Fan Clutch

[bpossel]

How do you test the fan clutch in order to determine if its working correctly or not???

Thanks!
Bob

[George Davis]

Bob,

here's what I've learned:

0.  Starting with engine stone cold.  Inspect the fan for any signs of fluid leakage.  Also, if possible, clean the front of the clutch, especially the center.  It gets dirty and the dirt can "insulate" the heat feeler somewhat.

1.  Next, grab a fan blade and wiggle it front to rear.  Should be no or only very slight play.

2.  Next, try to turn it.  You should feel some resistance, but it should turn easily and smoothly.

3.  Next, give it a spin.  It should turn about 1/2 to 1 revolution and stop.

4.  Now start the engine with hood open and jump out and listen.  You should hear significant fan/wind noise at first, which gradually dies down a bit over 10-20 seconds or so and then stays steady.

5.  Next, while the engine is running but still cold, take a rolled-up newspaper and try to stop the fan - carefully!  If the fan is turning to the left, your hand should be to the right with the paper pointing left, so it doesn't get thrown toward you or jam the fan.  Move the tip of the roll at an angle toward the blades until they are hitting, then increase pressure slowly.  You should be able to slow down and completely stop the fan.  Pull the paper away and the fan should immediately start turning again.

If it passes all these tests, it's "probably" good.  These tests don't actually test the lock-up of the fan when it gets hot, but if it passes all of these, it "probably" locks up like it should.  I'd guess that with the engine fully warmed up, you would not be able to stop the fan with the newspaper, but I don't recall that being an actual part of the test.

Good luck, be careful, and don't wear a tie while doing this!

George Davis
'69 280 SL Euro manual

[Vince Canepa]

George's steps are all good.  Additionally, to test the "lock-up" function, let the car idle with the radiator blocked.  A piece of cardboard inserted from below will work.  Let the coolant temperature rise to 195-200F.  Then remove the cardboard.  Run the engine up to 3,500 or so in neutral.  The fan should be engaged and produce significant fan noise.  As the coolant temp drops you should be able to hear the noise drop off, indicating the fan is slowing down - disengaging.  Note that these clutches never achieve 100% lock-up.

Vince Canepa
1967 250SL
113.043-10-001543
568H Signal Red
116 Caviar MB-Tex

[bpossel]

Thanks Vince and George!
Bob



bpossel  (Memphis, TN.)
'71 280SL  /  '97 E320

[Cees Klumper]

Wonder why there is actually this slipping clutch on our cars, when so many of them have overheating problems nowadays and we have the thermostat to control coolant temperature? I.e. would it make sense for those of us experiencing very hard to remedy overheating problems to install a non-slipping fan?

Cees ("Case") Klumper in Amsterdam
'69 white 280 SL automatic

[JPMOSE]

Cees...at some point (I believe 45MPH+) the air flow through the grill exceeds any benefit the fan offers.  The benefit of clutch (allowing slip) is better economy, performance and noise reduction at higher speeds.

Best Regards,

J. P. Mose
1968 250SL

[bpossel]

Cees,

Your post is sort of where I was heading with this area.  My car holds perfect temp until I come off the highway and then have to drive in stop and go traffic (outside air temp 90+ degrees).  If I am then stopped, idling for 10 minutes or longer (ie waiting because of an accident, etc) my engine temp starts to creap towards the "red".  The temp immediately drops once the car starts moving again. I have replaced my water pump, thermo, new H.E. Radiator, etc...  Just have not replaced the fan clutch.  Thought that maybe this clutch, if defective, would cause the heating issue during hot idle.?

Bob


bpossel  (Memphis, TN.)
'71 280SL  /  '97 E320

[Kenneth Gear]

Bob,

My car does the exactly the same thing.  I too have replaced the radiator, thermo, etc but not the fan clutch...yet!

So long as the car is moving my temp is fine but the moment I stop in traffic it immediately begins to creep up.

I haven't been able to find a sure fire rememdy to this in this forum but let me know if your fan clutch is the culprit.

As I recall, "Tom in Boise" is on a mission to remedy this tendency in these cars. i.e.,  Driving long distances in high temperature with the AC on.  Tom, have you got it figured out yet?

Ken G
1971 280 SL
Silver/red

[mdsalemi]

Along the general topic of cooling:

There is a company called Derale Cooling Products:

www.derale.com

And they have a complete line of electric fans, oil coolers, belt driven fans, etc.

