2003 GMC Sierra 1500 Pickup Owner's Manual - Page 415

The coolant level should be at or above the FULL COLD mark. If it isn't, you may have a leak at the pressure cap or in the radiator hoses, heater hoses, radiator, water pump or somewhere else in the cooling system. If there seems to be no leak, start the engine again. The engine cooling fan speed should increase when idle speed is doubled by pushing the accelerator pedal down. If it doesn't, your vehicle needs service. Turn off the engine. Notice: Engine damage from running your engine without coolant isn't covered by your warranty. See "Overheated Engine Protection Operating Mode" in the Index for information on driving to a safe place in an emergency. Heater and radiatc loses, and o t l ~ er-,.ne parts, can be very hot. Don't touch them. If you do, you can be burned. - - E Notice: When adding coolant, it is important that you use onlyDEX-COOL@(silicate-free) coolant. If coolant other than DEX-COOL@ added to is the system, premature engine, heater core or radiator corrosion may result. In addition, the engine coolant will require change sooner at 30,000 miles (50 000 km) or 24 months, whichever occurs first. Damage caused by the use of coolant other than DEX-COOL@ not covered by your new vehicle is warranty. Don't run the engineif there is a leak. If you run the engine, it could lose all coolant. That could cause an engine fire, and you could be burned. Get any leak fixed before you drive the vehicle. 5-40