2004 Chevrolet Colorado Owner's Manual - Page 297

The vehicle must be on a level surface. When your engine is cold, the coolant level should be at FULL COLD, or a little higher. When your engine is warm, the level should be above the FULL COLD level. Add coolant mixture at the recovery tank, but be careful not to spill it. Adding Coolant If you need more coolant, add the proper DEX-COOL® coolant mixture at the coolant recovery tank. {CAUTION: 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. Occasionally check the coolant level in the radiator. For information on how to add coolant to the radiator, see Cooling System on page 5-30. {CAUTION: Turning the radiator pressure cap when the engine and radiator are hot can allow steam and scalding liquids to blow out and burn you badly. With the coolant recovery tank, you will almost never have to add coolant at the radiator. Never turn the radiator pressure cap - even a little - when the engine and radiator are hot. Radiator Pressure Cap Notice: If the pressure cap is not tightly installed, coolant loss and possible engine damage may occur. Be sure the cap is properly and tightly secured. 5-27