Diamante, Eclipse, Galant, Lancer & Outlander
WARNING: This page does not describe the selected car, but rather 7 other vehicles, including the 2003 Mitsubishi Outlander, 2003 Mitsubishi Montero Sport, 2003 Mitsubishi Montero, 2003 Mitsubishi Lancer, and 2003 Mitsubishi Galant. However, it is still accessible from the selected car via links, so may be relevant.
Slowly pour coolant into radiator to brim. Install radiator cap. Start engine and warm up until thermostat opens. Race engine up to around 3000 RPM several times, then stop engine. When engine has cooled down, remove radiator cap and add coolant up to brim.