I did the cooling system overhaul with all the recomended oem and Stant parts. Before the overhaul I did a Thermocure flush. When replacing the water pump and thermostat the engine block was squeaky clean. I decided to flush one more time with distilled water just for grins. Burped all air out. Levels were good, Temps have been running at a steady 203. Two days ago the jeep over heated and started blowing water out of the radiator drain petcock. The petcock seemed to shut ok and held. This morning it happened again. The only thing that hasn't been replaced yet is the heater core which is the original. Parts used: Mopar radiator and water pump, Stant 195 thermostat, Hayden fan clutch, distilled water and a couple of quarts of Zerex G05 after the first incident. I'm not sure what to do next. I'm assuming the petcock is bad at this point.