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WARNING:Do not drive with your foot resting on the brake
pedal. This results in abnormally high brake temperatures,
excessive lining wear and increased stopping distances.
Before descending a long or steep hill, shift to a lower gear and avoid
continuous application of the brakes. Normally, choose the same gear to
descend the hill that you use to ascend the hill.
WARNING:Continuous application of the brakes causes the
brakes to overheat, resulting in a temporary loss of braking.
If brakes do not grip well
•If you have been driving through deep water, gently apply the brakes
several times while the vehicle is moving slowly.
•Let the brakes cool if you have been using them excessively, as in
mountain driving or after several fast, high-speed stops.
•Check brake adjustment.
•Check brake linings for excessive wear.
•Check system air pressure on vehicles equipped with air brakes.
HYDRAULIC BRAKES (IF EQUIPPED)
Full Power Brake System
This system incorporates standard braking, an anti-lock braking system
(ABS) and optional Power Park Brake into one fully-integrated hydraulic
brake system. With the Full Power Brake System, braking energy is
stored, similar to an air brake system, resulting in faster response times
and shorter stopping distances. This is accomplished using motor/pump
assemblies that pressurized the system by pumping brake fluid into
accumulators. This is similar to the air compressor of an air brake system
pressurizing the air tanks. The system includes a master cylinder that
provides the normal pedal “feel” and transfers the pedal force, via brake
fluid, to the main components of the system.
Note:The motor/pumps run momentarily with the ignition switch in the
on or run positions or the switch is in the off position and the brake
pedal is pressed.
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The parking brake warning lamp in
the instrument cluster illuminates,
and remains illuminated (when the
ignition is turned on), until the
parking brake is released.
Push the palm release lever on the
parking brake handle and push
down as far as possible to release
the brake. Driving with the parking
brake on causes the brakes to wear
out quickly and reduce fuel
economy.
WARNING:If the parking brake is fully released but the parking
brake warning lamp remains illuminated, the brakes may not be
working properly. See your dealer or a qualified service technician.
The parking brake is not recommended to stop a moving vehicle.
However, if the normal brakes fail, the parking brake can be used to stop
your vehicle in an emergency. Since the parking brake only applies
retardation to the rear wheels, the vehicle’s stopping distance increases
greatly and the handling of your vehicle is adversely affected.
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WARNING:Block the wheels to help prevent the vehicle from
moving.
WARNING:Unexpected and possibly sudden vehicle movement
may occur if these precautions are not taken.
Loosen the jam nut (1) and un-thread the adjustment rod (2) from the
chamber to reduce tension on the cable (3). Continue to un-thread the
adjustment rod all the way and remove it from the chamber. The nut and
shaft are metric.
AIR BRAKES (IF EQUIPPED)
General air brake information
After starting the engine, give the air compressor time to build up the air
pressure to 60 psi (414 kPa) before moving the vehicle.
WARNING:Do not drive or continue to drive if the low air
pressure buzzer is sounding or the brake warning light is lit. These
warnings indicate that air pressure is not to normal operating level.
Continued use of the vehicle could result in loss of braking ability.
WARNING:Avoid repeated light application of the brake pedal.
This depletes air pressure faster and could result in loss of
braking capability.
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Periodically check the air pressure
gauge while driving. Pressure should
range between approximately
100–125 psi (690–862 kPa). The air
compressor governor cut-in and
cut-out pressure settings are set at
the factory and are not adjustable.
When air pressure is insufficient
(below 60 psi [414 kPa]), a warning
light illuminates and a buzzer
sounds when the ignition is in the
on position.
This condition may be caused by excessive brake applications depleting
the system air pressure. If this condition occurs, stop driving the vehicle
until the compressor has fully recharged the air system.
WARNING:Do not move the vehicle when the air pressure is
insufficient because the brake system may be inoperative.
Select a gear ratio to help slow your vehicle before descending grades.
Supplement with brakes as required to safely slow the vehicle and avoid
overspeeding the engine.
Air chamber stroke indication
Air chamber push rods have orange stroke indicator markers that warn
when the braking system requires adjustment or repair. The orange
stripe is painted on the air chamber push rod at the slack adjuster stroke
dimension which requires service when visible during brake application.
Air brake inspection and adjustment or repairs should be performed by a
qualified service technician in accordance with the instructions in the
service manual.
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Cam brakes - automatic slack adjusters
Standard air brakes (cam) are
equipped with automatic brake
adjusters. Automatic adjustment
occurs during brake applications.
