2002 JEEP GRAND CHEROKEE Exhaust manifold

accessory drive belt (Refer to 7 - COOLING/ACCES-
SORY DRIVE/DRIVE BELTS - REMOVAL).
Add coolant to radiator to bring level to within 6.3
mm (1/4 in) of top of thermostat housing.
CAUTION: Avoid overheating. Do not operate
engine for an excessive period of time. Open drain-
cock immediately after test to eliminate boil over.
Start engine and accelerate rapidly three times, to
approximately 3000 rpm while observing coolant. If
internal engine combustion gases are leaking into
cooling system, bubbles will appear in coolant. If bub-
bles do not appear, internal combustion gas leakage
is not present.
DIAGNOSIS AND TESTING - COOLING SYSTEM
DEAERATION
As the engine operates, any air trapped in cooling
system gathers under the radiator cap. The next time
the engine is operated, thermal expansion of coolant
will push any trapped air past radiator cap into the
coolant reserve/overflow tank. Here it escapes to the
atmosphere into the tank. When the engine cools
down the coolant, it will be drawn from the reserve/
overflow tank into the radiator to replace any
removed air.
STANDARD PROCEDURE
STANDARD PROCEDUREÐDRAINING COOLING
SYSTEM 4.7L ENGINE
WARNING: DO NOT REMOVE THE CYLINDER
BLOCK DRAIN PLUGS (Fig. 7) OR LOOSEN THE
RADIATOR DRAINCOCK WITH SYSTEM HOT AND
UNDER PRESSURE. SERIOUS BURNS FROM
COOLANT CAN OCCUR.
(1) DO NOT remove radiator cap first. With engine
cold, raise vehicle on a hoist and locate radiator
draincock.
NOTE: Radiator draincock is located on the left/
lower side of radiator facing to rear of vehicle.
(2) Attach one end of a hose to the draincock. Put
the other end into a clean container. Open draincock
and drain coolant from radiator. This will empty the
coolant reserve/overflow tank. The coolant does not
have to be removed from the tank unless the system
is being refilled with a fresh mixture. When tank is
empty, remove radiator cap and continue draining
cooling system.
STANDARD PROCEDURE - REFILLING
COOLING SYSTEM 4.7L ENGINE
(1) Tighten the radiator draincock and the cylinder
block drain plug(s) (if removed).
CAUTION: Failure to purge air from the cooling sys-
tem can result in an overheating condition and
severe engine damage.
(2) Remove the cooling system bleed plug from the
radiator upper hose inlet housing. (Fig. 8)Fill system
using a 50/50 mixture of ethylene-glycol antifreeze
and low mineral content water, until coolant begains
coming out of the cooling system bleed hole. Install
the cooling system bleed plug. Fill radiator to top and
install radiator cap. Add sufficient coolant to the
reserve/overflow tank to raise level to FULL mark.
(3) With heater control unit in the HEAT position,
operate engine with radiator cap in place.
(4) After engine has reached normal operating
temperature, shut engine off and allow it to cool.
When engine is cooling down, coolant will be drawn
into the radiator from the reserve/overflow tank.
(5) Add coolant to reserve/overflow tank as neces-
sary.Only add coolant to the reserve/overflow
tank when the engine is cold. Coolant level in a
warm engine will be higher due to thermal
expansion.To purge the cooling system of all air,
this heat up/cool down cycle (adding coolant to cold
engine) must be performed three times. Add neces-
sary coolant to raise tank level to the FULL mark
after each cool down period.
Fig. 7 Drain PlugÐ4.7L Engine
1 - CYLINDER BLOCK DRAIN PLUG
2 - EXHAUST MANIFOLD AND HEAT SHIELD
7 - 12 COOLINGWJ
COOLING (Continued)

(7) After removing fan blade/viscous fan drive
assembly,do notplace viscous fan drive in horizon-
tal position. If stored horizontally, silicone fluid in
the viscous fan drive could drain into its bearing
assembly and contaminate lubricant.
CAUTION: Do not remove water pump pulley-to-wa-
ter pump bolts. This pulley is under belt tension.
(8) Remove four bolts securing fan blade assembly
to viscous fan drive .
CLEANING
Clean the fan blades using a mild soap and water.
Do not use an abrasive to clean the blades.
