2005 Pontiac GTO Owner's Manual - Page 219

How to Add Coolant to the Radiator Notice: Your engine has a specific radiator fill procedure. Failure to follow this procedure could cause your engine to overheat and be severely damaged. 1. You can remove the radiator pressure cap when the cooling system, including the radiator pressure cap and upper radiator hose, is no longer hot. See Engine Compartment Overview on page 5-12 for more information on the location of the radiator pressure cap. Turn the pressure cap slowly counterclockwise until it first stops. Do not press down while turning the pressure cap. If you hear a hiss, wait for that to stop. A hiss means there is still some pressure left. 2. Then keep turning the pressure cap, but now push down as you turn it. Remove the pressure cap. 3. Fill the radiator with the proper DEX-COOL® coolant mixture, up to the base of the filler neck. See Engine Coolant on page 5-23 for more information about the proper coolant mixture. 4. Rinse or wipe any spilled coolant from the engine and the compartment. 5. Then fill the coolant overflow reservoir to the bottom arrow on the dipstick. 6. Put the cap back on the coolant overflow reservoir, but leave the radiator pressure cap off. 7. Start the engine and let it run until you can feel the upper radiator hose getting hot. Watch out for the engine cooling fan. 8. By this time, the coolant level inside the radiator fill neck may be lower. If the level is lower, add more of the proper DEX-COOL® coolant mixture through the filler neck until the level reaches the base of the filler neck. 9. Then replace the radiator pressure cap. At any time during this procedure, if coolant begins to flow out of the filler neck, reinstall the pressure cap. Be sure the pressure cap is hand-tight and fully seated. 10. Check the coolant in the overflow reservoir. The level should be at the bottom arrow on the dipstick when the engine is cold. See your dealer, if necessary. 5-33