WARNING
Breathing brake lining dust (asbestos or non-
asbestos) could cause lung cancer or lung dis-
ease. Unless exposure can be reduced below legal
limits, wear an air purifying respirator approved
by MSHA or NIOSH at all times when servicing the
brakes, starting with removal of the wheels and
continuing through assembly.
To minimize the possibility of creating airborne brake
lining dust, clean the dust from the brake rotor, brake
caliper, and brake assembly, using an industrial-type
vacuum cleaner equipped with a high-efficiency filter
system. Then, using a rag soaked in water and
wrung until nearly dry, remove any remaining dust.
Do not use compressed air or dry brushing to clean
the brake assembly.
1. Apply the brake and chock the tires to prevent
vehicle movement.
2. Check the brake lining wear. On front and rear
axles, replace linings worn to less than 3/16 inch
(4.8 mm).
3. Make sure that the brake rotor and linings are
free of oil and grease.
NOTE: To replace the brake linings, see the ap-
plicable foundation brake section in Group 42 of
the Recreational Vehicle Chassis Workshop
Manual, or take the vehicle to an authorized
Freightliner dealer.
42–11 Brake Inspecting
IMPORTANT: This procedure should be per-
formed prior to lubrication of the brake compo-
nents.
Parking Brake Operational Check
CAUTION
Perform the following check in a clear safe area. If
the parking brakes fail to hold the vehicle, per-
sonal injury or property damage may result.
1. With the engine running, and air pressure at cut-
out pressure, set the parking brake.
2. Put the vehicle in the lowest gear and gently at-
tempt to move it forward. The vehicle should not
move. If the vehicle moves, the parking brakes
are not operating correctly and must be repaired
before the vehicle is returned to service. See
Group 42 of the Recreational Vehicle Chassis
Workshop Manual for repair procedures, or take
the vehicle to an authorized Freightliner dealer.
Brake Component Inspection
Air Disc Brakes
1. Park the vehicle on a level surface, shut down
the engine, and set the parking brake. Chock the
tires. Once the tires are chocked, release the
parking brake.
2. Grip the caliper/carrier assembly by the chamber
and verify that it slides in and out freely. Free
play movement is 0.024 to 0.043 in (0.6 to 1.1
mm).
Drum Brakes
1. Park the vehicle on a level surface, shut down
the engine, and set the parking brake. Chock the
tires. Once the tires are chocked, release the
parking brake.
WARNING
Manually adjusting an automatic slack adjuster to
bring the pushrod stroke within legal limits is
likely masking a mechanical problem. Adjustment
is not repairing. Before adjusting an automatic
slack adjuster, troubleshoot the foundation brake
system and inspect it for worn or damaged com-
ponents. Improperly maintaining the vehicle brak-
ing system may lead to brake failure, resulting in
property damage, personal injury, or death.
2. With the engine off, and 100 psi (690 kPa) of air
tank pressure, have an assistant apply and hold
an 80 to 90 psi (552 to 621 kPa) brake applica-
tion.
3. Check to see if the colored over-stroke band on
each brake chamber pushrod is exposed.
If a band shows, the stroke is too long. Check
the foundation brake components for wear or
damage, and repair as needed. See Group 42 of
the Recreational Vehicle Chassis Workshop
Brakes42
Recreational Vehicle Chassis Maintenance Manual, July 201842/10
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