GENERAL BRAKE INFORMATION
All standard equipment brakes are designed to be self-adjusting.
Automatic adjustment, when required, occurs whenever the brakes are
applied and released during forward or reverse operation. Refer to the
Scheduled Maintenance Guidechapter for scheduled maintenance.
Occasional brake noise is normal and often does not indicate a
performance concern with the vehicle’s brake system. In normal
operation, automotive brake systems may emit occasional or intermittent
squeal or groan noises when the brakes are applied. Such noises are
usually heard during the first few brake applications in the morning;
however, they may be heard at any time while braking and can be
aggravated by environmental conditions such as cold, heat, moisture,
road dust, salt or mud. If a “metal-to-metal,” “continuous grinding” or
“continuous squeal” sound is present while braking, the brake linings
may be worn-out and should be inspected by a qualified service
technician.
Know the required stopping distances for all driving conditions that may
be encountered. For longer brake lining life, take full advantage of engine
braking power when coming to a stop.
Do not drive with your foot resting on the brake pedal. This will
result 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 would use to ascend the hill.
Continuous application of the brakes will cause 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. (Air brakes only)
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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.
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.
Do not manually adjust the
automatic slack adjusters to
correct excessive pushrod stroke
as it may result in reduced brake
effectiveness and a vehicle crash.
Excessive pushrod stroke
indicates that a problem exists
with the automatic adjuster, with
the installation of the adjuster, or
with foundation brake components
that manual adjustment will not
remedy. Seek service from a
qualified facility for excessive
pushrod 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 will function for emergency
stopping. These systems are all controlled by the brake pedal in the
same manner as for normal stops.
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Do not connect a trailer’s hydraulic brake system directly to your
vehicle’s brake system. Your vehicle may not have enough
braking power and your chances of having a collision greatly increase.
Trailer lamps
Trailer lamps are required on most towed vehicles. Your vehicle may be
equipped with one of two possible trailer wiring designs. Make sure all
running lights, brake lights, turn signals and hazard lights are working.
See your dealer or trailer rental agency for proper instructions and
equipment for hooking up trailer lamps.
Driving while you tow
When towing a trailer:
• Keep your speed no faster than 70 mph (112 km/h) during the first
500 miles (800 km) of towing a trailer, and don’t make full throttle
starts.
• Turn off the speed control. The speed control may shut off
automatically when you are towing on long, steep grades.
• Consult your local motor vehicle speed regulations for towing a trailer.
• To eliminate excessive transmission shifting, use a lower gear. This will
also assist in transmission cooling.
• Anticipate stops and brake gradually.
• Do not exceed the GCWR rating or transmission damage may occur.
Servicing after towing
If you tow a trailer for long distances, your vehicle will require more
frequent service intervals. Refer to your Scheduled Maintenance Guide
for more information.
Trailer towing tips
• Practice turning, stopping and backing up before starting on a trip to
get the feel of the vehicle trailer combination. When turning, make
wider turns so the trailer wheels will clear curbs and other obstacles.
• Allow more distance for stopping with a trailer attached.
• If you are driving down a long or steep hill, shift to a lower gear. Do
not apply the brakes continuously, as they may overheat and become
less effective.
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Check to make sure that the axle mounting U-bolt nuts, attaching or
mounting bolts and nuts are securely tightened. Regularly check front
axle for damage, binding, worn parts and adequate lubrication.
At regular intervals, or during other scheduled maintenance, (tire
rotation/service, wheel bearing service, alignment, etc.) the kingpins
should be checked for excessive wear. Refer to the service manual for
proper procedures.
Toe-in setting - general inspection
Inspecting steer axle tires in the first 3,000–10,000 service miles
(4,800–16,000 service km) will generally show if tires are wearing
normally.
Rapid outside shoulder wear on both tires indicates too much toe-in.
Rapid inside shoulder wear on both tires indicates too much toe-out. In
P&D-type service, left-to-right steer tire tread life differentials up to 40%
can be observed depending on routes and other variables.
Follow the tire manufacturer’s recommended cold inflation pressure for
the tire size, load range (ply rating) and steer axle loading typical for
their operation (each steer axle tire will equal
1 2steer axle loading).