INSPECTION
WARNING: DO NOT ATTEMPT TO BEND OR
STRAIGHTEN FAN BLADES IF FAN IS NOT WITHIN
SPECIFICATIONS.
CAUTION: If fan blade assembly is replaced
because of mechanical damage, water pump and
viscous fan drive should also be inspected. These
components could have been damaged due to
excessive vibration.
(1) Remove fan blade assembly from viscous fan
drive unit (four bolts).(2) Lay fan on a flat surface with leading edge fac-
ing down. With tip of blade touching flat surface,
replace fan if clearance between opposite blade and
surface is greater than 2.0 mm (.090 inch). Rocking
motion of opposite blades should not exceed 2.0 mm
(.090 inch). Test all blades in this manner.
(3) Inspect fan assembly for cracks, bends, loose
rivets or broken welds. Replace fan if any damage is
found.
INSTALLATION
(1) Assemble fan blade to viscous fan drive.
Tighten mounting bolts to 27 N´m (20 ft. lbs.) torque.
(2) Thread the fan and fan drive onto the water
pump pulley.
CAUTION: When installing a serpentine accessory
drive belt, the belt MUST be routed correctly. If not,
the engine may overheat due to the water pump
rotating in the wrong direction. (Refer to 7 - COOL-
ING/ACCESSORY DRIVE/DRIVE BELTS - REMOVAL)
for correct belt routing.
ENGINE BLOCK HEATER
DESCRIPTION
DESCRIPTIONÐ4.7L ENGINE
WARNING: DO NOT OPERATE ENGINE UNLESS
BLOCK HEATER CORD HAS BEEN DISCONNECTED
FROM POWER SOURCE AND SECURED IN PLACE.
THE POWER CORD MUST BE SECURED IN ITS
RETAINING CLIPS AND ROUTED AWAY FROM
EXHAUST MANIFOLDS AND MOVING PARTS.
An optional engine block heater (Fig. 12) is avail-
able with all models. The heater is equipped with a
power cord. The cord is attached to an engine com-
partment component with tie-straps. The heater
warms the engine providing easier engine starting
and faster warm-up in low temperatures. The heater
is mounted in a core hole of the engine cylinder block
in place of a freeze plug with the heating element
immersed in engine coolant.
DESCRIPTIONÐ4.0L ENGINE
WARNING: DO NOT OPERATE ENGINE UNLESS
BLOCK HEATER CORD HAS BEEN DISCONNECTED
FROM POWER SOURCE AND SECURED IN PLACE.
THE POWER CORD MUST BE SECURED IN ITS
RETAINING CLIPS AND ROUTED AWAY FROM
EXHAUST MANIFOLDS AND MOVING PARTS.
Fig. 11 Fan and Viscous Fan Drive
1 - FAN AND FAN DRIVE
2 - WATER PUMP PULLEY
7 - 32 ENGINEWJ
RADIATOR FAN - 4.0L (Continued)

(3) Raise vehicle.
(4) Remove engine cylinder block drain plug(s)
located on the sides of cylinder block above the oil
pan rail (Fig. 16).
(5) Remove power cord from block heater.(6) Loosen screw at center of block heater. Remove
heater assembly (Fig. 17).
REMOVALÐ4.0L ENGINE
(1) Disconnect negative battery cable from battery.
(2) Drain coolant from radiator (Refer to 7 -
COOLING - STANDARD PROCEDURE).
(3) Raise vehicle.
(4) Remove engine cylinder block drain plug(s)
located on the sides of cylinder block above the oil
pan rail (Fig. 18).
(5) Remove power cord from block heater.
(6) Loosen screw at center of block heater. Remove
heater assembly (Fig. 19).
INSTALLATION
INSTALLATIONÐ4.7L ENGINE
(1) Thoroughly clean cylinder block core hole and
block heater seat.
(2) Insert block heater assembly with element loop
pointing at twelve o'clock (Fig. 17).
(3) With block heater fully seated, tighten center
screw to 2 N´m (17 in. lbs.) torque.
(4) Refill cooling system (Refer to 7 - COOLING -
STANDARD PROCEDURE).
(5) Start and warm the engine. Check for leaks.
INSTALLATIONÐ4.0L ENGINE
(1) Thoroughly clean cylinder block core hole and
block heater seat.
