air bleeding JEEP GRAND CHEROKEE 2002 WJ / 2.G Workshop Manual

NOTE: The front outer brake shoes are equipped
with a wear indicator. The indicator will produce an
audible noise when it contacts the rotor surface.
BRAKE CHATTER
Brake chatter is usually caused by loose or worn
components, or glazed/burnt lining. Rotors with hard
spots can also contribute to chatter. Additional causes
of chatter are out-of-tolerance rotors, brake lining not
securely attached to the shoes, loose wheel bearings
and contaminated brake lining.
THUMP/CLUNK NOISE
Thumping or clunk noises during braking are fre-
quentlynotcaused by brake components. In many
cases, such noises are caused by loose or damaged
steering, suspension, or engine components.
STANDARD PROCEDURE
STANDARD PROCEDURE - MANUAL BLEEDING
Use Mopar brake fluid, or an equivalent quality
fluid meeting SAE J1703-F and DOT 3 standards
only. Use fresh, clean fluid from a sealed container at
all times.
Do not pump the brake pedal at any time while
bleeding. Air in the system will be compressed into
small bubbles that are distributed throughout the
hydraulic system. This will make additional bleeding
operations necessary.
Do not allow the master cylinder to run out of fluid
during bleed operations. An empty cylinder will allow
additional air to be drawn into the system. Check the
cylinder fluid level frequently and add fluid as
needed.
Bleed only one brake component at a time in the
following sequence:
(1) Fill the master cylinder reservoir with brake
fluid.
(2) If calipers are overhauled, open all caliper
bleed screws. Then close each bleed screw as fluid
starts to drip from it. Top off master cylinder reser-
voir once more before proceeding.
(3) Attach one end of bleed hose to bleed screw
and insert opposite end in glass container partially
filled with brake fluid (Fig. 1). Be sure end of bleed
hose is immersed in fluid.
(4) Open up bleeder, then have a helper press
down the brake pedal. Once the pedal is down close
the bleeder. Repeat bleeding until fluid stream is
clear and free of bubbles. Then move to the next
wheel.
STANDARD PROCEDURE - PRESSURE
BLEEDING
Use Mopar brake fluid, or an equivalent quality
fluid meeting SAE J1703-F and DOT 3 standards
only. Use fresh, clean fluid from a sealed container at
all times.
Do not pump the brake pedal at any time while
bleeding. Air in the system will be compressed into
small bubbles that are distributed throughout the
hydraulic system. This will make additional bleeding
operations necessary.
Do not allow the master cylinder to run out of fluid
during bleed operations. An empty cylinder will allow
additional air to be drawn into the system. Check the
cylinder fluid level frequently and add fluid as
needed.
Bleed only one brake component at a time in the
following sequence:
Follow the manufacturers instructions carefully
when using pressure equipment. Do not exceed the
tank manufacturers pressure recommendations. Gen-
erally, a tank pressure of 51-67 kPa (15-20 psi) is suf-
ficient for bleeding.
Fill the bleeder tank with recommended fluid and
purge air from the tank lines before bleeding.
Do not pressure bleed without a proper master cyl-
inder adapter. The wrong adapter can lead to leak-
age, or drawing air back into the system. Use
adapter provided with the equipment or Adapter
6921.
Fig. 1 Bleed Hose Setup
1 - BLEED HOSE
2 - FLUID CONTAINER PARTIALLY FILLED WITH FLUID
WJBRAKES - BASE 5 - 5
BRAKES - BASE (Continued)

STANDARD PROCEDURE - MASTER CYLINDER
BLEEDING PROCEDURE
A new master cylinder should be bled before instal-
lation on the vehicle. Required bleeding tools include
bleed tubes and a wood dowel to stroke the pistons.
Bleed tubes can be fabricated from brake line.
(1) Mount master cylinder in vise with brass jaws.
(2) Attach bleed tubes to cylinder outlet ports.
Then position each tube end into the bottom of the
reservoir (Fig. 50).
