2008 Saturn Astra Owner's Manual - Page 209

Vehicle Service and Care 9-19 { 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 reservoir pressure cap when the cooling system, including the coolant reservoir pressure cap and upper radiator hose, is no longer hot. Turn the coolant reservoir 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. Coolant Reservoir Pressure Cap 2. Keep turning the coolant reservoir pressure cap slowly, and remove it. 3. Fill the coolant reservoir with the proper mixture, to the KALT/COLD mark. Wait about five minutes, then check to see if the level is below the mark. If the level is below the KALT/COLD mark, add additional coolant to bring the level up to the mark. Repeat this procedure until the level remains constant at the KALT/COLD mark for at least five minutes. 4. With the coolant reservoir pressure cap off, start the engine and let it run until you can feel the upper radiator hose getting hot. Watch out for the engine cooling fans. By this time, the coolant level inside the coolant reservoir might be lower. If the level is lower than the KALT/COLD mark, add more of the proper mixture to the coolant reservoir until the level reaches the KALT/COLD mark. 5. Replace the coolant reservoir pressure cap. Be sure the pressure cap is hand-tight and fully seated.