[dallas121469]

2000 Cherokee 4.0 liter engine. Had radiator leek. Installed new radiator and thermostat. Was fine for about 1500 miles then all of a sudden one day the coolant starts backing up into the overflow bottle. Coolant is not hot. Just seems to be building up pressure somewhere and forcing coolant into overflow. Engine itself gets very hot. No radiator fluid in oil. Then installed new water pump figuring coolant wasnt circulating. Wrong!!! Still forcing coolant into the overflow. WTF is going on? Going to try running without thermostat see if thats the problem. Any other help would be greatly appreciated.