I've searched and read a ton. Long story short I overheated twice the other day towing a boat and climbing a hill. I have a 99 4runner with 196,000. Let it cool and drove home an hour fine. My old fan clutch was very loose when hot, so I assumed it was shot. Went and had it replaced and now it seems as though it is working very hard all the time. I thought these clutches were suppose to disengage after a certain RPM, my new one does not. When the engine is cold the fan does have resistance, but will turn. Same when hot. I've flushed the cooling system and replaced the radiator cap. My mechanic says it could be the heavy duty tires I have that is making it work harder. This morning after sitting all night it sounded like a jet engine for way longer than usual, after about 15 mins of driving I stopped and at idle it was finally quiet, but the second I revved the engine it was loud again, all the way to 5,000 rpms.... Could he have installed the fan wrong, anyway for me to tell if it is backwards? Any help would be greatly appreciated, thanks.

The fan will turn even when the fan clutch is disengaged and the engine is running. High ambient temperature, condition of radiator, larger tires, climbing hills, etc. all increase the strain on the cooling system.

So there are no other parts in the fan clutch that can be bad like the bearing etc?