Runaway temperature issue!

[WrenchinBrit]

Hey All
5.4 Triton 2014 EL King
Had an issue maybe a month ago that the overflow bottle seemed high ... thought it was strange but it ran fine.
Today started and idled whilst I got ready to leave but a mile up the road noticed it slightly warm on the gauge ... continued to watch and sure enough was getting hotter until it climbed incrementally into the red. I shut off the truck and could see bubbling into the overflow. Allowed to cool and got the truck back at which point the temp normalized and idled fine with no fan ...but this completely full?
Ideas ?

 

[eddytheexpy]

This is sounding like a bad radiator cap my guy. It's like $10 and zero effort to swap. As far as parts cannons go, doing this as a complete guess is totally acceptable in my book. Not a bad place to start in the diagnostic process anyway.

 

[99WhiteC5Coupe]

View attachment 82933

Hey All
Had an issue maybe a month ago that the overflow bottle seemed high ... thought it was strange but it ran fine.
Today started and idled whilst I got ready to leave but a mile up the road noticed it slightly warm on the gauge ... continued to watch and sure enough was getting hotter until it climbed incrementally into the red. I shut off the truck and could see bubbling into the overflow. Allowed to cool and got the truck back at which point the temp normalized and idled fine with no fan ...but this completely full?
Ideas ?

It would be helpful if you posted the year, make and model of the vehicle - including the engine. There may be engine or year specific information that someone has.

 

[max78]

With the amount of information given here it could be, water pump, thermostat, cooling fan, or head gasket.

If it is able to maintain temperature at idle but overheats while driving, it could be a weak water pump, or blown head gasket.

If it randomly overheats here and there, or has temperature fluctuations that seemingly make no sense it could be your thermostat.

If it overheats while idling, but is fine when you are able to maintain 35mph or greater it could be a cooling fan not working properly.

It could also be any combination of these parts, you need to take a closer look or to narrow it down.

 

[Speed 330]

This is sounding like a bad radiator cap my guy. It's like $10 and zero effort to swap. As far as parts cannons go, doing this as a complete guess is totally acceptable in my book. Not a bad place to start in the diagnostic process anyway.

Thermostats and notorious for that make sure you get it Forward thermostat