in.) per minute or a total of 25 mm (1") soap bubble in 12
Pull Trailer Emergency Control out and remove
pipe plug from trailer emergency port (L). If valve passes
leakage check, the performance check should be made.
Install a duplex gauge or two single air gauges at
trailer service and emergency ports (M and L).
With 379 kPa (55 psi) in both primary and
instrument panel gauge and trailer emergency
port should read approximately the same.
The air gauge connected at trailer service port (M)
must not show pressure.Permissible leakage at exhaust
port is a 25 mm (1") soap bubble in three (3) seconds. 3.
Replenish air to 689-861 kPa (100-125 psi) in both
primary and secondary systems.
Bleed off secondary air reservoir.
With Trailer Emergency Control at instrument
panel pushed in, apply the hand control valve.
There should be a minimum of 586 kPa (85 psi)
at trailer service port (M).
Release hand control valve and apply brake
(foot) valve. Pressure at trailer service port (M)
should be within 35 kPa (5 psi) of air gauge at
Replenish air systems to 689-861 kPa (100125
psi) and bleed off the primary air reservoir.
instrument panel pushed in and hand control
Pressure at trailer service (M) should be within
35 kPa (5 psi) of air gauge at instrument panel.
Replenish complete air system to 689-861 kPa
Apply brake (foot) valve, pull Trailer Emergency
(red) knob out. The duplex gauge connected to
trailer service port (M) should record the same
value (689-861 kPa or 100125 psi) as gauge at
instrument panel. Gauge connected at trailer
emergency (L) should be O.
If valve passes the aforementioned leakage
tests and performance tests, it is considered a
serviceable valve. Remove duplex air gauge and
reassemble trailer service and emergency air lines.
1. Pull park brake control on instrument panel out,
to set parking brake. Be sure trailer emergency
control is pulled out.
2. Bleeding air system is not required since there
will be no air supplied the manifolded tractor
protection valve with 'he brake (foot) valve and
hand control valve released.
3. Mark all air lines in relation to valve to assist in
4. Disconnect air lines at valve. Disconnect stop
light switch wires.
5. Remove mounting bolts.
6. If tractor protection valve is being replaced
remove stop light switch.
Installation of the manifolded tractor protection valve
is basically the reverse of the removal. Be sure to
perform the service checks before returning the vehicle
Refer to Fig.4 for numbers in parenthesis.
1. Inspect the valve for visual damage. If casting is
broken or shows fractures, replace the complete
valve assembly. Remove stop light switch
assembly if it was not removed during the
removal of valve assembly.
2. Remove exhaust end cap (14) by removing
3. Press exhaust disc (13) in and remove snap ring
(16). Take precaution as exhaust disc is spring
loaded. Then remove exhaust disc.
4. Remove piston (10) from body (17).
5. Remove O-ring (11) from piston and O-ring (9)
6. Remove star washer (23) from body by prying it
out from bore. Then remove plug (22), O-ring
(20) and valve disc (21) from body.
7. Remove the eight cover screws (1) so that hand
control cover (2) and foot valve no. 2 can be
separated from check valve body (6).
8. Remove both check valve disc (3).
CTS-4079 - CHAPTER XI - Page 9