2003 GMC Sierra 1500 Pickup Owner's Manual - Page 409

What to Use Use a mixture of one-half clean, drinkable water and one-half DEX-COOL@ coolant which won't damage aluminum parts. If you use this coolant mixture, you don't need to add anythinq else. If you have to add coolant more than four times a year, have your dealer check your cooling system. Notice: If you use the proper coolant, you don't have to add extra inhibitors or additives which claim to improve the system.These can be harmful. Checking Coolant Addingonlyplain wa toyourcooling system can be dangerous. Plain water, or some other liquid such as alcohol, can boil before the proper coolant mixture will. Your vehicle's coolant warning system is set for the proper coolant mixture. With plain water or the wrong mixture, your engine could get too hot but you wouldn't get the overheat warning. Your engine could catch fire and you or others could be burned. Use a 50/50 mixture of clean, drinkable water and DEX-COOL@coolant. Notice: If you use an improper coolant mixture, your engine could overheat and be badly damaged. The repair cost wouldn't be covered by your warranty. Too much water in the mixture can freeze and crack theengine, radiator, heater core and other parts. The coolant surge tank is located in the engine compartment on the passenger's side of the vehicle. See Engine Compartment Overview on page 5-12 for more information on location. I 5-34