I'm fairly sure my fan clutch is shot but all my fans have been electric for 20 years or so and my knowledge of mechanical ones is limited to what I've read.

I've heard that the test is warming the engine up to operating temp, shutting it off and seeing if the fan can be spun by hand. If the fan spins freely, the clutch is shot. Is this true? My fan is easy to spin when the engine is warmed up.

Also, I've developed an engine speed based squeak/squeal that seems to coincide with when the fan would likely be operating. Has anyone ever heard of a squeaking fan clutch?

Pardon my ignorance on these, all my fans have been electric for the past 20 years.

 

Fan clutches are tricky. They work by viscosity changes in a silicon compound that allows a clutch to engage or disengage based on under hood temperature. The problem is that there's not a lot of difference in feeling between the two states and it's hard to tell by hand (at least that was my experience) whether it's engaged or not. The best way to tell is that when you rev a hot engine, the fan should really roar. Also, if there is any silicon (usually white) leaking from the face of the clutch assembly, it's bad.

I replaced the fan clutch but kind of wish I'd just saved the money to invest in a dual electric setup.

 

Any question on the fan clutch being bad/noisy coming into summer, replace it.

 

I get great benefits from a fan clutch for the ZJ Grand Cherokee V8.
It moves more air than stock and coupled with a maintained cooling system it is the big difference for steady temps in all conditions. For me it's miles of deep sand in summer heat (high RPM and slow speeds).
Also, idling with AC on does not creep up the engine temp.
NAPA part #272310

edit: F1Addict, I have read through your road trip adventures and I believe this fan clutch would serve you well.