1998 Saturn SL1 Low coolant light blinking with plenty of c

Just for maintenance reasons I have replaced the water pump and thermostat yesterday (6/10/10) after which the low coolant light/ temperature light are blinking and the temperature gauge got up just past the half way mark. Checked the coolant level and it's fine, I felt the top radiator hose and it felt hot.I drained the coolant again, replaced it, turned the heater on after replacing the coolant again as I started the car. The lights blinked again, I squeezed the top radiator hose a few times and the lights went out. Now the lights come on and go off every once in awhile while driving and the temperature gauge goes up. What did I miss? What should I check next?