suspension CHRYSLER CARAVAN 2003 Repair Manual

CONDITION POSSIBLE CAUSES CORRECTION
EXCESSIVE PEDAL
TRAVEL (ONE FRONT
WHEEL LOCKS UP
DURING HARD BRAKING)1. One of the two hydraulic circuits
to the front brakes is malfunctioning.1. Inspect system for leaks. Check
master cylinder for internal malfunction.
PEDAL PULSATES/
SURGES DURING
BRAKING1. Rear brake drum out of round or
disc brake rotor has excessive
thickness variation.1. Isolate condition as rear or front.
Reface or replace brake drums or
rotors as necessary.
PEDAL IS SPONGY 1. Air in brake lines. 1. Bleed brakes.
2. Power brake booster runout
(vacuum assist).2. Check booster vacuum hose and
engine tune for adequate vacuum
supply. Refer to power brake booster
diagnosis and testing.
PREMATURE REAR
WHEEL LOCKUP1. Contaminated brake shoe linings. 1. Inspect and clean, or replace shoes.
Repair source of contamination.
2. Inoperative proportioning valve
(non-ABS vehicles).2. Refer to proportioning valve
diagnosis and testing. Replace valve as
necessary.
3. Improper power brake booster
assist.3. Refer to power brake booster in the
diagnosis and testing section.
STOP/BRAKE LAMPS
S TAY O N1. Brake lamp switch out of
adjustment.1. Replace brake lamp switch.
2. Brake pedal binding. 2. Inspect and replace as necessary.
3. Obstruction in pedal linkage. 3. Remove obstruction.
4. Power Brake Booster not allowing
pedal to return completely.4. Replace power brake booster.
VEHICLE PULLS TO
RIGHT OR LEFT ON
BRAKING1. Frozen brake caliper piston. 1. Replace frozen piston or caliper.
Bleed brakes.
2. Contaminated brake shoe lining. 2. Inspect and clean, or replace shoes.
Repair source of contamination.
3. Pinched brake lines. 3. Replace pinched line.
4. Leaking piston seal. 4. Replace piston seal or brake caliper.
5. Suspension problem. 5. Refer to the Suspension group.
PARKING BRAKE -
EXCESSIVE HANDLE
TRAVEL1. Rear drum brakes or rear disc
brake parking brake shoes out of
adjustment.1. Adjust rear drum brake shoes, or
rear parking brake shoes on vehicles
with rear disc brakes.
STANDARD PROCEDURE - BASE BRAKE
BLEEDING
NOTE: This bleeding procedure is only for the vehi-
cle's base brakes hydraulic system. For bleeding
the antilock brakes hydraulic system, (Refer to 5 -
BRAKES - ABS - STANDARD PROCEDURE)CAUTION: Before removing the master cylinder
cover, thoroughly clean the cover and master cylin-
der fluid reservoir to prevent dirt and other foreign
matter from dropping into the master cylinder fluid
reservoir.
RSBRAKES - BASE5-7
BRAKES - BASE (Continued)
ProCarManuals.com

plug from the adjustment hole in each brake support
plate to provide visual access of the brake adjuster
star wheel.
To eliminate the condition where maximum adjust-
ment of the rear brake shoes does not allow the auto-
matic adjuster to operate when tested, back the star
wheel off approximately 30 notches. It will be neces-
sary to hold the adjuster lever away from the star
wheel to permit this adjustment.
Have the helper apply the brakes. Upon applica-
tion of the brake pedal, the adjuster lever should
move down, turning the adjuster star wheel. Thus, a
definite rotation of the adjuster star wheel can be
observed if the automatic adjuster is working prop-
erly. If one or more adjusters do not function prop-
erly, the respective drum must be removed for
adjuster servicing.
BRAKE LINES
DESCRIPTION - BRAKE TUBES AND HOSES
The brake tubes are steel with a corrosion-resis-
tant nylon coating applied to the external surfaces.
The flex hoses are made of reinforced rubber with fit-
tings at each end.
The primary and secondary brake tubes leading
from the master cylinder to the ABS ICU Hydraulic
Control Unit (HCU) or the non-ABS junction block
have a special flexible section. This flexible section is
required due to cradle movement while the vehicle is
in motion (The ICU and non-ABS junction block are
mounted to the cradle).If replacement of these
lines is necessary, only the original factory
brake line containing the flexible section must
be used.
