AIR BRACKES-GENERAL INFORMATION
OPERATIONAL CHECKS OF SPLIT AIR BRAKE
SYSTEM
GENERAL OPERATIONAL CHECK OF AIR SYSTEM
1.
Block wheels to prevent vehicle from moving.
2.
Inspect primary and secondary reservoir check
valve operation.
a.
Build 758 kPa (110 psi) of air in system.
b.
With ignition switch "ON," open drain cock at
supply
air
reservoir
and
completely
drain
reservoir. Low air pressure buzzer should come
on at approximately 483 kPa (70 psi).
c.
Both primary and secondary reservoirs should
retain air pressure.
d.
If loss of air is noted in either system by
observing the air gauges, the check valve could
be faulty.
3.
With the park brake control (yellow) and trailer
supply control (red) positioned in, open drain
cocks in primary and secondary reservoirs.
Trucks
The
park
brake
control
(yellow)
knob
should
automatically apply between 48-103 kPa (7-15.psi).
Tractors
a.
The red knob should pop out when reservoir with
highest pressure reaches 276 + 27.6 kPa (40 + 5
psi). The red knob could pop immediately if air
is
depleted
quickly
at
the
trailer
supply
(emergency) line.
b.
When air pressure in reservoir with higher
pressure reaches 207 + 27.6 kPa (30 + 5 psi)
the yellow knob may pop out. When air is
depleted to 172 + 27.6 kPa (25 + 5 psi), the
yellow knob must pop out.
4.
Close all reservoir drain cocks.
5.
Build up air supply in chassis system to
approximately 758 kPa (110 psi).
6.
With red knob pushed in, disconnect trailer
emergency coupling from bracket. The red knob
-should pop out instantaneously.
7.
If
red
knob
pops
out,
reconnect
trailer
emergency coupling. Position yellow knob in
released position (in) and red knob in applied
position (out).
8.
Check air pressure for leakage by observing air
gauges on instrument panel. Leakage should
not be greater than 13.8 kPa (2 psi) in one
minute.
9.
Open drain cock in secondary air reservoir.
Drain cock must be opened all the way for quick
loss of air. You will note loss of air by observing
air gauges. One system will show a loss of air.
With ignition switch on, low pressure indicator
buzzer should sound at approximately 483 kPa
(70 psi).
10.
Apply service brakes and observe the slack
adjusters and service brake chamber push rods.
Movement of the brake chamber push rods
should occur at axles as follows:
a.
Rear axles on all 4x2 vehicles and rear axles on
6x4 vehicles with initial split air system.
b.
Front and rear rear axles on 6x4 vehicles with
spring suspension system and refined split air
system.
c.
Steering and forward rear axles on 6x4 vehicles
with air suspension and refined split air system.
If movement is noted at other axles, the primary
reservoir was bled. Refer to Step 13. If brake
chamber push rod travel movement is as
described, the primary system is good.
11.
Close drain cock in secondary air reservoir.
12.
Build air supply in air system to 758 kPa (110
psi).
13.
Open drain cock in primary reservoir. Observe
opposite air pressure indicator for loss of air. Be
sure to open drain cock all the way.
14.
Apply service brakes and observe the slack
adjusters and service brake chamber push rods.
There should be movement of brake chamber
push rod travel as follows:
a.
Steering axle on all 4x2 vehicles and on straight
trucks with initial split air system the spring
brakes will apply and release until air pressure
drops to 48-241 kPa (7-35 psi), then full spring
brake application will occur.
b.
Forward rear axle on 6x4 vehicles with refined
split air system.
c.
Rear rear axle
along
with
parking
brake
application and release at forward rear axle on
6x4 vehicles with air suspension and refined split
air system. When checking system the parking
brakes will automatically apply on tractors when
air pressure is depleted to 172 + 27.kPa (25 + 5
psi).
15.
If movement of brake chamber push rods are as
described, the secondary system is functioning
as it should.
16.
Close all drain cocks and return vehicle to
service.
CTS-4154Y - Page 20
