Well its all fixed now... I found out from the previous owner that he never flushed it, only added more fluid when it "seemed low". Which isn't awful I guess, but assuming it has 200K+ miles... It needed a flush. That and after my overheating adventure (which I did add back into my radiator) I had about 1/2 gallon of coolant left. And my XJ swallowed 2 full gallons and could still take a bit more.

It you don't wanna read all that- previous owner was... Oblivious. And coolant was ridiculously low.