spring (22). This allows the rubber face of seal (16) to
seat against the valve body (21) and causes the
secondary piston exhaust seat "G" to move away from
the rubber face of seal (16). This allows the secondary
delivery air pressure to exhaust through cavity "K" and to
atmosphere around the exhaust port diaphragm (13).
Every Three Months or 32,000 km (20,000 Miles)
Clean any accumulated dirt, gravel or foreign matter
away from heel of treadle, plunger boot and mounting
Lubricate plunger, roller, roller pin and hinge pin using
Item 1 in LUBRICANT SPECIFI-CATIONS.
Check rubber plunger boot for cracks, holes or
deterioration and replace if required. Check mounting
plate for integrity.
Free pedal travel should be checked as follows. Be sure
plunger is in contact with spring retainer. The stop
button should be adjusted so that the roller and plunger
Clean exhaust port.
Every Year or 160,000 km (100,000 Miles)
It is recommended that inlet and exhaust valves, exhaust
diaphragm, O-rings and graduating spring be replaced if
they show signs of wear or deterioration.
Every Two Years or 322,000 km (200,000 Miles)
Disassemble brake valve, clean and inspect all parts.
Install new parts where they are found to be worn or
damaged and install repair kit parts.
Check the delivery pressure of both primary and
secondary systems using test gauges known to be
accurate. Depress the pedal or treadle to several
positions between the fully released and fully applied
positions and check the delivered pressure on the test
gauges to see that it varies proportionately with the
movement of brake pedal. After a full application is
released, reading on the test gauges should fall off to
zero promptly. It should be noted that the primary
system delivery pressure will be within 35 kPa (5 psi) of
the secondary system delivery pressure with both supply
reservoirs at the same pressure. This is normal for these
warning may indicate a malfunction in
one or the other brake systems, and
although the vehicle air brake system
may continue to function the vehicle
necessary repairs have been made and
both braking systems, including the
pneumatic and mechanical devices, are
operating normally. Always check the
vehicle brakes after performing brake
work and before returning vehicle to
Make and hold a high pressure application. Check
exhaust port for leakage. Using a soap solution, a
leakage of a 25 mm (1") soap bubble in 3 seconds is
If the brake valve does not function as described, the
valve should either be replaced or repaired.
Block wheel to prevent vehicle from moving.
Drain all air from all reservoirs.
Disconnect all supply and delivery lines at brake
valve. Mark all air lines in relation to valve to
assist reconnecting lines.
Remove fittings from valve. Mark these fittings
Remove valve from chassis.
Remove brake valve and treadle assembly by
removing three capscrews on outer bolt circle of
mounting plate. Basic valve alone may be
removed by removing three capscrews or nuts
on inner bolt circle.
Installation of brake valve is basically the reverse of
removal. Be sure to make service checks before
returning vehicle to service.
CTS-4079 - CHAPTER IV - Page 13