Drain the cooling system.
Refer to: Cooling System Draining, Filling and Bleeding - 2.3L Duratec-HE (MI4), Vehicles Without: Fuel Fired Booster Heater (303-03 Engine Cooling, General Procedures).
Refer to: Cooling System Draining, Filling and Bleeding - 2.3L Duratec-HE (MI4), Vehicles With: Fuel Fired Booster Heater (303-03 Engine Cooling, General Procedures).