2008 GMC Sierra 1500 Pickup Owner's Manual - Page 337

Checking Coolant The vehicle must be on a level surface. When your engine is cold, the coolant level should be at the FULL COLD mark. Adding Coolant If more coolant is needed, add the proper DEX-COOL® coolant mixture at the surge tank, but only when the engine is cool. {CAUTION: The coolant surge tank is located in the engine compartment on the passenger's side of the vehicle. See Engine Compartment Overview on page 5-12 for more information on location. You can be burned if you spill coolant on hot engine parts. Coolant contains ethylene glycol, and it will burn if the engine parts are hot enough. Do not spill coolant on a hot engine. When replacing the pressure cap, make sure it is hand-tight and fully seated. {CAUTION: Turning the surge tank pressure cap when the engine and radiator are hot can allow steam and scalding liquids to blow out and burn you badly. Never turn the surge tank pressure cap - even a little - when the engine and radiator are hot. 5-25