1998 Chevrolet Lumina Owner's Manual - Page 220
1998 Chevrolet Lumina Manual
Page 220 highlights
How to Add Coolant to the Radiator LOTICE: Your engine has aspecific radiator fill procedure. Failure tofollow this procedurecould cause your engine to overheat and beseverely damaged. Then keep turning the pressure cap, but now push down as you turn it. Remove the pressure cap. - 1. You can remove the radiator pressure cap when the cooling system, including the radiator pressure cap and upper radiator hose, is no longer hot. L - You can beburned if you spill coolant on hot engine parts. Coolant contains ethylene glycol and it will burn if the engineparts are hot enough. Don't spill coolant on hot engine. a Turn the pressure cap slowly counterclockwise until it first stops. (Don't press down while turning the pressure cap.) If you hear a hiss, wait for that stop. A hiss means to there is still some pressure left. 5-22