Freightliner Cascadia. Manual - part 23

12.3

Fan the service brakes to reduce system
air pressure to governor cut-in. Note that
the system once again builds to full pres-
sure and is followed by a purge at the
AD-IP air dryer exhaust.

12.4

Check for excessive leakage around the
head of the desiccant cartridge where it
contacts the end cover. With the com-
pressor in loaded mode (compressing
air), apply a soapy solution to these
areas, and observe that any leakage
does not exceed a 1-inch bubble in 1
second. If leakage exceeds this measure,
remove and re-install the desiccant
cartridge.

AD-9si and AD–IS

Park the vehicle on a level surface, apply the
parking brakes, and chock the tires.

Drain the air reservoirs.

Using a strap wrench or equivalent, loosen the
desiccant cartridge. Spin the cartridge off by
hand and discard it. See

Fig. 3

On the new desiccant cartridge, lubricate the
sealing rings with silicone grease.

IMPORTANT: Only use the silicone grease sup-
plied with Bendix replacement kits.

Screw the desiccant cartridge onto the body by
hand until the seal makes contact with the body.
Rotate the cartridge clockwise about one full
turn. Tighten the cartridge firmly.

42–03 Air Dryer Inspection

Park the vehicle on a level surface and apply the
parking brakes. Shut down the engine. Chock
the tires.

Check for moisture in the air brake system by
opening the reservoir drain cocks. Examine the
discharge. Some trace of water in the discharge
is normal. A discharge of a milky gray liquid indi-
cates excessive moisture is present in the air
system and the desiccant cartridge needs to be
replaced. See Group 42 of the vehicle Workshop
Manual for troubleshooting procedures. The fol-
lowing conditions could cause small amounts of
moisture to be found in the air system:

• An outside air source has been used to

charge the air brake system. This air did
not pass through the drying bed.

• Air usage is unusually high and not normal.

This may be due to accessory air demands
or some unusual air requirement that does
not allow the compressor to load and un-
load in a normal fashion. Check for air sys-
tem leaks.

• The air dryer has been installed on a sys-

tem that had previously been operated
without an air dryer. This type of system
will be saturated with moisture, and several
weeks of operation may be needed to fully
dry the system.

• The temperature range in your area fluctu-

ates more than 30 degrees in one day.
Small amounts of water can accumulate in
the air brake system due to condensation.
Under these conditions, the presence of
moisture is normal and should not be con-
sidered an indication of poor air dryer per-
formance.

Inspect the air dryer for external damage, and
check that the unit is tightly mounted on the
frame. If the air dryer mounting is loose, See

04/16/98

f421910

Desiccant Cartridge

Cartridge Sealing Ring

Threaded Base Post

Fig. 3, Desiccant Cartridge Replacement

Brakes

42/4

Group 42 of the vehicle Workshop Manual for
mounting instructions.

Turn on the ignition switch, but do not start the
engine.

Disconnect the harness connector from the air
dryer.

Connect a voltmeter to circuit 94 on the air dry-
er’s harness connector and to a body ground
point. Check for battery voltage. If voltage is not
found, check and repair the open or short to
ground in wire 94.

Connect a voltmeter between the two terminals
on the air dryer’s harness connector. If voltage is
not found, repair the open in the ground circuit
wiring.

Use an ohmmeter to check resistance between
the terminals on the end cover. See

Fig. 4

. The

end cover contains the heater/thermostat. If the
heater/thermostat is between 40 and 90°F (5 and
32°C), the heater/thermostat measured resis-
tance will be infinite ohms. If the measured resis-
tance is less than infinity, replace the
heater/thermostat.

Remove the heater/thermostat assembly and
place it in a freezer for about five minutes to cool
it below 40°F (5°C). Remove the cold
heater/thermostat assembly and check resis-
tance between the heater/thermostat terminals.
Resistance should be 1.5 to 3.0 ohms. As the
temperature of the heater/thermostat assembly
increases, the ohm reading will increase. When
the temperature goes above 45°F (7°C) mea-
sured resistance should be infinite ohms. If the
heater/thermostat does not operate as outlined,
replace it. If it does operate as outlined, install it.

42–04 Alcohol Evaporator

Cleaning and Inspection

Off Season

During the off season, drain the unit of alcohol. At
regular engine service intervals, open the drain cock
to remove moisture from the alcohol evaporator. Be-
fore reactivating the evaporator for the next freeze
season, drain, disassemble, inspect, and steam-
clean the unit of any sludge that may have accumu-
lated. It is advisable to replace any rubber parts
when assembling the alcohol evaporator. Perform
this service just before the freeze season.

Freeze Season Reactivation

Park the vehicle on a level surface and apply the
parking brakes. Shut down the engine. Chock
the tires.

Remove the filler cap, and check the cap tet-
raseal.

Remove the capscrews and reservoir from the
cover.

Remove the cover tetraseal.

Drain the air tank, and disconnect the line from
the evaporator outlet. Remove the check-valve
retainer, spring, and disc.

Install the disc, spring, and check-valve retainer,
and connect the line to the evaporator outlet.

Install the cover tetraseal.

06/04/96

f421384

End Cover Assembly

Heater/Thermostat Terminals

Fig. 4, End Cover Terminals Location

Brakes

42/5

Install the reservoir on the cover and tighten the
capscrews.

Fill the reservoir with 40 ounces (1183 mL) of
methyl alcohol, then install the filler cap.

42–05 Brake Inspection

Parking Brake Operational Check

IMPORTANT: This procedure should be per-
formed prior to lubrication of the brake compo-
nents.

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.

With the engine running, and air pressure at cut-
out pressure, set the parking brake.

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 vehicle Workshop Manual for
repair procedures.

Brake Component Inspection

Park the vehicle on a level surface, set the park-
ing brake, and 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.

With the engine off, and 100 psi (689 kPa) of air
tank pressure, have an assistant apply and hold
an 80 to 90 psi (550 to 620 kPa) brake applica-
tion.

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 vehicle Workshop Manual for inspection and
repair procedures.

Measure the applied chamber stroke.

See

Table 1

for the proper stroke for the type of

chamber being used. If the stroke is too short,
the brakes may drag or will not fully apply. Check
for improper operation or adjustment of the auto-
matic slack adjuster. See Group 42 of the ve-
hicle Workshop Manual.

Brakes

42/6

Brake Chamber Stroke Specifications

Chamber

Max Applied Stroke: inch (mm)

Manufacturer

Type

Size

†

Gunite

Standard Stroke

1-3/8 (35)

1-3/4 (44)

2 (51)

‡

2-1/4 (57)

Long Stroke

2 (51)

24 (2-1/2 inch rated

stroke)

24 (3 inch rated

stroke)

2-1/2 (64)

Haldex

Standard Stroke

1-3/8 (35)

1-3/4 (44)

2-1/2-Inch Extended Stroke

2 (51)

3-Inch Extended Stroke

2-1/2 (64)

Standard Stroke

2 (51)

Long Stroke

2-1/2 (64)

Meritor

Standard Stroke

Less than 1-1/2 (38)

Less than 1-3/4 (44)

Less than 1-7/8 (48)

Long Stroke

Less than 2 (51)

Standard Stroke

Brakes

42/7

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