I apologize in advance if there was a post with information regarding this issue, I couldn't find anything. The truck has the 6.0 gas engine with around 96k miles. Yesterday I was pulling a light load (small stock trailer with a 400lb steer) around 65 MPH for around 25 miles. The temp guage reached the 3/4 mark quickly and then went slightly above that mark, then nearly reached the red zone, the message "engine coolant is hot" appeared. The moment I get to town and start driving around at low RPM's the truck cools back down to the half way mark. Where should I start looking for problems? Coolant level is normal. I was not running A/C. I'm not sure of the gear ratio but I can tell you that at 65-70 MPH the RPM's are around 23-2500. Thanks! Also, the outside temp was around 95 here yesterday.

 

This sounds like a cooling fan problem. Electric fans or belt driven? If belt driven, you probably have a fan clutch failing.

 

How do I check the fan clutch?

 

I check the fan clutch a couple different ways. Mostly I check by feel. With the engine off give the fan blade a spin if it spins freely or feels excessively loose you have a bad clutch. If you don't feel like you can tell by how the clutch feels you can drive the truck and get it good and warm park in your driveway till it starts to get hot, put a shop fan in front of the grill and blow air thru the radiator if your temp goes down you need a new fan clutch. You will want to make sure the entire fan shroud is intact also.

 

Not sure why my posts are not showing up

 

Ok I'll try again. I usually check a couple different ways. First is usually by feel. With the engine off give the fan blade a spin if it spins freely or feels like it is excessively loose you have a bad clutch. If you can't tell by how it feels you can drive the truck and get it good and warm. Park in your driveway with engine idling once temp starts to go hot put a shop fan in front of grille and blow air thru radiator if temp goes down you need a clutch.

 

I can turn the fan but it's not super easy to spin. Also, the truck doesn't get hot until I pull a load at 23-2400 Rpms for a long distance. It stays cool at idle.