Content .. 430 431 432 433 ..

Chrysler PT Cruiser. Manual - part 432

(10) Install the rear brake rotor. (Refer to 5 -

BRAKES/HYDRAULIC/MECHANICAL/ROTOR

INSTALLATION)

(11) Install rear disc brake caliper. (Refer to 5 -

BRAKES/HYDRAULIC/MECHANICAL/DISC
BRAKE CALIPER - INSTALLATION)

(12) Install the tire and wheel assembly. Tighten

the wheel mounting nuts to a torque of 135 N·m (100
ft. lbs.).

(13) Adjust the parking brake shoes as necessary.

(Refer to 5 - BRAKES/PARKING BRAKE/SHOES -
ADJUSTMENTS)

(14) Lower the vehicle.

ADJUSTMENTS

ADJUSTMENT

NOTE: The parking brake shoes used in the drum-
in-hat park brake system do not automatically
adjust to compensate for brake shoe lining wear.
Therefore, it is necessary to manually adjust the
parking brake shoes.

NOTE: Before proceeding, (Refer to 5 - BRAKES -
WARNING) (Refer to 5 - BRAKES - CAUTION).

(1) Verify the parking brake lever is in the

released position.

(2) Raise the vehicle. (Refer to LUBRICATION &

MAINTENANCE/HOISTING - STANDARD PROCE-
DURE)

(3) Remove the rubber plug from the adjusting

hole in the disc brake caliper adapter.

(4) Adjust the parking brakes. Use the first bullet

point for the adjustment of the left side parking
brake shoes. Use the second bullet point for the
adjustment of the right side parking brake shoes.

• Insert a medium size screwdriver through

adjustment hole in the left backing plate. Position

the screwdriver against the star wheel on the park-
ing brake shoe adjuster. Using the screwdriver,
rotate the star wheel downward until a slight drag is
noticed when turning the rear tire and wheel assem-
bly. Then, using the screwdriver, slowly rotate the
star wheel upward, backing off the adjuster, just
enough to allow the rear tire and wheel assembly to
rotate without the parking brake shoes dragging. Do
not back off the adjuster star wheel more than two
clicks past the point of no drag. The parking brake
shoe-to-drum clearance is now properly set.

• Insert a medium size screwdriver through

adjustment hole in the right backing plate. Position
the screwdriver against the star wheel on the park-
ing brake shoe adjuster. Using the screwdriver,
rotate the star wheel upward until a slight drag is
noticed when turning the rear tire and wheel assem-
bly. Then, using the screwdriver, slowly rotate the
star wheel downward, backing off the adjuster, just
enough to allow the rear tire and wheel assembly to
rotate without the parking brake shoes dragging. Do
not back off the adjuster star wheel more that two
clicks past the point of no drag. The parking brake
shoe-to-drum clearance is now properly set.

(5) Install the rubber plug in the adjusting holes of

the disc brake caliper adapter.

(6) Lower the vehicle until the rear tires are just

clearing the floor.

(7) Reach inside the vehicle and fully apply and

release the park brakes two times after adjusting the
parking brake shoes.

(8) With the parking brake lever in the fully

applied position, attempt to hand rotate each rear
tire and wheel assembly to ensure that the parking
brake shoes are working.

(9) With the parking brake lever in the released

position, hand rotate each rear tire and wheel assem-
bly to ensure that the parking brake shoes are not
dragging.

5 - 80

BRAKES - BASE

SHOES - PARKING BRAKE (Continued)

