C3, TM 9-2320-211-20
b. Removal.
(2) Position the hydraulic line at the outlet fitting,
(1) Remove the four nuts from bolts securing metal
and tighten the connector (fig. 2-183).
shield to underside of air hydraulic cylinder, and remove
(3) Position the ventilation line at the elbow and
bolts and shield from cylinder (fig. 2-184).
tighten the connector (fig. 2-183).
(4) Position the yoke at the front end of the master
cylinder push rod on the lower end of the brake pedal
lever, install the yoke pin, and install the cotter pin in the
end of the yoke pin (fig. 2-177).
(5) Fill the master cylinder (a(2) above).
(6) Bleed the brakes (a(1) above).
a. Maintenance.
(1) Air leakage test.
(a) Operate the engine at a fast idle to build the air
pressure in the system up to normal operating pressure
(105-120 psi) as registered on the air pressure gage.
(b) When the air pressure reading on the gage is up
to normal (105-120 psi), shut off engine.
(c) If the air pressure drops appreciably, check the
lines and fittings for leaks (para 2-205).
(d) Tighten the connections and / or replace the lines
(2) Unscrew the connector securing the hydraulic
line (fig. 2-184) to the front of the air hydraulic cylinder,
and fittings in the area where a leak is discovered.
(e) Repeat (a), (b), and (c) above again. If the
and remove the line from the cylinder.
leakage malfunction has not been corrected by tightening
(3) Unscrew the connectors securing the four air
and / or replacement in (d) above, disconnect the air
lines to the top of the air hydraulic cylinder (fig. 2-184),
exhaust line from the air hydraulic cylinder exhaust port.
and unscrew the connector securing one air line to the
(f) Connect a flexible hose or bent tube to the
rear of the cylinder, and remove the five lines from the
cylinder.
exhaust port (hose or tube must be long enough so that
the end can be immersed in a jar of water), and immerse
the free end in a jar of water.
NOTE
Place identification tags on all lines to
(g) If bubbles appear in the water, a leaking control
valve is indicated, and the air hydraulic cylinder must be
facilitate installation of the air hydraulic
replaced.
cylinder.
(h) With the compressed air system fully charged,
(4) Unscrew the connector securing the hydraulic
apply the brakes and hold the pressure on the brake pedal
while observing the air pressure gage reading.
line from the master cylinder to the bottom center of the
(i) A loss of air pressure indicates a leaking control
air hydraulic cylinder (fig. 2-184), and remove the line
valve or leakage past the air hydraulic cylinder air piston.
from cylinder.
(5) Support the air hydraulic cylinder, remove the
In this case, the air hydraulic cylinder must be replaced.
two mounting bolts each from the front and rear
(2) Hydraulic Leakage Test.
mounting brackets (fig. 2-184) on the cylinder, and
(a) With the compressed air system fully charged,
apply the brakes. Hold the pressure on the brake pedal
remove the cylinder from the vehicle.
c. lnstallation.
while observing the air pressure gage reading.
(b) If the pedal gradually falls away under pressure,
(f) Position the air hydraulic cylinder under the
there is leakage in the hydraulic lines, wheel cylinders,
frame left side rail, and install the two mounting bolts at
master cylinder, or air hydraulic cylinder. Tighten the
the front and rear mounting brackets (fig. 2-184) on the
cylinder.
connections and / or replace the defective parts as
(2) Position the hydraulic line from the master
required.
cylinder at the fitting at the bottom center of the
(c) Disconnect the outlet line from the master
hydraulic cylinder (fig. 2-184) and tighten the connector.
cylinder and close the opening. Depress the brake pedal
and hold pressure on the pedal.
(3) Position the four air lines at the fittings and the
(d) If the pedal gradually falls away under pressure,
top of the air hydraulic cylinder (fig. 2-184), and tighten
leakage past the master cylinder piston is indicated. In
the connectors. Position the air line at the fitting at the
rear of the cylinder, and tighten the connector.
this case, replace the master cylinder.
outlet at the front end of the air hydraulic cylinder, and
bleeding operations as In paragraph 2-190a. Bleed the
tighten the connector.
upper bleeder valve first and the lower bleeder valve last.
