2002 JEEP GRAND CHEROKEE change time

teen seconds. Below about sixteen kilometers-per-
hour (ten miles-per-hour) the delay times are
doubled, from about one second to about thirty-six
seconds.
AUTOMATIC WIPE MODE
On models equipped with the optional automatic
wiper system, when the control knob on the control
stalk of the right (wiper) multi-function switch is
moved to one of the five Auto sensitivity positions,
the BCM sends an electronic message to the Rain
Sensor Module (RSM) over the Programmable Com-
munications Interface (PCI) data bus network indi-
cating the selected position. The RSM monitors an
area within the wipe pattern of the windshield glass
for the accumulation of moisture. Based upon inter-
nal programming and the selected sensitivity level,
when sufficient moisture has accumulated the RSM
sends the appropriate electronic wipe command mes-
sages to the BCM over the PCI data bus and the
BCM operates the front wiper system accordingly. As
the sensitivity level is set higher, the RSM is more
sensitive to moisture accumulation and will send
wipe commands more frequently. The BCM logic is
also programmed to provide an immediate wipe cycle
each time the control knob on the control stalk of the
right multi-function switch is moved from a non-au-
tomatic wipe position to one of the five Auto sensitiv-
ity positions, and another immediate wipe cycle each
time the control knob is moved from a lower Auto
sensitivity position to a higher Auto sensitivity posi-
tion.
MIST WIPE MODE
When the control stalk of the right (wiper) multi-
function switch is moved to the momentary Mist
position, the BCM energizes the wiper on/off relay for
as long as the Mist switch is held closed, then de-en-
ergizes the relay when the state of the Mist switch
input changes to open. The BCM can operate the
front wiper motor in this mode for only one low speed
cycle at a time, or for an indefinite number of
sequential low speed cycles, depending upon how
long the Mist switch is held closed.
WASH MODE
When the control stalk of the right (wiper) multi-
function switch is moved to the momentary front
Wash position while the control knob is in the Low or
High positions, the circuitry within the switch directs
battery current to the front washer pump/motor unit.
This will cause the front washer pump/motor unit to
be energized for as long as the front Wash switch is
held closed, and to de-energize when the front Wash
switch is released. When the control stalk of the
right (wiper) multi-function switch is moved to the
momentary front Wash position while the controlknob is in one of the Delay interval or Auto sensitiv-
ity positions, the front washer pump/motor operation
is the same. However, the BCM energizes the wiper
on/off relay to override the selected delay interval or
auto sensitivity level and operate the front wiper
motor in a continuous low speed mode for as long as
the front Wash switch is held closed, then de-ener-
gizes the relay and reverts to the selected delay mode
interval or auto sensitivity level several wipe cycles
after the front Wash switch is released. The BCM
detects the front Wash switch state through a hard
wired washer pump motor switch output circuit input
from the right multi-function switch.
WIPE-AFTER-WASH MODE
When the control stalk of the right (wiper) multi-
function switch is moved to the momentary front
Wash position while the control knob is in the Off
position, the BCM detects that switch state through
a hard wired washer pump motor switch output cir-
cuit input from the right multi-function switch. The
BCM responds to this input by energizing the wiper
on/off relay for as long as the Wash switch is held
closed, then de-energizes the relay several wipe
cycles after the front Wash switch is released. The
BCM monitors the changing state of the wiper motor
park switch through a hard wired front wiper park
switch sense circuit input. This input allows the
BCM to count the number of wipe cycles that occur
after the front Wash switch state changes to open,
and to determine the proper interval at which to de-
energize the wiper on/off relay to complete the wipe-
after-wash mode cycle.
DIAGNOSIS AND TESTING - FRONT WIPER &
WASHER SYSTEM
FRONT WIPER SYSTEM
If the front wiper motor operates, but the wipers
do not move on the windshield, replace the faulty
front wiper module. If the wipers operate, but chat-
ter, lift, or do not clear the glass, clean and inspect
the wiper system components as required. (Refer to 8
- ELECTRICAL/FRONT WIPERS/WASHERS -
INSPECTION) and (Refer to 8 - ELECTRICAL/
FRONT WIPERS/WASHERS - CLEANING). Refer to
the appropriate wiring information. The wiring infor-
mation includes wiring diagrams, proper wire and
connector repair procedures, details of wire harness
routing and retention, connector pin-out information
and location views for the various wire harness con-
nectors, splices and grounds.