OPERATION - BRAKE TUBES AND HOSES
The purpose of the chassis brake tubes and flex
hoses is to transfer the pressurized brake fluid devel-
oped by the master cylinder to the wheel brakes of
the vehicle. The flex hoses are made of rubber to
allow for the movement of the vehicle's suspension.
INSPECTION - BRAKE TUBES AND HOSES
Flexible rubber hose is used at both front brakes
and at the rear axle. Inspection of brake hoses
should be performed whenever the brake system is
serviced and every 7,500 miles or 12 months, which-
ever comes first (every engine oil change). Inspect
hydraulic brake hoses for surface cracking, scuffing,
or worn spots. If the fabric casing of the rubber hose
becomes exposed due to cracks or abrasions in the
rubber hose cover, the hose should be replaced imme-
diately. Eventual deterioration of the hose can take
place with possible burst failure. Faulty installation
can cause twisting, resulting in wheel, tire, or chassis
interference.
The brake tubing should be inspected periodically
for evidence of physical damage or contact with mov-
ing or hot components.
The flexible brake tube sections used on this vehi-
cle in the primary and secondary tubes from the
master cylinder to the ABS hydraulic control unit
connections must also be inspected. This flexible tub-
ing must be inspected for kinks, fraying and contact
with other components or with the body of the vehi-
cle.
BRAKE PADS/SHOES - FRONT
REMOVAL
REMOVAL - FRONT DISC BRAKE SHOES
(DISC/DISC BRAKES)
(1) Raise the vehicle. (Refer to LUBRICATION &
MAINTENANCE/HOISTING - STANDARD PROCE-
DURE).
(2) Remove both front wheel and tire assemblies.
(3) Begin on one side of the vehicle.
(4) Remove the anti-rattle clip from the outboard
side of the caliper and adapter.
(5) Remove the two caliper guide pin bolts.
(6) Remove caliper from caliper adapter and brake
rotor.
CAUTION: Supporting weight of caliper by the flex-
ible brake fluid hose can damage the hose.
(7) Using wire or cord, hang the caliper from the
front strut assembly (Fig. 12). Support the caliper
Fig. 11 Caliper Piston Seal Function For Automatic
Adjustment
1 - PISTON
2 - CYLINDER BORE
3 - PISTON SEAL BRAKE PRESSURE OFF
4 - CALIPER HOUSING
5 - DUST BOOT
6 - PISTON SEAL BRAKE PRESSURE ON
5 - 14 BRAKES - BASERS
HYDRAULIC/MECHANICAL (Continued)
ProCarManuals.com

Use only brake fluid that was stored in a tightly-
sealed container.
DO NOTuse petroleum-based fluid because seal
damage will result. Petroleum based fluids would be
items such as engine oil, transmission fluid, power
steering fluid etc.
SPECIFICATIONS
BRAKE FLUID
The brake fluid used in this vehicle must conform
to DOT 3 specifications (DOT 4 and DOT 4+ are
acceptable) and SAE J1703 standards. No other type
of brake fluid is recommended or approved for usage
in the vehicle brake system. Use only MopartBrake
Fluid or equivalent from a tightly sealed container.
CAUTION: Never use reclaimed brake fluid or fluid
from an container which has been left open. An
open container of brake fluid will absorb moisture
from the air and contaminate the fluid.
CAUTION: Never use any type of a petroleum-based
fluid in the brake hydraulic system. Use of such
type fluids will result in seal damage of the vehicle
brake hydraulic system causing a failure of the
vehicle brake system. Petroleum based fluids would
be items such as engine oil, transmission fluid,
power steering fluid, etc.
JUNCTION BLOCK
DESCRIPTION - NON-ABS JUNCTION BLOCK
A junction block is used on vehicles that are not
equipped with antilock brakes (ABS). The junction
block mounts in the same location as the integrated
control unit (ICU) does on vehicles equipped with
ABS. This allows for use of the same brake tube con-
figuration on all vehicles. The junction block is
located on the driver's side of the front suspension
cradle/crossmember below the master cylinder (Fig.
45).
It has six threaded ports to which the brake tubes
connect. Two are for the primary and secondary
brake tubes coming from the master cylinder. The
remaining four are for the chassis brake tubes going
to each brake assembly.
