I recently purchased a 2000 XJR. I was having an issue where when I would run the car hard and not give it a whole lot of cooldown time, when I parked the fans would kick on high and it would start puking coolant from the recovery tank under the left front headlight. It sounded like steam was being vented into the tank, which was causing it to sound like it was boiling in the tank and causing it to vent out of the little neck about 2/3 of the way up the tank. So after some research, I discovered that the two lines coming out of the front of the expansion tank (the tank near the cowl on the left hand side where more coolant is added) can get crossed if anyone ever does any work on it, and that could cause the issue I was experiencing. It is completely non-intuitive for them to cross, because they fit perfectly in their uncrossed state. But I decided I would try it and see if it fixed the issue. And it did! No more puking coolant all over my girlfriends driveway.

I know this issue has been covered a lot, but it was not clear to me what the "correct" configuration was, as well as several other issues like how to get the clips that hold the line into the expansion tank to disengage. So I'll add pictures here in a little bit to hopefully make this a little more clear and so people don't have to look through about 20 threads to figure this problem out like I did.

 

Hahahaha Yeah found this out as well by accident i snapped one of the those dam plastic lines the one going into the rad and when I got the new one wasnt paing attention and was in a hurry and had the same thing happen lol. It only took me till i got home from picking up the new line from jag and was wondering why it was puking so bad and I popped the hood and it was apparent then haha. Good to hear ya found it it can be quite confusing anf frustrating jag shoulda made them different sizes so there weasnt a mistake

 

Pics:

This is the proper configuration. Front of the car is to the left. I know it doesn't make sense if you just look at it, but this is the correct setup.



To remove these clips, squeeze the ring that runs around the outside over the open areas as shown. This will release the little teeth that go over the nipple coming out of the expansion tank.



Hope this helps!