The hard wired circuits and components of the
front wiper and washer system may be diagnosed
and tested using conventional diagnostic tools and
procedures. However, conventional diagnostic meth-
8R - 6 FRONT WIPERS/WASHERSWJ
FRONT WIPERS/WASHERS (Continued)

formations that grip the wiper blade element. Also
included in this unit is the latching, molded plastic
pivot block that secures the superstructure to the
wiper arm. All of the metal components of the wiper
blade have a satin black finish applied.
²Element- The wiper element or squeegee is the
resilient rubber member of the wiper blade that con-
tacts the glass.
²Flexor- The flexor is a rigid metal component
running along the length of each side of the wiper
element where it is gripped by the claws of the
superstructure.
All Grand Cherokee models have two 52.50 centi-
meter (20.67 inch) long windshield wiper blades with
non-replaceable rubber elements (squeegees). The
wiper blades cannot be adjusted or repaired. If faulty,
worn, or damaged the entire wiper blade unit must
be replaced.
OPERATION
The wiper blades are moved back and forth across
the glass by the wiper arms when the wipers are
being operated. The wiper blade superstructure is
the flexible frame that grips the wiper blade element
and evenly distributes the force of the spring-loaded
wiper arm along the length of the element. The com-
bination of the wiper arm force and the flexibility of
the superstructure makes the element conform to
and maintain proper contact with the glass, even as
the blade is moved over the varied curvature found
across the glass surface. The wiper element flexor
provides the claws of the blade superstructure with a
rigid, yet flexible component on the element which
can be gripped. The rubber element is designed to be
stiff enough to maintain an even cleaning edge as it
is drawn across the glass, but resilient enough to
conform to the glass surface and flip from one clean-
ing edge to the other each time the wiper blade
changes directions.
REMOVAL
NOTE: The notched retainer end of the wiper ele-
ment should always be oriented towards the end of
the wiper blade that is nearest to the wiper pivot.
(1) Lift the front wiper arm to raise the wiper
blade and element off of the glass, until the wiper
arm hinge is in its over-center position.
(2) To remove the wiper blade from the wiper arm,
push the pivot block latch release tab under the tip
of the arm and slide the blade away from the tip
towards the pivot end of the arm far enough to dis-
engage the pivot block from the hook (Fig. 10).
(3) Extract the hook formation on the tip of the
wiper arm from the opening in the wiper blade
superstructure ahead of the wiper blade pivot block/
latch unit.
CAUTION: Do not allow the wiper arm to spring
back against the glass without the wiper blade in
place or the glass may be damaged.
(4) Gently lower the wiper arm tip onto the glass.
INSTALLATION
NOTE: The notched retainer end of the wiper ele-
ment should always be oriented towards the end of
the wiper blade that is nearest to the wiper pivot.
(1) Lift the front wiper arm off of the windshield
glass, until the wiper arm hinge is in its over-center
position.
(2) Position the front wiper blade near the hook
formation on the tip of the arm with the notched
retainer for the wiper element oriented towards the
end of the wiper arm that is nearest to the wiper
pivot.
Fig. 9 Wiper Blade - Typical
1 - RELEASE TAB
Fig. 10 Wiper Blade Remove/Install - Typical
1 - RELEASE TAB
WJFRONT WIPERS/WASHERS 8R - 15
FRONT WIPER BLADE (Continued)

switch mounting housing. Tighten the screws to 2.5
N´m (22 in. lbs.).
(3) Reconnect the instrument panel wire harness
connector for the right multi-function switch to the
switch connector receptacle.
(4) Position the lower tilting steering column
shroud to the underside of the steering column (Fig.
18).
(5) Install and tighten the screw that secures the
lower tilting steering column shroud to the multi-
function switch mounting housing. Tighten the screw
to 1.9 N´m (17 in. lbs.).
(6) Position the upper tilting column shroud over
the steering column with the hazard warning switch
button inserted through the hole in the upper surface
of the shroud. Align the upper tilting steering column
shroud to the lower shroud and snap the two shroud
halves together.
(7) Reconnect the battery negative cable.