OPERATION - NON-ABS JUNCTION BLOCK
The junction block distributes the brake fluid com-
ing from the master cylinder primary and secondary
ports to the four chassis brake tubes leading to the
brakes at each wheel. Since the junction blockmounts in the same location as the ABS integrated
control unit (ICU), it allows for the common use of
brake tubes going to the brakes whether the vehicle
is equipped with or without ABS.
NOTE: Although the brake tubes coming from the
master cylinder to the junction block or ABS ICU
may appear to be the same, they are not. They are
unique to each brake system application.
REMOVAL - NON-ABS JUNCTION BLOCK
(1) Using a brake pedal depressor, move and lock
the brake pedal to a position past its first 1 inch of
travel. This will prevent brake fluid from draining
out of the master cylinder when the brake tubes are
removed from the junction block.
(2) Disconnect the battery negative cable.
(3) If the vehicle is equipped with speed control,
perform the following:
(a) Disconnect the battery positive cable.
(b) Remove the battery (Refer to 8 - ELECTRI-
CAL/BATTERY SYSTEM/BATTERY - REMOVAL).
(c) Disconnect the vacuum hose connector at the
tank built into the battery tray.
(d) Remove the screw securing the coolant filler
neck to the battery tray.
(e) Remove the battery tray (Refer to 8 - ELEC-
TRICAL/BATTERY SYSTEM/TRAY - REMOVAL).
(f) Remove the fasteners and move the speed
control servo off to the side, out of the way.
CAUTION: Before removing the brake tubes from
the junction block, the junction block and the brake
tubes must be thoroughly cleaned. This is required
to prevent contamination from entering the brake
hydraulic system.
(4) Remove the four chassis brake tubes from the
top of the junction block (Fig. 45).
(5) Remove the primary and secondary brake
tubes from the top of the junction block.
(6) Remove the bolts attaching the junction block
mounting bracket to the front suspension crossmem-
ber (Fig. 45), then remove the junction block.
INSTALLATION - NON-ABS JUNCTION BLOCK
(1) Install the junction block and mounting bracket
on the front suspension crossmember (Fig. 45).
Install the mounting bolts and tighten to a torque of
28 N´m (250 in. lbs.).
(2) Install the primary and secondary brake tubes
from the master cylinder in their ports. Tighten tube
nuts to a torque of 17 N´m (145 in. lbs.).Take care
not to twist tubes when tightening tube nuts.
They must be properly positioned to allow free
RSBRAKES - BASE5-33
FLUID (Continued)
ProCarManuals.com

movement with rubber isolated suspension
crossmember.
(3) Install the four chassis brake tubes into the
outlet ports of the junction block. Tighten all 6 tube
nuts to a torque of 17 N´m (145 in. lbs.).
(4) If the vehicle is equipped with speed control,
perform the following:
(a) Install the speed control servo with its
mounting nuts.
(b) Connect the wiring harness to the speed con-
trol servo.
(c) Install the battery tray (Refer to 8 - ELEC-
TRICAL/BATTERY SYSTEM/TRAY - INSTALLA-
TION).
(d) Install the screw securing the coolant filler
neck to the battery tray.
(e) Reconnect the vacuum hose connector at the
tank built into the battery tray.
(f) Install the battery (Refer to 8 - ELECTRI-
CAL/BATTERY SYSTEM/BATTERY - INSTALLA-
TION).
(g) Install the battery shield.
(5) Remove the brake pedal holder.
(6) Connect negative cable back on negative post of
the battery.
(7) Bleed the brake system thoroughly to ensure
that all air has been expelled from the hydraulic sys-
tem. (Refer to 5 - BRAKES - STANDARD PROCE-
DURE).
(8) Road test the vehicle to verify proper operation
of the brake system.
MASTER CYLINDER
DESCRIPTION
DESCRIPTION
The master cylinder is located on the power brake
booster in the engine compartment on the driver's
side (Fig. 46). This vehicle uses 3 different master
cylinders. Master cylinder usage depends on what
type of brake system the vehicle is equipped with.
CAUTION: Master cylinders are not interchangeable
between systems. Performance and stopping dis-
tance issues will result if the incorrect master cyl-
inder is installed on the vehicle.
For information on master cylinder application,
bore and type, view the following table:
BRAKE SYSTEMMASTER CYLINDER
BORE/TYPE
Disc/Drum - ABS23.8 mm (15/16 in.)
