1995 Buick Century Owner's Manual - Page 186

How to Add Coolant to the Radiator NOTICE: Your engine hasa specific radiator fill procedure. Failure to followthis procedure could cause your engine to overheat and be severely damaged. 2. Then keep turning the pressure cap, but now push down as you turn it. Remove the pressure cap. P 4- 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 capslowly to the left until it first stops. (Don't press down whileturning the pressure cap.) If you hear a hiss, wait for that to stop. A hiss means there is still some pressure left. 5-20