WASHER FLUID LEVEL
SWITCH
DESCRIPTION
The washer fluid level switch is a single pole, sin-
gle throw reed-type switch mounted near the front of
the washer reservoir, forward of the two washer
pump/motors (Fig. 20). Only the molded plastic
switch mounting flange and connector receptacle are
visible when the switch is installed in the reservoir.A short nipple formation extends from the inner sur-
face of the switch mounting flange, and a barb on the
nipple near the switch mounting flange is press-fit
into a rubber grommet seal installed in the mounting
hole of the reservoir. A small plastic float pivots on
the end of a bracket that extends from the switch
nipple formation. Within the float is a small magnet,
which actuates the reed switch. The washer fluid
level switch cannot be adjusted or repaired. If faulty
or damaged, the switch must be replaced.
OPERATION
The washer fluid level switch uses a pivoting,
oblong float to monitor the level of the washer fluid
in the washer reservoir. The float contains a small
magnet. When the float pivots, the changing proxim-
ity of its magnetic field will cause the contacts of the
small, stationary reed switch to open or close. When
the fluid level in the washer reservoir is at or above
the float level, the float moves to a vertical position
and the switch contacts open. When the fluid level in
the washer reservoir falls below the pivoting float,
the float moves to a horizontal position and the
switch contacts close. The switch is connected to the
vehicle electrical system through a dedicated take
out and connector of the left headlamp and dash wire
harness. The switch receives a five volt reference sig-
nal from the Body Control Module (BCM) through
the washer fluid switch output circuit. The switch is
grounded at all times through another take out of
the left headlamp and dash wire harness with a sin-
gle eyelet terminal connector that is secured under a
ground screw near the top of the left front fender
inner shield in the engine compartment.
When the switch closes, the BCM senses the volt-
age change on the circuit. The BCM is programmed
to send low washer fluid messages to the Electronic
Vehicle Information Center (EVIC) over the Program-
mable Communications Interface (PCI) data bus. The
EVIC is programmed to respond to this message by
displaying the Washer Fluid Low warning and send-
ing a chime request message back to the BCM over
the PCI data bus. Then the BCM generates an audi-
ble chime tone warning. A resistor within the washer
fluid level switch allows the BCM to monitor and
diagnose this circuit. The BCM will store a Diagnos-
tic Trouble Code (DTC) for any fault that it detects.
For retrieval of this fault information and further
diagnosis of the washer fluid level switch, the BCM,
the EVIC, the PCI data bus, the BCM message out-
puts to the EVIC that control the Low Washer Fluid
indicator, or the EVIC message outputs to the BCM
that control chime service, a DRBIIItscan tool and
the appropriate diagnostic information are required.
Fig. 20 Washer Fluid Level Switch (Viewed from
Bottom of Reservoir)
1 - REAR WASHER PUMP/MOTOR
2 - FRONT WASHER PUMP/MOTOR
3 - WASHER FLUID LEVEL SWITCH
WJFRONT WIPERS/WASHERS 8R - 25
RIGHT MULTI-FUNCTION SWITCH (Continued)

(1) The rear wiper arm must be indexed to the
motor output shaft with the rear wiper motor in the
park position to be properly installed. Place the
wiper arm onto the liftgate with the wiper arm sup-
port positioned on the park ramp and the pivot hole
on the end of the arm positioned over the rear wiper
motor output shaft.
(2) Position the ridge of the wiper arm support on
the liftgate park ramp in the Installation Position
(Fig. 10).
(3) With the wiper arm in the Installation Posi-
tion, push the pivot hole on the end of the wiper arm
down over the rear wiper motor output shaft.
(4) Install and tighten the nut that secures the
rear wiper arm to the rear wiper motor output shaft.
Tighten the nut to 18 N´m (160 in. lbs.).
(5) Close the rear wiper arm pivot cover.(6) Lift the rear wiper arm support away from the
park ramp, then place the wiper arm support in the
park ramp in the Park Position (Fig. 10).
REAR WIPER BLADE
DESCRIPTION
The rear wiper blade is secured by an integral
latching pivot block to the hook formation on the tip
of the rear wiper arm, and rests off the glass near
the base of the liftgate glass opening when the wiper
is not in operation. The wiper blade consists of the
following components:
²Superstructure- The superstructure includes
a stamped steel bridge and plastic links with claw
formations that grip the wiper blade element. Also
included in this unit is the latching, molded plastic
pivot block that secures the superstructure to the
wiper arm. All of the metal components of the wiper
blade have a satin black finish applied.
