How does one test a viscous radiator fan? - PeachParts Mercedes-Benz Forum

pberku · #1 03-22-2004, 10:04 PM

I suspect that my '95 E300 Diesel's viscous radiator viscous clutch fan is not functioning properly. The reason I say that is that my car runs hot, (but does not overheat) when idling.

How does one determine if this component is functioning properly or not?

Thanks

Phil

psfred · #2 03-22-2004, 10:23 PM

Visco clutch should drag the fan up to engine speed when it gets to something like 90C or so. You will hear it, usually roars when it's engaged.

It should also roar for a second or two when first started. All the fluid will collect in the bottom of the housing and cause the fan to engage until it spins out again.

Best way to check is to get engine hot enough that the fan should be engaged, then check for air flow at idle. Should be substantially higher than when cool. Next, shut the engine off while watching the fan. If it makes more than one revolution after the engine stops, it's not engaging, usually because all the oil has leaked out. This normally leaves a sticky, filthy mess on the fan clutch.

Peter

gsxr · #3 03-23-2004, 12:56 PM

The later style OM606 clutch is much harder to diagnose than the old 617 clutch (never played with a good 603 clutch, and the 603 # supercedes to the 606). My two 606 clutches are recent and known good but you can't hear them roar - period. The 617 fan is very obvious when it roars. The 617 clutch, when engaged, if you shut down the engine, stops with the engine like it was locked to the pulley. The 606 clutch does NOT do this. Also, the 606 clutch will always leak some fluid. Both of mine do that. You need to clean it periodically as the collected gunk affects operation. In addition, it won't work properly unless the radiator is hot in the area directly ahead of the clutch, AND there is airflow through the condenser+radiator. Lots of room for failure here outside the clutch itself!

My recommendation is to start the engine when cold, let it run for a few minutes, and press the stop button on the fuel filte (I think that's how you kill the OM606 under the hood). Watch the fan. It should spin quite a bit after the engine stops, freewheeling. Now get the engine as hot as you can, 90-100C, A/C running, etc... and repeat the same test. On my cars, when the clutch is engaged, you can't hear it roar but when you kill the engine, the fan stops within about 2 revolutions - big difference compared to cold. You may have a hard time getting the engine hot enough.

BTW, Phil - how hot does it get when idling? I'd suspect the radiator or thermostat before the fna clutch. Make sure the fins are clean, you'd be amazed how much crud can build up.

Rick Miley · #4 03-23-2004, 01:48 PM

Dave, there's no underhood shutoff for a 606. The electronic shutoff solenoid (literally a black box) is on the side of the IP. I looked and looked for some sort of shutoff but gave up when I found the spot on the W210 technical CD that says they eliminated it.

Oh, and thanks for the tips on the fan clutch. I think mine is belly up as it spins like crazy after shutoff in 100*C, 80*F ambient conditions.

gsxr · #5 03-23-2004, 01:52 PM

Really! Maybe I'm thinking of the 1995 E300, I would have sworn that had a shutoff near the fuel filter, instead of the injection pump. Sounds like all W210's have nothing, that's a bummer. I'd make sure the clutch is bad before replacing, they're not cheap. We can re-fill the old 603 clutch with new silicone oil but so far, nobody has figured out how to refill the 606 clutch:

Rick Miley · #6 03-23-2004, 02:00 PM

pberku, does yours have a shutoff button? Maybe it is only on the W210 that they dropped it.

I'm not replacing mine anytime soon as the electric fans keep it cool enough (never gets over 100, and stays at 80 while moving) and I don't have the time right now for proper diagnosis.

pberku · #7 03-23-2004, 03:53 PM

If you are referring to the emergency shut-off button than mine is right on top of the main fuel filter. Its actually a knob with the word "Stop" on it.

For some bizarre reason however it does not shut-off my engine when I fully close it. I took it off and looked at it, and I can't find a rational reason as to why it would not shut-off the engine when turned (clockwise). The mechanism itself works fine, yet the engine will keep on running. If I ever have to use it I will have a problem.

