freightliner Run Smart ARGOSY Driver Manual page 90

Brake System
Air Brake System
Brake System General Information
A dual air brake system consists of two independent
air systems that use a single set of brake controls.
Each system has its own reservoirs, plumbing, and
brake chambers. The primary system operates the
service brakes on the rear axle; the secondary sys-
tem operates the service brakes on the front axle.
Service brake signals from both systems are sent to
the trailer.
WARNING
Do not operate the vehicle with the front brakes
backed off or disconnected. Backing off or dis-
connecting the front brakes will not improve ve-
hicle handling and may lead to loss of vehicle
control, resulting in property damage or personal
injury.
Brake System Components
The warning light and audible alert activate if air
pressure drops below 64 to 76 psi (441 to 524 kPa)
in either system. If this happens, check the air pres-
sure gauges to determine which system has low air
pressure. Although the vehicle's speed can be re-
duced using the foot brake control pedal, either the
front or rear service brakes will not be operating at
full capacity, causing a longer stopping distance.
Bring the vehicle to a safe stop and have the air sys-
tem repaired before continuing.
IMPORTANT: In the event of a total loss of ser-
vice brakes with full system air pressure, use
the parking brake control valve (yellow knob) to
bring the vehicle to a complete stop in the saf-
est location possible.
Before a vehicle with insufficient system air pressure
can be moved, the spring parking brakes must be
released by applying an external air source at the
gladhands, or by manually caging the parking brake
springs.
WARNING
Do not release the spring parking brakes and
then drive the vehicle. There would be no means
of stopping the vehicle, which could result in se-
rious personal injury or vehicle damage. Before
12.1
releasing the spring parking brakes, make the
connection to a towing vehicle or chock the tires.
After correcting the brake system problem, uncage
the spring parking brakes before resuming normal
vehicle operation.
Primary Air Brake System
Loss of air pressure in the primary air system causes
the rear service brakes to become inoperative, and
the parking brake to engage. The secondary air sys-
tem will continue to operate the front brakes and the
trailer brakes (if equipped).
Secondary Air System
Loss of air pressure in the secondary air system
causes the front axle brakes to become inoperative.
The primary air system will continue to operate the
rear service brakes and the trailer brakes (if
equipped).
Brake System Operation
Before driving your vehicle, allow time for the air
compressor to build up a minimum of 100 psi (689
kPa) pressure in both the primary and secondary
systems. Monitor the air pressure system by observ-
ing the air pressure gauges and the low-air-pressure
warning light and buzzer. The warning light and
buzzer shut off when air pressure in both systems
reaches 64 to 76 psi (441 to 524 kPa).
IMPORTANT: Before driving the vehicle, secure
all loose items in the cab so that they will not fly
forward during a full brake application. Make
sure all passengers are wearing seat belts.
During normal brake stops, depress the foot brake
control pedal until braking action slows down the ve-
hicle. Increase or decrease the pressure on the
pedal so that the vehicle comes to a smooth, safe
stop. Apply the spring parking brakes if the vehicle is
to be parked.
IMPORTANT: An air brake proportioning system
may be used in tractor air brake systems when
the vehicle is not equipped with an antilock
braking system (ABS). When operating in bob-
tail mode, the rear brake chambers (on which
the axle load has been greatly reduced) receive
reduced (proportional) air pressure, while the
front axle brake chambers receive full (normal)