Pontiac 2003 Aztek Owner's Manual page 328

How to Add Coolant to the Radiator
Notice: Your engine has a specific radiator
fill procedure. Failure to follow this procedure could
cause your engine to overheat and be severely
damaged.
Turn the pressure cap slowly counterclockwise until
it first stops. (Don't press down while turning the
pressure cap.)
If you hear a hiss, wait for that to stop. A hiss
means there is still some pressure left.
i . You can remove i i e rauiaiur pressuli: cap
vvi-Iei-1
the cooling system, including the radiator pressure
cap and upper radiator hose, is no longer hot.
2. Then keep turning the pressure cap, but now push
down as you turn it. Remove the pressure cap.
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