Special applications may warrant a setting based on past experience with
the type of tire operating loads and conditions. Radial tires are more
sensitive to toe-in setting than bias ply tires. While not insensitive to
vehicle alignment, fine tuning school bus alignment to line-haul truck
standards will not drastically improve tire tread life.
It is essential that correct toe-in and tire pressure be maintained for
optimum tire wear.
Rear axle - general inspection
Check to make sure that the axle mounting U-bolts, attaching or
mounting bolts and nuts are securely tightened. Refer toU-bolt nut
torquein this chapter. Regularly check the rear axle for damaged,
binding or worn parts.
NoSpin Detroit Locker positive locking differential
Vehicles equipped with this type differential have the operator’s manual
supplied with the vehicle. Refer to this manual for maintenance checks.
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Supplement
USA(fus)
Maintenance and Specifications
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Brake system - general inspection
Your vehicle is equipped with non-asbestos brake linings. However,
exposure to excessive amounts of brake material (whether asbestos or
non-asbestos, fiberglass, mineral wool, aramid or carbon) may be a
potentially serious health hazard.
Note:Persons handling brake linings should follow all precautions listed
below:
1. Always wear a respirator approved by the National Institute of
Occupational Studies of Health (NIOSH) or Mine Safety and Appliance
(MSA) during all brake service procedures. Wear the respirator from
removal of the wheels through assembly.
2.Neveruse compressed air or dry brushing to clean brake parts or
assemblies.
3. Clean brake parts and assemblies in open air. During assembly,
carefully place all parts on the floor to avoid getting dust in the air. Use
an industrial vacuum cleaner with a HEPA filter system to clean dust
from the brake drums, backing plates and other brake parts. After using
the vacuum, remove any remaining dust with a rag soaked in water and
wrung until nearly dry.
4.Neveruse compressed air or dry sweeping to clean the work area.
Use an industrial vacuum cleaner with a HEPA filter system and rags
soaked in water until wrung until nearly dry. Dispose of used rags with
care to avoid getting dust in the air. Use an approved respirator when
emptying vacuum cleaners and handling used rags.
5.Worker clean-up:
Wash your hands before eating, drinking or
smoking. Vacuum your work clothes after use and then launder them
separately, without shaking them, to prevent fiber dust getting into the air.
Air brakes - inspection and adjustment
A regular schedule for periodic cleaning, lubrication, adjustment and
inspection should be established based on the type of vehicle operation.
It is difficult to predetermine an exact maintenance interval (time or
mileage), since vehicles will be used in a wide variety of applications and
conditions. If you are uncertain of the proper schedule and procedures
for your vehicle, contact your dealer.
Periodic checking of push rod travel or brake adjustment is essential for
effective braking. Push rod travel should be checked every service
interval to determine if adjustment is necessary. Brake chamber push
rods on original equipment chambers now incorporate a stroke indicator
to aid in adjustment checks; an orange paint marker near the base of the
push rod. If the push rod is clean and the brakes require adjustment, the
orange marker can be seen protruding from the chamber when the
brakes are applied.
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Do not manually adjust the automatic slack adjusters to correct
excessive pushrod stroke as it may result in reduced brake
effectiveness and a vehicle crash. Excessive pushrod stroke indicates
that a problem exists with the automatic adjuster, with the installation
of the adjuster, or with foundation brake components that manual
adjustment will not remedy. Seek service from a qualified facility for
excessive pushrod stroke.
Inspect the brake lining every maintenance interval. When brake lining or
blocks are worn to within 1/16 inch (1.6 mm) of rivets, brake lining must
be replaced. This inspection or adjustment should only be performed by
a qualified technician and must be in accordance with instructions
provided by the service manual.
Do not back off or disconnect the front brakes so that they are less
effective, letting the rear brakes do all the stopping of the vehicle. Do
not overlook the brakes on the trailer, either. Brake condition on the
trailer is just as important as the tractor. Proper brake balance on trucks
and tractor-trailers is essential for effective braking.
Once a year, the entire brake system must be inspected. Check the
following:
• Any rubber as it may deteriorate whenever used. Rubber brake
components should be inspected by a qualified technician and
replaced as necessary. Replacement intervals vary according to the
severity and length of vehicle service.
