overheating f250 v10

[cmyoung2]

1999 F250 V10 220000 miles When I leave in the morning, truck engine temp gauge will stay cold, no heat from heater. After about 5-6 miles temp will peg red. If I release a little pressure from the radiator cap everything will go back to normal and stay that way all day. I am thinking an air lock some how, but can't figure out how. Replaced the thermostat, no change. Don't see any leaks, but really haven't had much of a chance to look. So, water pump?, Lower radiator hose? All hoses and pump are original, never touched anything on the cooling system except change fluid (I think).
Any ideas on where to start?

 

[Diamondpilot]

If you have never touched a thing I would do a complete flush, new water pump, new cap, and maybe hoses. It owes you nothing so treat the old girl right.

I might even pull the rad and have it professionally cleaned.

Chris

 

[pmsmechanic]

Before I would do anything else I would try to find out from a service manual or someone who knows if you are bleeding the cooling system correctly. Some vehicles have a certain procedure that needs to be followed.