Fig. 15 Engine Block Heater 4.7L Engine
1 - ENGINE BLOCK HEATER
Fig. 16 Drain Plug - 4.7L Engine
1 - CYLINDER BLOCK DRAIN PLUG
2 - EXHAUST MANIFOLD AND HEAT SHIELD
Fig. 17 Engine Block Heater - 4.7L
1 - ENGINE BLOCK HEATER
7 - 34 ENGINEWJ
ENGINE BLOCK HEATER (Continued)

(4) Disconnect the instrument panel wire harness
connectors and the antenna coaxial cable connector
from the receptacles on the rear of the radio receiver.
(5) Remove the radio receiver from the instrument
panel.
INSTALLATION
WARNING: DISABLE THE AIRBAG SYSTEM
BEFORE ATTEMPTING ANY STEERING WHEEL,
STEERING COLUMN, SEAT BELT TENSIONER, SIDE
AIRBAG, OR INSTRUMENT PANEL COMPONENT
DIAGNOSIS OR SERVICE. DISCONNECT AND ISO-
LATE THE BATTERY NEGATIVE (GROUND) CABLE,
THEN WAIT TWO MINUTES FOR THE AIRBAG SYS-
TEM CAPACITOR TO DISCHARGE BEFORE PER-
FORMING FURTHER DIAGNOSIS OR SERVICE. THIS
IS THE ONLY SURE WAY TO DISABLE THE AIRBAG
SYSTEM. FAILURE TO TAKE THE PROPER PRE-
CAUTIONS COULD RESULT IN ACCIDENTAL AIR-
BAG DEPLOYMENT AND POSSIBLE PERSONAL
INJURY.
(1) Position the radio receiver to the instrument
panel.
(2) Reconnect the instrument panel wire harness
connectors and the antenna coaxial cable connector
to the receptacles on the rear of the radio receiver.
(3) Install the four mounting screws. Tighten the
screws to 2.2 N´m (20 in. lbs.).(4) Install the center upper bezel onto the instru-
ment panel. (Refer to 23 - BODY/INSTRUMENT
PANEL - INSTALLATION) for the procedures.
(5) Reconnect the battery negative cable.
RADIO NOISE SUPPRESSION
GROUND STRAP
DESCRIPTION
Radio Frequency Interference (RFI) and Electro-
Magnetic Interference (EMI) noise suppression is
accomplished primarily through circuitry internal to
the radio receivers. These internal suppression
devices are only serviced as part of the radio receiver.
External suppression devices that are used on this
vehicle to control RFI or EMI noise include the fol-
lowing:
²Radio antenna base ground
²Radio receiver chassis ground wire or strap
²Engine-to-body ground strap(s)
²Exhaust system-to-body and transmission
ground strap (4.7L engines only)
²Resistor-type spark plugs
²Radio suppression-type secondary ignition wir-
ing.
For more information on the spark plugs and sec-
ondary ignition components, refer to Ignition System
in Ignition System.
REMOVAL
REMOVAL - ENGINE-TO-BODY GROUND
STRAP
(1) Remove the screw that secures the engine-to-
body ground strap eyelet to the lower plenum panel
(Fig. 13) or (Fig. 14).
(2) On models with a 4.0L engine, remove the nut
that secures the engine-to-body ground strap eyelet
to the stud on the right rear side of the engine cyl-
inder head.
(3) On models with a 4.7L engine, remove the two
nuts that secure the engine-to-body ground strap eye-
lets to the studs on the right and left rear sides of
the engine intake manifold.
(4) Remove the engine-to-body ground strap eye-
let(s) from the stud(s) on the engine.
(5) Remove the engine-to-body ground strap from
the engine compartment.
Fig. 12 Radio Remove/Install
1 - INSTRUMENT PANEL
2 - SCREW (4)
3 - RADIO RECEIVER
8A - 18 AUDIOWJ
RADIO (Continued)

REMOVAL - EXHAUST-TO-BODY GROUND
STRAP
(1) Raise and support vehicle.
(2) Remove fasteners from exhaust, crossmember
and transmission/transfer case.
(3) Remove the ground strap.
INSTALLATION
INSTALLATION - ENGINE TO BODY GROUND
STRAP
(1) Position the engine-to-body ground strap into
the engine compartment.
(2) Install the engine-to-body ground strap eye-
let(s) onto the stud(s) on the engine.
