2005 Buick Century Owner's Manual - Page 233

Notice: If you use an improper coolant mixture, your engine could overheat and be badly damaged. The repair cost would not be covered by your warranty. Too much water in the mixture can freeze and crack the engine, radiator, heater core and other parts. If coolant has to be added more than four times a year, have your dealer check the cooling system. Notice: If you use the proper coolant, you do not have to add extra inhibitors or additives which claim to improve the system. These can be harmful. Checking Coolant The engine coolant recovery tank is located on the passenger's side of the vehicle at the rear of the engine compartment. See Engine Compartment Overview on page 5-12 for more information on location. The vehicle must be on a level surface. When the engine is cold, the coolant level should be at the COLD mark or a little higher. When the engine is warm, the level should be up to the HOT mark or a little higher. 5-23