2009 Pontiac G6 Owner's Manual - Page 274

{ CAUTION: Steam and scalding liquids from a hot cooling system can blow out and burn you badly. They are under pressure, and if you turn the surge tank pressure cap - even a little - they can come out at high speed. Never turn the cap when the cooling system, including the surge tank pressure cap, is hot. Wait for the cooling system and surge tank pressure cap to cool if you ever have to turn the pressure cap. If no coolant is visible in the surge tank, add coolant as follows: 1. Remove the coolant surge tank pressure cap when the cooling system, including the coolant surge tank pressure cap and upper radiator hose, is no longer hot. Turn the pressure cap slowly counterclockwise about two or two and one-half turns. If you hear a hiss, wait for that to stop. This will allow any pressure still left to be vented out the discharge hose. 2. Keep turning the pressure cap slowly and remove it. 3. Fill the coolant surge tank with the proper mixture to the FULL COLD mark. Wait about five minutes and then check to see if the level is below the mark. If the level is below the FULL COLD mark, add additional coolant to bring the level up to the mark. Repeat this procedure until the level remains constant at the FULL COLD mark for at least five minutes. 5-36