Hydraulic Brake System - freightliner WALK-IN VAN CHASSIS Operator's Manual

Hydraulic and Air Brake Systems

Hydraulic Brake System

General Information
The hydraulic brake system includes a power
booster, master cylinder, reservoir, hydraulic brake
lines, a brake rotor on each wheel hub, and a brake
caliper and pad assembly at each rotor. See
B
04/26/2012
A. Open caps and check fluid level.
B. Fill to this level.
Fig. 7.1, Hydraulic Brake Reservoir (MT-45 and MT-55)
IMPORTANT: Make sure that the fluid in the
master cylinder reservoirs is up to the level of
the ridge that surrounds the reservoir. Use only
heavy-duty brake fluid, DOT 3, in the hydraulic
brake system.
The master cylinder controls braking power to the
front and rear brakes. The Bendix Hydro-Max®
power booster is attached to the rear of the master
cylinder and is connected to the power steering sys-
tem (which provides pressurized power steering
fluid). An electrically powered "reserve" pump oper-
ates if there is inadequate fluid flow from the power
steering pump to the power booster. The brake sys-
tem warning light comes on if there is a problem
within the system. Bring the vehicle to a safe stop
and correct the problem before continuing operation
of the vehicle. See Group 42 of the Walk-In Van
Chassis Workshop Manual for hydraulic brake sys-
tem troubleshooting and adjustment procedures.
7.1
Fig.
A
f460513a
Operation
Before driving the vehicle, secure all loose items in
the cab so that they will not fly forward during a full
brake application. Check that the brake system warn-
ing light is off after releasing the hand brake. If the
warning light does not go off, correct the problem
7.1.
before continuing operation of the vehicle.
During normal braking stops, depress the foot brake
control pedal until braking action slows down the ve-
hicle. Increase or decrease the pressure on the
pedal so that the vehicle comes to a smooth, safe
stop. When the forward speed of the vehicle has de-
creased to almost the idling speed of the engine,
push the clutch pedal in (if equipped) and shift the
transmission into Neutral (N). Apply the hand parking
brake if the vehicle is to be parked.
Meritor WABCO® Antilock Braking
System (ABS)
The Meritor WABCO® Antilock Braking System
(ABS) is an electronic wheel speed monitoring and
control system that works with the hydraulic brake
system. ABS passively monitors vehicle wheel speed
at all times, but controlswheel speed during an emer-
gency or reduced-traction stop. In normal braking
applications, the standard hydraulic brake system is
in effect.
IMPORTANT: For proper ABS system operation,
the front and rear tires must rotate at speeds
within 16% of one another. Installing different
sized tires on just the front or rear axle will re-
sult in inaccurate wheel speed signals to the
ECU resulting in a reduced braking force, which
could lead to longer stopping distances.
ABS includes signal-generating tone wheels and sen-
sors located in the wheel hubs of each sensed axle.
The sensors transmit vehicle wheel speed informa-
tion to an electronic control unit (located on the
frame rail) that interprets these signals to calculate
wheel speed and a vehicle reference speed. If the
calculations indicate wheel lockup, the appropriate
control circuit signals the brake pressure modulator
to increase or decrease braking pressure until wheel
slip has been corrected.
The electronic control unit also has a safety circuit
that constantly monitors the wheel sensors, brake
pressure modulator, and the electrical circuitry. The
dash warning light (ABS) comes on after the ignition