BRAKES - ABS

TABLE OF CONTENTS

page

BRAKES - ABS

DESCRIPTION

DESCRIPTION - ANTILOCK BRAKE

SYSTEM - MK20E . . . . . . . . . . . . . . . . . . . . . 81

DESCRIPTION - ANTILOCK BRAKE

SYSTEM - MK25E . . . . . . . . . . . . . . . . . . . . . 82

DESCRIPTION - ELECTRONIC VARIABLE

BRAKE PROPORTIONING . . . . . . . . . . . . . . . 82

DESCRIPTION - TRACTION CONTROL

SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82

OPERATION

OPERATION - ANTILOCK BRAKE SYSTEM

. . 83

OPERATION - ELECTRONIC VARIABLE

BRAKE PROPORTIONING . . . . . . . . . . . . . . . 84

OPERATION - TRACTION CONTROL

SYSTEM - MK20E . . . . . . . . . . . . . . . . . . . . . 84

OPERATION - TRACTION CONTROL

SYSTEM - MK25E . . . . . . . . . . . . . . . . . . . . . 84

CAUTION

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85

DIAGNOSIS AND TESTING - INSPECTION

AND ROAD TEST

. . . . . . . . . . . . . . . . . . . . . 85

STANDARD PROCEDURE - ANTILOCK BRAKE

SYSTEM BLEEDING

. . . . . . . . . . . . . . . . . . . 86

SPECIFICATIONS

ABS FASTENER TORQUE

. . . . . . . . . . . . . . . 87

TONE WHEEL RUNOUT

. . . . . . . . . . . . . . . . 87

WHEEL SPEED SENSOR AIR GAP

. . . . . . . . 87

FRONT WHEEL SPEED SENSOR

DESCRIPTION

. . . . . . . . . . . . . . . . . . . . . . . . . 87

OPERATION

. . . . . . . . . . . . . . . . . . . . . . . . . . . 87

REMOVAL

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88

INSTALLATION

. . . . . . . . . . . . . . . . . . . . . . . . . 89

REAR WHEEL SPEED SENSOR

DESCRIPTION

. . . . . . . . . . . . . . . . . . . . . . . . . 89

OPERATION

. . . . . . . . . . . . . . . . . . . . . . . . . . . 90

REMOVAL

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90

INSTALLATION

. . . . . . . . . . . . . . . . . . . . . . . . . 91

TONE WHEEL

DESCRIPTION

. . . . . . . . . . . . . . . . . . . . . . . . . 91

OPERATION

. . . . . . . . . . . . . . . . . . . . . . . . . . . 91

INSPECTION

. . . . . . . . . . . . . . . . . . . . . . . . . . 91

TRACTION CONTROL SWITCH

REMOVAL

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92

INSTALLATION

. . . . . . . . . . . . . . . . . . . . . . . . . 92

HYDRAULIC CONTROL UNIT (HCU)

DESCRIPTION

DESCRIPTION - MK20E

. . . . . . . . . . . . . . . . 92

DESCRIPTION - MK25E

. . . . . . . . . . . . . . . . 93

OPERATION - HYDRAULIC CIRCUITS AND

VALVES

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94

INTEGRATED CONTROL UNIT (ICU) - MK20E

DESCRIPTION

. . . . . . . . . . . . . . . . . . . . . . . . . 99

OPERATION

. . . . . . . . . . . . . . . . . . . . . . . . . . 100

REMOVAL

. . . . . . . . . . . . . . . . . . . . . . . . . . . . 100

DISASSEMBLY - ICU

. . . . . . . . . . . . . . . . . . . 101

ASSEMBLY - ICU

. . . . . . . . . . . . . . . . . . . . . . 101

INSTALLATION

. . . . . . . . . . . . . . . . . . . . . . . . 102

INTEGRATED CONTROL UNIT (ICU) - MK25E

DESCRIPTION

. . . . . . . . . . . . . . . . . . . . . . . . 103

OPERATION

. . . . . . . . . . . . . . . . . . . . . . . . . . 103

REMOVAL

. . . . . . . . . . . . . . . . . . . . . . . . . . . . 103

DISASSEMBLY

. . . . . . . . . . . . . . . . . . . . . . . . 106

ASSEMBLY

. . . . . . . . . . . . . . . . . . . . . . . . . . . 106

INSTALLATION

. . . . . . . . . . . . . . . . . . . . . . . . 108

BRAKES - ABS

DESCRIPTION

DESCRIPTION - ANTILOCK BRAKE SYSTEM -
MK20E

The Antilock Brake System (ABS) prevents wheel

lockup under braking conditions on virtually any
type of road surface. Antilock braking is desirable
because a vehicle that is stopped without locking the
wheels retains directional stability and some steering
capability. This allows the driver to retain greater
control of the vehicle during braking.

