brake system JEEP LIBERTY 2002 KJ / 1.G Owner's Manual

a linear force against the secondary brake shoe. This
action presses the secondary shoe into contact with
the drum. Once the secondary shoe contacts the
drum, force is exerted through the strut. This force is
transferred through the strut to the primary brake
shoe causing it to pivot into the drum as well.
A gear type ratcheting mechanism is used to hold
the lever in an applied position. Parking brake
release is accomplished by the hand lever release
button.
A parking brake switch is mounted on the parking
brake lever and is actuated by movement of the
lever. The switch, which is in circuit with the red
warning light in the dash, will illuminate the warn-
ing light whenever the parking brakes are applied.
Parking brake is self-adjusting when the lever is
pulled. The cable tensioner, once adjusted at the fac-
tory, should not need further adjustment under nor-
mal circumstances.
ADJUSTMENTS
ADJUSTMENT - LOCK OUT
NOTE: The parking brake is self-adjusting, It can
not be adjusted.
(1) Remove the center floor console (Refer to 23 -
BODY/INTERIOR/FLOOR CONSOLE - REMOVAL).
(2) Pull up on the spring until the tab on the lever
passes the tab on the cable guide and install a punch
in the hole on the side then release (Fig. 46).(3) The park brake system is now locked out to
perform necessary repairs.
CABLES
REMOVAL
(1) Lock out the parking brake cables (Refer to 5 -
BRAKES/PARKING BRAKE - ADJUSTMENTS) (Fig.
46).
(2) Remove the rear seat (Refer to 23 - BODY/
SEATS/SEAT - REMOVAL).
(3) Remove the cable saddle bracket (Fig. 47).
(4) Disconnect the two cables from the front mount
(Fig. 48).
(5) Pull the carpet forward far enough in the rear
to gain access to the two parking brake cables thru
the floor (Fig. 47).
(6) Push the cables thru the floor with the grom-
mets.
(7) Remove the primary brake shoe hold down
spring and separate the shoes to gain access, Then
disconnect the cable from lever on brake shoe.
(8) Remove cables from backing plates by using a
screw driver to break off the tangs on the cable or a
proper sized box end wrench over the tangs.
INSTALLATION
(1) Install the cables into the support plate.
(2) Reconnect the cable to the lever on the brake
shoe, Install the primary brake shoe hold down
spring and the shoes.
Fig. 46 LOCK OUT CABLES
1 - PARKING BRAKE HANDLE
2 - PUNCH
3 - CABLE GUIDE
4 - CABLE
Fig. 47 MOUNTING BRACKETS
1 - MOUNTING SADDLE BRACKET
2 - PARK BRAKE CABLES
3 - CARPET
5 - 30 BRAKES - BASEKJ
PARKING BRAKE (Continued)

BRAKES - ABS
TABLE OF CONTENTS
page page
BRAKES - ABS
DESCRIPTION.........................32
OPERATION...........................32
DIAGNOSIS AND TESTING - ANTILOCK
BRAKING SYSTEM....................33
STANDARD PROCEDURE - ABS BRAKE
BLEEDING...........................33
SPECIFICATIONS.......................33
ELECTRICAL
DESCRIPTION.........................34
OPERATION...........................34FRONT WHEEL SPEED SENSOR
REMOVAL.............................34
INSTALLATION.........................34
REAR WHEEL SPEED SENSOR
REMOVAL.............................35
INSTALLATION.........................35
HCU (HYDRAULIC CONTROL UNIT)
DESCRIPTION.........................35
OPERATION...........................35
REMOVAL.............................36
INSTALLATION.........................36
BRAKES - ABS
DESCRIPTION
ANTILOCK BRAKING SYSTEM
The purpose of the antilock system is to prevent
wheel lockup during periods of high wheel slip. Pre-
venting lockup helps maintain vehicle braking action
and steering control.
The antilock CAB activates the system whenever
sensor signals indicate periods of high wheel slip.
