Pontiac G3 2009 Owner's Manual page 231

2. Then keep turning the pressure cap slowly and
remove it.
3. Fill the coolant surge tank with the proper mixture
to the Maximum mark on the coolant surge tank.
Wait about five minutes, then check to see if
the level is below the mark. If the level is below
the Maximum mark, add additional coolant to
bring the level up to the mark.
Repeat this procedure until the level remains
constant at the Maximum mark for at least
five minutes.
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