GM None Pontiac Aztek - Manual (Page 329)

3. After the engine cools, open the coolant air bleed
valves.
There are two bleed valves. One is located on the
thermostat housing. The other is located on the
thermostat bypass tube.
4. Fill the radiator with the proper DEX-COOL ® coolant
mixture, up to the base of the filler neck. See Engine
Coolant on page 5-22 for more information about the
proper coolant mixture.
If you see a stream of coolant coming from an air
bleed valve, close the valve. Otherwise, close
the valves after the radiator is filled.
5. Rinse or wipe any spilled coolant from the engine
and the compartment.
Housing Bypass Tube
5-33