SC V6 Overheat Spike at Highway Speeds

[AdventureTim]

Hey folks!

Wondering if anyone has experienced this before? My SC V6 (~95k miles) has recently started overheating in a very specific situation: when you first start it up and begin driving at highway speeds then shortly afterwards, the coolant gauge will spike and there’ll be an overheat warning. If you come to a stop (or even coast), the temps will rapidly descend to normal operating level and it won’t spike again for the rest of the trip. If I only drive around town after a fresh start, there is no overheat at all. It sounds to me like a sticking thermostat, but would appreciate other thoughts before I try to replace it.

 

[Rover Range]

Thermostat would be the most likely cause.

 

[16FujiDisco]

Any restricted performance warnings? Maybe a bad SC water pump?

 

[AdventureTim]

No warnings or anything of note on the IID Tool. I think I'll replace the thermostat with Lucky8's 82 degree version and do the water pump at the same time.

 

[powershift]

I'd replace the t-stat. I had mine done at 97k mi proactively.