2000 GMC Sierra 1500 Pickup Owner's Manual - Page 281

yellowblue How to Add Coolant to the Coolant Surge Tank 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.) CAUTION: Steam and scalding liquids from a hot cooling system can blow out and burn you badly. They are under pressure, and if you turn the coolant surge tank pressure cap -- even a little -- they can come out at high speed. Never turn the cap when the cooling system, including the coolant surge tank pressure cap, is hot. Wait for the cooling system and coolant surge tank pressure cap to cool if you ever have to turn the pressure cap. 5-14