Over heating

Ok I have been having trouble with my car overheating. My radiator did have a crack. But was told it could just be my thermostat is stuck because I did have coolant but it was not getting used. So I changed that. The next say I added more coolant and then headed to an interview about 30 mins out of my area. Halfway there my passenger realized my car was overheating. So I pulled over. At this point I'm convinced its the cracked radiator, which at this point was using the coolant up but it wasted awhile jug. I made it to a store and got more coolant. Headed back to passengers home and it was fine. A few hours later I headed home and had to stop 7 times. The car wasn't using coolant. Now today I have replaced the radiator with a brand new one and put everything I needed to in there and in the coolant reservoir. That was completed about 4 hrs ago (from 5:30 CDT) and the coolant reservoir is empty and my car was heating up again. This time it was coming from underneath the throttle. Where the thermostat cover is and the end of the upper house. I hear is noise as if pressure is coming out. What can this be that is causing this. What else am I gonna have to change?