Celica Forums General Discussion Engine and Performance Need help with temperature issues!

Hi all, I thought this would be a good place to start for figuring out this problem. (2001 Celica)

So basically, my Celica is completely fine apart from when I go on the highway, my temp gauge will shoot up to max, then come back down to half when I slow down. I figured this is odd because its about -5C out so it's not exactly hot, and didn't happen when i was stuck in traffic either. Only happens above 65/70mph. ECT sensor?

Additionally, if I shut it off when the temperature is "high" it REALLY does not want to start. Takes 10-15 tries and pushing the car lol. Could these problems be linked? It starts fine when I let it sit for a bit.

Any insight would definitely help, and sorry if this is posted in the wrong section i'm new

Your cooling system likely has a large air bubble, which is super hot, much hotter than the coolant.

That air bubble circulates in the system. When it goes past the engine temp sensor, it triggers an overheating signal.

Try bleeding air out of the system. On the hood there is a sketch and instructions how to bleed air out of radiator.