1993 Buick LeSabre Owner's Manual - Page 215

I How to Add Coolant to the Radiator #, A ' @ I 1. You can remove the radiator pressure cap when the cooling system, including the radiator pressure cap is Turn the and upper radiator hose, no longer hot. pressure cap slowly to left untilit first stops. the (Don't press down while turning the pressure cap.) If you hear ahiss, wait for thatto stop. A hiss means there is still some pressure left. 213