STARTING AND OPERATING THE VEHICLE OPERATING AUTOMATIC TRANSMISSIONS
Regional Haul
(R05/10) Y53-6033 – 101 –
Using the Brake System
NOTE: Today’s diesel engines have significant
torque and startability power at low RPMs. Com-
binations of engine speed and available torque
may overpower the vehicle’s parking brakes.
WARNING! Never drive your vehicle with the
parking brakes applied. Always release the
parking brakes prior to moving the vehicle.
Failure to disengage the parking brakes prior
to moving your vehicle could result in exces-
sive heat build-up of the brakes and start a
fire, possibly resulting in death, personal
injury or property damage.
The operation of the vehicle's braking system and many
vehicle accessories depends upon the storage and appli-
cation of a high-pressure air supply.
This air brake system is a multiple circuit type: it has a cir-
cuit for the front wheels, a separate circuit for the rear
wheels, and one for the trailer (tractors only). The system
is supplied by a compressor driven by the engine. The
vehicle's compressor takes outside air and compresses it,
usually to 100–130 psi (690–896 kPa). This compressed
air then goes to the reservoirs to be stored until needed.
When you operate your air brakes, the stored com-
pressed air flows into the chambers where it is used to
apply your truck and trailer brakes. That is why, when you
push down on the brake pedal, you do not feel the same
amount of pressure on the pedal that you do when you
apply the brakes on your car. All you are doing on your
truck is opening an air valve to allow air to flow into the
brake chambers.
WARNING! The brake system is a critical vehi-
cle safety system. For the safety of you and
others around you, have the vehicle submit-
ted for periodic preventive maintenance
checks as well as having any suspected prob-
lems immediately checked by an Authorized
Service Center. Failure to properly maintain
your brake system can lead to serious acci-
dents involving death or personal injury.