(3) On models with a 4.0L engine, install and
tighten the nut that secures the engine-to-body
ground strap eyelet to the stud on the right rear side
of the engine cylinder head. Tighten the nut to 5.6
N´m (50 in. lbs.).
(4) On models with a 4.7L engine, install and
tighten the two nuts that secure the engine-to-body
ground strap eyelets to the studs on the right and
left rear sides of the engine intake manifold. Tighten
the nuts to 11.3 N´m (100 in. lbs.).(5) Install and tighten the screw that secures the
engine-to-body ground strap eyelet to the lower ple-
num panel. Tighten the screw to 4.5 N´m (40 in. lbs.).
INSTALLATION - EXHAUST-TO-BODY GROUND
STRAP
(1) Install the ground strap to the exhaust, cross-
member and transmission/transfer case.
(2) Install the fasteners.
(3) Lower the vehicle.
REMOTE SWITCHES
DESCRIPTION
Remote radio control switches are included on
models equipped with the optional leather-wrapped
steering wheel. The two rocker-type switch units
(Fig. 15) are mounted in the upper spoke covers of
the rear (instrument panel side) steering wheel trim
cover. The switch unit on the left side is the seek
switch and has seek up, seek down, and preset sta-
tion advance switch functions. The switch unit on the
right side is the volume control switch and has vol-
ume up, volume down, and mode advance switch
functions.
Fig. 13 Engine-To-Body Ground Strap Remove/
Install - 4.0L Engine
1 - SCREW
2 - LOWER PLENUM PANEL
3 - ENGINE
4 - STUD
5 - NUT
6 - GROUND STRAP
Fig. 14 Engine-To-Body Ground Strap Remove/
Install - 4.7L Engine
1 - GROUND STRAP
2 - SCREW
3 - ENGINE
4 - STUD (2)
5 - NUT (2)
6 - LOWER PLENUM PANEL
WJAUDIO 8A - 19
RADIO NOISE SUPPRESSION GROUND STRAP (Continued)

DESCRIPTION - CONNECTOR, GROUND AND
SPLICE INFORMATION
CAUTION: Not all connectors are serviced. Some
connectors are serviced only with a harness. A typ-
ical example might be the Supplemental Restraint
System connectors. Always check parts availability
before attempting a repair.
IDENTIFICATION
In-line connectors are identified by a number, as
follows:
²In-line connectors located in the engine compart-
ment are C100 series numbers
²In-line connectors located in the Instrument
Panel area are C200 series numbers.
²In-line connectors located in the body are C300
series numbers.
²Jumper harness connectors are C400 series
numbers.
²Grounds and ground connectors are identified
with a ªGº and follow the same series numbering as
the in-line connectors.
²Splices are identified with an ªSº and follow the
same series numbering as the in-line connectors.
²Component connectors are identified by the com-
ponent name instead of a number. Multiple connec-
tors on a component use a C1, C2, etc. identifier.
LOCATIONS
Section 8W-91 contains connector/ground/splice
location illustrations. The illustrations contain the
connector name (or number)/ground number/splice
number and component identification. Connector/
ground/splice location charts in section 8W-91 refer-
ence the figure numbers of the illustrations.
The abbreviation T/O is used in the component
location section to indicate a point in which the wir-
ing harness branches out to a component. The abbre-
viation N/S means Not Shown in the illustrations
WARNING
WARNINGS - GENERAL
WARNINGSprovide information to prevent per-
sonal injury and vehicle damage. Below is a list of
general warnings that should be followed any time a
vehicle is being serviced.
WARNING: ALWAYS WEAR SAFETY GLASSES FOR
EYE PROTECTION.
WARNING: USE SAFETY STANDS ANYTIME A PRO-
CEDURE REQUIRES BEING UNDER A VEHICLE.WARNING: BE SURE THAT THE IGNITION SWITCH
ALWAYS IS IN THE OFF POSITION, UNLESS THE
PROCEDURE REQUIRES IT TO BE ON.
WARNING: SET THE PARKING BRAKE WHEN
WORKING ON ANY VEHICLE. AN AUTOMATIC
TRANSMISSION SHOULD BE IN PARK. A MANUAL
TRANSMISSION SHOULD BE IN NEUTRAL.
WARNING: OPERATE THE ENGINE ONLY IN A
WELL-VENTILATED AREA.
