Chevrolet 2000 Lumina Owner's Manual page 206

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. Don't spill coolant on a hot engine.
5-18
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 or valves.
There are two bleed valves. One is located on the
thermostat housing. The other is located on the
thermostat bypass tube.