Well, I guess that your findings make my point. Of course, I am not there to completely analyze your issue, but if the coolant is not warm/hot, the thermostat has not opened and there is no flow. Could the thermostat be stuck open? Sure. Personally, I would start the car from cold and watch and wait. Wait for the thermostat to open. The surging of the coolant tells me that the cooling system is working to purge air as it should and when the thermostat opens, if then working properly, you will almost instantly get warm/hot coolant flowing through the system. BTW, this will take longer than your two minutes starting from cold. Do you happen to know what degree thermostat is installed?I started it and waited roughly 2 minutes and it started overflowing again. Stuck my finger in the Coolant and it wasn’t hot. I didn’t include any information about the gauges because I am not certain they work. If we are assuming they work then the gauge reads cold when the coolant comes out.