²Element- The wiper element or squeegee is the
resilient rubber member of the wiper blade that con-
tacts the glass.
²Flexor- The flexor is a rigid metal component
running along the length of each side of the wiper
element where it is gripped by the claws of the
superstructure.
All Grand Cherokee models have a single 31.00
centimeter (12.20 inch) rear wiper blade with a non-
replaceable rubber element (squeegee). The wiper
blade cannot be adjusted or repaired. If faulty, worn,
or damaged the entire wiper blade unit must be
replaced.
OPERATION
The wiper blade is moved back and forth across the
glass by the wiper arm when the wiper system is in
operation. The wiper blade superstructure is the flex-
ible frame that grips the wiper blade element and
evenly distributes the force of the spring-loaded
wiper arm along the length of the element. The com-
bination of the wiper arm force and the flexibility of
the superstructure makes the element conform to
and maintain proper contact with the glass, even as
the blade is moved over the varied curvature found
across the glass surface. The wiper element flexor
provides the claws of the blade superstructure with a
rigid, yet flexible component on the element which
can be gripped. The rubber element is designed to be
stiff enough to maintain an even cleaning edge as it
is drawn across the glass, but resilient enough to
conform to the glass surface and flip from one clean-
ing edge to the other each time the wiper blade
changes directions.
Fig. 10 Rear Wiper Arm Installation
1 - LIFTGATE
2 - PARK RAMP
3 - REAR WIPER ARM
4 - INSTALLATION POSITION
5 - REAR WIPER ARM AND BLADE
6 - PARK POSITION
7 - PARK RAMP
8 - LIFTGATE
WJREAR WIPERS/WASHERS 8R - 43
REAR WIPER ARM (Continued)

8W-02 COMPONENT INDEX
Component Page
A/C Compressor Clutch................. 8W-42
A/C Pressure Transducer................ 8W-42
Accelerator Pedal Position Sensor......... 8W-30
Accessory Delay Relay.................. 8W-64
Adjustable Pedals..................... 8W-30
Airbags............................. 8W-43
Ambient Temperature Sensor............ 8W-45
Antennas............................ 8W-47
Ash Receiver Lamp.................... 8W-44
Auto Shut Down Relay................. 8W-30
Automatic Day/Night Mirror............. 8W-49
Automatic Headlamp Light Sensor/VTSS
LED.............................. 8W-39
Automatic Zone Control Module.......... 8W-42
Back-Up Lamp Relay................... 8W-51
Battery Temperature Sensor............. 8W-30
Battery............................. 8W-20
Blend Door Motor/Actuator.............. 8W-42
Blower Motor......................... 8W-42
Body Control Module................... 8W-45
Boost Pressure Sensor.................. 8W-30
Brake Lamp Switch.................... 8W-33
Camshaft Position Sensor............... 8W-30
Capacitors........................... 8W-30
Cargo Lamp.......................... 8W-44
Center High Mounted Stop Lamp......... 8W-51
Cigar Lighter......................... 8W-41
Circuit Breakers...................... 8W-12
Clockspring.................. 8W-33, 41, 43, 47
Coil On Plugs......................... 8W-30
Coil Rail............................. 8W-30
Combination Flasher................... 8W-52
Compact Disc Changer.................. 8W-47
Controller Antilock Brake............... 8W-35
Coolant Level Sensor................... 8W-45
Courtesy Lamps....................... 8W-44
Crankcase Heater..................... 8W-30
Crankshaft Position Sensor.............. 8W-30
Cylinder Lock Switches................. 8W-61
Data Link Connector................... 8W-18
Diagnostic Junction Port................ 8W-18
EGR Solenoid......................... 8W-30
Electric Brake........................ 8W-54
Electronic Speed Control Servo........... 8W-33
Engine Control Module................. 8W-30
Engine Coolant Temperature Sensor...... 8W-30
Engine Oil Pressure Sensor.............. 8W-30
Engine Starter Motor................... 8W-21
EVAP/Purge Solenoid................... 8W-30
Fog Lamps........................ 8W-50, 51
Fuel Injectors......................... 8W-30
Fuel Pressure Sensor................... 8W-30Component Page
Fuel Pressure Solenoid................. 8W-30
Fuel Pump........................... 8W-30
