It happed afterwards because I had to replace my temperature gauge housing. We the car was able to sit for a little while and cool down the ring inside the housing contracted enough to let all the antifrezze out.
When you drained and refilled the cooling system, did you allow the engine to reach full operating temperature before you put the radiator cap back on. You have to do this so the cooling system is not under pressure when the thermostat opens. Otherwise, air pockets which invariably form when the system is refilled cannot escape.
I took the radiator cap off and run it up to normal temp. and then when I was installing some Amps and testing them, it was sitting on a little hill going down and this the the needle reached the red.
Any other sugguestion?
The thermostat sounds like it's failed, I just replaced mine too, Do you get fan activation or do the fans only kick on high ?? If that's the case then you need to replace your fan harness.
My car just went through this VERY SAME THING.
So to recap, I replaced my fan harness (Burnt connector at resistor pack) and after that I was driving the car (1 week later) and the thermostat guage was acting wierd, I would rev the engine when it was about to overheat and the temp guage went DOWN !! That could mean only 1 thing, the thermostat was bad (stuck closed)
Replace the thermostat make sure the air bleeder valve on the thermostat is facing up and
try that, it fixed mine.