2000 Jeep Grand Cherokee • 4.0L 6 cylinder 4WD Automatic • 199,840 miles

Two months ago my wife was driving my Jeep home from work (it was during January - sub-zero temps) when it started to overheat - she didn't notice the temp gauge rising. She drove it until it completely shut down. Because of the cold, and not being able to get it into a mechanic it sat at our house until we could work on it. My son is a trained mechanic and we set about trying to determine if it was a workable situation. I had recently installed a new alternator and water pump just before this incident and since then we have put in a new radiator (the old one was cracked), serpentine belt, and belt tensioner. A complete oil change was done as well. We have purged the cooling system as best we can but there still seems to be a lot of air in the system. The heater core seems clear but I am not getting any heat in the cabin. Today as I tried to go to work it overheated again (after we thought we had it fixed) and I watched as coolant gushed out the overflow tube on the coolant reservoir. Please respond with any suggestions! I love this Jeep and would rather not get rid of it!
March 5, 2014.

Have you replaced the thermostat? Have you tried bleeding the heater core?

Thanks for the reply but I got my answer today. My son brought out a test kit to check for a warped head (by checking for exhaust gases in the coolant). Got a positive result. : ( I guess the next step is removing the head and having it milled (if possible) and replacing it with new gaskets and bolts.

Mar 5, 2014.
A bad head gasket will do it.