1994 JEEP CHEROKEE Service Repair Manual

gle 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.
(3) Control valve seat runout to a maximum of
0.0635 mm (0.0025 in.)Ð(Fig. 7).
VALVE STEM OIL SEAL REPLACEMENT
Valve stem oil seals are installed on each valve
stem to prevent rocker arm lubricating oil from en-
tering the combustion chamber through the valve
guide bores. One seal is marked INT (intake valve)
and the other is marked EXH (exhaust valve).
Replace the oil seals whenever valve service is per-
formed or if the seals have deteriorated.
VALVE GUIDES
The valve guides are an integral part of the engine
cylinder head and are not replaceable.
When the valve stem guide clearance is excessive,
the valve guide bores must be reamed oversize. Ser-
vice valves with oversize stems are available in 0.076
mm (0.003 inch) and 0.381 mm (0.015 inch) incre-
ments.
Corresponding oversize valve stem seals are also
available and must be used with valves having 0.381
mm (0.015 inch) oversize stems.
If the valve guides are reamed oversize, the
valve seats must be ground to ensure that the
valve seat is concentric to the valve guide.
VALVE STEM-TO-GUIDE CLEARANCE
MEASUREMENT
Valve stem-to-guide clearance may be measured by
either of the following two methods.
PREFERRED METHOD:
(1) Remove the valve from the head.
(2) Clean the valve stem guide bore with solvent
and a bristle brush.
(3) Insert a telescoping gauge into the valve stemguide bore approximately 9.525 mm (.375 inch) from
the valve spring side of the head (Fig. 8).
(4) Remove and measure telescoping gauge with a
micrometer.
(5) Repeat the measurement with contacts length-
wise to engine cylinder head.
(6) Compare the crosswise to lengthwise measure-
ments to determine out-of-roundness. If the measure-
ments differ by more than 0.0635 mm (0.0025 in.),
ream the guide bore to accommodate an oversize
valve stem.
(7) Compare the measured valve guide bore diam-
eter with specifications (7.95-7.97 mm or 0.313-0.314
inch). If the measurement differs from specification
by more than 0.076 mm (0.003 inch), ream the guide
bore to accommodate an oversize valve stem.
ALTERNATIVE METHOD:
(1) Use a dial indicator to measure the lateral
movement of the valve stem (stem-to-guide clear-
ance). This must be done with the valve installed in
its guide and just off the valve seat (Fig. 9).
(2) Correct clearance is 0.025-0.0762 mm (0.001-
0.003 inch). If indicated movement exceeds the spec-
ification ream the valve guide to accommodate an
oversize valve stem.
Valve seats must be ground after reaming the
valve guides to ensure that the valve seat is con-
centric to the valve guide.
VALVE SPRING TENSION TEST
Use Valve Spring Tester C-647 and a torque
wrench to test each valve spring for the specified ten-
sion value (Fig. 10).
Fig. 7 Measurement of Valve Seat Runout
Fig. 8 Measurement of Valve Guide Bore Diameter
9 - 64 4.0L ENGINEJ

Replace valve springs that are not within specifica-
tions.
INSTALLATION
(1) Thoroughly clean the valve stems and the
valve guide bores.
(2) Lightly lubricate the stem.
(3) Install the valve in the original valve guide
bore.
(4) Install the replacement valve stem oil seals on
the valve stems. If the 0.381 mm (0.015 inch) over-
size valve stems are used, oversize oil seals are re-
quired.
(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.
HYDRAULIC TAPPETS
Retain all the components in the same order as re-
moved.
REMOVAL
(1) Remove the engine cylinder head cover.
(2) Remove the bridge and pivot assemblies and
rocker arms by removing the capscrews at each
bridge. Alternately loosen each capscrew, one turn at
a time, to avoid damaging the bridges.
(3) Remove the push rods.
(4) Remove the intake and engine exhaust mani-
folds (refer to Group 11, Exhaust System and Intake
Manifold for the proper procedure).
(5) Remove the engine cylinder head and gasket.
(6) Remove the tappets through the push rod open-
ings in the cylinder block with Hydraulic Valve Tap-
pet Removal/Installation Tool C-4129-A (Fig. 11).
CLEANING
Clean each tappet assembly in cleaning solvent to
remove all varnish, gum and sludge deposits.
INSPECTION
Inspect for indications of scuffing on the side and
base of each tappet body.
