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Freightliner Business Class. Manual - part 31

Maximum Allowable Brake Chamber Stroke, with

Meritor Automatic Slack Adjusters

Chamber Size Effective Area:

square inches

Maximum Allowable

Stroke:

inches (mm)

(B minus A)

Less than 1-3/4 (44)

24 (long stroke)

Less than 2 (51)

Adjust the brakes whenever the applied stroke exceeds the maximum.

Table 4, Maximum Allowable Brake Chamber Stroke,

with Meritor Automatic Slack Adjusters

CAUTION

Before turning the adjusting nut, remove the
pressure-relief capscrew, gasket, pawl spring, and
pawl. If equipped with a pull-pawl assembly, raise
the relief cap as instructed. Failure to do so could
strip the teeth on the pawl.

4.4

Turn the adjusting nut one-eighth turn, as
shown in

Fig. 9

. Measure the stroke

again, and adjust until correct.

If the stroke varies or remains greater
than the specified range, check the brake
components, including the camshafts,
camshaft bushings, anchor pins, rollers,
chamber brackets, clevis, and clevis pins.
For instructions, see Group 42 of the

Business Class

Trucks Service Manual

4.5

If removed, install the pawl, pawl spring,
gasket, and pressure-relief capscrew.
Tighten the capscrew 15 to 20 lbf·ft (20 to
27 N·m). Or, remove the screwdriver from
the pull-pawl assembly (if equipped).

42–13 Automatic Slack

Adjuster Lubricating,
Meritor

Lubricate the slack adjuster using high-temperature,
water-proof grease NLGI grade 1, Texaco Thermotex
EP 1, Shell Darina No. 1, Marathon 528 heavy-duty,
Sunaplex No. 1 EP, Amdex No. 1 EP, or Philube B
No. 1. It should be smooth-textured, corrosion-
resistant grease, free of fillers and abrasives.

42–14 Automatic Slack

Adjuster Inspecting,
Meritor

Remove the pressure-relief capscrew, gasket,
pawl spring, and pawl. See

Fig. 6

, Ref. 5.

Examine the pawl for grease retention and condi-
tion. If the grease is in good condition, install the
pressure-relief capscrew, gasket, pawl spring,
and pawl; then, tighten the capscrew 15 to 20
lbf·ft (20 to 27 N·m). Lube the slack adjuster
through the grease fitting until lubricant is forced
out through the pressure-relief fitting (or pawl
slot). Then, if a hollow capscrew is used, install
and tighten it 15 to 20 lbf·ft (20 to 27 N·m).

If the grease is hardened, or the pawl is dry and
shows extreme wear, remove the slack adjuster.
Disassemble and clean it. Inspect the internal
parts. Install new seals and a new boot when
assembling; then, install and lubricate the slack
adjuster. See Group 42 of the

Business Class

Trucks Service Manual

42–15 Air Dryer Checking,

Bendix AD–9

During cold-weather operation, check the operation
of the end cover heater and thermostat assembly.

With the ignition on, check for voltage to the
heater and thermostat assembly. Unplug the
electrical connector at the air dryer, and place
the test leads of a voltmeter on each of the pins
of the male connector. If there is no voltage, look
for a blown fuse, broken wires, or corrosion in
the vehicle wiring harness. Check that a good
ground path exists.

Check the thermostat and heater operation. Turn
off the ignition switch and cool the end cover as-
sembly to below 40°F (4°C). Using an ohmmeter,
check the resistance between the electrical pins
in the female connector. The resistance should
be 1.5 to 3.0 ohms for the 12-volt heater assem-
bly.

Warm the end cover assembly to over 90°F
(32°C) and again check the resistance. It should
exceed 1000 ohms. If it does, the thermostat and

Brakes

Business Class Trucks Maintenance Manual, October 1998

42/10

heater assembly is operating properly. If it does
not, replace the purge-valve housing assembly,
which includes the heater and thermostat assem-
bly.

42–16 Air Dryer Desiccant

Replacing, Bendix AD–9

The desiccant change interval may vary from vehicle
to vehicle. Although typical desiccant cartridge life is
three years, many will perform adequately for a
longer period of time. To take maximum advantage of
desiccant life and ensure that replacement occurs
only when necessary, disassemble, clean, and in-
spect the air dryer. Replace the desiccant cartridge.
See Group 42 of the

Business Class Trucks Service

Manual

for instructions.

42–17 Air Brake Valve

Operation Checking,
Bendix R–14 and TC–7

Check the valve for proper operation; see Group 42
of the

Business Class

Trucks Service Manual

for

instructions.

42–18 Air Brake Valve Leak

Checking, Bendix TC–7

Check for leakage; see Group 42 of the

Business

Class

Trucks Service Manual

for instructions.

42–19 Air Reservoir Automatic

Drain Valve
Disassembly, Cleaning,
Inspecting, and
Lubricating, Bendix
DV–2

Disassemble the drain valve, clean the parts with
mineral spirits, and inspect the parts. Replace all rub-
ber parts and any worn or damaged parts; use only
genuine Bendix replacement parts or kits. Assemble
and install the valve, then check for proper operation
and leakage. See Group 42 of the

Business Class

Trucks Service Manual

for instructions.

42–20 Air Brake Valve

Disassembly, Cleaning,
and Inspecting, Bendix
E–12, QR–1, R–14, SR–1,
ST–3, TC–7, and TP–5

Disassemble each brake valve, clean the parts with
mineral spirits, and inspect the parts. Replace all rub-
ber parts and any worn or damaged parts; use only
genuine Bendix replacement parts or kits. Assemble
and install the valves, then check for proper opera-
tion and leakage. See Group 42 of the

Business

Class

Trucks Service Manual

for instructions.