For example, if you would like to increase your airflow at low speeds, you could consider one of their Tornado electric fans which come in sizes from 7" to 16" and can be mounted as pushers or pullers w/o airflow loss.  They also sell thermostatic control switches for these.

Of course if you have other problems, best solve them first.  And, of course, if you are a purist these will never do.  Then again isn't that the purist you just passed on the side of the highway with the overheated SL???

Before rushing out and buying these, there should be a discussion of coolant flow versus airflow...remember when you are stop and go it isn't just the airflow that has slowed down, but your coolant flow as well.  I think there has been some commentary on that before.

Michael Salemi
1969 280SL
Signal Red w/Black Leather
Restored

[peterm]

has anyone used these electric fans and can comment on the specfic one used, mounting procedure etc??  I discussed this with my mechanic years ago and we sort of abandoned the project,  all along, though ,I worry about being in heavy traffic, i hate to have the heat on and ac off but thats usually my solution

[JPMOSE]

A fan clutch can make an appreciable difference at idle (along with idle speed being too low).  My first car was my dad's 1969 Lincoln Continental (back in the early '70s).  It always ran hot in traffic.  I remember the problem being vastly improved by replacing the fan clutch. This is something that is often overlooked!  If your car has a new radiator, thermostat, good head gasket and clear passages/jackets in the engine....there is no reason the temp. gauge should go in the red.  Perhaps if the A/C is running on a hot day and one is sitting in traffic...this is possible.  The same 69 Lincoln mentioned above would overheat in slow traffic (even after the fan clutch was replaced) and it had the massive York piston compressor.  I believe 1972 was the first big year for rotory compressors and this helped a lot.

Trapped air in the cooling system will cause overheating too!

Best Regards,

J. P. Mose
1968 250SL

[bpossel]

Hi All,

Thanks for all the replies and info!

I have ordered a new fan clutch and will keep all of you posted as to the results.  Of course, only time will tell, and under multiple situations.

FYI...  this evening, as I drove the car home, I drove once again highway, then lots of stop and go, with lots of hot idle time in-between.  Tonight the temp held nicely at 180 and slightly above during hot idle.  However, the outside temp today was in the low 60's...

New fan clutch will tell the story...  If this doesnt work, then next step for me would be an electric fan for hot idle, with lots of long idle stops...

Regards,
Bob


bpossel  (Memphis, TN.)
'71 280SL  /  '97 E320

[Benz Dr.]

That's sort of how it works.
The clutch will engage when temps increase and you can clearly hear an increase in fan noise when it does and a rush of hot air. The thermo strip turns the fluid on or off inside of a coupling. If the fluid has leaked out it won't work.
Over a certain RPM a smal finger will move out by centrifugal force and shut a port off which closes off the fluid and makes the fan free wheel. If this didn't happen the fan could explode. I had this happen in a 450SL when the viso clutch was siezed up and every blade broke off at high RPM. Luckly it didn't destroy the rad or do any other damage - all the belts flew off though.
Testing for free movement is a very good idea. A  loose or sloppy fan when moved is a pretty good sign that it's worn out - new ones don't move at all.

Dan Caron's
 SL Barn
benzbarn@ebtech.net
 slbarn.mbz.org
  1 877 661 6061

[66andBlue]

 :?:  Is it correct that a 230SL (M127-981 motor) does not have a fan clutch?

Alfred
1966 blue 230SL automatic

[Naj ✝︎]

Alfred
 

quote:Is it correct that a 230SL (M127-981 motor) does not have a fan clutch?

Yes.
Mine had a fixed plastic fan (4 blade) and 3 hole fixing.
Hope this answers your other w/pump question as well. I guess you have to have the same length as what you have now.

naj

68 280SL

[ctaylor738]

High engine temps when idling are a problem with a lot of Mercedes, and an issue seems to be that the fan doesn't engage until the engine is very warm.  I noticed that the 113's have the same bi-metallic strip arrangement on the fan clutch as other models.  The strip bends with heat and releases a pin which allows fluid to flow and the fan to engage.

Here is a link to a site with a fix to make the fan engage at lower temps.  Look at #20.  If the 113 clutches work the same way, it might be worth a try.  There are some other topics on reducing engine temps.

http://pages.prodigy.net/jforgione/MB_S500.html

Chuck Taylor
107 Addict
Falls Church VA