all this discussion and no definite "technical" / "mechanical" failure identifiable does remind me of a similar problem i encountered some years ago: Being a rookie ;-(( , driving through some (read : MOST) of the muddy WET passages on a trail and being HAPPY to arrive at the camp-place with a "cool" looking jeep ( color= mud-brown all-over although normally it schould be yellow with a black top)
BY CLEANING IT UP, I RUINED ONE RADIATOR because of putting high water pressure directly unto it. IT got cleaned allright but the heating-ducts were all bend and proved to be useless afterwards ( no problem with water-flow, no problem with the thermostat , no problem with whatever INSIDE the system, the cooling "little pieces of metal" =OUTSIDE (excuse my english) were simply gone. SO: The system was working but couldn't release the heat. well: once you realize that: swapping in another (not damaged!) radiator body simply put all to normal. Lesson learned: Clean but don't overdue ( overpressure?) it
Just a thought, if your radiator suffered some severe cleaning you can "see it"
just wondering .-)
92YJ (2,5L 4cyl, K&N-Cyclone-restrictor.removed..., HP-exhaust,HD clutch, 2,5"SL,1"BL, Rancho, SYE, Revolver, Quick Disconnects, telescopic track-bar, 33*9.5*15MT)WARN9000