Fuel Tank Module..................... 8W-30
Fuses............................ 8W-10, 12
Fusible Link....................... 8W-10, 20
Grounds............................. 8W-15
Generator......................... 8W-20, 30
Glove Box Lamp...................... 8W-44
Glow Plugs........................... 8W-30
Headlamp Leveling Motor............... 8W-50
Heated Seats......................... 8W-63
High Beam Headlamps................. 8W-50
Hood Ajar Switch...................... 8W-39
Horns............................... 8W-41
Hydraulic Cooling Module............ 8W-30, 42
Idle Air Control Motor.................. 8W-30
Ignition Switch....................... 8W-10
Impact Sensors....................... 8W-43
Input Speed Sensor.................... 8W-31
Instrument Cluster.................... 8W-40
Intake Air Temperature Sensor........... 8W-30
Intake Port Swirl Actuator.............. 8W-30
Intrusion Transceiver Module............ 8W-49
Junction Block........................ 8W-12
Knock Sensor......................... 8W-30
Lamp Assemblies................... 8W-51, 52
Leak Detection Pump.................. 8W-30
License Lamps........................ 8W-51
Liftgate............................. 8W-61
Line Pressure Sensor................... 8W-31
Low Beam Headlamps.................. 8W-50
Low Beam Relay...................... 8W-50
Low Beam/Daytime Running Lamp Relay . . . 8W-50
Lumbar Motor........................ 8W-63
Lumbar Switch....................... 8W-63
Manifold Absolute Pressure Sensor........ 8W-30
Manual Temperature Control............. 8W-42
Mass Air Flow Sensor.................. 8W-30
Memory Set Switch................. 8W-62, 63
Mode Door Motor/Actuator............... 8W-42
Multi-Function Switch............... 8W-50, 53
Output Speed Sensor................... 8W-31
Overhead Map/Courtesy Lamp........... 8W-44
Oxygen Sensors....................... 8W-30
Park Brake Switch..................... 8W-40
Park Lamp........................... 8W-50
Park/Neutral Position Switch............ 8W-31
Park/Turn Signal Lamps................ 8W-50
Power Amplifier....................... 8W-47
Power Connector...................... 8W-41
Power Distribution Center............... 8W-10
Power Mirrors........................ 8W-62
WJ8W-02 COMPONENT INDEX 8W - 02 - 1

the same time, the power distribution system was
designed to provide ready access to these electrical
distribution points for the vehicle technician to use
when conducting diagnosis and repair of faulty cir-
cuits. The power distribution system can also prove
useful for the sourcing of additional electrical circuits
that may be required to provide the electrical current
needed to operate accessories that the vehicle owner
may choose to have installed in the aftermarket.
NOTE: DO NOT ATTEMPT TO SWAP POWER DIS-
TRIBUTION CENTERS FROM ONE VEHICLE TO
ANOTHER. MOST OF THESE ASSEMBLIES ARE
VEHICLE FEATURE SPECIFIC AND THEREFORE
NOT INTERCHANGEABLE. ALWAYS USE THE COR-
RECT PART NUMBERED ASSEMBLY WHEN DIAG-
NOSING OR REPLACING A POWER DISTRIBUTION
CENTER.
SPECIAL TOOLS
POWER DISTRIBUTION SYSTEMS
CIGAR LIGHTER OUTLET
DESCRIPTION
A cigar lighter outlet is standard equipment on
this model. On models equipped with the optional
Smoker's Package, the cigar lighter knob and heating
element are included. On models without the Smok-
er's Package, the cigar lighter outlet is equipped with
a snap fit plastic cap and is treated as an extra
accessory power outlet. The cigar lighter outlet is
installed in the instrument panel center lower bezel,
which is located near the bottom of the instrument
panel center stack area, below the heater and air
conditioner controls. The cigar lighter outlet is
secured by a snap fit within the center lower bezel.The cigar lighter outlet, plastic cap and the knob
and heating element unit are available for service
replacement. These components cannot be repaired
and, if faulty or damaged, they must be replaced.
OPERATION
The cigar lighter consists of two major components:
a knob and heating element unit, and the cigar
lighter base or outlet shell. The receptacle shell is
connected to ground, and an insulated contact in the
bottom of the shell is connected to battery current.
