Hi everyone, been chasing an issue and not sure where to go. I have a 2015 F150 King Ranch 3.5 ecoboost. When the ambient temperature is below -25c (if it's warmer, it won't overheat) the truck temperature starts rising to the point of wanting to overheat. However, if I drive below 70 km/hr it won't do it. I have changed the thermostat and coolant so far. Has anyone else had this issue and how did you fix it?

 

Welcome to the forum.

 

Are the front active air dam shutters freezing shut? Could also be a thermostat thats sticky/sticking but I'd check the shutters first I think.

 

I will check the shutters, didn't even think of them but wouldn't the air coming thru the upper grill be enough to cool it?
Thermostat has been changed, I put the old one in a pot of water and boiled until it opened. Used a thermometer at it opened at around 188 but I still put a new one in.