1999 Buick LeSabre Owner's Manual - Page 218

First Edition for Buick LeSabre Owner's Manual - 1999 yellowblue How to Add Coolant to the Radiator W-35-1020-S C-45-6704-T 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. 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 to stop. A hiss means there is still some pressure left. 5-16