Auto mechanic question?

i have a 1995 isuzu rodeo 3.2L v6 and it overheats.i changed the thermostat and it still overheats and i didnt see any coolant leaking from the weep hole on the water pump so what else could it be?the combs are falling out of the radiator but it still circulates in side the radiator.could it be the radiator? i dont think its the head gasket because there is no antifreeze in the oil.any opinion would be helpful