2006 Cadillac STS Owner's Manual - Page 341

If you have to add coolant more than once or twice a year, have your dealer check your cooling system. Notice: If you use extra inhibitors and/or additives in your vehicle's cooling system, you could damage your vehicle. Use only the proper mixture of the engine coolant listed in this manual for the cooling system. See Recommended Fluids and Lubricants on page 6-12 for more information. {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/FROID line on the side of the surge tank. Follow the arrow from the top of the tank down the side to the horizontal mark. If the CHECK COOLANT LEVEL message in the Driver Information Center (DIC) comes on and stays on, it means you are low on engine coolant. See DIC Warnings and Messages on page 3-79 for more information. Checking Coolant The coolant surge tank and pressure cap are located on the driver's side of the vehicle, toward the rear of the engine compartment. See Engine Compartment Overview on page 5-12 for more information on location. 5-29