Inspect each tappet base for concave wear with a
straightedge positioned across the base. If the base is
concave, the corresponding lobe on the camshaft is
also worn. Replace the camshaft and defective tap-
pets.
Fig. 9 Measurement of Lateral Movement of Valve
Stem
Fig. 10 Valve Spring Tester C-647
Fig. 11 Hydraulic Valve Tappet Removal/Installation
Tool C-4129-A
J4.0L ENGINE 9 - 65

LEAK-DOWN TEST
After cleaning and inspection, test each tappet for
specified leak-down rate tolerance to ensure zero-lash
operation (Fig. 12).
Swing the weighted arm of the hydraulic valve tap-
pet tester away from the ram of the Leak-Down
Tester 7980.
(1) Place a 7.925-7.950 mm (0.312-0.313 inch) di-
ameter ball bearing on the plunger cap of the tappet.
(2) Lift the ram and position the tappet (with the
ball bearing) inside the tester cup.
(3) Lower the ram, then adjust the nose of the ram
until it contacts the ball bearing. DO NOT tighten
the hex nut on the ram.
(4) Fill the tester cup with hydraulic valve tappet
test oil until the tappet is completely submerged.
(5) Swing the weighted arm onto the push rod and
pump the tappet plunger up and down to remove air.
When the air bubbles cease, swing the weighted arm
away and allow the plunger to rise to the normal po-
sition.
(6) Adjust the nose of the ram to align the pointer
with the SET mark on the scale of the tester and
tighten the hex nut.
(7) Slowly swing the weighted arm onto the push
rod.
(8) Rotate the cup by turning the handle at the
base of the tester clockwise one revolution every 2
seconds.
(9) Observe the leak-down time interval from the
instant the pointer aligns with the START mark on
the scale until the pointer aligns with the 0.125
mark. A normally functioning tappet will require 20-
110 seconds to leak-down. Discard tappets with leak-
down time interval not within this specification.
INSTALLATION
It is not necessary to charge the tappets with en-
gine oil. They will charge themselves within a very
short period of engine operation.(1) Dip each tappet in Mopar Engine Oil Supple-
ment, or equivalent.
(2) Use Hydraulic Valve Tappet Removal/Installa-
tion Tool C-4129-A to install each tappet in the same
bore from where it was originally removed.
(3) Install the exhaust and intake manifolds (refer
to Group 11, Exhaust System and Intake Manifold
for the proper procedure).
(4) Install the engine cylinder head and gasket.
(5) Install the push rods in their original locations.
(6) Install the rocker arms and bridge and pivot
assemblies at their original locations. Loosely install
the capscrews at each bridge.
(7) Tighten the capscrews alternately, one turn at
a time, to avoid damaging the bridges. Tighten the
capscrews to 28 Nzm (21 ft. lbs.) torque.
(8) Pour the remaining Mopar Engine Oil Supple-
ment, or equivalent over the entire valve actuating
assembly. The Mopar Engine Oil Supplement, or
equivalent 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.
(9) Install the engine cylinder head cover.
VALVE TIMING
Disconnect the spark plug wires and remove the
spark plugs.
Remove the engine cylinder head cover.
Remove the capscrews, bridge and pivot assembly,
and rocker arms from above the No.1 cylinder.
Alternately loosen each capscrew, one turn at a
time, to avoid damaging the bridge.
Rotate the crankshaft until the No.6 piston is at
top dead center (TDC) on the compression stroke.
Rotate the crankshaft counterclockwise (viewed
from the front of the engine) 90É.
Install a dial indicator on the end of the No.1 cyl-
inder intake valve push rod. Use rubber tubing to se-
cure the indicator stem on the push rod.
Set the dial indicator pointer at zero.
Rotate the crankshaft clockwise (viewed from the
front of the engine) until the dial indicator pointer
indicates 0.305 mm (0.012 inch) travel distance (lift).
The timing notch index on the vibration damper
should be aligned with the TDC mark on the timing
degree scale.
If the timing notch is more than 13 mm (1/2 inch)
away from the TDC mark in either direction, the
valve timing is incorrect.
If the valve timing is incorrect, the cause may be a
broken camshaft pin. It is not necessary to replace
the camshaft because of pin failure. A spring pin is
available for service replacement.
