That sounds a little like that could have been the A/C pressure equalizing.

 

mine makes that same noise from where the battery is, from what i have been told its the vaccum canister.

 

I would be looking to change the thermostat first.

 

These trucks are tested to the max in AZ pulling the max loads up mountains in 100 + heat to see how the trucks will handle this type of situation. Your setup on the truck will handle what you are doing with no problem so there is something else causing your over heating problem.

 

With those kinds of noises after he runs the truck. It sounds like maybe he could have some air bubbles in the system that might simply need to be purged?? Just an idea.

Mr86GT