2006 international 4300 DT466 tree trimming boom truck. Truck runs hot when you're driving over 50mph. Will idle on the job all day long and not get over 200° if you slow down to 40 miles per hour or less temperature drops back to the 200°range. It has new thermostat new radiator hoses new water pump flush has been run through the engine twice and the external radiator itself has been cleaned. Any ideas possibly bad radiator?
Does it have a viscous fan hub?
Auto transmission?
Pop the hood with the fan running and put a shirt on the radiator/cac, it should stay up by itself.
It Yes
Manual
Good suction by fan thru radiator
I used to look after a fleet of Internationals with DT466's in them. The viscous fan hub contains about 2 tablespoons full of a thick silicone liquid. Over time the liquid disappear s and the fan slows down and the engine starts to run hot under load. I would strongly suspect you need to replace the fan hub.
The fan is really hard to turn with engine off an seems to be pulling lots of air but at 55/60 mph hard to tell. Think I'll try a fan clutch before I confirm the radiator.