Fan clutch question
Lead Driver
Joined: Jun 2021
Posts: 5,221
Likes: 805
with engine OFF. try and spin fan, does it move with resistance. Does it have axial play (pull toward you, push away. shouldnt move much at all) When you crank engine and start, it should move at first and then within moments start slowing down. A timing light can be used to check this if you are motivated enough but you should be able to see it clearly slow down. it gets quieter lol
Cargo Master
Joined: Mar 2007
Posts: 2,825
Likes: 1,030
How I have always tested fan clutches is that most of them work with temperature. If you grab a fan clutch when the engine is cold and running, the fan clutch will stop. If you grab it when the engine is hot [air through the radiator is hot] you will loose your fingers. After 62 years, I still have my fingers and this is because I use a large/thick towel to attempt to slow the fan. Obviously, fingers could be lost, so take precautions. Just don't throw attempt to grab the fan quickly, usually you will have the towel slow down the blades. If it's hot, the towel will not slow down the fan what so ever.
Another way that sometimes works is when the engine is cold and running, when you shut off the engine, the fan clutch may freewheel to a stop. When the engine is piping hot [air through the radiator is hot], when the engine is shut off, the fan instantly stop.
The second way is safer, but not all fan clutches work that way.
Another way that sometimes works is when the engine is cold and running, when you shut off the engine, the fan clutch may freewheel to a stop. When the engine is piping hot [air through the radiator is hot], when the engine is shut off, the fan instantly stop.
The second way is safer, but not all fan clutches work that way.
Hotshot
Joined: Jul 2020
Posts: 10,469
Likes: 2,631
From: Near Salt Lake City
There is an old procedure in the books
This is it, from a (1989 Mustang service manual) (cooling system section 27)
You will not find many pros doing any testing like this with a strobe light
Hell, even a new ford fan clutch can be had for around 120 and the testing alone is 130?
You look for leaking oil (indicates a failure)
You can hit that thermostatic spring with a heat gun and watch it move the internal valve (or not) (indicating a failure)
You can then check its resistance to spinning and if there is enough oil in the clutch to cause the resistance
You are simply looking for that fan clutch to about lock up when it gets real hot
Good luck
This is it, from a (1989 Mustang service manual) (cooling system section 27)
You will not find many pros doing any testing like this with a strobe light
Hell, even a new ford fan clutch can be had for around 120 and the testing alone is 130?
You look for leaking oil (indicates a failure)
You can hit that thermostatic spring with a heat gun and watch it move the internal valve (or not) (indicating a failure)
You can then check its resistance to spinning and if there is enough oil in the clutch to cause the resistance
You are simply looking for that fan clutch to about lock up when it gets real hot
Good luck
Hotshot
Joined: Jul 2020
Posts: 10,469
Likes: 2,631
From: Near Salt Lake City
Well, they just about spin freely when cold if working correctly
It is hot that is the test
To make sure the vehicle does not overheat with the AC on
People complain of them roaring a bit when cold until the fluid warms up
That is normal for a good fan clutch
It is hot that is the test
To make sure the vehicle does not overheat with the AC on
People complain of them roaring a bit when cold until the fluid warms up
That is normal for a good fan clutch
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Tuned
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