1994 GMC Safari Owner's Manual - Page 200

1. You can remove the radiator pressure cap when the cooling system, no including the radiator pressure and upper radiator hose, is longer cap hot. Turn the pressurecap slowly to the left 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 thereis still some pressure left. 2. Then keep turning the pressure cap, but now push down as you turn it. Remove the pressure cap. 3. Fill the Radiator with the proper mix, up to the base of thefiller neck. 5-16