2009 GMC Envoy Owner's Manual - Page 332

8. Then replace the 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. 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. Engine Overheating The vehicle has several indicators to warn of engine overheating. You will find a coolant temperature gage on the vehicle's instrument panel. See Engine Coolant Temperature Gage on page 3-37 for more information. If the vehicle has a Driver Information Center (DIC), the display will show an Engine Coolant Hot/Engine Overheated message. See DIC Warnings and Messages on page 3-51 for more information. 6. Start the engine and let it run until you can feel the upper radiator hose getting hot. Watch out for the engine cooling fan. 7. By this time, the coolant level inside the radiator filler 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. 5-30