2002 JEEP GRAND CHEROKEE oil cap

CLEANING
Remove any original sealer from the cover sealing
surface of the engine cylinder head and clean the
surface using a fabric cleaner.
Remove all residue from the sealing surface using
a clean, dry cloth.
INSPECTION
Inspect the engine cylinder head cover for cracks.
Replace the cover, if cracked.
The original dark grey gasket material should
NOT be removed. If sections of the gasket material
are missing or are compressed, replace the engine
cylinder head cover. However, sections with minor
damage such as small cracks, cuts or chips may be
repaired with a hand held applicator. The new mate-
rial must be smoothed over to maintain gasket
height. Allow the gasket material to cure prior to
engine cylinder head cover installation.
INSTALLATION
The cylinder head cover is isolated from the cylin-
der head via grommets and a reusable molded rubber
gasket. The grommet and limiter are retained in the
cylinder head cover.
(1) If a replacement cover is installed, transfer the
CCV valve grommet and oil filler cap from the origi-
nal cover to the replacement cover.
(2) Install cylinder head cover and gasket (Fig. 13).
Tighten the mounting bolts to 10 N´m (85 in. lbs.)
torque.
(3) Connect the CCV hoses.(4) Install control cables and bracket on intake
manifold and tighten bolts to 8.7 N´m (77 in. lbs.)
torque.
(5) Connect control cables to throttle body linkage.
(6) Snap control cables into cylinder head cover
clip.
(7) Connect negative cable to battery.
INTAKE/EXHAUST VALVES &
SEATS
DESCRIPTION
The valves are made of heat resistant steel and
have chrome plated stems to prevent scuffing. All
valves use three bead locks to promote valve rotation
(Fig. 14).
STANDARD PROCEDURE - VALVE SERVICE
VALVE REFACING
Clean all carbon deposits from the combustion
chambers, valve ports, valve stems, valve stem
guides and head.
(1) Use a valve refacing machine to reface the
intake and exhaust valves to the specified angle.
(2) After refacing, a margin of at least 0.787 mm
(0.031 inch) must remain (Fig. 15). If the margin is
less than 0.787 mm (0.031 inch), the valve must be
replaced.
VALVE SEAT REFACING
Clean all carbon deposits from the combustion
chambers, valve ports, valve stems, valve stem
guides and head.
(1) Install a pilot of the correct size in the valve
guide bore. Reface the valve seat to the specified
angle with a good dressing stone. Remove only
enough metal to provide a smooth finish.
(2) Use tapered stones to obtain the specified seat
width when required.
Fig. 12 Engine Cylinder Head Cover
1 - TRANS CONTROL CABLE
2 - ACCELERATOR CABLE
3 - CONTROL CABLE BRACKET
4 - CYLINDER HEAD COVER
Fig. 13 Cylinder Head Cover Gasket Locator Pins at
#8
WJENGINE - 4.0L 9 - 23
CYLINDER HEAD COVER(S) (Continued)

(5) Position the valve spring and retainer on the
engine cylinder head and compress the valve spring
with Valve Spring Compressor Tool MD-998772A.
(6) Install the valve locks and release the tool.
(7) Tap the valve spring from side to side with a
hammer to ensure that the spring is properly seated
at the engine cylinder head. Also tap the top of the
retainer to seat the valve locks.
(8) Install the engine cylinder head (Refer to 9 -
ENGINE/CYLINDER HEAD - INSTALLATION).
ROCKER ARM / ADJUSTER
ASSEMBLY
DESCRIPTION
The rocker arms are made of stamped steel and
have a operational ratio of 1.6:1 (Fig. 21).
OPERATION
When the push rods are forced upward by the cam-
shaft lobes the push rod presses upward on the
rocker arms, the rocker arms pivot, forcing down-
ward pressure on the valves forcing the valves to
move downward and off from their seats.
REMOVAL
NOTE: This procedure can be done with the engine
in or out of the vehicle.
(1) Remove the cylinder head cover (Refer to 9 -
ENGINE/CYLINDER HEAD/CYLINDER HEAD
COVER(S) - REMOVAL).
(2) Check for rocker arm bridges which are caus-
ing misalignment of the rocker arm to valve tip area.
(3) Remove the capscrews at each bridge and pivot
assembly (Fig. 22). Alternately loosen the capscrews
one turn at a time to avoid damaging the bridges.
(4) Remove the bridges, pivots and corresponding
pairs of rocker arms (Fig. 22). Place them on a bench
in the same order as removed.
