I changed out the heater core and thermostat on my 99 Prix. I flushed the entire system. Started overheating like mad. Heater temp would fluctuate. Possibly an air bleed issue?

When running the motor with the heater on the air bleed screw would just sit there and hiss for over 30 minutes! No water. Only steam. I checked for coolant leaks and I am good. The oil is clean of water. Car runs fine it just gets incredibly hot!

How long should it take before I see water from the bleed screw? Possibly a bad thermostat?

Thanks!