1999 Cadillac DeVille Owner's Manual - Page 295

yellowblue Checking Coolant CAUTION: Turning the surge tank pressure cap when the engine and radiator are hot can allow steam and scalding liquids to blow out and burn you badly. Never turn the surge tank pressure cap -- even a little -- when the engine and radiator are hot. The vehicle must be on a level surface. When your engine is cold, the coolant level should be at the full cold mark, which is 2.5 inches (6.4 cm) below the base of the fill neck. Use a flashlight as necessary to see into the tank. The surge tank is located next to the engine block on the passenger's side of the engine. The cooling system is under a lot of pressure when it is hot. If the CHECK COOLANT LEVEL message appears on the Driver Information Center (DIC), you will need to add coolant. If the CHECK COOLANT LEVEL message comes on and stays on, it means you're low on engine coolant. For more information, see "Check Coolant Level Message" in the Index. 6-25