Don't Tread On Me!

There is no leak in the system. If I pull th radiator return hose, nothing comes out until the engine is quite warm. Then it alternates between a 1/4 inch stream and an occassional full 1 inch blast coming out. Only about 3/4 gallon total comes out of the system. I was going to pull the thrmostat, but people said it will mess up the computer system. Does that sound like the water pump? Any suggestions?