Conventional
Compensating Port
Disc/Drum - Non-ABS23.8 mm (15/16 in.)
Conventional
Compensating Port
Disc/Disc - ABS25.4 mm (1.0 in.)
Conventional
Compensating Port
Disc/Disc ABS With
Traction Control25.4 mm (1.0 in.) Dual
Center Port
Fig. 45 NON-ABS JUNCTION BLOCK
1 - MASTER CYLINDER
2 - JUNCTION BLOCK
3 - SUSPENSION CROSSMEMBER
4 - MOUNTING BOLTS
Fig. 46 Master Cylinder And Booster Location
1 - MASTER CYLINDER
2 - POWER BRAKE BOOSTER
5 - 34 BRAKES - BASERS
JUNCTION BLOCK (Continued)
ProCarManuals.com

Here is how the height sensing proportioning valve
differs from a standard proportioning valve. As the
height of the rear suspension changes, the height
sensing portion of the proportioning valve changes
the split point of the proportioning valve. When the
height of the rear suspension is low, the proportion-
ing valve interprets this as extra load and the split
point of the proportioning valve is raised to a higher
pressure to allow for more rear braking. When the
height of the rear suspension is high, the proportion-
ing valve interprets this as a light load and the split
point of the proportioning valve is lowered to a lower
pressure and rear braking is reduced.
The height sensing proportioning valve regulates
the pressure by sensing the load condition of the
vehicle through the movement of the proportioning
valve actuator lever (Fig. 72). As the position of the
rear axle changes, depending on the load the vehicle
is carrying, the movement is transferred to the pro-
portioning valve. The proportioning valve adjusts the
hydraulic pressure accordingly.
The height sensing proportioning valve allows the
brake system to maintain the optimal front to rear
brake balance regardless of the vehicle load condi-
tion. Under a light load condition, hydraulic pressure
to the rear brakes is minimized. As the rear load con-
dition increases, so does the hydraulic pressure to
the rear brakes.
DIAGNOSIS AND TESTING - PROPORTIONING
VALVE (HEIGHT SENSING)
CAUTION: The use of aftermarket load leveling or
load capacity increasing devices on this vehicle is
prohibited. Using air shock absorbers or helpersprings on this vehicle will cause the height sens-
ing proportioning valve to inappropriately reduce
the hydraulic pressure to the rear brakes. This inap-
propriate reduction in hydraulic pressure potentially
could result in increased stopping distance of the
vehicle.
When a premature rear wheel skid is obtained on a
brake application, it may be an indication that the
hydraulic pressure to the rear brakes is above the
specified output from the proportioning valve. This
condition indicates a possible malfunction of the
height sensing proportioning valve, which will
require testing to verify that it is properly controlling
the hydraulic pressure allowed to the rear brakes.
Premature rear wheel skid may also be caused by
contaminated front or rear brake linings.
Prior to testing a proportioning valve for function,
check that all tire pressures are correct. Also, ensure
the front and rear brake linings are in satisfactory
condition.It is also necessary to verify that the
brakes shoe assemblies on a vehicle being
tested are either original equipment manufac-
turers (OEM) or original replacement brake
shoe assemblies meeting the OEM lining mate-
rial specification. This vehicles brake system is
not balanced for aftermarket brake shoe assem-
bly lining material.
If both front and rear brakes check OK, proceed
with the following test procedure for the height sens-
ing proportioning valve.
(1) Road test the vehicle to determine which rear
wheel brake is exhibiting premature wheel skid.
(2) Raise vehicle. (Refer to LUBRICATION &
MAINTENANCE/HOISTING - STANDARD PROCE-
DURE)
(3) Remove the chassis brake tube going to the
rear brake in question at the proportioning valve.
Remove the chassis brake tube coming from the junc-
tion block at the proportioning valve (Fig. 73).
(4) Install the appropriate fittings from Pressure
Test Fittings, Special Tool 6833, into the open ports
of the proportioning valve.
(5) Install the previously removed brake lines into
the Pressure Test Fittings. Tighten all tube nuts to
17 N´m (145 in. lbs.).
(6) Install a pressure gauge from Gauge Set, Spe-
cial Tool C-4007-A into the open port on each pres-
sure test fitting. Bleed air out of hose from pressure
test fittings to pressure gauges at the pressure
gauges. Then bleed air out of the brake line being
tested at that rear wheel brake bleeder.
