Hello All, any help here is greatly appreciated. 2012 - F250 - 6.7 - 105,000 k. Last week heat was intermittently working, 2 days later no heat and temp gauge maxing out. Changed thermostat, checked fan, drained, flushed, and replaced coolant, also there has been no noise warning of water pump, I know that doesn't rule it out. Weird overheating since no overheating at idle and temp will drop back down while driving if I don't accelerate. Reading I have seen water pump - heater coil - etc. etc.. Just trying to get some feedback prior to shelling out $$$ to diagnosis.
Thanks in advance!

 

You'll get more action posting here....
https://www.ford-trucks.com/forums/forum205/

 

Thanks for the help

 

Remove cap from radiator overflow tank. Have some rev the engine with truck in PARK, up to 3000 rpm. Look inside overflow tank while engine revs. See bubbles? If so, that means you have a blown head gasket. Sometimes the coolant will get into the oil. If you see a milky substance on the dip stick, that also means blown head gasket.

Unless you have a leak in the cooling system. Do you smell a sweet odor under the hood? Any wet spots?

-- Dave