(5) Remove the push rods and place them on a
bench in the same order as removed.
CLEANING
Clean all the components with cleaning solvent.
Use compressed air to blow out the oil passages in
the rocker arms and push rods.
Fig. 20 Valve and Valve Components
1 - VALVE LOCKS (3±BEAD)
2 - RETAINER
3 - VALVE STEM OIL SEAL
4 - INTAKE VALVE
5 - EXHAUST VALVE
6 - VALVE SPRING
Fig. 21 Rocker ArmsÐTypical
1 - CAPSCREWS
2 - BRIDGE
3 - PIVOT ASSEMBLY
4 - PUSH RODS
5 - ROCKER ARMS
9 - 26 ENGINE - 4.0LWJ
INTAKE/EXHAUST VALVES & SEATS (Continued)

INSPECTION
Inspect the pivot surface area of each rocker arm.
Replace any that are scuffed, pitted, cracked or
excessively worn.
Inspect the valve stem tip contact surface of each
rocker arm and replace any rocker arm that is deeply
pitted.
Inspect each push rod end for excessive wear and
replace as required. If any push rod is excessively
worn because of lack of oil, replace it and inspect the
corresponding hydraulic tappet for excessive wear.
Inspect the push rods for straightness by rolling
them on a flat surface or by shining a light between
the push rod and the flat surface.
A wear pattern along the length of the push rod is
not normal. Inspect the engine cylinder head for
obstruction if this condition exists.
INSTALLATION
NOTE: This procedure can be done with the engine
in or out of the vehicle.
(1) Lubricate the ball ends of the push rods with
MopartEngine Oil Supplement, or equivalent and
install push rods in their original locations. Ensurethat the bottom end of each push rod is centered in
the tappet plunger cap seat.
(2) Using MopartEngine Oil Supplement, or
equivalent, lubricate the area of the rocker arm that
the pivot contacts. Install rocker arms, pivots and
bridge above each cylinder in their originally position
(Fig. 23).
(3) Loosely install the capscrews through each
bridge.
(4) At each bridge, tighten the capscrews alter-
nately, one turn at a time, to avoid damaging the
bridge. Tighten the capscrews to 28 N´m (21 ft. lbs.)
torque.
(5) Install the engine cylinder head cover (Refer to
9 - ENGINE/CYLINDER HEAD/CYLINDER HEAD
COVER(S) - INSTALLATION).
VALVE STEM SEALS
DESCRIPTION
The valve stem seals (Fig. 24) are made of rubber
and incorporate a garter spring to maintain consis-
tent lubrication control.
Fig. 22 Rocker Arm
1 - CAPSCREWS
2 - BRIDGE
3 - PIVOT ASSEMBLY
4 - PUSH RODS
5 - ROCKER ARMS
Fig. 23 Rocker Arm
1 - CAPSCREWS
2 - BRIDGE
3 - PIVOT ASSEMBLY
4 - PUSH RODS
5 - ROCKER ARMS
WJENGINE - 4.0L 9 - 27
ROCKER ARM / ADJUSTER ASSEMBLY (Continued)

(2) Remove cap screws, bridge and pivot assem-
blies and rocker arms (Refer to 9 - ENGINE/CYLIN-
DER HEAD/ROCKER ARM / ADJUSTER ASSY -
REMOVAL) for access to each valve spring to be
removed.
(3) Remove push rods.Retain the push rods,
bridges, pivots and rocker arms in the same
order and position as removed.
(4) Inspect the springs and retainer for cracks and
possible signs of weakening.
(5) Remove the spark plug(s) adjacent to the cylin-
der(s) below the valve springs to be removed.
(6) Connect an air hose to the adapter and apply
air pressure slowly. Maintain at least 621 kPa (90
psi) of air pressure in the cylinder to hold the valves
against their seats. For vehicles equipped with an air
conditioner, use a flexible air adaptor when servicing
the No.1 cylinder.
(7) Tap the retainer or tip with a rawhide hammer
to loosen the lock from the retainer. Use Valve Spring
Compressor Tool MD-998772A to compress the spring
and remove the locks (Fig. 27).
(8) Remove valve spring and retainer (Fig. 27).
(9) Remove valve stem oil seals (Fig. 27). Note the
valve seals are different for intake and exhaust
valves. The top of each seal is marked either INT
(intake/black in color) or EXH (exhaust/brown in
color). DO NOT mix the seals.
INSTALLATION
NOTE: This procedure can be done with the engine
cylinder head installed on the block.
