Gidday Terry. It takes a certain amount of horsepower to turn a non clutched fan, all the time. A thermal clutch only costs a similar amount of power when engaged. Out on the highway, when there is sufficient airflow, they will be disengaged, in town in stop and go traffic where you need it, they will be engaged.
I always prefer thermal, over non-thermal.

The 84 Cougar, 86 Mustang GT, and 92 Mustang GT all had 5.0L and thermal clutches from factory and all had 5.0L’s.

There were only 2 times I had high temperatures.

The cause was running the air conditioning while boulevard cruising on a hot humid evening and going up the Grapevine.

I was aware of the potential when both happened.

Turned the a/c off for a few minutes and everything was fine.

Btw, all OBS trucks had thermal clutches as well.

Last edited by Nos681 (3/27/2025 7:49 PM)

Disadvantages?  Not sure I can think of any.  I suppose in theory its one more thing that can fail, but I don't think I've ever actually seen one fail.

Advantages would be freeing up otherwise wasted HP, AND also better mileage.  Temperature control should also be better (faster warm ups and better maintenance of operating temperature).

I think the only vehicles I still have them on are my F250s.  I've never heard the one in my 5.4 truck.  The one in the Diesel sounds like a tractor trailer is under the hood when it comes on.  Of course, if it comes on things have gone horribly wrong.  I only ever heard it run when I was drastically low on coolant due to a blown head gasket.  If everything is right that truck and its 7 gallons of coolant don't seem to need the fan, even while towing (unless maybe I hooked like a D8 dozer to it or something absurd).