Fan clutch confusion . - PeachParts Mercedes-Benz Forum

The Gears · #1 05-23-2012, 03:22 PM

After read some posts on fan clutch problems I still don't know if there is a sure fire way to tell if the fan clutch is operating correctly or not.
Is there a way?
Thanks.

tangofox007 · #2 05-23-2012, 03:40 PM

Static tests don't work; the clutch has to be spinning for the fluid to do its magic.
After running for a couple of minutes, the fan should continue to spin following shut-down when the engine is cold. If hot, the fan should stop almost immediately.

vstech · #3 05-23-2012, 05:01 PM

step one: take car out for a drive and get it good and hot.

step two: creep to a stop somewhere so airflow from driving is limited, and coolant temp should be at maximum.

step three: with engine still running put the car in park and open the hood, go around to the driver's side of the car, and while looking towards the fan, push the engine stop lever, and watch how long the fan spins.
stops very quickly, clutch is ok. spins and spins, bad. if it INSTANTLY stops, it's also bad.

Zulfiqar · #4 05-23-2012, 05:07 PM

I think its more of testing airflow.

under normally soft coupling the fan should try to follow engine speed when hot, meaning you should feel increased air being moved by the fan above idle speed.

thats how the fan clutch works on my car and if it reaches 100 on the gauge then the fan slowly couples fully and you can hear it roar.

But my clutch has been refilled by me, so I cannot comment on how a perfectly operational OM606 clutch should work.

86-300sdl · #5 05-23-2012, 05:17 PM

Just went through this with my 603...TangoFox's guide above is a great starting point. Others use the rolled up paper test.

Bottom line...If you "think it is not working so well" it probably is sick.

Problem is these things degrade to where at required ambient / radiator temps the fan is not spinning as fast as it should be at various RPMs thus not pulling enough air when ya need it i.e. accelerating etc. So as in my case it passed the hot cold / start stop / "is it spinning?" test or at least appeared so.

Then I read about the rolled news paper test....Motor was hot and running at idle, ambient air very hot, fan spinning, held the end of the rolled news paper accross the top of the fan blades and the fan stopped with little effort

Then I read gsxr's comments in some archives where he and his other smart minds were actually measuring fan speed based on motor temp, and rpm. They found that although the clutch seemed to be working based on casual observation, in some cases the clutch appeared to be actually slipping (too much) thus not performing as desired.

So I follwed a few threads about renewing the silicon fluid in the clutch chamber and what do you know? The clutch works well now and the fan is very quick to cool radiator fluid. To the point the needle does not really move like before.

Now my clutch (aftermarket) had about 50,000 miles on it and about 3 years old. No obvious signs of leakage i.e. wet oil on the clutch streaming outward.

My thinking now is if you suspect it is not working so well it is probably sick. New aftermarkets are around $110 on up. A refill job runs about $15: Silicon Fluid 10,000 vis (or less) from a hobby shop, 1/4" hex head set screw, drill bit <1/4", 1/4" tap...and a heat gun, hairdryer, or 250* oven and you are in.

P.S. Sure glad I did not replace my 5 year old radiator if you know what I mean! That day will come soon enough.

tangofox007 · #6 05-23-2012, 05:23 PM

Quote:

Originally Posted by Zulfiqar

I think its more of testing airflow.

With something like this?

Test and Measurement Products : OMNI Controls Online

It might seem a little expensive, but remember that it can also be used to verify that your blower fan is working.

vstech · #7 05-23-2012, 07:24 PM

I think this would better suit the needs of the job...

meter

although the manometer in TF's post could show vacuum, if a hole is drilled in the shroud...

Zulfiqar · #8 05-24-2012, 02:31 PM

Quote:

Originally Posted by 86-300sdl

Just went through this with my 603...TangoFox's guide above is a great starting point. Others use the rolled up paper test.

Bottom line...If you "think it is not working so well" it probably is sick.

Problem is these things degrade to where at required ambient / radiator temps the fan is not spinning as fast as it should be at various RPMs thus not pulling enough air when ya need it i.e. accelerating etc. So as in my case it passed the hot cold / start stop / "is it spinning?" test or at least appeared so.

Then I read about the rolled news paper test....Motor was hot and running at idle, ambient air very hot, fan spinning, held the end of the rolled news paper accross the top of the fan blades and the fan stopped with little effort

Then I read gsxr's comments in some archives where he and his other smart minds were actually measuring fan speed based on motor temp, and rpm. They found that although the clutch seemed to be working based on casual observation, in some cases the clutch appeared to be actually slipping (too much) thus not performing as desired.

So I follwed a few threads about renewing the silicon fluid in the clutch chamber and what do you know? The clutch works well now and the fan is very quick to cool radiator fluid. To the point the needle does not really move like before.