CAUTION: Install oil seals carefully to prevent dam-
age from the sharp edges of the valve spring lock
grove.
(1) Lightly push the valve seal over the valve stem
and valve guide boss. Be sure the seal is completely
seated on the valve guide boss.
(2) Install valve spring and retainer (Fig. 28).
(3) Compress the valve spring with Valve Spring
Compressor Tool MD-998772A and insert the valve
locks. Release the spring tension and remove the
tool. Tap the spring from side-to-side to ensure that
the spring is seated properly on the engine cylinder
head.(4) Release air pressure and disconnect the air
hose. Remove the adaptor from the spark plug hole
and install the spark plug.
(5) Repeat the procedures for each remaining valve
spring to be removed.
(6) Install the push rods. Ensure the bottom end of
each rod is centered in the plunger cap seat of the
hydraulic valve tappet.
(7) Install the rocker arms, pivots and bridge
(Refer to 9 - ENGINE/CYLINDER HEAD/ROCKER
ARM / ADJUSTER ASSY - INSTALLATION) at their
original location.
(8) Install the engine cylinder head cover (Refer to
9 - ENGINE/CYLINDER HEAD/CYLINDER HEAD
COVER(S) - INSTALLATION).
Fig. 27 Valve and Valve Components
1 - VALVE LOCKS (3±BEAD)
2 - RETAINER
3 - VALVE STEM OIL SEAL
4 - INTAKE VALVE
5 - EXHAUST VALVE
6 - VALVE SPRING
WJENGINE - 4.0L 9 - 29
VALVE SPRINGS (Continued)

ENGINE BLOCK
CLEANING
Thoroughly clean the oil pan and engine block gas-
ket surfaces.
Use compressed air to clean out:
²The galley at the oil filter adaptor hole.
²The front and rear oil galley holes.
²The feed holes for the crankshaft main bearings.
Once the block has been completely cleaned, apply
Loctite PST pipe sealant with Teflon 592 to the
threads of the front and rear oil galley plugs. Tighten
the plugs to 34 N´m (25 ft. lbs.) torque.
INSPECTION
(1) It is mandatory to use a dial bore gauge to
measure each cylinder bore diameter (Fig. 29). To
correctly select the proper size piston, a cylinder 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 micrometer.
(2) Measure the inside diameter of the cylinder
bore at three levels below top of bore. Start perpen-
dicular (across or at 90 degrees) to the axis of the
crankshaft and then take two additional reading.(3) Measure the cylinder bore diameter crosswise
to the cylinder block near the top of the bore. Repeat
the measurement near the middle of the bore, then
repeat the measurement near the bottom of the bore.
(4) Determine taper by subtracting the smaller
diameter from the larger diameter.
(5) Rotate measuring device 90É and repeat steps
above.
(6) Determine out-of-roundness by comparing the
difference between each measurement.
(7) If cylinder bore taper does not exceed 0.025
mm (0.001 inch) and out-of-roundness does not
exceed 0.025 mm (0.001 inch), the cylinder bore can
be honed. If the cylinder bore taper or out- of-round
condition exceeds these maximum limits, the cylinder
must be bored and then honed to accept an oversize
piston. A slight amount of taper always exists in the
cylinder bore after the engine has been in use for a
period of time.
CAMSHAFT & BEARINGS
DESCRIPTION
The camshaft is made of gray cast iron with twelve
machined lobes and four bearing journals (Fig. 30).
When the camshaft rotates the lobes actuate the tap-
pets and push rods, forcing upward on the rocker
arms which applies downward force on the valves.
Fig. 28 Valve and Valve
1 - VALVE LOCKS (3±BEAD)
2 - RETAINER
3 - VALVE STEM OIL SEAL
4 - INTAKE VALVE
5 - EXHAUST VALVE
6 - VALVE SPRINGFig. 29 Cylinder Bore Measurement
9 - 30 ENGINE - 4.0LWJ
VALVE SPRINGS (Continued)

REMOVAL
REMOVAL - CAMSHAFT BEARINGS
The camshaft rotates within four steel-shelled,
babbitt-lined bearings that are pressed into the cyl-
inder block and then line reamed. The camshaft
bearing bores and bearing diameters are not the
same size. They are stepped down in 0.254 mm
(0.010 inch) increments from the front bearing (larg-
est) to the rear bearing (smallest). This permits eas-
ier removal and installation of the camshaft. The
camshaft bearings are pressure lubricated. Camshaft
end play is maintained by the thrust plate.
