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| [GMCnet] Re: Radiator cooling fan [message #366844 is a reply to message #366839] |
Fri, 17 September 2021 10:02   |
James Hupy
Messages: 6806
Registered: May 2010
Karma:
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Senior Member |
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I will try to explain this one more time. Both Steve Ferguson and I have
presented seminars on this subject more than once, and probably will again,
if the Good Lord allows me enough time.
Fan clutches are filled with a very special silicone fluid that gets
more viscosity when it is heated, unlike hydrocarbon and synthetic oils
that thin out, or less viscous, when they are heated. If you look at the
finned surface of a fan clutch, you will see in the center of it a flat
shaped spring coiled in a circle with several wraps. One end is anchored to
the clutch body, and the other end is connected to linkage that disappears
inside the clutch. That linkage operates a valve that circulates that
viscous fluid to expose it to more driven fin like elements, and that in
turn makes the clutch "lock up" or drive the fan at a speed higher than it
is when the spring is not expanded. Clear as mud, right?
Simple answer, is that it is hot air that has an effect on the spring!
NOT HOT COOLANT. HOT COOLANT heats the air that passes through the
radiator, and that activates the spring, etc, etc.
Remember this. The higher the air flow volume through the radiator,
the less heat is concentrated in a smaller volume of air. So, that is why
the clutches seldom lock up at highway speed, and more when the coach is
moving slower. Also, the clutch is behind the curve, the coolant has
already gained more heat, reflected in your coolant temp gage indication,
before the air gains enough temp to activate that little spring.
More to it than space allows here, so, catch me at a rally someplace,
and I will explain in detail.
Jim Hupy
Salem, Oregon
On Fri, Sep 17, 2021, 5:22 AM tom geiger wrote:
> Todd, just went out and tested the fan clutch and it did spin with some
> resistance so I guess its working then. It is for sure spinning the fan
> when
> I first start it up. The aftermarket temp gage shows temps in and around
> 200+ as my OEM gage shows the 1/4 mark. I may be fine on engine temp but
> wanted to check with a accurate temp gage test kit to make sure. I’ve
> been having what seems to be knocking that seems to be starting up when
> engine is at full temp. I just want to make sure the engine is operating
> at proper temps.
>
> Thanks,
> TG
> --
> Tom Geiger
> 76 Eleganza II
> KCMO
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