Chevrolet C6H042 Owner's Manual page 185

4. Put the release stud, nut and flat washer into
the chamber.
5. Turn the stud clockwise a quarter of a turn.
5-18
3. Remove the rubber
cap from the rear of
the chamber.
7. At the repair facility, apply air pressure of at least
70 psi (480 kPa) to the brake chambers, either from
an external air supply or the vehicle's air system.
8. Turn the stud nut counterclockwise several turns.
Remove the stud from the chamber.
9. Put the stud into the side of the chamber, and replace
the rubber cap.
6. Using a wrench, turn
the stud nut clockwise
several turns to release
the brakes. Follow the
same procedure to
release the other brake.