Also check the following, if there is an aircon condenser check for possible blockage, check also the clutch fan if equipped (add silicone oil), Although water pump impeller seldom gets too rusted, it is also a possibility. Another is the fan shroud (it could be broken or missing parts), Fan Belt Slipping is another one. Better also check the temperature gauge itself, if it is telling an accurate temperature. It could also be a mistime engine which would produce more heat. And finally the radiator itself. It could be partially clogged.