2005 Buick Century Owner's Manual - Page 241

2. Keep turning the pressure cap, but now push down as you turn it. Remove the pressure cap. 3. After the engine cools, open the coolant air bleed valves. There are two bleed valves. One is located on the thermostat housing. {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. The other is located on the thermostat bypass tube. 5-31