2006 Jeep Liberty overheating...

Hey guys, i have an issue with my 06 Jeep liberty
overheating and its diving me nuts...no pun
intended... it is overheating and im all out of ideas
as to why. Ive changed the thermostat three times
(checked them before installation and they all
worked), new water pump, new Coolant temp
sensor and wires/plugs, oil change, used the stop
leak gasket sealer (to the tee...followed directions
to the minute and letter), bled the air from the
system, etc. The fans are working properly, and
everything seems to check out. The only thing i
didnt replace was the radiator, but it has backflow
and as many times as ive flushed it bc of using the
stop leak, i know it isnt leaking anywhere...
Any ideas before i say heck with it and just sell it?