1997 Buick Century Owner's Manual - Page 248

2. Then 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 valve orvalves. 3100 V6 (VIN Code M): There are two bleed valves. One is located on the thermostat housing. The other is located on the thermostat bypass tube. 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. Don't spill coolant on a hot engine. 5-22