(1) Remove the camshaft (Refer to 9 - ENGINE/
ENGINE BLOCK/CAMSHAFT & BEARINGS (IN
BLOCK) - REMOVAL).
NOTE: It is not advisable to attempt to replace cam-
shaft bearings unless special removal and installa-
tion tools are available, such as recommended tool
8544 Camshaft Bushing Remover Installer.
(2) Using Special tool 8544 Camshaft Bushing
Remover Installer, remove the camshaft bearings.
REMOVAL - CAMSHAFT
WARNING: THE COOLANT IN A RECENTLY OPER-
ATED ENGINE IS HOT AND PRESSURIZED.RELEASE THE PRESSURE BEFORE REMOVING
THE DRAIN COCK, CAP AND DRAIN PLUGS.
(1) Disconnect negative cable from battery.
(2) Drain the cooling system (Refer to 7 - COOL-
ING - STANDARD PROCEDURE).
(3) Remove the radiator (Refer to 7 - COOLING/
ENGINE/RADIATOR - REMOVAL) and condenser
(Refer to 24 - HEATING & AIR CONDITIONING/
PLUMBING/A/C CONDENSER - REMOVAL), if
equipped with A/C.
(4) Remove the engine cylinder head cover (Refer
to 9 - ENGINE/CYLINDER HEAD/CYLINDER
HEAD COVER(S) - REMOVAL).
(5) Remove the rocker arms, bridges and pivots
(Refer to 9 - ENGINE/CYLINDER HEAD/ROCKER
ARM / ADJUSTER ASSY - REMOVAL).
(6) Remove the push rods.
(7) Remove the engine cylinder head and gasket
(Refer to 9 - ENGINE/CYLINDER HEAD - REMOV-
AL).
(8) Remove the hydraulic valve tappets from the
engine cylinder block (Refer to 9 - ENGINE/ENGINE
BLOCK/HYDRAULIC LIFTERS (CAM IN BLOCK) -
REMOVAL).
(9) Remove the vibration damper (Refer to 9 -
ENGINE/ENGINE BLOCK/VIBRATION DAMPER -
REMOVAL).
(10) Remove the timing case cover (Refer to 9 -
ENGINE/VALVE TIMING/TIMING BELT / CHAIN
COVER(S) - REMOVAL).
(11) Rotate the crankshaft until the crankshaft
sprocket timing mark is aligned on centerline with
the camshaft sprocket timing mark (Fig. 32).
(12) Remove the timing chain and sprockets (Refer
to 9 - ENGINE/VALVE TIMING/TIMING BELT/
CHAIN AND SPROCKETS - REMOVAL).
(13) Remove the front bumper and/or grille, as
required.
(14) Remove the two thrust plate retaining screws,
thrust plate and camshaft (Fig. 31).
INSPECTION
INSPECTION - CAMSHAFT BEARINGS
(1) Inspect the bearing journals for uneven wear
pattern or finish.
(2) Inspect the bearings for wear.
INSPECTION - CAMSHAFT
(1) Inspect the cam lobes for wear.
(2) Inspect the camshaft position sensor drive gear
for wear.
(3) If the camshaft appears to have been rubbing
against the thrust washer, examine the oil pressure
Fig. 30 CamshaftÐTypical
1 - CAMSHAFT
2 - LOBES
3 - BEARING JOURNAL
WJENGINE - 4.0L 9 - 31
CAMSHAFT & BEARINGS (Continued)

BEARING-TO-JOURNAL CLEARANCE
(1) Wipe the oil from the connecting rod journal.
(2) Use short rubber hose sections over rod bolts
during installation.
(3) Lubricate the upper bearing insert and install
in connecting rod.
(4) Use piston ring compressor to install the rod
and piston assemblies. The oil squirt holes in the
rods must face the camshaft. The arrow on the piston
crown should point to the front of the engine (Fig.
38). Verify that the oil squirt holes in the rods face
the camshaft and that the arrows on the pistons face
the front of the engine.
(5) Install the lower bearing insert in the bearing
cap. The lower insert must be dry. Place strip of Plas-
tigage across full width of the lower insert at the cen-
ter of bearing cap. Plastigage must not crumble in
use. If brittle, obtain fresh stock.
(6) Install bearing cap and connecting rod on the
journal and tighten nuts to 45 N´m (33 ft. lbs.)
torque. DO NOT rotate crankshaft. Plastigage will
smear, resulting in inaccurate indication.
