The fan clutch ALWAYS slips (on purpose) so as to limit the HP used by the engine to turn it. At high engine speeds, even when severely overheated, the fan should not even approach engine speed.

For more information, consult Jim Rowe's (of Metric Mechanic fame)comments in the "BMW Enthusiasts' Companion."

I don't hesitate to try to stop it with a single finger myself (carefully inserted, mind you). If with the engine idling, you can stop it with a single finger and spin it backwards, and it spins backwards for more than 2 seconds, then I say replace it.

Bob

The test is to see if the clutch is indeed locking up as it should at higher temps, and thus letting the fan run at full engine speed. If you can stop it at high operating temps with a rolled up newspaper, then it's bad.

David

P.S. I have not had one go bad like that quickly--but I'll also say that replacing my bad clutch didn't do much for the fact my car sometimes runs at 2/3. I suppose the radiator will need to be done sooner or later, but I have a sneaky suspicion that's the way this car has always run with the thermostat it has. It never overheats, just goes up to 2/3 in heavy traffic. I think it's okay. The fan clutch doesn't seem to be very helpful in this regard, however.