2008 Pontiac G6 Owner's Manual - Page 275

{CAUTION: You can be burned if you spill coolant on hot engine parts. Coolant contains ethylene glycol and it will burn if the engine parts are hot enough. Do not spill coolant on a hot engine. 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. Then 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, 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. 5-39