GMC 2003 C4C042 Owner's Manual page 366

(39) = Air brake service:
j
Inspect brake lines and hoses for proper hook
binding, leaks, cracks, chafing, etc. Inspect drum
brake linings for wear or cracks. Inspect other brake
parts at each wheel, including drums, wheel
cylinders and piston heat shields, boots and wheel
speed sensor wiring. Check brake pedal for excessive
free play or travel (or every 6 months, whichever
occurs first) and have serviced if needed. Check
brakes more often if driving habits and conditions
result in frequent braking. Replace air dryer cartridge
only if excessive oil or moisture is present. A small
amount of oil in the system is normal and should not
be considered as a reason to replace the cartridge.
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Test air lines for leaks; tighten as needed. Replace
compressor filter.
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Inspect air parking brake chamber for leaks and
damage. Inspect lines and hoses for leaks, cracks,
chafing, etc. Also check all attachments for
tightness, wear or damage. Note: The spring brake
section of the rear brake diaphragms are
-
non serviceable.
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Replace the air compressor filter element, mounted
on the air compressor. For remote air compressor
intake service, refer to engine air cleaner filter
replacement.
7-20
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Remove, disassemble, clean and inspect the safety
valve, standard brake chamber, quick release valve,
-
up,
quick release/double check valve combination,
parking brake control valve, double check valve,
pressure protection valve and alcohol injector.
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Remove, disassemble and clean the application
valve; replace parts showing wear.
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Remove, disassemble, clean and inspect the spring
brake control valve; replace rubber parts.
(40) = Clean and lubricate air brake automatic slack
adjuster. Check pushrod travel and auto adjustment
operation. Have serviced if needed.
(41) = Air brake chamber service: Check operation,
mounting, clamps and air lines and check for leaks.
(42) = Trailer brake hand control valve service: Check
operation; lubricate cam and follower.
(46) = Tighten the wheel stud nuts to the specified
torque values at 100 miles (160 km). Thereafter, tighten
them 1,000 miles (1 600 km) after each time the wheel
is removed. See "Tightening the Wheel Nuts" in
the Index.