I have a 2002 F250 V10 that is running hot. Truck runs fine at first and then after a while the temperature gauge rises to the red, engine bogs down and heater blows cold the entire time. I replaced the thermostat which didn't fix the problem. Took it to a shop and shared my suspicion that I thought it was maybe the heater core. they insisted that it was the radiator. I purchased a brand new aluminum radiator and that didn't fix the problem. I was thinking about bypassing the heater core this weekend but thought I'd check out here to see if anyone has run across this before?

 

I do not believe the heater core should have any influence over the cooling system to cause the engine to overheat.
The radiator,thermostat ,water pump, cooling fan ,yes.
Since you replaced the rad and thermostat might be a good idea to check if the cooling fan is moving as it should when temp goes up.
The clue of no heat at anytime could be due to the heater being air bound and requiring it to be bled (removing the upper heater hose and allowing the air to
escape). Sometimes the water pump impeller corrodes away or breaks loose from the water pump shaft rendering the water pump ,useless !
The cooling system is designed to cut power to alternating cyls with an overheat condition so as to prevent engine damage. If the engine has been driven much in the overheated condition head gasket problems could come up.
How many miles on the odometer?
How long is , "A while after the engine has run" ?

 

Thank you for your reply. Fan is moving fine. The first time this happened was back in February. I immediately turned around and switched vehicles. Truck has about 143k on it. motor is otherwise very strong until it hits the red. Takes about 15 minutes. I can pull over and turn off the engine, restart and the gauge will drop back down to normal for a about 5 more minutes. I haven't driven it since other than after I replaced the radiator. Stayed close to the house to make sure that I could get back in time if it started to run hot which it did.

 

Removing 10 spark plugs can be a chore, but you would be looking for possible coolant contamination on one or more plugs. If no difference is found ,perform a cooling system pressure test to confirm no other leaks. If all that passes , remove and physically confirm water pump integrity.