Overheating HELP!!!

Overheating HELP!!!
2012 Jeep Grand Cherokee Limited Auto 4x4 MY12
3.0-litre V6 turbodiesel
160,00Ks

Sorry I know it?s a long read!
Hi, I have a very illusive and frustrating issue with my jeep overheating, for year it was great, and towing our van was great most of the times until I replaced the oil cooler that let oil residue throughout the cooling system.
replaced the oil cooler, flushed the system, all god, well we hoped!
Weeks later towing the van a hose popped of the radiator, pulled over, cooled down tried to continue but no good, kept on overheating, got the car towed home
Back to the mechanic, we proceeded to change the water pump, thermostat, temperature switch hoses, still no good when towing.
Back to the mechanic, replaced the radiator, 16% blocked, This must be it, NO GOOD, still over heated when towing.
NEXT, checked for combustion leak with a test kit, The fluid did not change.
Then, one day simply driving up a long hill it overheated, Far-out, this is crazy!
they following weekend i did the same him, in third and made it to the other side.
The next morning, i tried again in DRIVE, not good it overheated, Transmission temperature was fine, fan was working, everything is new, engine oil is good, did another combustion leak test, all good, what could if be?
so I went ahead and and even tried a block seal head gasket fix, this also did not work after anther test run.
In a nut shell, the car runs great around town, not loosing water, fan works when is should, everything in the cooling system in new, flushed around a dozen time even a new coolant bottle.
WHAT COULD IT BE!!!!!!!!!!
Any thoughts would be greatly appreciated.
Fab