42–21 Brake Lining Wear

Checking, Hydraulic
Disc Brakes

Before checking lining wear with the wheel removed,
review the following brake lining exposure warnings.

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 reduce asbestos exposure below legal limits,
apply one of the following methods: (1) An
enclosed-cylinder vacuum system equipped with a
High Efficiency Particulate Air (HEPA) filter; (2) A
solvent spray system that keeps the asbestos-
contaminated parts wet until they can be placed in
a sealed and labelled plastic bag.

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.

Check lining wear.

Brakes

Business Class Trucks Maintenance Manual, October 1998

42/11

1.1

Apply the parking brakes. Chock the tires
to prevent vehicle movement.

1.2

Remove one or more of the lining inspec-
tion plugs, and measure brake lining
thickness.

1.3

On front and rear axles, replace linings
worn to less than 1/16 inch (1.6 mm).

1.4

Make sure that the brake rotor and linings
are free of oil and grease.

1.5

Install the inspection plug(s).

If the wheel and hub assembly is removed from
the axle, check lining wear. Replace the linings
on all brake assemblies if worn to less than 1/16
inch (1.6 mm) at the thinnest point.

NOTE: To replace the brake linings, see the ap-
plicable foundation brake section in Group 42 of
the

Business Class

Trucks Service Manual.

42–22 Brake Lines Checking,

Hydraulic Disc Brakes

Check all hydraulic lines and fittings for damage,
leakage, or looseness.

Replace damaged or leaking components, and
tighten loose fittings.

42–23 Power Booster

Checking, Bendix
Hydro-Max

Check for proper operation; see Group 42 of the

Business Class

Trucks Service Manual

for instruc-

tions.

42–24 Automatic Slack

Adjuster Lubricating,
Gunite

Lubricate the slack adjuster until grease flows from
the grease relief opening. See

Fig. 10

. For tempera-

tures to –40°F (–40°C), use Lubriplate Aero; for tem-
peratures to –20°F (–29°C), use Texaco Multifak
EP-2 or Mobil Grease No. 77.

42–25 Automatic Slack

Adjuster Inspecting and
Adjusting, Gunite

Inspect the slack adjuster for structural damage.
Replace the slack adjuster if needed.

Inspect the slack adjuster boot for cuts or tears.
If the boot is damaged, replace it (see

Fig. 10

2.1

Remove the two clevis pins.

2.2

Rotate the worm shaft adjusting hexnut
counterclockwise to move the link away
from the clevis. About 45 lbf·ft (60 N·m) is
needed. You will hear a clicking sound.

f420653a

10/27/93

7/16-Inch Adjusting
Hexnut

Grease Fitting

Boot

Link

Brake Chamber Piston
Rod

Clevis

1/2-Inch Clevis Pin

1/4-Inch Clevis Pin

Grease Relief
Opening

10. Slack Adjuster Spline

Fig. 10, Gunite Automatic Slack Adjuster

Brakes

Business Class Trucks Maintenance Manual, October 1998

42/12

Remove the old boot from the link.

2.3

Install a new boot on the link, heavy sec-
tion down. Be careful not to damage the
boot.

2.4

Seat the boot so that the bottom of the
boot is in the boot insert, and the top is in
the groove of the link.

2.5

Rotate the adjusting hexnut clockwise
until the 1/4-inch hole in the clevis lines
up with the hole in the link.

Install the 1/4-inch clevis pin and the cot-
ter pin.

2.6

Tap the clevis upward or downward until
the large hole in the slack adjuster lines
up with one in the clevis.

Install the 1/2-inch clevis and the cotter
pin.

WARNING

Make sure both clevis pins are installed. Failure to
do so will cause the slack adjuster to work incor-
rectly, which could lead to loss of braking control.
This could result in an accident causing personal
injury or property damage.

Check for correct chamber stroke.

3.1

With the brakes fully released, use a ruler
to measure the distance from the bottom
of the brake chamber to the center of the
large clevis pin. See

Fig. 11

, Ref. A.

3.2

Build air pressure to at least 85 psi (585
kPa). Apply the brakes, then measure the
distance from the bottom of the brake
chamber to the center of the large clevis
pin. See

Fig. 11

, Ref. B. The difference

between the measurements is the brake
chamber stroke.

Compare this measurement with those
shown in

Table 5

If the brake chamber stroke exceeds the mea-
surements shown in

Table 5

, check the founda-

tion brakes for problems such as worn cams,
bushings, pins and rollers, or broken springs.
Repair or replace as needed. For instructions,

see Group 42 of the

Business Class

Trucks

Service Manual

If there are no problems with the foundation
brakes, manually adjust the slack adjuster as
follows:

5.1

Turn the adjusting hexnut three-quarters
of a turn counterclockwise. See

Fig. 10

Maximum Allowable Brake Chamber Stroke, with

Gunite Automatic Slack Adjusters

Chamber Size

Maximum Allowable Stroke

Less than 1-3/8 inches (35 mm)

Less than 1-3/4 inches (44 mm)

24 (long stroke)

Less than 2 inches (51 mm)

Table 5, Maximum Allowable Brake Chamber Stroke,

with Gunite Automatic Slack Adjusters

5.2

Keeping the wrench on the adjusting hex-
nut, have someone apply the brakes sev-
eral times while you watch the hexnut. It

f420434b

09/27/94

A. With the brakes released, measure this distance.
B. With the brakes applied, measure this distance.

Fig. 11, Brake Stroke Check, Gunite Automatic Slack

Adjuster

Brakes

Business Class Trucks Maintenance Manual, October 1998

42/13

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