Fig. 12 Leak-Down Tester 7980
9 - 66 4.0L ENGINEJ

VIBRATION DAMPER
REMOVAL
(1) Disconnect negative cable from battery.
(2) Remove the serpentine drive belt and fan
shroud.
(3) Remove the vibration damper retaining bolt
and washer.
(4) Use Vibration Damper Removal Tool 8068 to
remove the damper from the crankshaft (Fig. 1).
INSTALLATION
(1) Apply Mopar Silicone Rubber Adhesive Sealant
to the keyway in the crankshaft and insert the key.
With the key in position, align the keyway on the vi-
bration damper hub with the crankshaft key and tap
the damper onto the crankshaft.
(2) Install the vibration damper retaining bolt and
washer.
(3) Tighten the damper retaining bolt to 108 Nzm
(80 ft. lbs.) torque.
(4) Install the serpentine drive belt and tighten to
the specified tension (refer to Group 7, Cooling Sys-
tems for the proper specifications and procedures).
(5) Connect negative cable to battery.
TIMING CASE COVER OIL SEAL REPLACEMENT
This procedure is done with the timing case cover
installed.
(1) Disconnect negative cable from battery.
(2) Remove the serpentine drive belt.
(3) Remove the vibration damper.
(4) Remove the radiator shroud.
(5) Carefully remove the oil seal (Fig. 2). Make
sure seal bore is clean.
(6) Position the replacement oil seal on Timing
Case Cover Alignment and Seal Installation Tool
6139 with seal open end facing inward. Apply a light
film of Perfect Seal, or equivalent, on the outside di-
ameter of the seal. Lightly coat the crankshaft with
engine oil.(7) Position the tool and seal over the end of the
crankshaft and insert a draw screw tool into Seal In-
stallation Tool 6139 (Fig. 3). Tighten the nut against
the tool until it contacts the cover.
(8) Remove the tools. Apply a light film of engine
oil on the vibration damper hub contact surface of
the seal.
(9) Apply Mopar Silicone Rubber Adhesive Sealant
to the keyway in the crankshaft and insert the key.
With the key inserted in the keyway in the crank-
shaft, install the vibration damper, washer and bolt.
Lubricate and tighten the bolt to 108 Nzm (80 ft. lbs.)
torque.
(10) Install the serpentine belt and tighten to the
specified tension (refer to Group 7, Cooling Systems
for the proper specifications and procedures).
(11) Install the radiator shroud.
(12) Connect negative cable to battery.
TIMING CASE COVER
REMOVAL
(1) Disconnect negative cable from battery.
(2) Remove the vibration damper (Fig. 4).
(3) Remove the fan and hub assembly and remove
the fan shroud.
Fig. 1 Vibration Damper Removal Tool 8068
Fig. 2 Timing Case Cover Oil Seal Removal
Fig. 3 Timing Case Cover Oil Seal Installation
J4.0L ENGINE 9 - 67

(4) Remove the accessory drive brackets that are
attached to the timing case cover.
(5) Remove the A/C compressor (if equipped) and
generator bracket assembly from the engine cylinder
head and move to one side.
(6) Remove the oil pan-to-timing case cover bolts
and timing case cover-to-cylinder block bolts.
(7) Remove the timing case cover and gasket from
the engine. Make sure the tension spring and thrust
pin do not fall out of the preload bolt.
(8) Pry the crankshaft oil seal from the front of the
timing case cover (Fig. 4).
CLEANING
Clean the timing case cover, oil pan and cylinder
block gasket surfaces.
INSTALLATION
(1) Install a new crankshaft oil seal in the timing
case cover. The open end of the seal should be toward
the inside of the cover. Support the cover at the seal
area while installing the seal. Force it into position
with Seal Installation Tool 6139.
(2) Position the gasket on the cylinder block.
(3) Position the timing case cover on the oil pan
gasket and the cylinder block. Make sure the tension
spring and thrust pin are in place in the camshaft
preload bolt.
(4) Insert Timing Case Cover Alignment and Seal
Installation Tool 6139 in the crankshaft opening in
the cover (Fig. 5).
(5) Install the timing case cover-to-cylinder block
and the oil pan-to-timing case cover bolts.
(6) Tighten the 1/4 inch cover-to-block bolts to 7
Nzm (60 in. lbs.) torque. Tighten the 5/16 inch front
cover-to-block bolts to 22 Nzm (192 in. lbs.) torque.
