Verification of piston packings
a) Apply air to blind end cap port of cylinder, allowing piston to travel its full
stroke.
b) Disconnect air line from rod end cap port (head) of cylinder.
c) Apply pressure with your thumb to the open port. Maintain a few seconds
and try to feel if air pressure is building up under your thumb. The affirmative
would mean that the piston packing is leaking and therefore should be
replaced.
d) Repeat steps a), b) and c) to verify the other piston packing. Pressure
should be applied at rod end and piston rod should be retracted.