The cigar lighter receives battery voltage from a fuse
in the junction block when the ignition switch is in
the Accessory or On positions.
The cigar lighter knob and heating element are
encased within a spring-loaded housing, which also
features a sliding protective heat shield. When the
knob and heating element are inserted in the outlet
shell, the heating element resistor coil is grounded
through its housing to the outlet shell. If the cigar
lighter knob is pushed inward, the heat shield slides
up toward the knob exposing the heating element,
and the heating element extends from the housing
toward the insulated contact in the bottom of the
outlet shell.
Two small spring-clip retainers are located on
either side of the insulated contact inside the bottom
of the outlet shell. These clips engage and hold the
heating element against the insulated contact long
enough for the resistor coil to heat up. When the
heating element is engaged with the contact, battery
current can flow through the resistor coil to ground,
causing the resistor coil to heat.
When the resistor coil becomes sufficiently heated,
excess heat radiates from the heating element caus-
ing the spring-clips to expand. Once the spring-clips
expand far enough to release the heating element,
the spring-loaded housing forces the knob and heat-
ing element to pop back outward to their relaxed
position. When the cigar lighter knob and element
are pulled out of the outlet shell, the protective heat
shield slides downward on the housing so that the
heating element is recessed and shielded around its
circumference for safety.
DIAGNOSIS AND TESTING - CIGAR LIGHTER
OUTLET
For complete circuit diagrams, refer toHorn/Ci-
gar Lighter/Power Outletin Wiring Diagrams.
(1) Check the fused B(+) fuse in the junction block.
If OK, go to Step 2. If not OK, repair the shorted cir-
cuit or component as required and replace the faulty
fuse.
(2) Turn the ignition switch to the On position.
Check for battery voltage at the fused B(+) fuse in
Terminal Pick Kit 6680
8W - 97 - 2 8W-97 POWER DISTRIBUTIONWJ
POWER DISTRIBUTION (Continued)

It is not necessary to charge the tappets with
engine oil. They will charge themselves within a very
short period of engine operation.
(1) Dip each tappet in MopartEngine Oil Supple-
ment, or equivalent.
(2) Use Hydraulic Valve Tappet Removal/Installa-
tion Tool to install each tappet in the same bore from
where it was originally removed.
(3) Install the cylinder head (Refer to 9 - ENGINE/
CYLINDER HEAD - INSTALLATION).
(4) Install the push rods in their original locations.
(5) Install the rocker arms and bridge and pivot
assemblies at their original locations. Loosely install
the capscrews at each bridge.
(6) Tighten the capscrews alternately, one turn at
a time, to avoid damaging the bridges. Tighten the
capscrews to 28 N´m (21 ft. lbs.) torque.
(7)
Pour the remaining MopartEngine Oil Supple-
ment, or equivalent over the entire valve actuating
assembly. The MopartEngine Oil Supplement, or equiv-
alent must remain with the engine oil for at least 1 609
km (1,000 miles). The oil supplement need not be
drained until the next scheduled oil change.
(8) Install the cylinder head cover (Refer to 9 -
ENGINE/CYLINDER HEAD/CYLINDER HEAD
COVER(S) - INSTALLATION).
PISTON & CONNECTING ROD
DESCRIPTION
The pistons (Fig. 55) are made of a high strength
aluminum alloy, the piston skirts are coated with a
solid lubricant (Molykote) to reduce friction and pro-
vide scuff resistance. The connecting rods are made
of cast iron.
STANDARD PROCEDURE - PISTON FITTING
(1) To correctly select the proper size piston, a cyl-
inder bore gauge, capable of reading in 0.003 mm
(.0001 in.) INCREMENTS is required. If a bore
gauge is not available, do not use an inside microme-
ter.
(2) Measure the inside diameter of the cylinder
bore at a point 49.5 mm (1-15/16 inches) below top of
bore. Start perpendicular (across or at 90 degrees) to
the axis of the crankshaft at point A and then take
an additional bore reading 90 degrees to that at point
B (Fig. 57).
(3) The coated pistons will be serviced with the
piston pin and connecting rod pre-assembled.The
coated piston connecting rod assembly can be
used to service previous built engines and
MUST be replaced as complete sets.Tin coated
pistons should not be used as replacements for coated
pistons.
