Brake Adjustment
PART 8: MAINTENANCE AND SERVICE
Air System
• Build up air pressure in the system to the governor
cut-out point.
• Stop the engine.
• Release the parking brakes (push in the yellow knob).
• Watch the rate of air pressure drop. The rate of drop
should not be more than 2 psi (14 kPa) per minute.
• Now start the engine and build up the air pressure
again.
• Stop the engine. Ensure that the parking brakes are
still released (i.e., the yellow knob is pushed in).
• Fully apply the service brakes.
• Watch the rate of air pressure drop registered by the
air gauge. The rate of drop should not be more than 3
psi (21 kPa) per minute.
• If you
fi
nd excessive leakage, a leakage test should
be made at the air line connections and at all air brake
control units. To perform a leakage test, refer to the
detailed instructions in the Peterbilt Maintenance Man-
ual, or take your vehicle to an authorized Peterbilt
dealer.
Drum Brakes
Have brake drum linings and disc brake pads inspected by
a quali
fi
ed mechanic for wear at regular intervals according
to the maintenance schedule. In severe service or offhigh-
way applications inspect the linings more frequently.
Automatic Slack Adjusters
Periodically check the Brake Chamber Stroke. Replace the
slack adjuster if proper stroke cannot be maintained.
Operational checks of automatic slack adjusters
• Measure brake chamber stroke with the spring brake
released and the air pressure no less than 100 psi (690
kPa).
• Brake Chamber Stroke is the difference between the
applied and the retracted position of the air chamber
pushrod.
• A correctly installed and functioning auto slack ad-
juster will produce the following strokes:
– 148 –
Y53-6015
R(08/07)
Summary of Contents for Peterbilt 320
Page 1: ......
Page 2: ......
Page 4: ......
Page 210: ...PART 11 SUBJECT INDEX Windshield Washer Reservoir 29 206 Y53 6015 R 08 07 ...
Page 212: ...Peterbilt Motors Company P O Box 90208 Denton Texas 76202 ...