2003 Pontiac Sunfire Owner's Manual - Page 236

Park the vehicle on a level surface. You can 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 (left) 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. 3. Then fill the coolant surge tank with the proper mixture, to the hash mark on the label. Wait about five minutes, then check to see if the level is below the hash mark. If the level is below the hash mark, add additional coolant to bring the level up to the hash mark. Repeat this procedure until the level remains constant at the hash mark for at least five minutes. 5-31