Hello everyone. A friend of mine has a 06 XJ8 and he told me to look at it because he said it has a coolant leak. On my way driving his car to my home to look at it, it overheated and the engine cut off on me. I restarted it and parked at the gas station that was thankfully only 100ft. away, let it cool down for 1hr. 30min. I filled the reservoir with water started it back up and drove it home. The engine started back up with no problems. He needed a thermostat housing assembly so I replaced it filled the car up with antifreeze, bled the air out and drove it back to him. It did not overheat on the way back to his home and the temp did not rise above the halfway mark. He called me two days later and told me his car overheated again. I told him to let it cool for at least an hour fill it with water and drive it home. He decided not to wait to cool it down and drove it home the way it was. I called him later on to ask him if he made it home and he told me the engine cut off on him 3 times on the way home from the overheat. After he told me this I was worried that he blew his head gasket driving it like that. The next day I came over his house and put a pressure tester on it, no leaks, filled it with antifreeze and cranked it up. It started and the engine runs fine with no shakes. I opened the bleeder and let air out in case the coolant reservoir still had air in it. I drove it about 20 min. and it overheated again. What could be wrong with it? Sorry for this long write up I just wanted to get all the details in.

 

Hello, sorry to hear about your problems . Devil is in details and diagnosing coolant issues may not be as easy as it looks . I am pretty sure you will be able get clinching answers from our tech guys

 

It will probably be one of a few things. It may still have air in the system from the previous service which will need to be removed with a vacuum filler, the thermostat randomly sticks closed ( don't know if that was replaced with the housing?), the electric fans don't work properly, or the head gaskets have let go. My bet is on air in the system or thermostat. The engine management system in these cars will not let the engine get hot enough to damage itself, so headgaskets don't seem to be a likely cause.

 

I checked on all the things you suggested and I ended up telling him to go get a coolant flush and it got all the air out and fixed his overheating issue. Thanks for your help.

 

Thanks for your feedback, good to see it was fixed

 

I had very similar issues. I found out that there was a small crack at the base of the nipple of the reservoir. I did not see this small issue during my inspection when the issue occurred. I found out later - via this forum, that this is a common issue with Jag. I paid to have the reservoir replaced - God forbid someone make it as simple as replacing the cap which also housed the nipple! Either way...all is well now. Take a look at the nipple on the reservoir....VERY CLOSELY.

 

Glad to hear you got it fixed!