Peterbilt Medium Duty Truck Owner's Manual - Peterbilt Motors
Peterbilt Medium Duty Truck Owner's Manual - Peterbilt Motors
Peterbilt Medium Duty Truck Owner's Manual - Peterbilt Motors
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STARTING AND OPERATING THE VEHICLE<br />
to the trailer, and (3) protect the tractor air supply in case<br />
of separation of the air lines connecting the tractor to the<br />
trailer.<br />
Hydraulic Brakes<br />
WARNING! Do not operate the vehicle in the<br />
event of a malfunction in any air or hydraulic<br />
circuit. Such a malfunction may prevent the<br />
brake system from operating properly, and<br />
could result in an accident, causing death or<br />
personal injury. The vehicle should not be<br />
operated until the system is repaired and both<br />
braking circuits, including all pneumatic,<br />
hydraulic, and mechanical components are<br />
working properly.<br />
The operation of the vehicle's braking system is based on<br />
the principle of hydraulics. Hydraulic action begins when<br />
force is applied to the brake pedal. This force creates<br />
hydraulic pressure in the master cylinder and is amplified<br />
with assistance of a power booster. The supplemental<br />
boost in force is developed when pressurized power steering<br />
fluid from the steering pump presses on the master<br />
USING THE BRAKE SYSTEM<br />
cylinder piston. As a safety precaution, the pressurized<br />
fluid from the master cylinder has two mutually independent<br />
circuits. The primary circuit supplies the front wheels<br />
while the secondary circuit supplies the rear wheels. The<br />
displaced fluid from the master cylinder travels through<br />
brake pipes terminating at the wheel cylinders which actuate<br />
the brake pad mechanisms. Actuation of these mechanisms<br />
force the brake pads against the rotors to stop the<br />
wheels.<br />
A reserve electric motor pump provides a redundant<br />
power source for the hydraulic booster in the event normal<br />
flow from the power steering pump is interrupted. <strong>Manual</strong><br />
braking is also available in the event both the power and<br />
reserve systems are inoperative.<br />
WARNING! Never drive your vehicle with the<br />
parking brakes applied. Always release the<br />
parking brakes prior to moving the vehicle.<br />
Failure to disengage the parking brakes prior<br />
to moving your vehicle could result in excessive<br />
heat build-up of the brakes and start a<br />
fire, possibly causing death, personal injury or<br />
porperty damage.<br />
<strong>Medium</strong> <strong>Duty</strong> (R05/09) Y53-6027 – 121 –
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