In any case thanks for the great info on the viscous fan clutch. I will have to wait for a hot day to do the further testing that was suggested. Last year my car was reaching over 105 degrees when idling. I changed the thermostat 3 weeks ago, but last week when it was 35F outside and with the car idling for 15 minutes the temperature started climbing towards and just past the 100F mark. It should not have gone that high with such a low ambient temperature, but, I'll have to wait for a hot day before I can test the clutch as suggested.

Also if someone does have an idea as to why the emergency shut-off knob does not work on this 95 E300 Diesel, I will very much appreciate it. I shoul mention that I did take it out and looked at the mechanism itself, and it works fine, so I am very puzzeld.

Phil

gsxr · #8 03-23-2004, 03:58 PM

Phil,

You are correct, 100C+ when temps are near freezing is not a good sign. I seriously doubt it's the clutch though. Since the t-stat is new, I'd consider a citric acid flush first, and after proving the clutch is OK, possibly consider the radiator as the culprit... usually the bad fan clutch will cause more problems at speed, under load, not really at idle (unless it's barely turning at idle!)

Oh yeah - if the new t-stat you put in 3 weeks ago is not OE/OEM Wahler or Behr, change it out with the proper part. That has been an issue for other people and a new OE/OEM item fixed it.

Sorry, I'm no help on the fuel shutoff issue - wish I could help...

pberku · #9 03-23-2004, 04:19 PM

The new thermostat is a "Whaler" rated for 85c so I assume its Ok, The previous one was probably also OK but I changed it a I thought that it was the cause of my problem. At highway speeds, or while driving in the city the temperature is normal, the problem only occurs while idling or crawling in traffic, and before any one asks, Yes I am using Merecdes Yellow antifreeze.

I guess gsxr is right, the next thing I'll try is a Radiator flush

Phil

gsxr · #10 03-23-2004, 04:31 PM

First thing I would try is carefully inspecting the condensor & radiator fins to make sure they are clean & bug-free. Try to clear them out with compressed air and/or a garden hose/nozzle, make sure that's all clear. If so, my next step would be the citric acid treatment, which is kind of a pain but worth a try before a new radiator. Has the car always received coolant changes every 3 years (max) up to now? If so, the radiator SHOULD be ok... if not, the radiator is suspect...

pberku · #11 03-23-2004, 05:16 PM

I bought this car two years ago and when purchased it had the Mercedes antifreeze in it. The owner was was the original owner so I assume that that what he had always used.

The radiator and condenser fins look clean from both the back and the front but I suppose that it could still be partially plugged.

jcyuhn · #12 03-23-2004, 06:04 PM

At the risk of hijacking this thread, anybody have a source for the required silicone oil to rejuvenate a 603 fan clutch?

- JimY

Rick Miley · #13 03-23-2004, 09:32 PM

It's from Toyota. Oldsouth describes it on the second page here.

ericnguyen · #14 03-23-2004, 10:02 PM

Dear jcyuhn :

Just go to any Toyota dealer and they should have the fan clutch silicone fluid in stock.

The part numbers are 08816-03001 (3,000 Cst), 08816-06001 (6,000 Cst), and 08816-10001 (10,000 Cst), respectively.

The higher the Cst number is, the stronger the clutch engagement will be (i.e. it will spin faster when it engages at appropriately high temperature ~ 100 C)/

A stokes (St) is a unit of kinematic viscosity. One centistokes (cSt)
is 1/100 of a stokes. FYI, water is ~ 1 cSt, so the 3,000 Cst silicon fluid is 3000 times more "denser" than water.

For synthetic engine oils with 10W-30 weight, they usually have a kinematic viscosity of about 60 cSt at 40°C and 10 cSt at 100°C. So you see that these fan clutch silicone fluids are so much more viscous than engine oils.

Also, silicone fluid is not subject to viscosity degradation while the viscosity of engine oils, gear oils etc... is very much dependent upon temperature, and is subject to viscosity breakdown due to high temperature and shear stress, because their VII (viscosity Index Improvers) are simply added polymers (long chains of molecules. So fan clutches use silicone fluids for 2 major reasons:

1) They inherently have very high kinematic viscosity.
2) They are not (or only very negligibly) subject to viscosity degradation.

Eric

jcyuhn · #15 03-23-2004, 10:35 PM

Thanks guys. More than I ever wanted to know

Of course, that's what this place is all about...

- JimY