2010 Hummer H3 Owner's Manual - Page 287

Vehicle Care 10-21 { WARNING 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 surge tank pressure cap - even a little - they can come out at high speed. Never turn the cap when the cooling system, including the surge tank pressure cap, is hot. Wait for the cooling system and surge tank pressure cap to cool if you ever have to turn the pressure cap. If coolant is needed, add the proper mixture directly to the radiator, but be sure the cooling system is cool before this is done. 3. Fill the radiator with the proper DEX‐COOL coolant mixture, up to the base of the filler neck. See Engine Coolant on page 10‑19 for more information about the proper coolant mixture. 1. Remove the radiator pressure cap when the cooling system, including the upper radiator hose, is no longer hot. Turn the pressure cap slowly counterclockwise about one full turn. If you hear a hiss, wait for that to stop. A hiss means there is still some pressure left. 2. Keep turning the cap to remove it. 4. Fill the coolant recovery tank to the FULL COLD mark. 5. Reinstall the cap on the coolant recovery tank, but leave the radiator pressure cap off.