edd1em

My car never overheats, but due the fact that I had a oil leak(oil cooler) a few months ago I performed the following: I bought a pressure tester for my car. (PepBoys $83) I understand the cap opens at 13lbs, so the system usually runs at 11-12lbs. I pressurized the system to 13lbs, it holds pressure perfectly(at least the oil cooler is not leaking!!!yey, yey, hoorah). At 13lbs when you unscrew the air realese screw, water SQUIRTS out and thats at only a 1/4" turn. I squeezed the upper radiator hose and it was solid. Now when I took the tester off, that same hose felt like a hose and the water comming out of the valve is almost nothing. So my diagnosis is that my waterpump is almost not working.... But my question is, how do you pressurize the system? Is it a buildup process? I understand the cap opens and releases water at 13lbs (mine at 12lbs but thats ok, for now...). Anyone have any ideas?