We have an '85 F-150 and we have a problem with it running hotter than it should. We have changed the water pump, put in a new thermistat and it still runs to the M mark on the Normal word on the Temp gauge. Around town with only doing 20-25 mph it stays down where it belongs but out on the highway at 65 mph it climbs to above half way. How can I correct that? That is without trading off the p-up.

 

Have you tried doing a radiator flush?