Coolant temperature is driving me crazy, reading between 145-155 on ultra gauge after replacing head gasket and full coolant drain, had replaced original thermostat with a factory 180, tried switching it back and it did go up about 5 degrees, bled it multiple times per procedure and tried a new 3rd thermostat, I’m convinced that the temperature is correct as I have put a thermal temp gauge on the block and radiator hoses and it is reading 150, I have checked belt routing and coolant hose routing and am at a loss. Does anyone have any ideas ?

 

If your temp reading is correct I’m pretty sure your new thermostat is faulty

 

Why are messing with the POS factory thermostat? Use an inline and you can swap thermostat elements with no coolant loss. And yes, you have a faulty thermstat. I have three new factory style thermostats I am willing to give away if someone wants to pay the shipping cost for them, I will never used them.