WARNING: KEEP AWAY FROM MOVING PARTS
WHEN THE ENGINE IS RUNNING, ESPECIALLY THE
FAN AND BELTS.
WARNING: TO PREVENT SERIOUS BURNS, AVOID
CONTACT WITH HOT PARTS SUCH AS THE RADIA-
TOR, EXHAUST MANIFOLD(S), TAIL PIPE, CATA-
LYTIC CONVERTER AND MUFFLER.
WARNING: DO NOT ALLOW FLAME OR SPARKS
NEAR THE BATTERY. GASES ARE ALWAYS
PRESENT IN AND AROUND THE BATTERY.
WARNING: ALWAYS REMOVE RINGS, WATCHES,
LOOSE HANGING JEWELRY AND AVOID LOOSE
CLOTHING.
DIAGNOSIS AND TESTING - WIRING HARNESS
TROUBLESHOOTING TOOLS
When diagnosing a problem in an electrical circuit
there are several common tools necessary. These tools
are listed and explained below.
²Jumper Wire - This is a test wire used to con-
nect two points of a circuit. It can be used to bypass
an open in a circuit.
WARNING: NEVER USE A JUMPER WIRE ACROSS
A LOAD, SUCH AS A MOTOR, CONNECTED
BETWEEN A BATTERY FEED AND GROUND.
²Voltmeter - Used to check for voltage on a cir-
cuit. Always connect the black lead to a known good
ground and the red lead to the positive side of the
circuit.
CAUTION: Most of the electrical components used
in today's vehicles are Solid State. When checking
voltages in these circuits, use a meter with a 10 -
megohm or greater impedance rating.
WJ8W-01 WIRING DIAGRAM INFORMATION 8W - 01 - 7
WIRING DIAGRAM INFORMATION (Continued)

REMOVAL
REMOVAL - CAMSHAFT BEARINGS.......31
REMOVAL - CAMSHAFT................31
INSPECTION
INSPECTION - CAMSHAFT BEARINGS.....31
INSPECTION - CAMSHAFT..............31
INSTALLATION
INSTALLATION - CAMSHAFT BEARINGS . . . 32
INSTALLATION - CAMSHAFT............32
CONNECTING ROD BEARINGS
STANDARD PROCEDURE - FITTING
CONNECTING ROD BEARINGS..........33
CRANKSHAFT
DESCRIPTION.........................35
CRANKSHAFT MAIN BEARINGS
STANDARD PROCEDURE - FITTING
CRANKSHAFT MAIN BEARINGS..........36
REMOVAL.............................39
INSPECTION..........................40
INSTALLATION.........................40
CRANKSHAFT OIL SEAL - FRONT
REMOVAL.............................41
INSTALLATION.........................41
CRANKSHAFT OIL SEAL - REAR
REMOVAL.............................42
INSTALLATION.........................42
HYDRAULIC LIFTERS
DESCRIPTION.........................43
REMOVAL.............................43
CLEANING............................43
INSPECTION..........................43
INSTALLATION.........................43
PISTON & CONNECTING ROD
DESCRIPTION.........................44
STANDARD PROCEDURE - PISTON FITTING . 44
REMOVAL.............................45
INSTALLATION.........................46
PISTON RINGS
STANDARD PROCEDURE - PISTON RING
FITTING.............................47
VIBRATION DAMPER
REMOVAL.............................49
INSTALLATION.........................49STRUCTURAL SUPPORT
REMOVAL.............................49
INSTALLATION.........................50
LUBRICATION
DESCRIPTION.........................50
OPERATION...........................50
DIAGNOSIS AND TESTING
DIAGNOSIS AND TESTING - ENGINE OIL
PRESSURE..........................51
DIAGNOSIS AND TESTING - ENGINE OIL
LEAK...............................51
OIL
STANDARD PROCEDURE - ENGINE OIL
SERVICE............................53
OIL FILTER
REMOVAL.............................53
INSTALLATION.........................54
OIL PAN
DESCRIPTION.........................54
REMOVAL.............................54
INSTALLATION.........................55
ENGINE OIL PRESSURE SENSOR
DESCRIPTION.........................56
OPERATION...........................56
OIL PUMP
REMOVAL.............................56
INSTALLATION.........................57
INTAKE MANIFOLD
DESCRIPTION.........................57
DIAGNOSIS AND TESTING - INTAKE
MANIFOLD LEAKAGE..................57
REMOVAL.............................57
INSTALLATION.........................57
EXHAUST MANIFOLD
DESCRIPTION.........................58
REMOVAL.............................58
INSTALLATION.........................58
TIMING BELT / CHAIN COVER(S)
REMOVAL.............................58
INSTALLATION.........................58
TIMING BELT/CHAIN AND SPROCKETS
REMOVAL.............................60
INSTALLATION.........................60
ENGINE - 4.0L
DESCRIPTION
The 4.0 Liter (242 CID) six-cylinder engine is an
In-line, lightweight, overhead valve engine. This
engine is designed for unleaded fuel.
