It sounds to me like a plugged radiator. Take off the raidator cap and try pushing the engine dip stick down the tubes in your radiator. If it goes in hard or stops before hitting the lower tank, it is time to take it to a raidator shop.
Also try driving your truck at 65 mph and then come to a quick stop. Shut off the engine and run your hand oner the fins of the raidator looking for hot or cool spots. This would also indicate a plugged core.
Marlin
he said the radiator is new