High wheel slip can be described as the point where
wheel rotation begins approaching 20 to 30 percent of
actual vehicle speed during braking. Periods of high
wheel slip occur when brake stops involve high pedal
pressure and rate of vehicle deceleration.
Battery voltage is supplied to the CAB ignition ter-
minal when the ignition switch is turned to Run posi-
tion. The CAB performs a system initialization
procedure at this point. Initialization consists of a
static and dynamic self check of system electrical
components.
The static check occurs after the ignition switch is
turned to Run position. The dynamic check occurs
when vehicle road speed reaches approximately 30
kph (18 mph). During the dynamic check, the CAB
briefly cycles the pump and solenoids to verify oper-
ation.
If an ABS component exhibits a fault during ini-
tialization, the CAB illuminates the amber warning
light and registers a fault code in the microprocessor
memory.
ELECTRONIC BRAKE DISTRIBUTION
The electronic brake distribution (EBD) functions
like a rear proportioning valve. The EBD system usesthe ABS system 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 outlet valves located in the HCU.
OPERATION
ANTILOCK BRAKING SYSTEM
During normal braking, the master cylinder, power
booster and wheel brake units all function as they
would in a vehicle without ABS. The HCU compo-
nents are not activated.
During antilock braking fluid pressure is modu-
lated according to wheel speed, degree of slip and
rate of deceleration. A sensor at each wheel converts
wheel speed into electrical signals. These signals are
transmitted to the CAB for processing and determi-
nation of wheel slip and deceleration rate.
The ABS system has three fluid pressure control
channels. The front brakes are controlled separately
and the rear brakes in tandem. A speed sensor input
signal indicating a high slip condition activates the
CAB antilock program. Two solenoid valves are used
in each antilock control channel. The valves are all
located within the HCU valve body and work in pairs
to either increase, hold, or decrease apply pressure as
needed in the individual control channels. The sole-
noid valves are not static during antilock braking.
They are cycled continuously to modulate pressure.
Solenoid cycle time in antilock mode can be mea-
sured in milliseconds.
ELECTRONIC BRAKE DISTRIBUTION
Upon entry into EBD the inlet valve for the rear
brake circuit is switched on so that the fluid supply
from the master cylinder is shut off. In order to
decrease the rear brake pressure the outlet valve for
5 - 32 BRAKES - ABSKJ

the rear brake circuit is pulsed. This allows fluid to
enter the low pressure accumulator (LPA) in the
HCU resulting in a drop in fluid pressure to the rear
brakes. In order to increase the rear brake pressure
the outlet valve is switched off and the inlet valve is
pulsed. This increases the pressure to the rear
brakes. This will continue until the required slip dif-
ference is obtained. At the end of EBD braking (no
brake application) the fluid in the LPA drains back to
the master cylinder by switching on the outlet valve
and draining through the inlet valve check valve. At
the same time the inlet valve is switched on to pre-
vent a hydraulic short circiut in case of another
brake application.The EBD will remain functional
during many ABS fault modes. If the red and amber
warning lamps are illuminated the EBD may have a
fault.
DIAGNOSIS AND TESTING - ANTILOCK
BRAKING SYSTEM
The ABS brake system performs several self-tests
every time the ignition switch is turned on and the
vehicle is driven. The CAB monitors the systems
input and output circuits to verify the system is oper-
ating correctly. If the on board diagnostic system
senses that a circuit is malfunctioning the system
will set a trouble code in its memory.
NOTE: An audible noise may be heard during the
self-test. This noise should be considered normal.NOTE: The MDS or DRB III scan tool is used to
diagnose the ABS system. For additional informa-
tion refer to the Electrical, Electronic Control Mod-
ules section. For test procedures refer to the
Chassis Diagnostic Manual.
STANDARD PROCEDURE - ABS BRAKE
BLEEDING
ABS system bleeding requires conventional bleed-
ing methods plus use of the DRB scan tool. The pro-
cedure involves performing a base brake bleeding,
followed by use of the scan tool to cycle and bleed the
HCU pump and solenoids. A second base brake bleed-
ing procedure is then required to remove any air
remaining in the system.
