Make sure nothing is clogged in the block
Is the fan functioning?
No that's a clogged radiator issue. However if the engine over heats to much, the head will warp and you'll need a new one. Replace your radiator, Engine Coolant Temperature Sensor, and thermostat.
Be more informative on "over heats". Is it being driven along time before it over heats? Is the guage showing hot but not boiling out the radiator, is there steam coming from under the hood, is there a sign of leaking under the passenger side dash or under the firewall on the ground, have you had the thermostate replaced, is the water pump leaking?
Coolant at proper level? System air bound and needs to be purged? Water pump not circulating coolant? Defective thermostat? Collapsed radiator hose?
Sounds like you need a radiator coolant flush or you need a bigger radiator for your vehicular transport thingy.
If the Chevy Celebrity radiator is smaller that the Saturn radiator it might well overheat from not enough cooling capacity. If the Chevy Celebrity radiator is the same size or larger than the Saturn radiator I would think it would not over heat.
bad thermostat or bad heat gasket
Check; coolant, fan, fan clutch and fan clutch solenoid, blocked or partially blocked lines and coolant gallery.
The heat is exhausted by the radiator. If that is blocked then the heat will build up.
bad fan clutch, clogged radiator.....................when you turn the defrost on, the heater core is acting like the radiator...............good luck, Mike
Next would be the water pump the symptom you describe along with the items you replaced point toward low coolant flow. Dont rule out excessive corrosion in the radiator as this will reduce flow as well. Always make sure you have a good radiator cap.
Well a possibility is a problem with the radiator, either it needs to be fixed, replaced, or has no radiator fluid in it to cool the engine.