[hiyabradHO]

Is there some magic to know if the fan clutch is working? When the car is cold (and engine not running) the clutch spins free, meaning I can make it spin with my fingers.

After driving the car last night, I turned the engine off and the clutch still spun free.

Should it be engaged and not spin when hot??

Thanks,

[unruhjonny]

my guess;
when cold, does the fan seem to have some resistance to spinning free?

IIRC the thermostatic coil on it essentially locks it up when it gets hotter - so if there is some resistance when it's cold, I would think that the resistance would increase as it warms up.

[necdb3]

The clutches are commonly engaged when initially started after sitting overnight. Sometimes you'll start the car, hear it engaged then after minute hear it disengage. The fluid falls inside and engages it when it sits for a long period.

Once it's been run, the clutch will engage when enough heat is sensed. The common problem with them is the fluid will leak out. Once the fluid leaks out, it doesn't have the ability to engage. The spring in front is bi metallic and controls the fluid valve inside

With the engine running, you should be able to listen to the sound of the fan engage and disengage. Get it up to normal operating temp, air off if you have it, and just let the car idle. You can also usually feel the difference in the amount of air the fan moves when it engages and disengages.

[hiyabradHO]

What are you folks using when the original fan clutch stops working? What are you replacing it with?

[azbirds]

I don't know what kind of heat you deal with, but in Phoenix my clutch engages within ten minutes and stays that way when on surface streets and calms down some on the freeways, but stays engaged until I shut it off. It does not freewheel when I do shut it off. I hear the Napa heavy duty works good, but haven't needed a new one.

[Formulabruce]

I use a thermostatic clutch, however there are centrifugal clutches available.

[azbirds]

Mine is a heavy duty thermostatic unit. I think it was only 109° outside for my drive home today.��

[Formulas]

Shouldnt spin easy like free wheeling should always be some resistance.. they are cheap enough and easy enough to change out

[Aaron65]

Somewhere I read to watch the fan as you shut the engine off...if it stops spinning in less than a revolution or so, it's good. That seems to make sense, but I don't know if it's a valid, scientific test.

[azbirds]

That test has worked for me.

[1971455HO]

Originally Posted by Aaron65

Somewhere I read to watch the fan as you shut the engine off...if it stops spinning in less than a revolution or so, it's good. That seems to make sense, but I don't know if it's a valid, scientific test.

I can't say within a revolution or so but certainly within about a second .That was always my rule of thumb. I have seen the opposite that tend to spin freely for as much as 6-7 seconds. If they're that bad, your car will run hot in bumper to bumper slow traffic. Even when its cold it should not spin freely. It should have enough resistance to only spin about a half a revolution using just your hand to spin it. And stop almost immediately when hot during engine shut-down.