Thermostat?

[Gordon shamway]

Hello everyone, I have one issue now. I need your opinion.
About 2 month ago I changed mine coolant at the same time set up "check valve".
That time coolant temp was fine, no problem (keep 198-205).
But recently coolant temp increase by little and little(210-220).

I notice that coolant temp down 220 to 203 soon when stop the car (gear position N ) then open wide gas pedal when coolant temp was 220F.

I checked coolant hoses in engine room, inlet hose was hot, but outlet hose was cool.
I guess this condition is Thermostat stack. If you have any opinion, tell me please.

PS somebody have experience remove thermostat yourself, tell me how to remove this one, GM manual say when remove thermostat, you have to remove EX manifold and turbo unit. but I do not want do that.

[bob]

Mine went to 237 degrees. To make a long story short, it was the coolant cap. This $14 part was allowing air in the system.

[Gordon shamway]

<bob
Thanks bob! I read your comment in another
topic. I ordered coolant cup light now.
If you no trouble tell me what happen to
occur your process.