GMC 4000 Series Service Manual page 215

Sec. 5B
Page 208
Subject
Brake System Equipment
Brake System Maintenance
Brake Adjustments ...............................................209
Slack A d j u s t e r s ...................................................... 212
Brake Chambers (Standard)
Air T a n k s .................................................................214
Air Tank Check Valve
Safety Valve ..........................................................215
Pressure Protection Valve
Quick Release Valve ........................................... 216
Moisture Ejector Valve
Brake Application V a l v e s .................................... 217
Air Lines .................................................................219
Air Pressure Gauge ........................................... 220
Low Air Pressure S w i t c h .................................... 221
Trailer Brake C o n t r o l s ........................................221
I.C.C. Brake System E q u ip m e n t......................221
Trailer Brake Hand Control V a l v e s ...............221
BRAKE SYSTEM EQUIPMENT
The air brake system com prises a group of
devices, some of which maintain a supply of com ­
pressed air, some of which direct and control the
flow of the com pressed air, and others which trans­
form the energy of com pressed air into the mech­
anical force and motion necessary to apply the
brakes. Refer to figure 1 for typical schematic
diagram.
Information in this section covers all stand­
ard air brake equipment, as well as other units
which are used as optional equipment on some
models.
There are two basically different types of air
actuated brakes used on vehicles covered by this
manual. One type is the cam-type brake which is
energized by an air chamber and slack adjuster
arrangement. The other is called Stopmaster,
which is a complete assembly consisting of two
air chambers connected to two brake shoes through
tubes containing push-rod-and plunger assem blies.
All information relative to Stopmaster brakes is
found under the heading of "Stopmaster Brakes"
in this section. Unless otherwise specified, all
pedals, valves, controls, etc., covered in this
manual apply to both cam-type and Stopmaster
type brake system s.
Refer to AIR COMPRESSOR AND GOVERNOR
(SEC. 6T) for information relative to air com­
p ressors and governors.
G M C S E R V I C E M A N U A L
SECTION 5B
Ait Q n& k& i
INDEX
Page No.
.................................... 208
................................ 208
.............................213
........................................215
................................ 216
.................................... 216
Subject
Trailer Emergency Air Supply Control Valves 222
Tractor Protection (Breakaway) Valves
Double Check Valve and Stop Light Switch . . 223
Front Brake Limiting Valve and Two-Way
Control Valve .................................................. 224
DD3 Brake Actuator System
Inversion V a l v e ......................................................230
Push-Pull Control Valve
Synchro V a l v e ......................................................... 231
Anchorlok Brake C h a m b ers................................ 232
Front Brake Shoes and Anchor Pins
"S" Cam Rear Brakes
Brake Drums ......................................................... 236
Stopmaster Brakes ...............................................236
"Fail-Safe" Brakes ...............................................244
S p e c ific a tio n s ......................................................... 248
Troubleshooting Chart - General
Troubleshooting Chart - S to p m a s te r ...............252
BRAKE SYSTEM M AINTENANCE
Normal operation of braking system n ece ssi­
tates periodic tests, inspection, and adjustments to
assure safe, efficient operation. Test, inspection
and adjustment procedures for each air brake con­
trol unit are described under individual headings
in this section. Since the vehicles covered by this
Maintenance Manual will be used in a wide variety
of operation types, it is impossible to fix mainten­
ance intervals (either time or mileage) which will
satisfactorily suit all conditions. Therefore, any
such intervals stated in these maintenance pro­
cedures must be related to the type of usage to
which a particular vehicle is put. Obviously, a
truck used in city "stop and start" driving will re­
quire different service operations and intervals
than one hauling "over the road" for long distance.
With this in mind, all service intervals should be
related to a specific vehicle.
Compression and subsequent cooling of air
causes the moisture in the air to condense. This
moisture collects in air tank and should be drained
daily. Drain cocks are provided at bottom of air
tanks for this purpose. Satisfactory draining is
accomplished only by leaving the drain cocks open
after com pressed air has escaped and until all
drainage stops.
Some vehicles are equipped with a moisture
ejector valve (optional), which eliminates the need
for daily drainage of air tanks. For description of
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