2006 GMC Savana Van Owner's Manual - Page 278

How to Add Coolant to the Radiator for Gasoline Engines If your vehicle has a diesel engine, see "How to Add Coolant to the Radiator" under "Van Models" in the Cooling System section of the DURAMAX® Diesel Supplement for the proper radiator fill procedure. 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. 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. 3. Fill the radiator with the proper DEX-COOL® coolant mixture, up to the base of the filler neck. See Engine Coolant on page 5-21 for more information about the proper coolant mixture. 5-30