overheating

[Summers]

I have a 1991 Explorer, my truck is running so hot, it has been on the line of overheating all of the time. It seems to happen more when I am going uphill. I have the Haynes manual and thought the problem was the water pump, so I replaced my water pump, fan and fan clutch. Took it out for a short test drive, down the freeway and up a big hill, and it didn't help; I'm still overheating. I'm going to replace the thermostat, but from the troubleshooting part of the manual, I don't think that's it. Anybody have suggestions?

 

[RobertFord]

It could be your thermostat is broken. If it doesn't completely open, perhaps the flow of coolant through the engine is restricted and your engine overheats. It's just a guess, but a new thermostat doesn't cost much and is somewhat easy to replace.

 

[arco777]

Run a compression test and/or cooling system pressurization test to check for blown head gasket, or check for water vapor in the exhaust.