2005 Pontiac GTO Owner's Manual - Page 212

If the coolant overflow reservoir is completely empty, add coolant to the radiator. See Engine Overheating on page 5-26. Radiator Pressure Cap Notice: If the pressure cap is not tightly installed, coolant loss and possible engine damage may occur. Be sure the cap is properly and tightly secured. See Engine Compartment Overview on page 5-12 for information on location. {CAUTION: Turning the radiator pressure cap when the engine and radiator are hot can allow steam and scalding liquids to blow out and burn you badly. With the coolant recovery tank, you will almost never have to add coolant at the radiator. Never turn the radiator pressure cap - even a little - when the engine and radiator are hot. Occasionally check the coolant in the radiator. For information on how to add coolant to the radiator, see Cooling System on page 5-29. Engine Overheating Immediate action is required if your engine overheats. This is indicated by the coolant temperature gage and the Engine Temp Hot message on the trip computer display. See Engine Coolant Temperature Gage on page 3-28 and Trip Computer on page 3-33 for more information. 5-26