Car dumping coolant into overflow tank causing it to spill.

Honda Civic 1999, 125k miles 1.5l engine

Car dumping antifreeze on the reservoir tank and filling to the point that it spills the antifreeze. I have change the thermostat, radiator, radiator cap and the radiator fan kicks in so it's working. The car overheats quicker when the AC is on. Also when stop at a light the temperature gauge starts going up but when I put the car on neutral and rev up the engine to higher rpm it starts coming back down. I have heard that it might be the water pump or a blown head gasket.