ANTI-LOCK BRAKES potx

ANTI-LOCK
BRAKES
ANTI
LOCK BRAKES
ANTI
-
LOCK

BRAKES
 ABS, (Anti-Lock brake system)

ABS
allows the driver to maintain steering

ABS

allows

the

driver

to

maintain

steering

control of the vehicle while in hard braking
situations
situations

.
ANTI
LOCK BRAKES
ANTI
-
LOCK

BRAKES
 Computerized ABS is
designed to keep the
wheels from locking
as the brakes are
applied
applied
.
 A locked wheel
provides very little or
provides

very

little

or

no directional control.
ANTI
LOCK BRAKES
ANTI
-

LOCK

BRAKES
 The following slides show the common
A
BS com
p
onents.
p
 Some components are part of both the
conventional and ABS system
conventional

and

ABS

system
.
Rear Backing Plate
ANTI
LOCK BRAKES
ANTI
-
LOCK

BRAKES
 When operating a vehicle with ABS never
p
um
p
the brakes.
pp
 Doing so will make the ABS system
ineffective
ineffective
.
 Always apply firm pressure.
ANTI
LOCK BRAKES
ANTI
-
LOCK

BRAKES
 Drivers may experience a pulsation in the
brake
p
edal
,
or
p
edal kick back durin
g
an
p,p g

ABS stop. This is normal and not to be
confused with a conventional brake
p
edal
p
pulsation
ANTI
LOCK BRAKES
ANTI
-
LOCK

BRAKES
Master
Pressure
Cylinder
Assembly
Speed
Sensor
Pressure

Valve
Dump/Vent Valve
Anti-Lock
Brake Module
Anti Lock
Brake

Module
12 V

ANTI
LOCK BRAKES
ANTI
-
LOCK

BRAKES
 Major components of the anti-lock brake
s
y
stem consist of a
y
 Brake control module,

Solenoid valve assembly,

Solenoid

valve

assembly,
 Speed sensor's

Wiring and the amber ABS brake warning

Wiring
,
and

the

amber

ABS

brake

warning

light.
ANTI
LOCK BRAKES
ANTI
-
LOCK

BRAKES
 Brake Control Module:
 The brake control module is a com
p
ute
p
that receives information from the speed
sensor and compares it to the speed of
other wheels.
 When one wheel is approaching lock-up
pressure can be vented allowing the wheel
nearing lock-up to speed up.
ANTI
LOCK BRAKES

ANTI
-
LOCK

BRAKES
 If a wheel is to fast pressure can be
increased to slow down the wheel.
 If both wheel are approximately the same
speed the brake control module can enter
speed

the

brake

control

module

can

enter

a pressure hold mode of operation.
ANTI
LOCK BRAKES
ANTI
-
LOCK

BRAKES
 Solenoid Valve Assembly:
Is a
p
air of valves that can:
p
A. Increase pressure
B
Hold pressure steady
B
.
Hold

pressure

steady

C. Decrease pressure
ANTI
LOCK BRAKES
ANTI
-
LOCK

BRAKES
During pressure increase
mode of operation fluid is
allowed to flow through
both solenoids to the brake
caliper

Solenoid 1
Pressure increase
caliper
Solenoid 2
Pressure decrease/Vent
lid
so
l
eno
id
Brake line under pressure
Brake fluid line not under pressure
ANTI
LOCK BRAKES
ANTI
-
LOCK

BRAKES
During Pressure Hold
mode of o
p
eration both
p
solenoids are closed and
no additional fluid is
allowed to flow to brake
calipers
Solenoid 1
Pressure increase

calipers
.
Solenoid 2
Pressure decrease/Vent
Pressure

decrease/Vent
ANTI
LOCK BRAKES
ANTI
-
LOCK

BRAKES
During Pressure Vent mode
the
p
ressure increase solenoid
p
is closed. The Vent solenoid
opens allowing fluid to vent
into an accumulator chamber
Solenoid 1
Pressure increase
Solenoid 2
Pressure decrease/Vent
Pressure

decrease/Vent
ANTI

LOCK BRAKES
ANTI
-
LOCK

BRAKES
 ABS system can maintain extremely high
static
p
ressure and must be disabled
p
before attempting repairs.

Normally pumping brake 20
-
30 times will

Normally

pumping

brake

20
30

times

will

release pressure.
ANTI
LOCK BRAKES
ANTI
-
LOCK

BRAKES
 ABS brake system are

Integrated

Integrated

 Nonintegrated
ANTI
LOCK BRAKES
ANTI
-
LOCK

BRAKES
 An integrated system has the master
c
y
linder and control valve assembl
y
made
yy
together.


A nonintegrated has the master cylinder

A

nonintegrated

has

the

master

cylinder

and control valve assembly made
separate
separate
.
ANTI
LOCK BRAKES
ANTI
-
LOCK

BRAKES
 ABS operates using the same hydraulic
p
rinci
p

al as conventional brakes.
pp
 ABS system only operates when wheel
lock
-
up is emanate
lock
up

is

emanate
.
 A bussing noise and bakes pedal vibration
is normal during ABS operation
is

normal

during

ABS

operation
.
ANTI
LOCK BRAKES
ANTI
-
LOCK

BRAKES
 To determine if wheel
lock-up is about to
occur vehicles a
wheel speed sensor.

ANTI
LOCK BRAKES
ANTI
-
LOCK

BRAKES
 There 3 ABS
configurations
 1. channel normally
RWAL (rear wheel
anti
-
lock)
anti
lock)
 In a one channel
RWAL system the rear
wheels are controlled
together