2004 Buick Regal Owner's Manual - Page 244

1. The radiator pressure cap can be removed when the cooling system, including the radiator pressure cap and upper radiator hose, is no longer hot. If a hiss is heard, wait for that to stop. A hiss means there is still some pressure left. 2. Then keep turning the pressure cap, but now push down as you turn it. Remove the pressure cap. {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. 3. Remove the 3800 Series II V6 engine cover shield to access the bleed valve. 5-36