1991 ford f-150, 4x4, 4.9 liter, automatic, with plow and it keeps overheating over expressway driving mostly. I have changed thermostat to 160 degrees and upper hose. Radiator is a little over 1 year old. Help please???
At highway speeds, the plow on front of the truck could be blocking the airflow thru the radiator. Have you tried removing the plow to see if the overheating stops?
By the way, put the proper temp thermostat back in. That 160 degree stat is only going to result in poorer fuel economy.
if you had the plow on before over heating then it may not be the problem. check rad cap and see if it blowing off before it should. this will lower boiling point of water. replace with proper cap . I have seen the lower hose suck shuck at high speeds some of the new hoses does not have a wire inside to hold hose inshape. some times you have to transfer old wire to new hose. you could have pump going bad also . if thermostat is to low the water will flow to quick and not stay in rad long enough to cool down . rad could cloged
I agree that it could be the plow blocking airflow. I also agree that the radiator could be clogged. And I agree that the T-stat should be replaced with the proper temp T-stat. Also, the impellars blades on the water pump could be eroded and the volume accordingly reduced.
It’s a ‘91. With a V-8 motor workin’ hard and creating lots of heat. The cooling system needs to be thoroughly gone over. If it were mine and the radiator and water pump were original, I’d probably just change both of them. When plowing you need the system to be in good shape.