(3) Fill reservoir with fresh brake fluid.
(4) Press cylinder pistons inward with wood dowel.
Then release pistons and allow them to return under
spring pressure. Continue bleeding operations until
air bubbles are no longer visible in fluid.
REMOVAL
(1) Remove the wire connector from the brake fluid
level sensor.
(2) Remove brake lines from master cylinder.
(3) Remove nuts that attach master cylinder to
booster studs (Fig. 51).
(4) Remove master cylinder from booster.
INSTALLATION
NOTE: Bleed new master cylinder on bench before
installation, refer to Service Procedures.
(1) Have an assistant depress the brake pedal
while guiding the master cylinder on the booster rod
and mounting studs.
CAUTION: Do not depress brake pedal too hard and
ensure the booster rod is in the master cylinder pis-
ton or booster/master cylinder damage will occur.(2) Install master cylinder mounting nuts and
tighten nuts to 25 N´m (18 lb. lbs.).
NOTE: Use original or factory replacement nuts only.
(3) Install brake lines and tighten to 16 N´m (144
in. lbs.).
(4) Install fluid level sensor connector.
(5) Fill and bleed brake system.
PEDAL
DESCRIPTION
DESCRIPTION - STANDARD PEDAL
A suspended-type brake pedal is used, the pedal
pivots on a shaft mounted in the pedal support
bracket. The bracket is attached to the dash panel.
The brake pedal assembly and pedal pad are the
only serviceable component.
DESCRIPTION - ADJUSTABLE PEDALS
The Adjustable Pedals System (APS) is designed to
enable the fore and aft repositioning of the brake and
accelerator pedals. This results in improved ergonom-
ics in relation to the steering wheel for taller and
shorter drivers. Being able to adjust the pedal posi-
Fig. 50 Master Cylinder Bleeding
1 - BLEEDING TUBES
2 - RESERVOIR
Fig. 51 Master Cylinder Mounting
1 - MOUNTING NUT
2 - SENSOR CONNECTOR
3 - MOUNTING NUT
4 - BRAKE LINES
WJBRAKES - BASE 5 - 25
MASTER CYLINDER (Continued)

BRAKES - ABS
TABLE OF CONTENTS
page page
BRAKES - ABS
DESCRIPTION.........................41
OPERATION...........................41
DIAGNOSIS AND TESTING - ANTILOCK
BRAKES............................42
STANDARD PROCEDURE - BLEEDING ABS
BRAKE SYSTEM......................42
SPECIFICATIONS
TORQUE CHART......................42
ELECTRIC BRAKE
DESCRIPTION.........................43
OPERATION...........................43
FRONT WHEEL SPEED SENSOR
DESCRIPTION.........................43
OPERATION...........................43
REMOVAL.............................43INSTALLATION.........................43
G-SWITCH
DESCRIPTION.........................44
OPERATION...........................44
REMOVAL.............................44
INSTALLATION.........................44
REAR WHEEL SPEED SENSOR
DESCRIPTION.........................45
OPERATION...........................45
REMOVAL.............................45
INSTALLATION.........................46
HCU (HYDRAULIC CONTROL UNIT)
DESCRIPTION.........................46
OPERATION...........................46
REMOVAL.............................47
INSTALLATION.........................47
BRAKES - ABS
DESCRIPTION
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 hydraulic system is a three channel design.
The front brakes are controlled individually and the
rear brakes in tandem.
The ABS electrical system is separate from other
vehicle electrical circuits. A separate controller oper-
ates the system.
OPERATION
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 30kph (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.
ANTILOCK BRAKING
The antilock system prevents lockup during high
slip conditions by modulating fluid apply pressure to
the wheel brake units.
Brake fluid apply pressure is modulated according
to wheel speed, degree of slip and rate of decelera-
tion. A sensor at each wheel converts wheel speed
into electrical signals. These signals are transmitted
to the CAB for processing and determination 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 con-
trol 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 solenoid valves are not static during antilock
braking. They are cycled continuously to modulate
pressure. Solenoid cycle time in antilock mode can be
measured in milliseconds.
