Sorry if this has been covered but couldn't find anything on it. A friend just bought a 96 xj with a 4.0 for $500. During the test drive the heater valve blew apart after 1.5 miles. We got a used one put it on and the same thing after 12 miles, coolant everywhere. Is something causing this or just another bad heater valve? Bought a new one, so far so good but the temp light came on after 5 miles and 25 minutes of idling. Water pump and thermostat have been replaced.