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Viscous fan coupler: testing bi-metal strip
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Posted 9/22/2014 12:31 PM
jnicol
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Date registered: May 2008
Location: Cranbrook, B.C. Canada
Vehicle(s): 91 300GD, 911 (993), Dodge Durango, Subaru rally
Posts: 680
500
Viscous fan coupler: testing bi-metal strip

After years of suspecting a faulty viscous fan coupler I have decided to remove the mechanical fan and install an electric one.

With the mechanical fan sitting on the bench I noticed quite a bit of crud in and around the bi-metal strip on the viscous coupler. 'Hey!', I thought, 'maybe that's my problem'. So I have cleaned out all the crud and would like to 'bench test' it. I have heated it up with a heat gun and see that the strip does expand and lift. But I can't see what this change is impacting - I cannot see what it is moving when it moves.

Can anyone tell me how this is supposed to function and how I might be able to 'bench test' it? I might just reinstall if it works, or leave it on the shelf (vertically) if I want to go back to it in the future.

Thanks!




(Viscous coupler.jpg)



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#224064
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Posted 9/22/2014 3:10 PM
AlanMcR
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Date registered: Apr 2006
Location: US, CA, Los Altos
Vehicle(s): G300DT E300DT 230SL
Posts: 3500
2000
RE: Viscous fan coupler: testing bi-metal strip

The movement is very slight.  I think it bows out, but I can't recall exactly.  It pushes on a pin that alters the path of fluid in the clutch. 

The problem with most older clutches is that the fluid has leaked out.  That is why there was a lot of crud on the front.  The only way oil gets there is from the clutch itself.  There are methods to reintroduce silicone fluid.  I doubt they work for long as the leak is still there.

#224068 - in reply to #224064
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Posted 9/23/2014 10:02 AM
jnicol
Elite Veteran




Date registered: May 2008
Location: Cranbrook, B.C. Canada
Vehicle(s): 91 300GD, 911 (993), Dodge Durango, Subaru rally
Posts: 680
500
Re: Viscous fan coupler: testing bi-metal strip

Yes, it bows out. Under the strip is a green glob that looks like chewed gum pressed in there. Maybe behind/in that is something that moves. That it just affects the direction of fluid makes some sense as there does not appear to be anything large that moves.

In the name of science, since this unit is most likely done, I will take it apart and do some research into the function....
#224080 - in reply to #224064
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Posted 9/23/2014 1:57 PM
kerry460
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Date registered: Apr 2006
Location: tasmania australia
Vehicle(s): 1984 300GD LWB WAGEN
Posts: 611
500
RE: Viscous fan coupler: testing bi-metal strip

G,,day . it moves a small diameter pin , which opes a different path for the silicon to flow .
you can replenish the fluid , and it will most likely work perfectly for many more years .
to get fluid in , clamp the shaft or flange in a vice . remove strip , take out pin , heat hub with hot air gun , turning hub whilst heating .
as hub cools dribble silicon into hole . turning hub while doing it.
slow and tedious but it works .
how much ??????? trial and error .
cheers,
kerry
#224084 - in reply to #224064
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Posted 10/4/2014 11:40 PM
H1LM002G55
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Date registered: Mar 2010
Location: S Florida / Geneva / Jeddah
Vehicle(s): 500 GE, G55, LM002, H1
Posts: 1796
1000
Re: Viscous fan coupler: testing bi-metal strip

You can have your old Visco Fan repaired.

Send it to Jono at AMG East in Atlanta, Georgia Area.

www.blueridgemb.com
#224253 - in reply to #224064
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Posted 10/5/2014 3:23 PM
jnicol
Elite Veteran




Date registered: May 2008
Location: Cranbrook, B.C. Canada
Vehicle(s): 91 300GD, 911 (993), Dodge Durango, Subaru rally
Posts: 680
500
Re: Viscous fan coupler: testing bi-metal strip

I'm now running well with an electric fan in place of the mechanical one. Thanks for the tip on the repair. Will likely do that and keep the part as back up.
#224263 - in reply to #224064
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Posted 10/6/2014 10:05 AM
H1LM002G55
Expert




Date registered: Mar 2010
Location: S Florida / Geneva / Jeddah
Vehicle(s): 500 GE, G55, LM002, H1
Posts: 1796
1000
Re: Viscous fan coupler: testing bi-metal strip

That is what I did...I saved my repaired one as a spare. The AMG visco-clutch was about $1,000 USD. Nice having a spare just in case...
#224278 - in reply to #224263
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