(1) Perform base brake bleeding,(Refer to 5 -
BRAKES - STANDARD PROCEDURE) OR (Refer to
5 - BRAKES - STANDARD PROCEDURE).
(2) Connect scan tool to the Data Link Connector.
(3) Select ANTILOCK BRAKES, followed by MIS-
CELLANEOUS, then ABS BRAKES. Follow the
instructions displayed. When scan tool displays TEST
COMPLETE, disconnect scan tool and proceed.
(4) Perform base brake bleeding a second time,(Re-
fer to 5 - BRAKES - STANDARD PROCEDURE) OR
(Refer to 5 - BRAKES - STANDARD PROCEDURE).
(5) Top off master cylinder fluid level and verify
proper brake operation before moving vehicle.
SPECIFICATIONS
TORQUE SPECIFICATIONS
DESCRIPTION N´m Ft. Lbs. In. Lbs.
Hydraulic Control
Unit/Controller Antilock
Brakes Mounting Nuts14.1 Ð 125
Hydraulic Control
Unit/Controller Antilock
Brakes Brake Lines20.3 Ð 180
Controller Antilock Brakes
Mounting Screws1.8 Ð 16
Wheel Speed Sensors
Front Mounting Bolt12 Ð 132
Wheel Speed Sensor
Rear Mounting Bolt9Ð80
KJBRAKES - ABS 5 - 33
BRAKES - ABS (Continued)

REAR WHEEL SPEED SENSOR
REMOVAL
(1) Raise vehicle on hoist.
(2) Disconnect the sensor wire harness.
(3) Remove mounting stud from the sensor (Fig. 2).
(4) Remove sensor.
INSTALLATION
(1) Connect harness to sensor.Be sure seal is
securely in place between sensor and wiring
connector.
(2) Install O-ring on sensor (if removed).
(3) Insert sensor in differential housing.
(4) Install the sensor mounting stud and tighten to
9 N´m (80 in. lbs.).
(5) Install the sensor electical connector.
(6) Lower vehicle.
HCU (HYDRAULIC CONTROL
UNIT)
DESCRIPTION
The HCU consists of a valve body, pump motor,
and wire harness.
OPERATION
Accumulators in the valve body store extra fluid
released to the system for ABS mode operation. The
pump provides the fluid volume needed and is oper-
ated by a DC type motor. The motor is controlled by
the CAB.The valves modulate brake pressure during
antilock braking and are controlled by the CAB.
The HCU provides three channel pressure control
to the front and rear brakes. One channel controls
the rear wheel brakes in tandem. The two remaining
channels control the front wheel brakes individually.
During antilock braking, the solenoid valves are
opened and closed as needed. The valves are not
static. They are cycled rapidly and continuously to
modulate pressure and control wheel slip and decel-
eration.
During normal braking, the HCU solenoid valves
and pump are not activated. The master cylinder and
power booster operate the same as a vehicle without
an ABS brake system.
During antilock braking, solenoid valve pressure
modulation occurs in three stages, pressure increase,
pressure hold, and pressure decrease. The valves are
all contained in the valve body portion of the HCU.
PRESSURE DECREASE
The outlet valve is opened and the inlet valve is
closed during the pressure decrease cycle.
A pressure decrease cycle is initiated when speed
sensor signals indicate high wheel slip at one or
more wheels. At this point, the CAB closes the inlet
then opens the outlet valve, which also opens the
return circuit to the accumulators. Fluid pressure is
allowed to bleed off (decrease) as needed to prevent
wheel lock.
Once the period of high wheel slip has ended, the
CAB closes the outlet valve and begins a pressure
increase or hold cycle as needed.
PRESSURE HOLD
Both solenoid valves are closed in the pressure
hold cycle. Fluid apply pressure in the control chan-
nel is maintained at a constant rate. The CAB main-
tains the hold cycle until sensor inputs indicate a
pressure change is necessary.
