Pontiac Repair: Over heating, o ring, thermostat

Question
i have replaced the thermostat, flushed radiator. car still overheating so i took thermostat out and ran it with our it to make sure it wasn't my water pump, car stayed the right temperature so water pump worked, when i put it back together i purposely put the thermostat in upside down to see if it was in wrong. when i did that the the car stayed cool but the O ring on the thermostat was leaking so i went to autozone to get an new one, while there i looked up the way the thermostat went in and i had it right the first time. when i put it all back together i put it in right side up and it over heated again. what is my problem? what do i do to fix it?

Answer
Hi Jared;
What model and year cars is this? what engine? does it have A/C does the A/C still work? if the a/c still works turn it on with the car running assuming it's warm enough there for the a/c to run after a minute or 2 the cooling fan(S) should come on due to the a/c working if the a/c runs and the fans don't come on that is a place to start looking.