NOTE: Actuator rod is a linear spring and is meant
to flex by design. When rod is raised, it will have
some curvature to it.
Fig. 72 HEIGHT SENSING PROPORTIONING VALVE
1 - PROPORTIONING VALVE
2 - ACTUATOR LEVER
3 - AXLE BRACKET
4 - REAR AXLE
RSBRAKES - BASE5-49
PROPORTIONING VALVE (Continued)
ProCarManuals.com

ROTOR RUNOUT
On-vehicle rotor runout is the combination of the
individual runout of the hub face and the runout of
the rotor. (The hub and rotor runouts are separable).
To measure rotor runout on the vehicle, first remove
the tire and wheel assembly. Reinstall the wheel
mounting nuts on the studs, tightening the rotor to
the hub. Mount the Dial Indicator, Special Tool
C-3339, with Mounting Adaptor, Special Tool SP-
1910 on steering arm. The dial indicator plunger
should contact braking surface of rotor approximately
ten millimeters from edge of rotor (Fig. 76). Check
lateral runout on both sides of the rotor, marking the
low and high spots on both. Runout limits can be
found in the specification table in this section. (Refer
to 5 - BRAKES/HYDRAULIC/MECHANICAL/RO-
TOR - SPECIFICATIONS)
If runout is in excess of the specification, check the
lateral runout of the hub face. Before removing the
rotor from the hub, place a chalk mark across both
the rotor and the one wheel stud closest to where the
high runout measurement was taken. This way, the
original mounting spot of the rotor on the hub is
indexed (Fig. 77).
Remove the rotor from the hub.
NOTE: Clean the hub face surface before checking
runout. This provides a clean surface to get an
accurate indicator reading.Mount Dial Indicator, Special Tool C-3339, and
Mounting Adaptor, Special Tool SP-1910, to the steer-
ing knuckle. Position the indicator stem so it contacts
the hub face near the outer diameter. Care must be
taken to position stem outside of the stud circle, but
inside of the chamfer on the hub rim (Fig. 78).
Hub runout should not exceed 0.03 mm (0.0012
inch). If runout exceeds this specification, the hub
must be replaced. (Refer to 2 - SUSPENSION/
FRONT/HUB / BEARING - REMOVAL)(Refer to 2 -
SUSPENSION/REAR/HUB / BEARING - REMOVAL)
If the hub runout does not exceed this specifica-
tion, install the rotor back on the hub, aligning the
chalk marks on the rotor with a wheel mounting
Fig. 75 Checking Rotor For Thickness
1 - CALIPER
Fig. 76 Checking Rotor Runout
1 - SPECIAL TOOL SP-1910
2 - 10 MILLIMETERS FROM EDGE
3 - DISC SURFACE
4 - SPECIAL TOOL C-3339
Fig. 77 Marking Rotor and Wheel Stud
1 - CHALK MARK
5 - 52 BRAKES - BASERS
ROTOR (Continued)
ProCarManuals.com

SUPPORT PLATE - DRUM
BRAKE
REMOVAL
(1) Using a brake pedal depressor, move and
secure brake pedal to a position past its first 1 inch
of travel. This will prevent brake fluid from draining
out of master cylinder when brake tube is remove
from wheel cylinder.
(2) Raise vehicle. (Refer to LUBRICATION &
MAINTENANCE/HOISTING - STANDARD PROCE-
DURE).
(3) Remove wheel and tire assembly.
(4) Disconnect brake tube from rear of wheel cylin-
der. Cap open ends
(5) Remove brake drum.
(6) Remove brake shoes from brake support plate.
(Refer to 5 - BRAKES/HYDRAULIC/MECHANICAL/
BRAKE PADS/SHOES - REMOVAL).
(7) Remove the 2 bolts attaching the wheel cylin-
der to the brake support plate.
(8) Remove the wheel cylinder from the brake sup-
port plate.
(9) Disconnect the park brake cable from the park
brake actuation lever.
(10) Using a suitable tool such as a 14 mm box
wrench (Fig. 84) or an aircraft type hose clamp, com-
press the flared legs on park brake cable retainer.
Then pull the park brake cable out of brake support
plate.
(11) Remove the rear hub and bearing. (Refer to 2
- SUSPENSION/REAR/HUB / BEARING -
REMOVAL)(12) Remove the rear brake support plate from the
rear axle.
