Hey guys, wife’s XJ is driving me crazy. 6 months ago the original radiator blew so I replaced it with an aluminum one and replaced the thermostat. Ran good for about three weeks and ever since then it has been a weird mix of either running well or overheating. I have done every diagnostic in the FSM and everything she told me ChatGPT says to do, to include a new head gasket and it still over heats. The only time it hasn’t overheated is when I did a chemical flush. Drove it for twenty... XJ overheating