Have you checked the fan clutch, if it hasn't already been replaced? If its leaking or doesn't make a pronounced 'whoosh' from time to time as you're driving, it may be worn. Also, even though you may have a new radiator, the a/c condenser is still in front of it. If its clogged with dirt, leaves and insects, etc, it will impede airflow through the radiator. Try washing it from behind, with a pressure washer, at a reasonable setting, or at one of those self serve car washes. If you do that, cover the air intake snorkel with a bag while washing it to keep water out of the intake hose. Have you tried a pressure test of the system?

Regards, 'Uncle Olaf'