Tighten the oil pan-to-cover 1/4 inch bolts to 14 Nzm
(120 in. lbs.) torque. Tighten the oil pan-to-cover 5/16
inch bolts to 18 Nzm (156 in. lbs.) torque.
(7) Remove the cover alignment tool.(8) Apply a light film of engine oil on the vibration
damper hub contact surface of the seal.
(9) Apply Mopar Silicone Rubber Adhesive Sealant
to the keyway in the crankshaft and insert the key.
With the key inserted in the keyway in the crank-
shaft, install the vibration damper, washer and bolt.
Lubricate and tighten the bolt to 108 Nzm (80 ft. lbs.)
torque.
(10) Install the A/C compressor (if equipped) and
generator bracket assembly.
(11) Install the engine fan and hub assembly and
shroud.
(12) Install the serpentine drive belt and tighten to
obtain the specified tension.
(13) Connect negative cable to battery.TIMING CHAIN AND SPROCKETS
REMOVAL
(1) Disconnect negative cable from battery.
(2) Remove the fan and shroud.
(3) Remove the serpentine drive belt.
(4) Remove the crankshaft vibration damper.
(5) Remove the timing case cover.
(6) Rotate crankshaft until the ``0'' timing mark is
closest to and on the center line with camshaft
sprocket timing mark (Fig. 6).
(7) Remove the oil slinger from the crankshaft.
(8) Remove the tension spring and thrust pin from
the preload bolt (Fig. 7). Remove the camshaft
sprocket retaining preload bolt and washer.
(9) Remove the crankshaft sprocket, camshaft
sprocket and timing chain as an assembly.
Installation of the timing chain with the timing
marks on the crankshaft and camshaft sprockets
properly aligned ensures correct valve timing. A
worn or stretched timing chain will adversely affect
valve timing. If the timing chain deflects more than
Fig. 4 Timing Case Cover Components
Fig. 5 Timing Case Cover Alignment and Seal
Installation Tool 6139
9 - 68 4.0L ENGINEJ

12.7 mm (1/2 inch) replace it. The correct timing
chain has 48 pins. A chain with more than 48 pins
will cause excessive slack.
INSTALLATION
Assemble the timing chain, crankshaft sprocket
and camshaft sprocket with the timing marks
aligned (Fig. 6).
(1) Apply Mopar Silicone Rubber Adhesive Sealant
to the keyway in the crankshaft and insert the key.
With the key in the keyway on the crankshaft, in-
stall the assembly on the crankshaft and camshaft.
(2) Install the camshaft sprocket retaining preload
bolt and washer (Fig. 7). Tighten the preload bolt to
108 Nzm (80 ft. lbs.) torque.
(3) To verify correct installation of the timing
chain, turn the crankshaft to position the camshaft
sprocket timing mark as shown in Fig. 8. Count the
number of chain pins between the timing marks of
both sprockets. There must be 15 pins.
(4) Install the crankshaft oil slinger.
(5) Replace the oil seal in the timing case cover.(6) Lubricate the tension spring, thrust pin and
pin bore in the preload bolt with Mopar Engine Oil
Supplement, or equivalent. Install the spring and
thrust pin in the preload bolt head (Fig. 6).
(7) Install the timing case cover and gasket.
(8) With the key installed in the crankshaft key-
way, install the vibration damper, washer and bolt.
Lubricate and tighten the bolt to 108 Nzm (80 ft. lbs.)
torque.
(9) Install the serpentine drive belt and tighten to
the specified tension (refer to Group 7, Cooling Sys-
tem for the proper procedure).
(10) Install the fan and hub (or Tempatrol fan) as-
sembly. Install the shroud.
(11) Connect negative cable to battery.CAMSHAFT
REMOVAL
WARNING: THE COOLANT IN A RECENTLY OPER-
ATED ENGINE IS HOT AND PRESSURIZED. RE-
LEASE THE PRESSURE BEFORE REMOVING THE
DRAIN COCK, CAP AND DRAIN PLUGS.
(1) Disconnect negative cable from battery.
(2) Drain the cooling system. DO NOT waste reus-
able coolant. If the solution is clean, drain it into a
clean container for reuse.
(3) Remove the radiator or radiator/condenser, if
equipped with A/C (refer to Group 7, Cooling System
for the proper procedure).