(7) Remove the bearing cap and determine amount
of bearing-to- journal clearance by measuring the
width of compressed Plastigage (Fig. 39).Plastigageshould indicate the same clearance across the
entire width of the insert. If the clearance var-
ies, it may be caused by either a tapered jour-
nal, bent connecting rod or foreign material
trapped between the insert and cap or rod.
(8) If the correct clearance is indicated, replace-
ment of the bearing inserts is not necessary. Remove
the Plastigage from crankshaft journal and bearing
insert. Proceed with installation.
(9) If bearing-to-journal clearance exceeds the
specification, install a pair of 0.0254 mm (0.001 inch)
undersize bearing inserts. All the odd size inserts
must be on the bottom. The sizes of the service
replacement bearing inserts are stamped on the
backs of the inserts. Measure the clearance as
described in the previous steps.
(10) The clearance is measured with a pair of
0.0254 mm (0.001 inch) undersize bearing inserts
installed. This will determine if two 0.0254 mm
(0.001 inch) undersize inserts or another combination
Fig. 36 Locking Tab Inspection
1 - ABNORMAL CONTACT AREA CAUSED BY LOCKING TABS
NOT FULLY SEATED OR BEING BENT
Fig. 37 Scoring Caused by Insufficient Lubrication
or Damaged Crankshaft Journal
Fig. 38 Rod and Piston Assembly Installation
Fig. 39 Measuring Bearing Clearance with
Plastigage
1 - PLASTIGAGE SCALE
2 - COMPRESSED PLASTIGAGE
9 - 34 ENGINE - 4.0LWJ
CONNECTING ROD BEARINGS (Continued)

is needed to provide the correct clearance. Refer to
CONNECTING ROD BEARING FITTING CHART .
CONNECTING ROD BEARING FITTING CHART
CRANKSHAFT JOURNAL CORRESPONDING ROD BEARING INSERT
Color Code Diameter Upper Insert Size Lower Insert Size
Yellow53.2257 - 53.2079 mm
Yellow - Standard Yellow - Standard
(2.0955 - 2.0948 in.)
Orange53.2079 - 53.1901 mm
Yellow - StandardBlue - Undersize (2.0948 - 2.0941 in.)
0.0178 mm (0.0007 in.) 0.025 mm (0.001 in.)
Undersize
Blue53.1901 - 53.1724 mm
Blue - Undersize Blue - Undersize (2.0941 - 2.0934 in.)
0.0356 mm (0.0014 in.) 0.025 mm (0.001 in.) 0.025 mm (0.001 in.)
Undersize
Red52.9717 - 52.9539 mm
Red - Undersize Red - Undersize (2.0855 - 2.0848 in.)
0.254 mm (0.010 in.) 0.254 mm (0.010 in.) 0.254 mm (0.010 in.)
Undersize
(11)FOR EXAMPLE:If the initial clearance was
0.0762 mm (0.003 inch), 0.025 mm (0.001 inch)
undersize inserts would reduce the clearance by
0.025 mm (0.001 inch). The clearance would be 0.002
inch and within specification. A 0.051 mm (0.002
inch) undersize insert would reduce the initial clear-
ance an additional 0.013 mm (0.0005 inch). The
clearance would then be 0.038 mm (0.0015 inch).
(12) Repeat the Plastigage measurement to verify
your bearing selection prior to final assembly.
(13) Once you have selected the proper insert,
install the insert and cap. Tighten the connecting rod
bolts to 45 N´m (33 ft. lbs.) torque.
SIDE CLEARANCE MEASUREMENT
Slide snug-fitting feeler gauge between the con-
necting rod and crankshaft journal flange (Fig. 40).
(Refer to 9 - ENGINE - SPECIFICATIONS). Replace
the connecting rod if the side clearance is not within
specification.
CRANKSHAFT
DESCRIPTION
The crankshaft is constructed of nodular cast iron.
The crankshaft is a crosshaped four throw design
with eight counterweights for balancing purposes.The crankshaft is supported by seven select main
bearings with the number three serving as the thrust
washer location. The main journals of the crankshaft
are cross drilled to improve rod bearing lubrication.
The select fit main bearing markings are located on
the crankshaft counter weights. The crankshaft rear
oil seal is a two piece design. The front oil seal is a
one piece design retained in the timing chain cover
(Fig. 41).
Fig. 40 Checking Connecting Rod Side Clearance -
Typical
WJENGINE - 4.0L 9 - 35
CONNECTING ROD BEARINGS (Continued)