WJBRAKES - ABS 5 - 41

DIAGNOSIS AND TESTING - ANTILOCK
BRAKES
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 section. For test proce-
dures refer to the Chassis Diagnostic Manual.
STANDARD PROCEDURE - BLEEDING ABS
BRAKE SYSTEM
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.
(Refer to 5 - BRAKES - STANDARD PROCEDURE)
OR (Refer to 5 - BRAKES - STANDARD PROCE-
DURE).
(5) Top off master cylinder fluid level and verify
proper brake operation before moving vehicle.
SPECIFICATIONS
TORQUE CHART
TORQUE SPECIFICATIONS
DESCRIPTION N´m Ft. Lbs. In. Lbs.
G-Sensor Bolt 5.6 Ð 50
Hydraulic Control Unit/Controller
Antilock Brakes
Mounting Bolts12 9 125
Hydraulic Control Unit/Controller
Antilock Brakes
Brake Lines16 Ð 144
Hydraulic Control Unit/Controller
Antilock Brakes
CAB Screws1.8 Ð 16
Wheel Speed Sensors
Front Sensor Bolt12-14 106-124 Ð
Wheel Speed Sensors
Rear Sensor Bolt12-14 106-124 Ð
5 - 42 BRAKES - ABSWJ
BRAKES - ABS (Continued)

FUEL DELIVERY
DESCRIPTION
The fuel delivery system consists of:
²the fuel pump module containing the electric
fuel pump, fuel gauge sending unit (fuel level sensor)
and a separate fuel filter located at bottom of pump
module
²a separate combination fuel filter/fuel pressure
regulator
²fuel tubes/lines/hoses
²quick-connect fittings
²fuel injector rail
²fuel injectors
²fuel tank
²fuel tank filler/vent tube assembly
²fuel tank filler tube cap
²accelerator pedal
²throttle cable
OPERATION
The fuel tank assembly consists of: the fuel tank,
fuel tank shield, fuel tank straps, fuel pump module
assembly, fuel pump module locknut/gasket, and fuel
tank check valve (refer to Emission Control System
for fuel tank check valve information).
A fuel filler/vent tube assembly using a pressure/
vacuum, 1/4 turn fuel filler cap is used. The fuel
filler tube contains a flap door located below the fuel
fill cap.
Also to be considered part of the fuel system is the
evaporation control system. This is designed to
reduce the emission of fuel vapors into the atmo-
sphere. The description and function of the Evapora-
tive Control System is found in Emission Control
Systems.
Both fuel filters (at bottom of fuel pump module
and within fuel pressure regulator) are designed for
extended service. They do not require normal sched-
uled maintenance. Filters should only be replaced if
a diagnostic procedure indicates to do so.
DIAGNOSIS AND TESTING
FUEL PRESSURE LEAK DOWN TEST
Use this test in conjunction with the Fuel Pump
Pressure Test and Fuel Pump Capacity Test.
Check Valve Operation:The electric fuel pump
outlet contains a one-way check valve to prevent fuel
flow back into the tank and to maintain fuel supply
line pressure (engine warm) when pump is not oper-
ational. It is also used to keep the fuel supply line
full of gasoline when pump is not operational. After
the vehicle has cooled down, fuel pressure may drop
to 0 psi (cold fluid contracts), but liquid gasoline willremain in fuel supply line between the check valve
and fuel injectors.Fuel pressure that has
dropped to 0 psi on a cooled down vehicle
(engine off) is a normal condition.When the elec-
tric fuel pump is activated, fuel pressure should
immediately(1±2 seconds) rise to specification.
Abnormally long periods of cranking to restart a
hotengine that has been shut down for a short
period of time may be caused by:
²Fuel pressure bleeding past a fuel injector(s).
²Fuel pressure bleeding past the check valve in
the fuel pump module.
²A defective fuel filter/pressure regulator.
Two #6539, 5/16º, Fuel Line Pressure Test Adapter
Hose Tools are required for the following tests.
