TRUCK SERVICE MANUAL
BRAKES-AIR
inlet port. Also connect a manifold with an air gauge and
ASSEMBLY (Fig. 2)
close manual shut-off valve to outlet. With air control
Lubricate O-rings, O-ring sealing surfaces and
valve in "out" position, open manual valve to build up
piston-to-body surfaces with Item 3 of LUBRICANT
100-125 psi to inlet port. Shut off manual valve. No air
SPECIFICATIONS.
leakage is allowed around piston or through casting
1. Install O-ring on piston and insert piston into
surfaces. Permissible leakage at exhaust port is a 1"
body, aligning hex on piston to hex on body.
soap bubble in 6 seconds.
2. Position valve assembly over end of piston, then
position washer over piston stud end against
Push control valve in and build up 100-125 psi at
metal face of valve.
both inlet and outlet. Shut off manual valve and repeat
3. Install nut and torque as specified on Fig.
above leakage test.
2. Piston should move smoothly back and forth in
Pull control valve out. Outlet port pressure should
body.
exhaust to zero through valve.
4. Install spring with small end against valve disc.
5. Position O-ring over end cap. Align end cap
Operation Test
over spring and push end cap into body Hold
end cap to prevent spring pushing end cap out.
Begin with zero pressure at inlet and outlet. Hold
control valve "in" and open manual valve to allow 45 psi
6. Install snap ring in valve body groove.
pressure to build up at both inlet and outlet. Control of
Plunger should move in and out by applying force to
valve should remain "in" at 45 psi and above.
move plunger in and releasing it.
Before releasing vehicle for service perform
Second check is accomplished with 100-125 psi in both
SERVICE CHECKS as outlined.
inlet and outlet ports and both manual shut-off valves
closed. Slowly open manual valve at outlet to bleed
TWO-WAY CONTROL VALVE
down pressure.
The spring brake control should
(WAGNER ELECTRIC TYPE PB)
automatically move "out" when air pressure at inlet port
reaches 28-35 psi.
DESCRIPTION
If spring brake control valve does not perform as
The type PB control valve is a push-pull air valve,
described it should be repaired or replaced.
providing on-off manual control when an air system
requires a simple non-metered application and exhaust
DISASSEMBLY (Fig. 2) NOTE
of air pressure. It is used as the Trailer Emergency
Brake Valve (control valve for the tractor protection
Note:
Before moving spring brake
valve) in a combination vehicle protection system to
control valve from vehicle drain all air
change the system for normal operation with trailer
from all reservoirs,
connected and to discharge the system in an emergency
1. After valve is removed from vehicle, inspect it for
or bob-tailed tractor operation.
damage. If casting is broken or shows fractures
replace valve assembly.
OPERATION
2. Carefully remove end cap snap ring.
Applied Position
3. End cap, O-ring and spring can be removed
Valve knob will be pushed in to release trailer
now.
emergency. The reservoir port is open and exhaust port
4. Remove nut, washer and valve assembly.
is sealed. The delivery port is always open and air flows
from reservoir into system.
5. Pull piston with the knob out end of body and
remove O-ring from piston.
Released Position
Valve knob is pulled out to apply trailer emergency
CLEANING AND INSPECTION
system or operate tractor without trailer. The reservoir
Wash all metal parts in cleaning solvent. Inspect
port is sealed and exhaust port is open. Pressure in the
body and end cap seats. Face of seats must be flat and
emergency system at delivery now flows through exhaust
smooth with no cracks or nicks.
port.
Use new parts supplied in repair kit.
160
