what would cause...

[Davis]

...my thermostat to stop working after i fixed my heater core. i was getting no heat, so i pulled the heater core and flushed it. i get heat now, but the thermostat doesnt open. the motor gradually gets hotter and hotter till it would overheat if i kept driving it. i am pretty confused here. any ideas?

 

[BlackBII]

Could be coincidence, It could have froze up sometime around while you fixin the core, take it out and see.....

 

[HAPPY_RANGER_GUY]

Air

Make sure you have all the air bubbles out of the system and top off the coolant level. Sometimes takes little effort to get all the air out.

T.