The engine cylinder head has dual quench-type
combustion chambers that create turbulence and fast
burning of the air/fuel mixture. This results in better
fuel economy.
The cylinders are numbered 1 through 6 from front
to rear. The firing order is 1-5-3-6-2-4 (Fig. 1).The crankshaft rotation is clockwise, when viewed
from the front of the engine. The crankshaft rotates
within seven main bearings. The camshaft rotates
within four bearings.
The engine Build Date Code is located on a
machined surface on the right side of the cylinder
block between the No.2 and No.3 cylinders (Fig. 2).
The digits of the code identify:
²1st DigitÐThe year (8 = 1998).
²2nd & 3rd DigitsÐThe month (01 - 12).
²4th & 5th DigitsÐThe engine type/fuel system/
compression ratio (MX = A 4.0 Liter (242 CID) 8.7:1
compression ratio engine with a multi-point fuel
injection system).
9 - 2 ENGINE - 4.0LWJ

CONDITION POSSIBLE CAUSES CORRECTION
3. Worn or incorrect gapped spark
plugs3. Clean plugs and set gap. (Refer to
8 - ELECTRICAL/IGNITION
CONTROL/SPARK PLUG -
CLEANING).
4. Dirt or water in fuel system 4. Clean system and replace fuel
filter
5. Faulty fuel pump 5. Install new fuel pump
6. Incorrect valve timing 6. Correct valve timing
7. Blown cylinder head gasket 7. Install new cylinder head gasket
8. Low compression 8. Test cylinder compression. (Refer
to 9 - ENGINE - DIAGNOSIS AND
TESTING).
9. Burned, warped, or pitted valves 9. Install/Reface valves as necessary
10. Plugged or restricted exhaust
system10. Install new parts as necessary
11. Faulty ignition coil rail 11. Test and replace, as necessary.
(Refer to 8 - ELECTRICAL/IGNITION
CONTROL/COIL RAIL - REMOVAL).
ENGINE STALLS OR ROUGH
IDLE1. Carbon build-up on throttle plate 1. Remove throttle body and
de-carbon. (Refer to 14 - FUEL
SYSTEM/FUEL INJECTION/
THROTTLE BODY - REMOVAL) for
correct procedure.
2. Engine idle speed too low 2. Check Idle Air Control circuit.
3. Worn or incorrectly gapped spark
plugs3. Replace or clean and re-gap spark
plugs. (Refer to 8 - ELECTRICAL/
IGNITION CONTROL/SPARK PLUG
- CLEANING)
4. Faulty coil rail 4. Test and replace, if necessary.
(Refer to 8 - ELECTRICAL/IGNITION
CONTROL/COIL RAIL - REMOVAL)
5. Intake manifold vacuum leak 5. Inspect intake manifold gasket and
vacuum hoses. Replace if necessary.
(Refer to 9 - ENGINE/MANIFOLDS/
INTAKE MANIFOLD - DIAGNOSIS
AND TESTING).
ENGINE MISSES ON
ACCELERATION1. Worn or incorrectly gapped spark
plugs1. Replace spark plugs or clean and
set gap.
2. Spark plug cables defective or
crossed2. Replace spark plug cables.
3. Dirt in fuel system 3. Clean fuel system
4. Burned, warped or pitted valves 4. Install new valves
5. Faulty coil rail 5. Test and replace as necessary.
(Refer to 8 - ELECTRICAL/IGNITION
CONTROL/COIL RAIL - REMOVAL)
WJENGINE - 4.0L 9 - 5
ENGINE - 4.0L (Continued)