INSTALLATION
(1) Install the 4 hub and bearing to axle mounting
bolts into the mounting holes in the flange of the
rear axle.
(2) Install the rear brake support plate on the 4
mounting bolts installed in the flange of the rear axle
(Fig. 85).
(3) Install the rear hub and bearing (and connect
wheel speed sensor where applicable) stopping short
of installing the brake drum. (Refer to 2 - SUSPEN-
SION/REAR/HUB / BEARING - INSTALLATION)
(4) Install the rear park brake cable into its
mounting hole in the rear brake support plate.
(5) Install the park brake cable on the park brake
actuation lever.
(6) Apply sealant such as Mopar Gasket-In-A-Tube
or equivalent around the wheel cylinder opening in
the brake support plate.
(7) Install wheel cylinder onto brake support.
Install and tighten the wheel cylinder to brake sup-
port plate attaching bolts to 8 N´m (75 in. lbs.)
torque.
(8) Install brake tube into wheel cylinder. Tighten
tube nut to a torque of 17 N´m (145 in. lbs.) torque.
(9) Install the rear brake shoes on the brake sup-
port plate. (Refer to 5 - BRAKES/HYDRAULIC/ME-
CHANICAL/BRAKE PADS/SHOES -
INSTALLATION).
(10) Install brake drum.
(11) Install wheel and tire.
(12) Tighten wheel stud nuts to 135 N´m (100 ft.
lbs.).
Fig. 84 Removing Park Brake Cable From Brake
Support Plate
1 - PARK BRAKE CABLE
2 - CABLE RETAINER
3 - 14 mm BOX WRENCH
4 - BRAKE SUPPORT PLATE
Fig. 85 Brake Support Plate Mounted On Bearing
Attaching Bolts
1 - REAR BRAKE SUPPORT PLATE
2 - HUB/BEARING MOUNTING BOLTS
5 - 56 BRAKES - BASERS
ProCarManuals.com

BRAKES - ABS
TABLE OF CONTENTS
page page
BRAKES - ABS
DESCRIPTION
DESCRIPTION - ANTILOCK BRAKE
SYSTEM............................75
DESCRIPTION - ANTILOCK BRAKE
SYSTEM (EXPORT)....................75
DESCRIPTION - ELECTRONIC VARIABLE
BRAKE PROPORTIONING...............75
DESCRIPTION - TRACTION CONTROL
SYSTEM............................76
OPERATION
OPERATION - ANTILOCK BRAKE SYSTEM . . 76
OPERATION - ELECTRONIC VARIABLE
BRAKE PROPORTIONING...............77
OPERATION - TRACTION CONTROL
SYSTEM............................77
CAUTION
CAUTIONS..........................78
STANDARD PROCEDURE - ANTILOCK BRAKE
SYSTEM BLEEDING...................78
SPECIFICATIONS
ABS FASTENER TORQUE...............79
TONE WHEEL RUNOUT................79
WHEEL SPEED SENSOR AIR GAP........79
FRONT WHEEL SPEED SENSOR
REMOVAL.............................79
INSTALLATION.........................80
REAR WHEEL SPEED SENSOR - AWD
REMOVAL.............................80INSTALLATION.........................80
REAR WHEEL SPEED SENSOR - FWD
REMOVAL.............................81
INSTALLATION.........................81
TONE WHEEL
INSPECTION - TONE WHEEL..............82
TRACTION CONTROL SWITCH
DIAGNOSIS AND TESTING - TRACTION
CONTROL SWITCH....................82
HYDRAULIC/MECHANICAL
OPERATION - HYDRAULIC CIRCUITS AND
VALVES .............................83
HCU (HYDRAULIC CONTROL UNIT)
DESCRIPTION.........................89
OPERATION...........................89
ICU (INTEGRATED CONTROL UNIT)
DESCRIPTION.........................89
OPERATION...........................90
REMOVAL
REMOVAL - LHD......................90
REMOVAL - RHD......................91
DISASSEMBLY - ICU....................93
ASSEMBLY - ICU.......................94
INSTALLATION
INSTALLATION - LHD..................94
INSTALLATION - RHD..................95
BRAKES - ABS
DESCRIPTION
DESCRIPTION - ANTILOCK BRAKE SYSTEM
This section covers the physical and operational
descriptions and the on-car service procedures for the
Mark 20e Antilock Brake System and the Mark 20e
Antilock Brake System with traction control.