Now my clutch (aftermarket) had about 50,000 miles on it and about 3 years old. No obvious signs of leakage i.e. wet oil on the clutch streaming outward.

My thinking now is if you suspect it is not working so well it is probably sick. New aftermarkets are around $110 on up. A refill job runs about $15: Silicon Fluid 10,000 vis (or less) from a hobby shop, 1/4" hex head set screw, drill bit <1/4", 1/4" tap...and a heat gun, hairdryer, or 250* oven and you are in.

P.S. Sure glad I did not replace my 5 year old radiator if you know what I mean! That day will come soon enough.

There is a very high risk of the fan blowing apart if the clutch does not decouple at high revs, this can happen due to using fluid too thick or too much of it or both, it can also happen on too much thinner fluid.

I had overfilled it and when I revved the engine the fan spun along with it till 5600 rpm (governor stop) and I could see the fan blades bend backwards - scary. I removed some fluid and added some thinner fluid because my fan uses very light plastic blades.

it should decouple at about 4000 rpm, if you rev the engine to 3000 the fan should roar and blow a gust, now hold the accelerator on full the pump governor should hold the rpm at max, note your fan airflow and speed, it should have returned to freewheeling, it will catch once the engine comes back to idle.

cook · #9 05-24-2012, 09:55 PM

Do the above fan clutch tests apply to the 617.95x engines too?

86-300sdl · #10 05-25-2012, 12:23 AM

Quote:

Originally Posted by Zulfiqar

There is a very high risk of the fan blowing apart if the clutch does not decouple at high revs, this can happen due to using fluid too thick or too much of it or both, it can also happen on too much thinner fluid.

I had overfilled it and when I revved the engine the fan spun along with it till 5600 rpm (governor stop) and I could see the fan blades bend backwards - scary. I removed some fluid and added some thinner fluid because my fan uses very light plastic blades.

it should decouple at about 4000 rpm, if you rev the engine to 3000 the fan should roar and blow a gust, now hold the accelerator on full the pump governor should hold the rpm at max, note your fan airflow and speed, it should have returned to freewheeling, it will catch once the engine comes back to idle.

So anybody know what speed we need to worry about a stock metal fan coming apart i.e. exploding? I don't go much ovr 3200....if that is in the danger zone maybe I'll just order a new fan clutch...

Zulfiqar · #11 05-25-2012, 09:02 AM

I believe its the same for the metal fan too, its not material related but related to the blade and pitch (someone with experience in this can explain better).

But go ahead refill your clutch, its easy and if your fan acts locked up remove and suck some fluid out.

86-300sdl · #12 05-25-2012, 12:03 PM

Just wondering if the fan will fall apart below 3,500 rpms.

So for example if the fan is locked up is there a danger of it coming apart at rpms below 3,500 rpm.

The Gears · #13 05-28-2012, 03:06 AM

I did the hot shut off test and the fan spun for 4-5 seconds after engine shut down. At over a hundred bucks for a new clutch the refill option is looking good. If the fluid is gone will new fluid just leak out of a worn seal? Can new fluid be injected in through the expansion pin below the bi-metal plate? How will I know when the clutch is filled to the correct capacity?
That new clutch price may not be that bad after all.

Zulfiqar · #14 05-28-2012, 01:18 PM

The silicon fluid will leak out eventually in any clutch, if your fan clutch mounting bearing is not noisy you can inject new fluid from the pin aperture, if your fan has only slight resistance when turning it on a cold engine then a good injection quantity would be 10 to 15cc.

Put in 10cc install fan and shroud on car then drive around, it should start to behave normally, if it still does not like to couple at the correct temperature add more fluid. if its sticky to couple your fluid is too thick. It should very smoothly couple and decouple when working properly.

The final safety check should be the decoupling rpm when hot, if its not decoupling there is too much fluid in the clutch. I would suggest you use 3000 or 5000 cst fluid as they are thinner and would easily allow the fan to decouple at high rpm.

putting in the fluid is a slow process, it can be acclerated by heating the fan clutch for the air to expand and then contract hence sucking new fluid in. Also note that if your radiator has a cold spot right in front of the fan clutch then even a new clutch will not work, it needs blazing hot air from the radiator to work.

The Gears · #15 06-04-2012, 02:01 AM

Zulfigar. Thanks for the info. I tried the heat and cool to draw liquid in through the pin port with no success. I have read on this board that someone drilled and tapped a 1/4 - 20 hole some where on the clutch for fill. I would like to try that but need to know were to drill so not to screw up something inside. Also what about the ships from drilling and tapping the case. There is no way to keep all the bits out.
If as you say the clutch will always leak a little at a time then I want an easy way to do a top up when the heating problem arises again.