Inspect brakes for proper
adjustment at the intervals listed in
theScheduled Maintenance Guide
chapter.
WARNING:Do not manually adjust the automatic slack
adjusters to correct excessive push rod stroke as it may result in
reduced brake effectiveness and a vehicle crash. Excessive push rod
stroke indicates that a problem exists with the automatic adjuster, with
the installation of the adjuster, or with foundation brake components
that manual adjustment does not remedy. Seek service from a qualified
facility for excessive push rod stroke.
Emergency air brake
All vehicles are equipped with a dual brake system. In the unlikely event
of a failure of one system, the second system functions for emergency
stopping. These systems are all controlled by the brake pedal in the
same manner as for normal stops.
WARNING:Do not continue to operate the vehicle with a
failure of one of the brake systems. Take the vehicle to your
dealer for service immediately.
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Air brake reservoir draining
WARNING:Failure to drain air brake reservoirs can result in a
reduction or loss of braking ability due to fluid accumulation in
the reservoir and/or possible freeze-up during cold weather.
Drain all the air brake reservoirs
daily, completely to 0 psi/kPa, by
opening the draincock at the ends
of the tanks (where accessible.
Pull-chains are used when the
drains are undercab or otherwise
inaccessible). Close draincock after
complete draining. Air tanks
equipped with automatic moisture
ejector valves may also be drained
manually as required to maintain a
dry air system. Contact your dealer if you are unsure of the air reservoir
locations or the draining procedure.
Parking brake
WARNING:Do not use the gearshift selector in place of the
parking brake; unexpected and possible sudden vehicle
movement may occur if these precautions are not taken. Always set
the parking brake fully AND make sure the gearshift selector is in R
(Reverse) for vehicles equipped with manual transmission, N (Neutral)
for vehicles with automatic transmission (except Allison 2200
transmission) or P (Park) (Allison 2200 transmission).
If the service brakes should fail to operate while the vehicle is in motion,
you can make an emergency stop with the parking brake. Since the
parking brake only applies stopping power to the rear wheels, the
vehicle’s stopping distance greatly increases and the handling of the
vehicle is adversely affected. Repairs should be made immediately to an
inoperative air brake system circuit.
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Parking brake control (knob)
Pull the yellow parking brake knob
out to apply the parking brake. Push
the knob in to release the parking
brake.
WARNING:This control is used for parking only. Do not leave
the vehicle unattended after setting the parking brake without
placing the transmission in R (Reverse) for manual transmission, N
(Neutral) for automatic transmission (except Allison 2200
transmission) or P (Park) (Allison 2200 transmission). Use of wheel
chocks is also recommended in hilly or off-road usage.
The
light illuminates and
remains illuminated (when the
ignition is turned to the on position)
until the parking brake is released.
Releasing spring brake with air pressure
The air system in all vehicles with spring-actuated rear wheel parking
brakes is equipped with a tank valve located on the supply or service air
tank for connection to an outside air supply. The valve permits the
system to be recharged with air from an outside source, releasing the
spring-actuated parking brakes. The vehicle may then be towed in an
emergency.
An outside air source can be used only if the protected system is in
operating condition. If air pressure cannot be restored in the protected
air system, the spring-actuated brakes must be released manually.
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Releasing spring brake manually
WARNING:Do not attempt to disassemble the parking brake
chamber under any circumstances. The high spring load may
cause serious injury if the chamber clamps are removed.
If air pressure is released from the spring brake chamber the power spring
applies the brake and, unless air pressure can be re-established, the spring
brake must be released as follows in order to move the vehicle.
WARNING:Block the wheels to help prevent the vehicle from
moving.
WARNING:Unexpected and possibly sudden vehicle movement
may occur if these precautions are not taken.
Impact wrenches should not be used as they may damage the piston and
prevent proper caging of the spring. Do not apply more than 50 ft-lb
(68 N•m) torque to the release bolt nut.
1. Remove the stud tool and nut
from the carrying pocket on the
brake chamber assembly.
2. Remove the access plug from the
end of the spring chamber.
3. Insert the release stud through
the opening in the chamber and into
the spring pressure plate.
4. Turn the release stud one-quarter
turn to engage the stud tangs with
the slot in the pressure plate. Keep
the stud engaged and install the nut
on the release stud.
5. Tighten the nut until the spring is
fully caged and the brakes are
released. Do not loosen or remove
the release stud and nut unless the brake chamber is completely
assembled and is securely clamped.
6. When the air pressure is restored, unscrew and remove the release
stud and install in the carrying pocket. Install the access plug.
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