We have a 78 F-350 that has been overheating and can't figure out why. It started last summer when hauling about 3400 lbs of soybean seed about 12 miles. We had driven over empty to get the seed and on the way home she just kept getting hotter, by the time I pulled into the yard she was boiling over. Ran water through the radiator with a garden hose to cool her down. We change the coolant and thermostat and it still does the same thing. Also what is the best wt. of oil to use in this vechicle. It is only driven about 200 miles per year, but they are hard ones.

 

I would start by having the radiator checked out and/or replacing it and the water pump.

Trail Rider

 

My '84 F150 went through two radiators. The radiator is highly suspect and in my case was easy to test. I just rubbed my finger across the cooling fins lightly and watched the rotten fins crumble into dust. This is not conducive to cooling. As noted in the above post, whenever you fix the cooling system it is a good idea to replace the thermostat. It's cheap insurance.

 

 

dieselman, i have a 77 f100 with 352m and c6. it too was running hot. i noticed it when i was driving around town. i stopped to get gas and noticed water dripping from under the radiator. i t also leaked when driving on interstates hwys.
i just changed the radiator. i put in the heavest duty one i could find. it cost around $200.00. it still seems to get hot. i just keep driving it. i probably should change the thermastat.
don't worry about the water pump. those things are ok unless they wear out and when they wear out water will leak out real bad. if it's bad, it's obvious.
i've heard these motors are bad about overheating.
good luck and keep us posted on what you do.