PRESSURE INCREASE
The inlet valve is open and the outlet valve is
closed during the pressure increase cycle. The pres-
sure increase cycle is used to counteract unequal
wheel speeds. This cycle controls re-application of
fluid apply pressure due to changing road surfaces or
wheel speed.
Fig. 2 REAR WHEEL SPEED SENSOR
1 - DIFFERENTIAL HOUSING
2 - MOUNTING BOLT
3 - WHEEL SPEED SENSOR
KJBRAKES - ABS 5 - 35

REMOVAL
(1) Install prop rod on the brake pedal to keep
pressure on the brake system.
(2) Remove negative battery cable from the bat-
tery.
(3) Pull up on the CAB harness connector release
(Fig. 3)and remove connector.
(4) Remove brake lines from the HCU.
(5) Remove HCU/CAB mounting nuts and bolt
(Fig. 4) and remove HCU/CAB.
INSTALLATION
(1) Install HCU/CAB on the mounting studs.
(2) Install mounting nuts and bolt. Tighten to 11.5
N´m (102 in. lbs.).
(3) Install brake lines to the HCU and tighten to
19 N´m (170 in. lbs.).
(4) Install wiring harness connector to the CAB
and push down on the release to secure the connec-
tor.
(5) Install negative battery cable to the battery.
(6) Bleed ABS brake system (Refer to 5 - BRAKES
- STANDARD PROCEDURE).Fig. 3 CAB HARNESS CONNECTOR RELEASE
1 - ABS MODULE
2 - ELECTRICAL CONNECTOR
Fig. 4 HCU/CAB MOUNTING
1 - HCU
2 - CAB
3 - HCU/CAB BRACKET
4 - MOUNTING NUTS AND STUDS
5 - MOTOR
5 - 36 BRAKES - ABSKJ
HCU (HYDRAULIC CONTROL UNIT) (Continued)

BRAKES
TABLE OF CONTENTS
page page
POWER BRAKE BOOSTER
REMOVAL - RHD........................1INSTALLATION - RHD.....................1
POWER BRAKE BOOSTER
REMOVAL - RHD
(1) Remove the air box (Refer to 9 - ENGINE/AIR
INTAKE SYSTEM/AIR CLEANER ELEMENT -
REMOVAL).
(2) Relocate the cruise control servo to gain access
to the booster for removal.
(3) Remove the brake lines from the master cylin-
der.
(4) Remove the master cylinder (Refer to 5 -
BRAKES/HYDRAULIC/MECHANICAL/MASTER
CYLINDER - REMOVAL).
(5) Disconnect vacuum hose from booster check
valve.
(6) Remove knee blocker under the steering colum-
n,(Refer to 23 - BODY/INSTRUMENT PANEL/KNEE
BLOCKER - REMOVAL).
(7) Remove the brake light switch.(Refer to 8 -
ELECTRICAL/LAMPS/LIGHTING - EXTERIOR/
BRAKE LAMP SWITCH - REMOVAL)
(8) Remove retaining clip that secures booster
push rod to brake pedal (Fig. 1).
(9) Remove nuts attaching booster to the dash
panel (Fig. 2).(10) In engine compartment, slide booster studs
out of dash panel, tilt booster upward, and remove
booster from engine compartment.
INSTALLATION - RHD
(1) Align and position booster on the dash panel.
(2) Install booster mounting nuts. Tighten nuts
just enough to hold booster in place.
(3) Slide booster push rod onto the brake pedal.
Then secure push rod to pedal pin with retaining
clip.
NOTE: Lubricate the pedal pin with Mopar multi-
mileage grease before installation.
(4) Tighten booster mounting nuts to 39 N´m (29
ft. lbs.).
(5) Install the brake light switch.
(6) Install the knee blocker,(Refer to 23 - BODY/
INSTRUMENT PANEL/KNEE BLOCKER - INSTAL-
LATION).
