Did you put a thermostat in? With mine, I burp it for the first run, otherwise it will overheat and spew out coolant. After the temperature reached 212, I shut it down and pull the top heater hose at the block. A bunch of steam rushes out and then coolant starts to come out. At this point I shove the hose back on. I then leave it for a few minutes to let the thermostat open and then run it again.
