GMC 4000 Series Service Manual page 246

regardless of which direction adjusting bolt is
turned.
6. Install spring, gasket and bolt.
7. Install anchor plunger components as des­
cribed under "Brake Actuation Components."
8. Install brake shoes and brake chamber as
detailed under applicable procedures.
INITIAL ADJUSTMENT
If a new installation has just been made as
described above, start engine and build up required
amount of air pressure in system . Then pump the
brake pedal until the automatic adjuster system
adjusts enough to provide sufficient brake for safe
driving. Final adjustment is made with the vehicle
in motion, by pumping the pedal.
SERVICING STANDARD STOPMASTER
BRAKE CHAMBERS
It is recommended that all brake chambers be
removed, disassembled, inspected and thoroughly
cleaned at the time that brakes are relined or at
one year periods, whichever occurs first (also
dependent upon type of operation and operator ex­
perience). Thorough cleaning, proper lubrication
and replacement of any worn parts on a preventive
maintenance basis will assure proper operation
of the system at all tim es.
Instructions covering the removal and service
of standard chambers follows (refer to fig. 31):
REMOVAL AND DISASSEMBLY
1. Disconnect air lines from chambers.
2. Using a punch, drive lock washer protru­
sions from notches in spanner nut and spider
housing.
3. Using a spanner wrench or a punch and
hammer, loosen spanner nut which secures air
chamber to brake spider housing.
4. Remove air chamber assembly from brake
spider housing.
G M C S E R V I C E M A N U A L
Figure 31 — Standard Stopmaster Air Cham ber Components
5. Remove bolt and nut which secure clamp­
ing ring.
6. Scribe a mark across the pressure housing
and the non-pressure housing to assure proper
reassem bly.
7. Remove diaphragm, rod, boot and guide
from housings.
CLEANING AND INSPECTION
1. Clean all metal parts thoroughly, using a
suitable cleaning fluid. Blow dry with air or wipe
dry with cloth. (Do not use solvent on diaphragm.)
2. Examine diaphragm and replace with new
part if any signs of wear or deterioration are
evident.
3. Inspect pressure housing for scratches,
scores, or excessive wear. Examine all parts for
obstructions and remove any foreign matter.
4. Examine diaphragm plate rod boot for de­
terioration or cracks. If deterioration or other
damage is evident, replace. In order to replace
boot it is necessary to remove the plastic guide
from the end of the rod. If the guide is damaged or
worn, it too should be replaced. Apply a liberal
amount of rubber cement to boot flange and mating
surface on non-pressure housing.
BRAKE CHAMBER ASSEMBLY
AND INSTALLATION
1. Install boot, rod, guide and diaphragm in
non-pressure housing.
2. Position pressure housing on non-pressure
housing so that scribe marks made at disassembly
are aligned.
3. Install clamping ring on assembly and s e ­
cure with bolt and nut.
4. Install air chamber in brake spider housing
until it ,rbottoms" in spider. Then back off not
more than one full turn to position chamber ports
in line with air tubes. The plastic guide will as­
sure proper positioning of the wedge. At this point
lock the air chamber in position by tightening the
Sec. 5B
Page 239
AIR BRAKES