(1) Release fuel system pressure. Refer to Fuel
Pressure Release Procedure.
(2) Raise vehicle.
Fuel Line Identification:The fuel filter/pressure
regulator is located in front of the fuel tank and
above the rear axle. It is transversely mounted to a
chassis crossmember (left-to-right). The filter/regula-
tor is equipped with 3 fuel line fittings (2 at one end
and 1 at the other end). The single fitting facing the
left side of the vehicle is the supply line to the fuel
rail (Fig. 1) . The 2 fittings facing the right side of
the vehicle are connected to the fuel tank. Of these 2
fittings, the fitting towards thefrontis used for fuel
return to the fuel tank. The fitting towards therear
is a pressure line. Thisrearfitting must be discon-
nected for the following step.
(3) See previous step. Disconnect fuel pressure line
atrearof filter/regulator. This is a 5/169quick-con-
nect fitting (Fig. 1) . Refer to Quick-Connect Fittings
for procedures.
(4) Obtain correct Fuel Line Pressure Test Adapter
Hose Tool # 6539 for 5/16º fuel lines. Connect one
end of this Special Tool into the disconnected fuel
pressure line. Connect the other end of the Tool into
fitting on filter/regulator.
(5) Lower vehicle.
(6) Disconnect the fuel inlet line at fuel rail. Refer
to Quick-Connect Fittings for procedures. On some
engines, air cleaner housing removal may be neces-
sary before fuel line disconnection.
(7) Obtain a second Fuel Line Pressure Test
Adapter Hose Tool # 6539 for 5/16º fuel lines. Con-
nect this tool between disconnected fuel line and fuel
rail (Fig. 2) .
(8) Connect the 0-414 kPa (0-60 psi) fuel pressure
test gauge (from Gauge Set 5069) to the test port on
the appropriate Adaptor Tool.NOTE: The DRB III
Scan Tool along with the PEP module, the 500
psi pressure transducer, and the transducer-to-
test port adapter may also be used in place of
the fuel pressure gauge.
14 - 2 FUEL DELIVERYWJ

FRONT SERVO
DESCRIPTION
The kickdown servo (Fig. 98) consists of a two-land
piston with an inner piston, a piston rod and guide,
and a return spring. The dual-land piston uses seal
rings on its outer diameters and an O-ring for the
inner piston.
OPERATION
The application of the piston is accomplished by
applying pressure between the two lands of the pis-
ton. The pressure acts against the larger lower land
to push the piston downward, allowing the piston rod
to extend though its guide against the apply lever.
Release of the servo at the 2-3 upshift is accom-
plished by a combination of spring and line pressure,
acting on the bottom of the larger land of the piston.
The small piston is used to cushion the application of
the band by bleeding oil through a small orifice in
the larger piston. The release timing of the kickdown
servo is very important to obtain a smooth but firm
shift. The release has to be very quick, just as the
front clutch application is taking place. Otherwise,
engine runaway or a shift hesitation will occur. To
accomplish this, the band retains its holding capacity
until the front clutch is applied, giving a small
amount of overlap between them.
DISASSEMBLY
(1) Remove seal ring from rod guide (Fig. 99).(2) Remove small snap-ring from servo piston rod.
Then remove piston rod, spring and washer from pis-
ton.
(3) Remove and discard servo component o-ring
and seal rings.
CLEANING
Clean the servo piston components (Fig. 100) with
solvent and dry them with compressed air.
INSPECTION
Inspect the servo components (Fig. 101). Replace
the springs if collapsed, distorted or broken. Replace
the guide, rod and piston if cracked, bent, or worn.
Discard the servo snap-ring if distorted or warped.
Check the servo piston bore for wear. If the bore is
severely scored, or damaged, it will be necessary to
replace the case.
Replace any servo component if doubt exists about
condition. Do not reuse suspect parts.
ASSEMBLY
Clean and inspect front servo components.
(1) Lubricate new o-ring and seal rings with petro-
leum jelly and install them on piston, guide and rod.
