2003 GMC Sierra 1500 Pickup Owner's Manual - Page 416

How to Add Coolant to the Coolant Surge Tank Gasoline Engines If you haven't found a problem yet, check to see if coolant is visible in the surge tank. If coolant is visible but the coolant level isn't at or above the FULL COLD mark, add a 50/50 mixture of clean, drinkable water and DEX-COOL@ 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 on page 5-33 for more information. out at nigh speea. Never IUe cap when the cooling system, including the coolant surge tank pressurecap, is hot. Wait for the cooling system and coolant surge tank pressure cap to cool if you ever have to turn the pressure cap. 1 come ~~ ~ If no coolant is visible in the surge tank, add coolant as follows: 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 CAUTION: (Continued) 5-41