i know that the fan usually runs on startup for a few seconds, will it do this even if the clutch is bad? also I cleaned up my radiator and the front of the fan and it had a lot of gunk on the external spring of the theromstat on the clutch, has anyone known of a clutch not working because of the spring being too gunked up?

 

mine ran all the time because of a bad clutch.

 

That spring is a bi-metallic spring, it is like the thermostat in your house only it works backwards.
When the spring gets hot it locks the clutch, when the spring cools it unlocks the clutch.
So with it being full of road grim all that will happen is that the grime will act like insulation and it wont lock the clutch at 200*F like it is supposed to but it will lock it at maybe 215*F for example.

If your fan comes on when you first start the truck in the morning and then shuts off after a few min then the clutch is still good.
If it stays on all the time or does not come on at all then it is bad and needs to be replaced.
If that is the case you have the option to hold off on replacement until spring.
If/when you do buy a new fan clutch after you get it home you must let it sit vertical for 24 hours before you install it.

 

cool that is good news, mine kicks on at startup, but its gotten very hot several times and i can't recall it ever kicking on. I thought a head gasket job would solve my problems but it didn't. I figure the fan not kicking in is causing the problem, I can drive all I want at highway speed but when I stop or off road it climbs so i figure the radiator is cooling just at low speed its not getting enough air flow. I want to get it strait this week so I can drive it at the uwharie rally next weekend.

 

also if I have to replace it, I remember someone saying ther is a generic one you can get for alot cheaper. anyone recall this?

 

Yeah I think you need to do some drilling though!

When it gets hot enough you should be able to hear it kick in. it will always spin just not enough to pull any air. I thought mine was gone because it did not kick in. It turned out to be the Tstat jammed closed. so the radiator never got any heated coolant going through. It is the hot radiater that heats up the bi metal on the fan clutch. So I had a motor boiling over but a fan clutch that was still cool.

Have you tested your Tstat?
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AntiChrist has the part numbers for the aftermarket fan clutch.
I thought I had saved the #'s but I guess not.
Advance Auto, $50 or so.

 

Spike why does it have to sit Vertical ?

 

A viscous fan clutch is full of fluid.
There are different chambers inside the clutch.
When the clutch spins the fluid moves to the outside of the chambers and then when the bi-metallic spring locks up it moves the fluid into a different chamber thus locking the clutch.
When the fan clutch lays on its back or font the fluid settles into all of the different chambers and if you install it and then run the engine without letting the fluid settle back into its normal place you run the risk of ruining the fan clutch.
It is just like after you move a refrigerator when you move, you need to let it sit over night before you plug it in so all the compressor oil settles back into the compressor.

 

the thermostat is ok, I've replaced it, done head gasket, have a receipt for a water pump 22000 miles ago, so the only two suspects I have left are the radiator and fan. it runs fine for everyday here and there driving. it takes about 45-60 minutes of driving to even reach a point of the needle climbing past 9:00 but it will stay there at highway speed till I slow or stop then it climbs so i think the radiator is still functioning well, maybe not 100% but good enough to keep things cool but without the fan kicking in when it gets hot, slowing down makes it climb.