Early production vehicles feature an antilock

brake system designated Mark 20e (MK20e).
This system is available with or without traction con-
trol.

The traction control system reduces wheel slip and

maintains traction at driving speeds below 64 km/h
(40 mph) when road conditions call for traction assis-
tance. For more information on traction control,
(Refer to 5 - BRAKES - ABS - DESCRIPTION).

All vehicles equipped with ABS use electronic vari-

able brake proportioning (EVBP) to balance front-to-
rear braking when the brakes are applied in the
partial braking range. For more information on elec-
tronic brake distribution, (Refer to 5 - BRAKES -
ABS - DESCRIPTION).

BRAKES - ABS

5 - 81

This system shares most base brake hardware

used on vehicles without ABS. Included in the ABS
system is an integrated control unit (ICU) and four
wheel speed sensors. Although similar to vehicles
without ABS, a different master cylinder and brake
tubes are used.

The MK20e ICU is made up of the Hydraulic Con-

trol Unit (HCU) and the Controller Antilock Brake
(CAB). For additional information on these compo-
nents, (Refer to 5 - BRAKES/HYDRAULIC/ME-
CHANICAL/HCU (HYDRAULIC CONTROL UNIT) -
DESCRIPTION) (Refer to 8 - ELECTRICAL/ELEC-
TRONIC

CONTROL

MODULES/CONTROLLER

ANTILOCK BRAKE - DESCRIPTION).

DESCRIPTION - ANTILOCK BRAKE SYSTEM -
MK25E

The Antilock Brake System (ABS) prevents wheel

Normal

Launch

production

vehicles

are

equipped with an antilock brake system desig-
nated MK25e. This system is available with or with-
out traction control.

The traction control system reduces wheel slip and

maintains traction at driving speeds below 64 km/h
(40 mph) when road conditions call for traction assis-
tance. For more information on traction control,
(Refer to 5 - BRAKES - ABS - DESCRIPTION).

All vehicles equipped with ABS use electronic vari-

This system shares most base brake hardware

The MK25e ICU is made up of the Hydraulic Con-

trol Unit (HCU) and the Antilock Brake Module
(ABM). For additional information on these compo-
nents, (Refer to 5 - BRAKES/HYDRAULIC/ME-
CHANICAL/HCU (HYDRAULIC CONTROL UNIT) -
DESCRIPTION) (Refer to 8 - ELECTRICAL/ELEC-
TRONIC CONTROL MODULES/ANTILOCK BRAKE
MODULE - DESCRIPTION).

DESCRIPTION - ELECTRONIC VARIABLE
BRAKE PROPORTIONING

Vehicles equipped with ABS use electronic variable

brake proportioning (EVBP) to balance front-to-rear
braking. The EVBP is used in place of a rear propor-
tioning valve. The EVBP system uses the ABS sys-
tem to control the slip of the rear wheels in partial
braking range. The braking force of the rear wheels
is controlled electronically by using the inlet and out-
let valves located in the integrated control unit
(ICU).

EVBP activation is invisible to the customer since

there is no pump motor noise or brake pedal feed-
back.

DESCRIPTION - TRACTION CONTROL SYSTEM

Traction control reduces wheel slip and maintains

traction at the driving wheels at speeds below 64
km/h (40 mph) when road surfaces are slippery. The
traction control system reduces wheel slip by braking
the wheel that is losing traction.

The traction control system may be turned off or

on by depressing the traction control switch button
located on the instrument panel (Fig. 1).

Fig. 1 Traction Control Switch Location

1 - TRACTION CONTROL SWITCH

5 - 82

BRAKES - ABS

BRAKES - ABS (Continued)

OPERATION

OPERATION - ANTILOCK BRAKE SYSTEM

There are a few performance characteristics of the

MK20e and MK25e Antilock Brake Systems that may
at first seem abnormal, but in fact are normal. These
characteristics are described below.

NORMAL BRAKING

Under normal braking conditions, the ABS func-

tions the same as a standard base brake system with
a diagonally split master cylinder and conventional
vacuum assist.

