyway, I think it's often just my colleagues winding me up more than anything! So apologies.

Hi daddyiojiggy - welcome to the thread. Wow, that must have been a mamouth read if you started from the beginning!

Both the 119.970 and 119.980 have the MB clutch 119 200 00 22 which is identical to mine - not surprising since my SL500 engine is a 119.972 I suppose...

Here's a post I made about refilling over on the SL forum Viscous clutch/fan repair

I used Dow Cow Corning 200 Fluid but the recommended VFC fluid is Dow Corning 211. The 200 has identical viscous temperature characteristics but comparing data sheets the 211 may have better sheer strength and high temperature properties than 200.

Simply remove the pin and use a 5ml syringe, I pumped in around 30ml on my first refill and 40ml on my second - of course the vloume is debatable and so I simply kept filling until it started to significantly tighten.

One obvious thing I have learnt is that if you need to refill, then the clutch has a leak - and I know of no repair. The leak emanates from the centre bearing and over time gives the inside of your fan shroud an unwanted fine coat of silicone!

Hope this is of some use..

Lea

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'93 R129 500SL-32
'89 190E 2.6 - sold in 2002

http://antron.pwp.blueyonder.co.uk/i...nature/Sig.jpg