Actually, the 5.9L (which I assume is the engine he has) has a viscous fan with a thermostatic spring, which are prone to failure.
The fan drive clutch is a fluid coupling containing silicone oil. Fan speed is regulated by the torque-carrying capacity of the silicone oil. The more silicone oil in the coupling, the greater the fan speed, and the less silicone oil, the slower the fan speed.
The fan drive clutch uses a heat-sensitive, coiled bimetallic spring connected to an opening plate. This unit causes the fan speed to increase with a rise in temperature and to decrease as temperature decreases.
If the fan is not working properly, it will cause it to over heat.
To check the clutch fan thermostatic spring, disconnect the bimetal spring and rotate 90°counterclockwise. This disables the temperature-controlled, free-wheeling feature and the clutch performs like a conventional fan. If this cures the overheating condition, replace the clutch fan. If it does not cure the overheating problem, re-connect the spring and check cooling system.
You can also check the fan by checking to see if it will move laterally. Meaning if you take the fan blades on each side (engine NOT running of course) and see if it will move. If it does, then the bearing may be failing.
Then turn the fan blades by hand (again, not running) and there should be some resistance in turning the blades. If there is not, the fan hub has failed or is failing. This movement should not exceed 1/4 inch (6.5 mm) as measured at the fan tip. If this lateral movement does not exceed specifications, there is no cause for replacement.
I've had to replace a bunch of these fan hubs.