Overheating 1999 Pontiac Grand Am

My granddaughter’s 1999 Pontiac Grand Am is overheating & blowing the antifreeze. Radiator was checked out OK, engine was replaced with 69000 miles, and check out OK - still overheating. Help! Any ideas?

Are the radiator’s cooling fans operating when the engine gets hot?
Has the thermostat been replaced?
Has the cooling system been “burped” to remove entrapped air?

In ADDITION to VDC’s questions,

Under what conditions is it overheating?
HOW was the radiator “checked out”? A radiator can flow fluid but the tubes be too clogged up to dissipate heat.
Have the hoses been checked?
Has the water pump been checked?
WHY was the engine replaced? Was it replaced with a like engine?