• Condition of brake drums, brake chambers and slack adjusters.
• System for air leaks.
• Hose or pipes for rust, damage and deterioration.
• Operation of service and parking brakes.
Some parts such as air brake chamber diaphragm, air compressor and air
cleaner should be inspected periodically and replaced if considered
unserviceable.
Air brakes - air dryer
Performance of desiccant or after-cooler type air dryers is dependent on
climatic conditions in which your vehicle is operating. Maintenance
schedules must be established for each specific operation.
The use of an air dryer on a vehicle does not eliminate the need to
periodically drain the air reservoirs.
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Air brakes - desiccant air dryer
Inspect for moisture in the air system by opening reservoirs, drain cocks
or valves and checking for presence of water. The presence of small
amounts of water due to condensation is normal and should not be
considered as an indication that the dryer is not functioning properly.
The desiccant cartridge should be replaced or rebuilt when it has been
determined that the desiccant is contaminated and does not have
adequate water absorption capacity. The desiccant change interval may
vary; it is generally recommended that the desiccant be replaced every
12 months (yearly). If experience has shown that extended or shortened
life has resulted for a particular installation, then the yearly interval can
be increased or decreased accordingly.
Hydraulic brakes - inspection and adjustment
A regular schedule for periodic cleaning, lubrication, adjustment and
inspection should be established based on the type of vehicle operation.
It is difficult to predetermine an exact maintenance interval (time or
mileage), since vehicles will be used in a wide variety of applications and
conditions. If you are uncertain of the proper schedule and procedures
for your vehicle, contact your dealer.
Inspect the brake lining every maintenance interval. Establish inspection
intervals that provide for lining replacement before damage to the disc
occurs. Excessive lining wear may expose the backing plate to the disc
causing scoring of the disc faces.
This inspection should be performed by a qualified technician and must
be in accordance with instructions provided by the service manual.
Note:Hydraulic brake system are power assisted. Braking capabilities
will be greatly reduced without engine assist.
Hydraulic brakes - fluid level
Fluid level should be at the bottom edge of the ring on each reservoir fill
port. Do not fill the master cylinder to the top of the reservoir.
Note: If brake fluid requires attention to maintain a proper master
cylinder level, this is an indication of either severe operation (pad wear)
or fluid system leakage. A more frequent and thorough brake inspection
will be required.
Hydraulic brakes - fluid precautions
The HydroMax brake system consists of two completely separate
hydraulic systems operating with two different and incompatible fluids;
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power steering fluid and hydraulic brake fluid. Failure to observe
precautions preventing the contamination of either system with fluid
from the other will result in swelling and deterioration of rubber parts
leading to reduced brake performance and eventual brake failure.
To avoid fluid contamination, the following should always be observed:
1. Use only fluids specified (or equivalent) and properly identified.
2. Add fluids only to the following locations:
•Power steering fluid to the power steering fluid pump reservoir
• Brake fluid to the brake master cylinder
Hydraulic brakes - brake lines, hoses and fittings
Inspect these components every 4,000 miles (6,000 km).
• Check lines for kinks, dents, corrosion or rupture.
• Check hoses for abrasions, kinks, soft spots or rupture, collapse,
cracks, twists or loose frame supports. When replacing a hose, be sure
there is adequate clearance to the hose to avoid an abrasion to the
new hose.
• Examine all connections for leaks.
• Repair or replace brake line tubes, hoses or fittings as required.
Driveline parking brake
Parking brake adjustment should only be performed by a qualified
technician, and in accordance with the instructions in the service
manual.
Use wheel chocks and exercise caution when inspecting under
the vehicle. A vehicle roll-away could result in property damage,
personal injury or death.
Catalytic converter
If your diesel engine is equipped with a catalytic converter, it is
important to review the maintenance schedule to ensure proper
functioning of the catalytic converter. Also, take precautions not to
damage the catalytic converter when servicing your engine or storing
your vehicle.
Note: If your vehicle is equipped with a catalytic converter/muffler, do
not blend waste oil with Diesel fuel. Operate only on low sulfur (less
than 500 parts per million sulfur) diesel fuel with a cetane value of 45 or
higher.
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