Not familiar with that model so don't know if it has a water pump or is convection (thermo-siphon) cooled.
Fan and fan belt in good condition and working?
If equipped with a water pump, pump working, not leaking, thermostat installed and working?
Hoses in good shape, not collapsing?
Proper coolant mixture, not just plain water?
Interior of radiator clean as well? No plugged cores or scale floating around in the tank?
Signs of air bubbles or oil in the coolant (head gasket issues)