2010 GMC Savana 2500 Cargo Owner's Manual - Page 293

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. Do not 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. 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 DEX-COOL® coolant mixture, up to the base of the filler neck. See Engine Coolant on page 6-28 for more information about the proper coolant mixture. 6-31