fan clutch test clarification - Page 2 - PeachParts Mercedes-Benz Forum

John Schroader · #16 04-07-2011, 11:46 AM

This is information that I needed. Thanks, folks, for the good advice.

leathermang · #17 04-07-2011, 11:53 AM

Quote:

Originally Posted by tangofox007

..... Since the clutch depends on centrifugal force to operate, ....

Are you sure about that ?
Can you explain why you think that ?

leathermang · #18 04-07-2011, 12:02 PM

Quote:

Originally Posted by babymog

.....Also, as mentioned, the clutch is a speed-limiting device for the fan. If it is somehow locked up you run the risk of the fan coming apart at high RPMs like a BMW fan, which can also get expensive.

I think you have made some wrong assumptions.
The fan clutch limits the speed of the fan at high speeds to save energy...and increase cooling ..... if the forced air through the radiator it coming in faster than the fan would be pulling it... then you are actually creating a relatively " solid " object ( one of the same problem old west windmills had with high winds...they could not capture them because the multiblades turning fast look solid and the air stream goes around it... ) in the way of the air flow through the radiator. Letting it ' free wheel ' at higher speeds takes away most of that impediment...
My fan is bolted to the front of my 240 engine because it is cheaper to do it that way.... and noisy.... and I am not in fear at 120 mph of the fan flying apart....

babymog · #19 04-07-2011, 12:56 PM

It is outlined in the Mercedes 124 FSM, and well known among BMW folks.

ivandrocco · #20 04-11-2011, 10:16 AM

I'm getting a replacement clutch soon, but in the meantime wanted to pose a few more questions.

So my fan clutch seems to be seized, so it's spinning all the time. My car runs consistently between 90-100c, below 100c under normal driving, just over 100c if I push it on the highway. I've read people attributing high running temps to a disengaged fan clutch. If my clutch is running all the time, AND i'm running hot, what should I be looking out for when I get a good working clutch put it?

tangofox007 · #21 04-11-2011, 10:33 AM

Quote:

Originally Posted by leathermang

Are you sure about that ?
Can you explain why you think that ?

Maybe "centrifugal force" is not precisely correct, but the clutch assembly has to be spinning in order for the viscous fluid to behave correctly. The pumping action results from a difference in speed between the shaft and the body of the clutch. That is why the clutch is initially engaged at a cold start. Which is also why static "tests" of the clutch are pretty useless.

leathermang · #22 04-11-2011, 12:35 PM

Quote:

Originally Posted by tangofox007

Maybe "centrifugal force" is not precisely correct, but the clutch assembly has to be spinning in order for the viscous fluid to behave correctly. The pumping action results from a difference in speed between the shaft and the body of the clutch. That is why the clutch is initially engaged at a cold start. Which is also why static "tests" of the clutch are pretty useless.

That is much closer to my understanding of the process... if it worked on bearings being thrown to the outside...as some clutches do... centrifugal would be correct... but I think this situation has to do with temperature and changes in viscosity and friction..

leathermang · #23 04-11-2011, 12:51 PM

Quote:

Originally Posted by babymog

It is outlined in the Mercedes 124 FSM, and well known among BMW folks.

It is ' outlined' as compared to stated ?

How about quoting it .. or give reference to the page it is ' outlined ' on ?

BMW people do not take our answers for gospel....and we only have your word for them ' knowing ' that... are you a BMW Spy ?

I know a group who is convinced the world is flat... I will put you in touch with them if you want me to... " it is well known " among them that the world is flat... so that pretty much proves it...

Now to your second interesting concept.....

"Also, as mentioned, the clutch is a speed-limiting device for the fan. If it is somehow locked up you run the risk of the fan coming apart at high RPMs like a BMW fan, which can also get expensive. "--babymog

Do you think there is a difference in the 'RPM high end capabilities of the 617 turbo and the 240d ? No, there are not...and the 240d fan is bolted on without any ' speed limiting clutch ' ( to fail )..... you think they made a cheaper less strong fan to place into the 617 turbo which would fly apart if the viscous fan clutch were to lock up and made a stronger one for the 240d ? Not likely... but if you can actually document anything close to that I will apologize and take it all back... but ' BMW owners know this' does not cut it...

You were bluffing when you typed that stuff.... go and remove it ...and I will remove this critique of those statements.... this is not a fantasy forum .. we attempt to base stuff on facts so that people do not get unnecessarily misled.

babymog · #24 04-11-2011, 01:04 PM

Hmm, what have I done to cause you to start bashing my posts today?