ABS BRAKING

ABS operation is available at all vehicle speeds

above 5–8 km/h (3–5 mph). If a wheel locking ten-
dency is detected during a brake application, the
brake system enters the ABS mode. During ABS
braking, hydraulic pressure in the four wheel circuits
is modulated to prevent any wheel from locking.
Each wheel circuit is designed with a set of electric
solenoids to allow modulation, although for vehicle
stability, both rear wheel solenoids receive the same
electrical signal. Wheel lockup may be perceived at
the very end of an ABS stop and is considered nor-
mal.

During an ABS stop, the brakes hydraulic system

is still diagonally split. However, the brake system
pressure is further split into four control channels.
During antilock operation of the vehicle’s brake sys-
tem, the wheels are controlled independently and are
on separate control channels.

The system can build, hold and release pressure at

each wheel, depending on signals generated by the
wheel speed sensors (WSS) at each wheel and
received at the Controller Antilock Brake (MK20e) or
Antilock Brake Module (MK25e).

NOISE AND BRAKE PEDAL FEEL

During ABS braking, some brake pedal movement

may be felt. In addition, ABS braking will create
ticking, popping, or groaning noises heard by the
driver. This is normal and is due to pressurized fluid
being transferred between the master cylinder and
the brakes. If ABS operation occurs during hard
braking, some pulsation may be felt in the vehicle
body due to fore-and-aft movement of the suspension
as brake pressures are modulated.

At the end of an ABS stop, ABS is turned off when

the vehicle is slowed to a speed of 5–6 km/h (3–4
mph). There may be a slight brake pedal drop any-
time that the ABS is deactivated, such as at the end
of the stop when the vehicle speed is less than 5
km/h (3 mph) or during an ABS stop where ABS is
no longer required. These conditions exist when a

vehicle is being stopped on a road surface with
patches of ice, loose gravel, or sand on it. Also, stop-
ping a vehicle on a bumpy road surface activates
ABS because of the wheel hop caused by the bumps.

TIRE NOISE AND MARKS

Although the ABS system prevents complete wheel

lockup, some wheel slip is desired in order to achieve
optimum braking performance. Wheel slip is defined
as follows: 0 percent slip means the wheel is rolling
freely and 100 percent slip means the wheel is fully
locked. During brake pressure modulation, wheel slip
is allowed to reach up to 25–30 percent. This means
that the wheel rolling velocity is 25–30 percent less
than that of a free rolling wheel at a given vehicle
speed. This slip may result in some tire chirping,
depending on the road surface. This sound should not
be interpreted as total wheel lockup.

Complete wheel lockup normally leaves black tire

marks on dry pavement. The ABS will not leave dark
black tire marks since the wheel never reaches a
fully locked condition. However, tire marks may be
noticeable as light patched marks.

START-UP CYCLE

When the ignition is turned on, a popping sound

and a slight brake pedal movement may be noticed.
The ABS warning indicator lamp will also be on for
up to 5 seconds after the ignition is turned on. These
conditions occur as part of an ABS self-diagnosis test
performed by the antilock brake system. The popping
noise is the result of brief activation of the solenoids
inside the integrated control unit (ICU).

DRIVE-OFF CYCLE

When the vehicle is first driven off, a humming

may be heard or felt by the driver at approximately
25–40 km/h (15–25 mph). This is caused by brief acti-
vation of the ABS pump motor on the ICU and is a
normal function of ABS as the system is performing
a diagnosis check.

PREMATURE ABS CYCLING

Symptoms of premature ABS cycling include: click-

ing sounds from the solenoid valves; pump/motor
running; and pulsations in the brake pedal. Prema-
ture ABS cycling can occur at any braking rate of the
vehicle and on any type of road surface.

Premature ABS cycling is a condition that needs to

be correctly assessed when diagnosing problems with
the antilock brake system. It may be necessary to use
a scan tool to detect and verify premature ABS
cycling.

Check the following common causes when diagnos-

ing premature ABS cycling: damaged tone wheels;
incorrect tone wheels; damaged steering knuckle

BRAKES - ABS

5 - 83

BRAKES - ABS (Continued)

Content .. 430 431 432 433 ..