(4) The coating material is applied to the piston
after the final piston machining process. Measuring
the outside diameter of a coated piston will not pro-
vide accurate results (Fig. 56). Therefore measuring
the inside diameter of the cylinder bore with a dial
Bore Gauge isMANDATORY. To correctly select the
proper size piston, a cylinder bore gauge capable of
reading in 0.003 mm (.0001 in.) increments is
required.
(5) Piston installation into the cylinder bore
requires slightly more pressure than that required
for non-coated pistons. The bonded coating on the
piston will give the appearance of a line-to-line fit
with the cylinder bore.
Fig. 55 Piston and Connecting Rod Assembly
Fig. 56 Moly Coated Piston
1 - MOLY COATED
2 - MOLY COATED
9 - 44 ENGINE - 4.0LWJ
HYDRAULIC LIFTERS (Continued)

(5) If the leak is not detected, very slowly turn the
crankshaft and watch for leakage. If a leak is
detected between the crankshaft and seal while
slowly turning the crankshaft, it is possible the
crankshaft seal surface is damaged. The seal area on
the crankshaft could have minor nicks or scratches
that can be polished out with emery cloth.
CAUTION: Use extreme caution when crankshaft
polishing is necessary to remove minor nicks and
scratches. The crankshaft seal flange is especially
machined to complement the function of the rear oil
seal.
(6) For bubbles that remain steady with shaft
rotation, no further inspection can be done until dis-
assembled.
OIL
STANDARD PROCEDURE - ENGINE OIL
SERVICE
ENGINE OIL CHANGE
Change engine oil at mileage and time intervals
described in Maintenance Schedules.
Run engine until achieving normal operating tem-
perature.
(1) Position the vehicle on a level surface and turn
engine off.
(2) Hoist and support vehicle on safety stands.
(3) Remove oil fill cap.
(4) Place a suitable drain pan under crankcase
drain.
(5) Remove drain plug from crankcase and allow
oil to drain into pan. Inspect drain plug threads for
stretching or other damage. Replace drain plug if
damaged.
(6) Install drain plug in crankcase.
(7) Replace engine oil filter. (Refer to 9 - ENGINE/
LUBRICATION/OIL FILTER - REMOVAL).
(8) Lower vehicle and fill crankcase with specified
type of engine oil (Refer to LUBRICATION & MAIN-
TENANCE/FLUID TYPES - DESCRIPTION) and
amount of engine oil (Refer to LUBRICATION &
MAINTENANCE - SPECIFICATIONS).
(9) Install oil fill cap.
(10) Start engine and inspect for leaks.
(11) Stop engine and inspect oil level. Refer to
CRANKCASE OIL LEVEL INSPECTION .
USED ENGINE OIL DISPOSAL
Care should be exercised when disposing used
engine oil after it has been drained from a vehicle
engine.
CRANKCASE OIL LEVEL INSPECTION
CAUTION: Do not overfill crankcase with engine oil,
oil foaming and oil pressure loss can result.
The engine oil level indicator (Dipstick) is located
at the right rear of the 4.0L engine. Inspect engine
oil level approximately every 800 kilometers (500
miles). Unless the engine has exhibited loss of oil
pressure, run the engine for about five minutes
before checking oil level. Checking engine oil level on
a cold engine is not accurate.
To ensure proper lubrication of an engine, the
engine oil must be maintained at an acceptable level.
The acceptable levels are indicated between the ADD
and SAFE marks on the engine oil dipstick (Fig. 74).
(1) Position vehicle on level surface.
(2) With engine OFF, allow approximately ten min-
utes for oil to settle to bottom of crankcase, remove
engine oil dipstick.
(3) Wipe dipstick clean.
(4) Install dipstick and verify it is seated in the
tube.
(5) Remove dipstick, with handle held above the
tip, take oil level reading (Fig. 74).
(6) Add oil only if level is below the ADD mark on
dipstick.
OIL FILTER
REMOVAL
CAUTION: Do not use oil filter with metric threads.
The proper oil filter has SAE type 3/4 X 16 threads.
An oil filter with metric threads can result in oil
leaks and engine failure.
Fig. 74 Engine Oil DipstickÐ4.0L Engine
1 - DIPSTICK
2 - ADD
3 - SAFE
WJENGINE - 4.0L 9 - 53
LUBRICATION (Continued)