Ok, so I went through all of the troubleshooting flow charts in the TM and my fan/clutch system is functioning as designed. I then decided to drain/flush the cooling system. I tested the coolant that came out and it was almost pure antifreeze. After a few drain and fills with water running to operating temp each time I got most of it out. The last straight water flush I ran distilled water to displace the tap water I had been using, and ran it for a day. Bingo. The fan cycled as it was supposed to while driving at highway speeds(50mph). I then drained and refilled with 50/50 antifreeze mix. Here's where it gets weird. After putting antifreeeze back in it the symptoms returned. Engine heats up normally, but after the fan kicks on the first time it never cools the engine quite enough to cycle off. Btw, neither the original coolant nor the water I ran through it had very much contamination when drained. And in case anyone is wondering I captured and bottled up all of the old coolant to dispose of at my friendly neighborhood auto parts.
Maybe it is normal.
But there is the possibility your radiator is not quite doing it's job.
Have you had it cleaned professionally at any time?
Why I ask is that straight water is the most effective coolant.
Adding antifreeze actually makes the system less effective at cooling.
Of course we must run antifreeze.
I am thinking you may have a partially restricted radiator or weak thermostat or both that is causing your engine to stay warmer than normal which is causing the issues with the fan coupler.
Or maybe there is nothing wrong.
I would start by getting a temperature reading from a second device.
Check before and after the thermostat and at the entrance and exit of the radiator.
If that radiator is at all questionable it might be a good time to get it checked out.