(7) If original master cylinder is being installed,
check condition of seal at rear of master cylinder.
Replace seal if cut, or torn.
(8) Clean cylinder mounting surface of brake
booster. Use shop towel wetted with brake cleaner for
Fig. 1 BOOSTER PUSH ROD
1 - BRAKE PEDAL
2 - BOOSTER ROD
Fig. 2 BOOSTER MOUNTING
1 - BRAKE BOOSTER
KJBRAKES 5s - 1

this purpose. Dirt, grease, or similar materials will
prevent proper cylinder seating and could result in
vacuum leak.
(9) Align and install master cylinder on the
booster studs. Install mounting nuts and tighten to
17.5 N´m (155 in. lbs.).
(10) Connect vacuum hose to booster check valve.
(11) Remount the cruise control servo to the origi-
nal location. Tighten bracket mounting nuts to 17.5
N´m (155 in. lbs.).(12) Connect and secure the brake lines to HCU
and master cylinder. Start all brake line fittings by
hand to avoid cross threading.
(13) Connect the wire to fluid reservoir.
(14) Install the air box.
(15) Fill and bleed base brake system,(Refer to 5 -
BRAKES - STANDARD PROCEDURE).
(16) Verify proper brake operation before moving
vehicle.
5s - 2 BRAKESKJ
POWER BRAKE BOOSTER (Continued)

BRAKES
TABLE OF CONTENTS
page page
POWER BRAKE BOOSTER
REMOVAL - RHD........................1INSTALLATION - RHD.....................1
POWER BRAKE BOOSTER
REMOVAL - RHD
(1) Remove the air box (Refer to 9 - ENGINE/AIR
INTAKE SYSTEM/AIR CLEANER ELEMENT -
REMOVAL).
(2) Relocate the cruise control servo to gain access
to the booster for removal.
(3) Remove the brake lines from the master cylin-
der.
(4) Remove the master cylinder (Refer to 5 -
BRAKES/HYDRAULIC/MECHANICAL/MASTER
CYLINDER - REMOVAL).
(5) Disconnect vacuum hose from booster check
valve.
(6) Remove knee blocker under the steering colum-
n,(Refer to 23 - BODY/INSTRUMENT PANEL/KNEE
BLOCKER - REMOVAL).
(7) Remove the brake light switch.(Refer to 8 -
ELECTRICAL/LAMPS/LIGHTING - EXTERIOR/
BRAKE LAMP SWITCH - REMOVAL)
(8) Remove retaining clip that secures booster
push rod to brake pedal (Fig. 1).
(9) Remove nuts attaching booster to the dash
panel (Fig. 2).(10) In engine compartment, slide booster studs
out of dash panel, tilt booster upward, and remove
booster from engine compartment.
INSTALLATION - RHD
(1) Align and position booster on the dash panel.
(2) Install booster mounting nuts. Tighten nuts
just enough to hold booster in place.
(3) Slide booster push rod onto the brake pedal.
Then secure push rod to pedal pin with retaining
clip.
NOTE: Lubricate the pedal pin with Mopar multi-
mileage grease before installation.
(4) Tighten booster mounting nuts to 39 N´m (29
ft. lbs.).
(5) Install the brake light switch.
(6) Install the knee blocker,(Refer to 23 - BODY/
INSTRUMENT PANEL/KNEE BLOCKER - INSTAL-
LATION).
(7) If original master cylinder is being installed,
check condition of seal at rear of master cylinder.
Replace seal if cut, or torn.
(8) Clean cylinder mounting surface of brake
booster. Use shop towel wetted with brake cleaner for
Fig. 1 BOOSTER PUSH ROD
1 - BRAKE PEDAL
2 - BOOSTER ROD
Fig. 2 BOOSTER MOUNTING
1 - BRAKE BOOSTER
KJBRAKES 5s - 1

this purpose. Dirt, grease, or similar materials will
prevent proper cylinder seating and could result in
vacuum leak.
