2004 Cadillac Seville Owner's Manual - Page 294

1. 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) until it first stops. Do not press down while turning the pressure cap. If you hear a hiss, wait for that to stop. A hiss means there is still some pressure left. 2. Press down on the pressure cap and keep turning it slowly. Remove the cap. 3. Then fill the coolant surge tank with the proper mixture, to or above the fill mark at the forward edge of the surge tank. 5-34