What does it mean when the overflow tank bubbles after replacing the thermostat and coolant bleeder valve?

It sounds like it was just pushing out the air bubbles out of the system.

I see, the temp gage doesn't show it's overheating, but when I stop the car it just bubbles until it cools down. Also when I replaced the coolant bleeder valve because it was leaking, I run the car with the bleeder open and nothing but steam comes out even at operating temp, but still doesn't show it's overheating, and clues why??

I wonder if you have an air lock somewhere in the system that's preventing the antifreeze from flowing in certain areas.

I might try suggesting running with the bleeder valve open until it starts coming out as liquid.

air in the rad replace rad cap

What do i do it running hot