2001 GMC Sierra 1500 Pickup Owner's Manual - Page 319

NOTICE: When adding coolant, it is important that you use only DEX-COOLR (silicate-free) coolant. If coolant other than DEX-COOL is added to 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-COOLR is not covered by your new vehicle warranty. If there seems to be no leak, start the engine again. See if the engine cooling fan speed increases when idle speed is doubled by pushing the accelerator pedal down. If it doesn't, your vehicle needs service. Turn off the engine. How to Add Coolant to the Coolant Surge Tank --Gasoline Engines If you haven't found a problem yet, but the coolant level isn't at or above the FILL COLD mark, add a 50/50 mixture of clean, drinkable water and DEX-COOLR coolant at the coolant surge tank, but be sure the cooling system, including the coolant surge tank pressure cap, is cool before you do it. See "Engine Coolant" in the Index for more information. 5-13