I have no knowledge of the 61x applications, just the 602/603 as installed in the 124/126/201, I'm sorry if I stepped on your 123 ego.

leathermang · #25 04-12-2011, 02:42 AM

You posted two false statements about the physics of the fan. One of them Wildly False..

I asked you why you thought what you posted was correct and you give me an answer which made it clear that you had no reasonable basis to state those things. If you had any reference in the 124 FSM like you claimed...all you had to do was reference or quote it...

And now you try to attribute my posts to 123 Ego... not so... it is PHYSICS Ego if anything.... Why you would want to mislead others on the forum I do not know. I gave you a full day to take it down the false information and make all this go away.

The main physics governing the viscous fan operation is not centrifugal force.
The fan will not sling itself apart even at three times the rpm's which our engines can turn.

babymog · #26 04-12-2011, 11:59 AM

I didn't mention centrifugal force operating the fan, that was another helpful member (tangofox007). You did do a fine job of comparing it to a windmill though, for whatever reason.

The fan's maximum speed is governed by the clutch in the 60X, look it up yourself.

I and many others here post information that we have gleaned over years of experience with these cars, and are as helpful as we can be without having to re-visit the manuals etc. to document each answer we give. You do the same, so your hostile demand for documetation is out of line and un-necessary until you document every answer you give. If you wish to read the fan clutch test and replacement sections in the 602 manual feel free to do so.

Most people here know me and know that I don't post anything as a "bluff", am helpful and accurate as any other senior member here. I post for them, and you are welcome to pound sand and kindly put me on your ignore list.

I don't know why you are trying so hard to get something started, but I'm not playing your game so give it up. I have read the rules for posting, and nowhere does it say that one must put up with and comply with leathermang's hostility and demands for further documetation at his whim, I did see the rule about no trolling however.

Have a nice day.

tangofox007 · #27 04-12-2011, 12:58 PM

Quote:

Originally Posted by leathermang

The main physics governing the viscous fan operation is not centrifugal force.

A bit of additional research suggests that it is, in fact, centrifugal force that provides the pressure that is responsible for moving the viscous fluid from the aux chamber to the operating chamber, as controlled by the position of the thermostatic valve.

Either way, the important point is this: the clutch has to be spinning in order to work. The absence of centrifugal force causes the fluid to pool in the operating chamber, resulting in clutch engagement at initial start-up.

cjlipps · #28 04-12-2011, 01:02 PM

I'm not 100% sure of this but my understanding of the operation of a viscous fan clutch is:
A bi-metallic spring (which obviously expands unevenly when heated) changes the pitch of the vanes inside the clutch which causes the fluid to impinge on them at a different angle with changes in temperature thereby changing the amount of energy imparted to the fan blades.
Again, not sure, and I'll freely admit that I came up with that assessment by looking carefully at several fan clutches out of older American cars years ago.
Feel free to correct me.

tangofox007 · #29 04-12-2011, 01:10 PM

Quote:

Originally Posted by cjlipps

I'm not 100% sure of this but my understanding of the operation of a viscous fan clutch is:
A bi-metallic spring (which obviously expands unevenly when heated) changes the pitch of the vanes inside the clutch which causes the fluid to impinge on them at a different angle with changes in temperature thereby changing the amount of energy imparted to the fan blades.
Again, not sure, and I'll freely admit that I came up with that assessment by looking carefully at several fan clutches out of older American cars years ago.
Feel free to correct me.

The main variable is the location of the viscous fluid, not blade angle.

whunter · #30 04-12-2011, 04:12 PM

http://www.daviescraig.com.au/Fan_Clutches-b-content.aspx

http://www.popularmechanics.com/cars/how-to/maintenance/1772922

Viscous Fan/Clutch Repair
Viscous Fan/Clutch

http://findarticles.com/p/articles/mi_m0FZX/is_4_66/ai_62371176/

On the issue of fan blades fracturing:

In the 1960's, 1970's and early 1980's many manufacturers had serious issues with fan blades breaking up at speed.

MB issues where minor (compared to most companies at the time) and generally disappeared when they changed to plastic blades.

There where QC issues with some of the aluminum blades, and more are failing due to age/corrosion now.

IMO: It is smart to change to the plastic blade fan when possible.

.