(9) Align and install master cylinder on the
booster studs. Install mounting nuts and tighten to
17.5 N´m (155 in. lbs.).
(10) Connect vacuum hose to booster check valve.
(11) Remount the cruise control servo to the origi-
nal location. Tighten bracket mounting nuts to 17.5
N´m (155 in. lbs.).(12) Connect and secure the brake lines to HCU
and master cylinder. Start all brake line fittings by
hand to avoid cross threading.
(13) Connect the wire to fluid reservoir.
(14) Install the air box.
(15) Fill and bleed base brake system,(Refer to 5 -
BRAKES - STANDARD PROCEDURE).
(16) Verify proper brake operation before moving
vehicle.
5s - 2 BRAKESKJ
POWER BRAKE BOOSTER (Continued)

The cooling system also provides a means of heat-
ing the passenger compartment and cooling the auto-
matic transmission fluid (if equipped). The cooling
system is pressurized and uses a centrifugal water
pump to circulate coolant throughout the system.
OPERATION - HOSE CLAMPS
The spring type hose clamp applies constant ten-
sion on a hose connection. To remove a spring type
hose clamp, only use constant tension clamp pliers
designed to compress the hose clamp.
DIAGNOSIS AND TESTING
DIAGNOSIS AND TESTING - ON-BOARD
DIAGNOSTICS (OBD)
COOLING SYSTEM RELATED DIAGNOSTICS
The powertrain control module (PCM) has been
programmed to monitor certain cooling system com-
ponents:
²If the engine has remained cool for too long a
period, such as with a stuck open thermostat, a Diag-
nostic Trouble Code (DTC) can be set.
²If an open or shorted condition has developed in
the relay circuit controlling the electric radiator fan,
a Diagnostic Trouble Code (DTC) can be set.
If the problem is sensed in a monitored circuit
often enough to indicated an actual problem, a DTC
is stored. The DTC will be stored in the PCM mem-
ory for eventual display to the service technician.
(Refer to 25 - EMISSIONS CONTROL - DESCRIP-
TION).
ACCESSING DIAGNOSTIC TROUBLE CODES
To read DTC's and to obtain cooling system data,
(Refer to 25 - EMISSIONS CONTROL - DESCRIP-
TION).
ERASING TROUBLE CODES
After the problem has been repaired, use the DRB
scan tool to erase a DTC. Refer to the appropriate
Powertrain Diagnostic Procedures service informa-
tion for operation of the DRB scan tool.
DIAGNOSIS AND TESTING - PRELIMINARY
CHECKS
ENGINE COOLING SYSTEM OVERHEATING
Establish what driving conditions caused the com-
plaint. Abnormal loads on the cooling system such as
the following may be the cause:
²PROLONGED IDLE
²VERY HIGH AMBIENT TEMPERATURE
²SLIGHT TAIL WIND AT IDLE
²SLOW TRAFFIC
²TRAFFIC JAMS
²HIGH SPEED
²STEEP GRADES
Driving techniques that avoid overheating are:
²Idle with A/C off when temperature gauge is at
end of normal range.
(1) TRAILER TOWING:
Consult Trailer Towing section of owners manual.
Do not exceed limits.
(2) RECENT SERVICE OR ACCIDENT REPAIR:
Determine if any recent service has been per-
formed on vehicle that may effect cooling system.
This may be:
²Engine adjustments (incorrect timing)
²Slipping engine accessory drive belt(s)
²Brakes (possibly dragging)
²Changed parts. Incorrect water pump, or pump
rotating in wrong direction due to belt not correctly
routed
²Reconditioned radiator or cooling system refill-
ing (possibly under filled or air trapped in system).
NOTE: If investigation reveals none of the previous
items as a cause for an engine overheating com-
plaint, refer to following Cooling System Diagnosis
charts.
These charts are to be used as a quick-reference
only. Refer to the group text for information.
Fig. 2 Spring Clamp Size Location
1 - SPRING CLAMP SIZE LOCATION
KJCOOLING 7 - 3
COOLING (Continued)