overheating engine

Hi davidg, sounds like the sending unit for the fan is bad. Depending on what kind of motor you have, my Cummins was on the thermostat housing. If you find it, with the engine running, run a jumper wire across the terminals and see if the fan goes on. Be careful.

 

Could be the radiator is just plugged with bugs and dirt. How many miles / years since it was removed from the truck and properly cleaned? What kind of environment are you working in? If it's a lot of dirt like logging or something like that, a radiator can get plugged up pretty quick. It could actually be lots of things: A thermostat sticking, a water pump w/ the impeller slipping on the shaft (seen that more than once) or one that's just worn out, fan clutch failure, slipping or broken fan belt ---lots of possibilities including sensor or ecm problem.

 

I don't know, fan clutches aren't that expensive, but it's kind of a big job to replace it. In my older BC Cummins, the clutch was air operated, meaning, an electric sensor went to a solenoid that triggered an air valve that engaged the fan. So I'd make sure all that other stuff is working before you go with the clutch. Unless it's a vicious drive, like on a A/C equipped car, where oil in the fan hub gets hot from air coming through the radiator, and engages the fan, but it's probably air driven.

 

If its running otherwise, just not enough for the hills then its probably the clutch. Not a big deal but as others have stated theirs a few different types which can change how difficult / time consuming the swap out is.

 

If its a horton fan and 99 out of 100 are you put a nine sixteenths bolt in the fan find the other hole and it will run all the time until you get it fixed