4-22 AIR SYSTEM - Continued
Install three new O-rings (2 of 11) and (12) in grooves of lower static piston assembly (24).
The larger diameter O-ring is installed in groove nearest to bottom of piston assembly.
Install new O-rings (6) and (7) on relay piston (22) and new O-ring (9) on No 1 circuit piston (25).
Carefully clamp No 1 circuit piston (25) in a soft-jawed vise taking care not to damage the exhaust seat or
the outside diameter. Assemble the new rubber spring (10) over the center stem of the center of the
piston, then the spring seat (19), and the new spring seat nut (16).
Tighten the spring seat nut until the end of the piston stem and the spring seat nut are flush.
Insert relay piston spring (5), and relay piston (22) in top end of lower static piston (24). Install No 1 circuit
piston spring (8) and No 1 circuit piston assembly (25) in the bottom of lower static piston (24).
Install stem bolt (21) through bore of relay piston (22). Invert entire lower static piston assembly and
position over a screwdriver mounted in a vise. Engage screwdriver blade in slot in head of stem.
Depress No 1 circuit piston assembly (25) against spring until locking groove is accessible through
rectangular hole in side of lower static piston (24). Engage a screwdriver or wire in locking groove and
release pressure on piston.
Install stem spring (23), spring seat (15), and stem nut (14) Torque to 20 - 30 in. lb (2.3 - 3.4 Nm).
Install upper static piston assembly (13) in valve body
Install lower static piston assembly (24) In valve body Install retainer (18), making certain locking tabs
engage boss on valve body.
Install and test the valve assembly as detailed in INSTALLATION preceding.