when the reservoir with the highest pressure reaches
276 27 kPa (40 5 psi). If air is depleted quickly, the
red knob could pop immediately. Leakage at exhaust
port must not exceed a 25 mm (1") bubble in 5 seconds.
With the engine off, apply the foot valve
depleting the air lower. Air must start to escape
from the exhaust port when the air pressure in
the reservoir with the higher pressure reaches
207 27.6 kPa (30 5 psi). The yellow knob
may pop out at this time.
With the engine off, deplete the air system
further with the foot valve. At 172 27.6 kPa (25
5 psi) the yellow knob must pop out and
maintain supply pressure. Leakage at exhaust
port should not exceed 25 mm (1") bubble in 5
Rebuild the supply pressure to at least 276 kPa
(40 psi). Push in the yellow knob; the yellow
knob must remain in. Leakage at the exhaust
port should not exceed a 25 mm (1") bubble in 5
Charge the system to 817 kPa (120 psi) and
push both knobs in. Pull the red knob out. The
yellow knob must remain in.
Push the red knob in and pull the yellow knob
out. The red knob must pop out almost
Install a gauge to monitor tractor spring brake
delivery pressure. Apply 817 kPa (120 psi) to
both primary and secondary reservoirs. Push in
the yellow knob. Delivery pressure should equal
the pressure in the primary reservoir. Reduce
the pressure in the primary reservoir. Delivery
pressure and primary reservoir pressure should
descend together to 724-621 kPa (105-90 psi) at
which point the dual cir, lit supply (double check)
valve shuttle should switch to the secondary
reservoir and delivery pressure should increase
to the secondary reservoir pressure. After the
primary reservoir pressure is reduced to zero, a
leakage of a 12.7 mm (1/2") bubble in 5 seconds
is permitted at the primary reservoir opening.
Close the leak which had been created at the
Leaving the yellow knob in, recharge the
secondary reservoir to 817 kPa (120 psi).
The delivery pressure should also read 817 kPa
(120 psi).Recharge the primary reservoir to 689
kPa (100 psi). Slowly vent the secondary
reservoir. As the secondary reservoir pressure
and the delivery line pressure descend between
793-724 kPa (115-105 psi), the dual circuit
supply (double check) valve shuttle should
switch to the primary CTS-4079 C reservoir,
causing the delivery line pressure to adjust to the
primary reservoir pressure.
Close all vents or leakage points and charge
both reservoirs to 817 kPa (120 psi). Position
the red knob out and the yellow knob in. Develop
a leak in the spring brake delivery line and hold
the yellow knob in. The primary reservoir
pressure must reduce to zero and the secondary
reservoir pressure to 138-207 kPa (20-30 psi).
The dual circuit supply valve shuttle should cycle
several times during this leakdown period.
Block and hold vehicle by means other than the
Bleed air system completely.
Remove bezel panel and remove instrument
panel access cover, to expose valve body cover
plates, Item 1 of Fig. 12.
Mark or identify all air lines connected to valve.
Then disconnect air lines.
Remove valve assembly from instrument panel.
Remove all fittings from the rear of the valve.
Note the direction of all fittings.
Assemble fittings in rear of valve. Apply a non-
hardening sealing compound to fittings. Do not
assume. that the fittings will seal themselves to
the body. Maximum torque to apply to the fittings
is 14 Nm (10 ft. lbs.).
Assemble valve to instrument panel.
Connect air lines to their respective fittings (refer
to Fig. 7 for porting designation).
Charge air system and perform Service Checks
Remove the identification tags.
After checking the serviceability of valve, reinstall
the bezel and instrument panel access cover.
It should be unnecessary to remove the valve
assembly to accomplish the normal service in replacing
the components. Be sure to block the wheels and drain
all air reservoirs. Remove the trim bezel to expose the
valve cover plates. It is recommended that the valve be
serviced by replac-
CTS - 4079 - CHAPTER IX - Page 9