1987 Toyota Celica cooling system

I recently had the coolent in my car changed. I've never had any problems with the cooling system, I just felt that it was a good preventive maintenance thing to do since it hadn't been changed in the 6 years and 36000 miles since I bought it. Ten days later, I arrive home and pull into the garage and hear a sound under the hood like a boiling pot of water. I take it back to the place that changed the coolent and they changed it again, saying that it might be an air bubble in the system. Later that day a small amount of steam shows from under the hood and the heat gauge goes up unusually high. Again when I get home, I hear the sound of a boiling pot of water. When I open the hood, the overfill take is full of antifreeze and is boiling like a pot of water and a small amount of steam is coming out near the tank. This lasts about 5 minutes and then the fluid is drawn back into the radiator. What is happening?