Running Hot

My guess is that the antifreeze concentration is to high. Antifreeze does a great job of dumping heat and a poor job of absorbing it. When the concentration is to high insufficient heat is absorbed from the engine and when the coolant hits the new radiator it "dumps" what little it has absorbed. This effects the opening point of the thermostat, cooler upper hose and coolant, and if there is a fan clutch involved the cooler radiator causes the clutch to engage later. The result is a warmer running engine. If the engine has a fixed fan the heat is pulled out of the coolant even more and the engine runs even warmer. It could also be as simple as a failing thermostat if it was not replaced or an incorrect or faulty one if it was. As for the air pocket theory, if the coolant level is correct the system most likely has purged itself. If the level is low it definitely purged itself and needs to be topped off. All later engines have a purge hose that runs from the highest point in the cooling system to the surge tank. Earlier engines with a catch tank sometimes needed to be run with the cap loose to purge air.
Randy