2011 Ford F150, 5.0

I've had issues with the truck overheating after about 20 minutes of driving. It seems to get up to normal temp pretty quick, hold and then the temp spikes to overheat. I pull off to the side and it cools back to normal temp within a few minutes. Continue on my way and it repeats after another 10 or 15 minutes.

I've noticed the top radiator hose is warm, but the bottom stays cool to the touch. The electric fan kicks on and seems to be working fine, no issues with the water pump that I can see. I thought it was a thermostat issue, but I put a new one in and it still persists. I bypassed my heater core due to a leak in the cabin while I save some cash to get it replaced (It's more then I'm willing to do on my own right now) It's also holding coolant without any signs of a leak.

At this point I'm stumped as to whether it is a clogged radiator, air trapped in the system or some other problem. Any thoughts or solutions?


  • Fairly easy to start the vehicle when cold, radiator cap off. Preferably front wheels on a slight incline so the nose is higher than the tail. Idle until the engine has warmed up and the thermostat opens. Look for bubbles in the radiator neck. Once the bubbles have completely stopped, top up the coolant and test again. I can't be sure this is your issue, but this simple procedure will rule out the effects of trapped air.
    – SteveRacer
    May 8, 2019 at 3:38


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