1998 Cadillac DeVille Owner's Manual - Page 272

4. With the coolant surge tank pressure cap start the off, engine and let run until you can feel the upper it radiator hose getting hot. Watch out the engine for cooling fans. By this time, the coolant level inside the coolant If surge tank may be lower. the level is lower, add more of the proper mixture to the coolant surge tank until the level reaches about2.5 inches (6.4 cm) below the base of the filler neck. 5. Then replace the pressure cap. Be sure the arrows this. on the pressure cap line up like Start the engine and allow it to warm If the CHECK up. COOLANT LEVEL message does not appear on the is Driver Information Center, coolant at the proper fill level. If a CHECK COOLANT LEVEL message does appear, repeat Steps 1 through 3 or see your dealer.