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.
1. Check lining wear.
Brakes 42
Business Class Trucks Maintenance Manual, October 1998 42/11
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