This morning I replaced my thermostat. After it was done I took the radiator cap off and started the car. After it reached operating temp I was only able to add a small amount of coolant (makes sense since only a small amount came out when I replaced the t-stat). Later, when I drove it to school, the low coolant light was going on and off every 2 minutes or so. I opened the hood at school and there are no leaks and the resevoir is full. This means I have air in the system, correct? How do I remove the air in the system?