b. Disconnect, cap and tag lines and fittings to
emergency piston grommet, and relay piston grommet
item to be replaced, until item is free.
leakage. A combined leakage as indicated by a one-
c. Reverse steps a. and b. above to install item
inch (2.54 cm) soap bubble in not less than two seconds
is permissible. Release the service brake application.
(4) With tractor and trailer air brake system
4-79. Reservoir a. Removal.
fully charged, move the tractor protection control valve
to "emergency" position or close the emergency line cut-
out cock on the tractor and uncouple the trailer
(1) Block trailer wheels and drain air from
emergency line coupling. Note that trailer brakes apply
promptly. Check at valve, and at the emergency line
(2) Remove trailer release valve.
(a) Refer to figure 4-72 and disconnect,
coupling at the front of the trailer for leakage. No
leakage is permissible at emergency line coupling.
cap and tag the lines to the trailer release valve.
(b) Unscrew the valve and pipe nipple
Reconnect and recharge tractor and trailer air brake
system, noting that trailer brakes release at a maximum
from the relay-emergency valve.
(c) Reverse steps (a) and (b) above to
of 65 psi (4.5695 kg per sq cm) trailer emergency line
pressure as the trailer air brake system is recharged to
full normal operating pressure.
(3) Refer to figure 4-72. Disconnect, cap
(5) With tractor and trailer air brake systems
and tag lines to valve.
fully charged, stop engine. Reduce pressure by making
(4) Remove mounting bolts and take
a series of at least five brake applications and note that
valve from reservoir.
trailer brakes apply automatically at approximately 45
(5) Refer to figure 4-72. Disconnect lines
psi. (3.1635 kg per sq cm) tractor reservoir pressure or
and remove fittings connected to reservoir.
at the automatic emergency setting of the tractor
(6) Remove attaching parts at mounting
protection equipment, if installed.
brackets and lift off reservoir.
b. Installation. Reverse procedures in a. Above
c. Inspection. Inspect exterior of reservoir for
unpainted areas, and corrosion.
a. Refer to figure 4-72. Open drain cock to drain
d. Test. Pressure test for leaks, using water
air pressure from system.
pressure only, at not more than 150 pounds per square
inch (10.545 kg per sq cm).
Section XVII. FRAME
4-80. Pintle Hook
c. Cleaning, Inspection and Repair. Wash all parts
in a cleaning solvent. Inspect the grease fittings and
spring for breaks or damage. Replace if broken or
damaged. Inspect the threads for damage. Replace if
the frame, and remove the pintle hook.
broken or damaged. Inspect the threads for damage,
Refer to figure 4-77 and
and repair or replace nuts and capscrews. Inspect the
disassemble the pintle hook.
latch, lock, and pintle hook for breaks or cracks. Weld
minor cracks. Replace parts, if badly damaged. Inspect
Dry cleaning solvent, P-D-680 or P-S-661,
the pins for wear or other damage; replace if worn or
used to clean parts is potentially dangerous
d. Reassembly. Refer to figure 4-77 and assemble
to personnel and property. Use in a well-
the pintle hook.
ventilated area as the fumes are dangerous if
e. Installation. Reverse step a. above.
inhaled. Avoid repeated and prolonged skin
contact. Do not use near open flame or
4-81. Landing Gear and Braces
excessive heat. Flash point of solvent is
a. Removal and Disassembly.