I am having this overheating with this car only when I install the thermerstat, I had replaced the head gaskets, water pump, radiator. The car runs good without the thermerstat but I then get no heat in the car. I also changed all cooling system hoses.
Disconnect the heater hose on the engine anything coming out? Could also be a bad new Stat. Bear in mind a clogged-up hose or core will not cause the engine to overheat. The engine has its on in and out passages.
Maybe the heater hose is collasped or the heater core is clogged.