Are you fans turning on? If not, check the two wire coolant temp sensor, could be loose or you might have a short somewhere. Also make sure you're bleeding the system properly. I will usually fill the system up, leaving the radiator cap off and turn the car on. Then I'll squeeze the inlet hose to squeeze some air out. Once the thermostat opens I'll top off the system then watch for bubbles, then once no bubbles are present I will replace the cap then I'll use the bleeder screw on the thermostat housing to remove the rest of the air. I've never had a problem by using this method.