The purpose of the antilock brake system (ABS) is
to prevent 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.
DESCRIPTION - ANTILOCK BRAKE SYSTEM
(EXPORT)
Four-wheel disc antilock brakes are standard on all
models. The Mark 20e antilock brake system is used
on all models. Depending on whether the vehicle is a
left-hand drive (LHD) or right-hand drive (RHD)
model, the integrated control unit (ICU) is located in
one of two locations. On LHD models, the ICU is
mounted above the front suspension cradle/cross-
member below the master cylinder. On RHD models,
the ICU is located behind the front suspension cra-
dle/crossmember on the left side of the vehicle.
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-
RSBRAKES - ABS5-75
ProCarManuals.com

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 56
km/h (35 mph) when road surfaces are slippery. The
traction control system reduces wheel slip by braking
the wheel that is losing traction.
HYDRAULIC SHUTTLE VALVES
Two pressure relief hydraulic shuttle valves are
included on vehicles with traction control. These
valves are located inside the HCU and cannot be ser-
viced separately from the HCU.
TRACTION CONTROL LAMP
The traction control function lamp is located in the
transmission range indicator display of the instru-
ment cluster, displaying TRAC, TRAC OFF or nei-
ther depending on system mode.
The TRAC OFF lamp is controlled by a Traction
Control Off switch that is a momentary contact type
switch. The Traction Control Off switch is located on
the steering column upper shroud.
OPERATION
OPERATION - ANTILOCK BRAKE SYSTEM
There are a few performance characteristics of the
Mark 20e Antilock Brake System that may at first
seem abnormal, but in fact are normal. These char-
acteristics 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 3±5 mph. If a wheel locking tendency 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 mod-ulation, 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 normal.
During an ABS stop, the brakes hydraulic system
is still diagonally split. However, the brake system
pressure is further split into three control channels.
During antilock operation of the vehicle's brake sys-
tem, the front wheels are controlled independently
and are on two separate control channels, and the
rear wheels of the vehicle are controlled together.
The system can build 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 (CAB).
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 3±4 mph. There
may be a slight brake pedal drop anytime that the
ABS is deactivated, such as at the end of the stop
when the vehicle speed is less than 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, stopping a vehicle on a bumpy road sur-
face 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.
5 - 76 BRAKES - ABSRS
BRAKES - ABS (Continued)
ProCarManuals.com

(8) Remove the 3 bolts (Fig. 20) attaching the ICU
mounting bracket to the front suspension crossmem-
ber.
(9) Remove ICU and the mounting bracket as a
unit from the vehicle.
(10) Remove the 3 bolts (Fig. 21) mounting the
ICU to the mounting bracket. Separate the ICU from
the mounting bracket.
(11) For the procedure on separating and attaching
the CAB to the HCU, refer to DISASSEMBLY.DISASSEMBLY - ICU
(1) Remove the ICU from the vehicle. (Refer to 5 -
BRAKES/HYDRAULIC/MECHANICAL/ICU (INTE-
GRATED CONTROL UNIT) - REMOVAL)
(2) Disconnect the pump/motor wiring harness
from the CAB (Fig. 22).
(3) Remove the 4 bolts (Fig. 23) attaching the CAB
to the HCU.
(4) Remove the CAB from the HCU (Fig. 24).
Fig. 20 ICU To Suspension Cradle Mounting Bolts
1 - HCU MOUNTING BRACKET BOLTS
2 - HCU MOUNTING BRACKET BOLT
3 - CAB
4 - HCU MOUNTING BRACKET
5 - HCU
Fig. 21 ICU Mounting Bolts
1 - HCU
2 - HCU MOUNTING BOLTS
3 - HCU MOUNTING BRACKET
Fig. 22 INTEGRATED CONTROL UNIT (ICU)
1 - PUMP/MOTOR
2 - HCU
3 - PUMP/MOTOR CONNECTOR
4 - CAB
Fig. 23 (TYPICAL) CAB Attaching Bolts
1 - MOUNTING BOLTS
2 - CAB
3 - HCU VALVE BLOCK
RSBRAKES - ABS5-93
ICU (INTEGRATED CONTROL UNIT) (Continued)
ProCarManuals.com