Peterbilt Medium Duty Trucks Operator's Manual after 1-07

Using the Brake System
• After the engine is started, warmed up, and you are
ready to get under way, turn the exhaust brake switch
ON for added braking effect.
WARNING! Do not use the engine retarder when
operating on road surfaces with poor traction
(such as wet, icy, or snow covered roads or
gravel). Retarders can cause the wheels to skid
on a slippery surface. You could lose control of
the vehicle and/or jackknife if the wheels begin
to skid, resulting in an accident.
However, if your vehicle is equipped with Rockwell/WABCO
anti-lock brakes (ABS), the operation of the exhaust brake (if
turned ON) will be controlled by the ABS. For more ABS
information, see “Anti-Lock Braking System” on page 81.
For more information on when and how to use the engine
retarder in your vehicle, see the owner’s manual for the
engine brake that is included with your vehicle.
Brake Components
Operating Instructions
The following is a brief description of the air/brake system. It
is intended to supply you with general information on how the
system works. For complete information see the Medium
Duty Maintenance Manual.
Compressor: supplies air to the system. System pressure is
controlled by the governor.
Governor: controls the air pressure in the system by actuating
the compressor discharge mechanism. Its cut-out pressure
is 115 to 125 psi (793 to 862 kPa). Its preset cut-in
pressure is set to between 13 to 25 psi (90 to 172 kPa) below
the cut-out pressure setting (cut-out and cut-in interval is not
adjustable).
Safety Valve: installed on the supply reservoir outlet. It
should “vent off” at 150 psi (1034 kPa) permitting air to
escape.
Air Dryer (Option): collects and removes moisture and contaminants
from the air as it travels from the compressor to the
wet tank (reservoir).
– 86 – Y53-6008 Medium Duty (R10/06)