(2) Install rod in piston. Install spring and washer
on rod. Compress spring and install snap-ring (Fig.
102).
Fig. 98 Front Servo
1 - VENT
2 -PISTON ROD
3 - PISTON
4 - SPRING
5 - RELEASE PRESSURE
6 - APPLY PRESSURE
Fig. 99 Front Servo
1 - PISTON RINGS
2 - O-RING
3 - SNAP-RING
4 - SEAL RING
5 - PISTON ROD GUIDE
6 - SNAP-RING
7 - SERVO SPRING
8 - PISTON ROD
9 - SERVO PISTON
WJAUTOMATIC TRANSMISSION - 42RE 21 - 77

INSTALLATION
INSTALLATION - RECIRCULATION DOOR
VACUUM ACTUATOR
(1) Install the recirculation door vacuum actuator
on the HVAC housing and tighten the mounting
screws to 2.2 N´m (20 in. lbs.).
(2) Engage the recirculation door actuating rod
with the recirculation door lever.
(3) Engage the recirculation door pivot connection
with the door pivot pin.
(4) Plug in the vacuum harness connector to the
recirculation door vacuum actuator.
(5) Install the instrument panel in the vehicle.
Refer to Instrument Panel System for the procedures.
INSTALLATION - RECIRCULATION DOOR
ELECTRIC ACTUATOR
(1) Install the recirculation door actuator on the
recirculation door housing and tighten the mounting
screws to 2.2 N´m (20 in. lbs.).
(2) Install the recirculation door housing on the
HVAC unit and tighten the mounting screws to 2.2
N´m (20 in. lbs.).
(3) Plug in the wire harness connector to the recir-
culation door actuator.
(4) Install the instrument panel in the vehicle.
Refer to Instrument Panel System for the procedures.
VACUUM CHECK VALVE
DESCRIPTION
Two vacuum check valves (non AZC only) are
installed on the vacuum supply system. One is on the
accessory vacuum supply line in the engine compart-
ment, near the vacuum tap on the engine intake
manifold. A second vacuum check valve is located on
the bottom of the HVAC unit behind the passenger
front floor duct on the black vacuum line. The vac-
uum check valves are designed to allow vacuum to
flow in only one direction through the accessory vac-
uum supply circuits.
OPERATION
The use of a vacuum check valve helps to maintain
the system vacuum needed to retain the selected A/C
Heater mode settings. The check valve will prevent
the engine from bleeding down system vacuum
through the intake manifold during extended heavy
engine load (low engine vacuum) operation.
The vacuum check valve cannot be repaired and, if
faulty or damaged, it must be replaced.
REMOVAL
(1) Unplug the HVAC vacuum supply line connec-
tor at the vacuum check valve near the engine intake
manifold vacuum adapter fitting.
(2) Note the orientation of the check valve in the
vacuum supply line for correct installation.
(3) Unplug the vacuum check valve from the vac-
uum supply line fittings.
INSTALLATION
(1) Plug in the vacuum check valve at the vacuum
supply line fittings, noting the orientation of the
check valve in the vacuum supply line for correct
installation.
(2) Plug in the HVAC vacuum supply line connec-
tor at the vacuum check valve near the engine intake
manifold vacuum adapter fitting.
VACUUM RESERVOIR
DESCRIPTION
The vacuum reservoir is mounted in the right front
of the vehicle behind the headlamp mounting module
(Fig. 22). The headlamp mounting module and head-
lamp assembly must be removed from the vehicle to
access the vacuum reservoir for service. Refer to
Lamps/Lighting for the procedures.
OPERATION
Engine vacuum is stored in the vacuum reservoir.
The stored vacuum is used to operate the vacuum-
Fig. 21 RECIRCULATION DOOR HOUSING
1 - RECIRCULATION DOOR HOUSING
2 - ATTACHING SCREWS
24 - 34 CONTROLSWJ
RECIRCULATION DOOR ACTUATOR (Continued)