Nabawasan ba yung coolant? If yes, may tagas yan somewhere, look for possible leaks, unahin mo tingnan sa radiator.

Kung hindi naman nabawasan yung coolant, unahin mo tingnan yung radiator fans kung nag-aautomatic, dapat sabay umandar yung dalawang fan with aircon turned-on. Much better kung dalhin mo na sa repair shop.