How to tell if a clutch fan is working?

My buddies '89 5.0 running hot , we put a waterpump already, and themo, still getting hot. Tried a different pressure cap, no luck. The fan has alot of dirt acumilated on the themo side, but I'm not sure how to tell if its working or not. You feel wind off it idling, but it don't seem to be blowing off idle as much as it should.

With the motor off, it should NOT spin freely.
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I thought it was opposite: the fan doesnt engage until it gets hot, therefore it should spin freely when cold??[img]/phpBB/images/smiles/icon_confused.gif[/img]
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by-metal inside the clutch hub will bend with heat ,and engage the blades ,as thats the way the units i had worked,but they are not rated for high rpm, check fan section of summit book to verify ok bill
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They are not as rpm restricted as you may think.... Surely the plastic portion of the fans are rather shoddy in their balance, (which explains the massive amount of water pump failures I see from broken shafts due to seized bearings caused by this fact). Bu I have revved many of them up to 6000 rpm's w/o any untoward problems arising...

If it's bad it will spin free'r when the engine is hot. It should not be able to free spin more than 1 revolution with the engine hot and turned off...

Upon a cold start the fluid in the clutch will engage it for a minute or so untill it marms slightly. That is why we hear the lous Whirrrr sound when starting up engines with the fan clutch systems, and they get quiet after a couple moments.
When the flius in the clutch get's so warm it's consistancy engages the fan more so than at cooler temperaturesand increases it's pull upon the air through the radiator.

FE
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yes i agree lots of us have sent them spinning over their intended rpm , only saying in summit, the flex fans are good enough to have a between 8,000 and 10,000 rating and the clutch fans have none ok bill
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