i am starting to go with Big Jim here & it sounds like a head gasket. my 90 xj was a total whore about the coolant system when i had to breach it once. but wow man you have replaced alot.

how about the lower radiator hose collapsing?? i remember my old 318 doing that alot. used to have to put in valve springs from 454's or 500's LOL just to keep it open.

maybe you had rust or debris or something in the system & after all of the work it worked into a spot & is stopping or seriously restricting the flow?

do you have a temp guage or dummy light in the jeep? maybe you need to see what your temp is when the puking starts?

93 xj stroked 4.2 w/4.0 head avenger supercharged 6.5" long arm 35" buckshots rubicon 44's front & rear