(4) Remove the air conditioner condenser and re-
ceiver/drier assembly as a charged unit, if equipped
(refer to Group 24, Heating and Air Conditioning).
Fig. 6 Crankshaft/Camshaft AlignmentÐTypical
Fig. 7 Camshaft Sprocket Preload Bolt
Fig. 8 Verify Sprocket/Chain InstallationÐTypical
J4.0L ENGINE 9 - 69

(5) Remove the distributor cap and mark the posi-
tion of the rotor.
(6) Remove the distributor and ignition wires.
(7) Remove the engine cylinder head cover.
(8) Remove the rocker arms, bridges and pivots.
(9) Remove the push rods.
(10) Remove the engine cylinder head and gasket.
(11) Remove the hydraulic valve tappets from the
engine cylinder head.
(12) Remove the vibration damper.
(13) Remove the timing case cover.
(14) Remove the timing chain and sprockets.
(15) Remove the front bumper and/or grille, as re-
quired.
(16) Remove the camshaft (Fig. 9).
INSPECTION
Inspect the cam lobes for wear.
Inspect the bearing journals for uneven wear pat-
tern or finish.
Inspect the bearings for wear.
Inspect the distributor drive gear for wear.
If the camshaft appears to have been rubbing
against the timing case cover, examine the oil pres-
sure relief holes in the rear cam journal. The oil
pressure relief holes must be free of debris.
INSTALLATION
(1) Lubricate the camshaft with Mopar Engine Oil
Supplement, or equivalent.
(2) Carefully install the camshaft to prevent dam-
age to the camshaft bearings (Fig. 9).
(3) Install the timing chain, crankshaft sprocket
and camshaft sprocket with the timing marks
aligned.
(4) Install the camshaft sprocket retaining preload
bolt. Tighten the bolt to 108 Nzm (80 ft. lbs.) torque.
(5) Lubricate the tension spring, the thrust pin
and the pin bore in the preload bolt with Mopar En-
gine Oil Supplement, or equivalent. Install the
spring and thrust pin in the preload bolt head.(6) Install the timing case cover with a replace-
ment oil seal (Fig. 10). Refer to Timing Case Cover
Installation.
(7) Install the vibration damper (Fig. 10).
(8) Install the hydraulic valve tappets.
(9) Install the engine cylinder head.
(10) Install the push rods.
(11) Install the rocker arms and pivot and bridge
assemblies. Tighten each of the capscrews for each
bridge alternately, one turn at a time, to avoid dam-
aging the bridge.
(12) Install the engine cylinder head cover.
(13) Install the serpentine drive belt and tighten to
the specified tension (refer to Group 7, Cooling Sys-
tem for the proper procedure).
(14) Rotate the crankshaft until the No.1 piston is
at the TDC position on the compression stroke.
(15) Install the distributor, cap and ignition wires.
Install the distributor so that the rotor is aligned
with the mark made during removal. The rotor
should be aligned with the No.1 cylinder spark plug
terminal on the cap when the distributor housing is
fully seated on the cylinder block.
During installation, lubricate the hydraulic
valve tappets and all valve components with Mo-
par Engine Oil Supplement, or equivalent. The
Mopar Engine Oil Supplement, or equivalent
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.
(16) Install the A/C condenser and receiver/drier
assembly, if equipped (refer to Group 24, Heating
and Air Conditioning).
CAUTION: Both service valves must be opened be-
fore the air conditioning system is operated.
(17) Install the radiator, connect the hoses and fill
the cooling system to the specified level (refer to
Group 7, Cooling System for the proper procedure).
Fig. 9 Camshaft
Fig. 10 Timing Case Cover Components
9 - 70 4.0L ENGINEJ

(18) Check the ignition timing and adjust as nec-
essary.
(19) Install the grille and bumper, if removed.
(20) Connect negative cable to battery.
CAMSHAFT PIN REPLACEMENT
REMOVAL
WARNING: DO NOT LOOSEN THE RADIATOR
DRAIN COCK WITH THE SYSTEM HOT AND PRES-
SURIZED BECAUSE SERIOUS BURNS FROM COOL-
ANT CAN OCCUR.
(1) Disconnect negative cable from battery.
(2) Drain the radiator. DO NOT waste reusable
coolant. Drain the coolant into a clean container.
(3) Remove the fan and shroud.
(4) Disconnect the radiator overflow tube, radiator
hoses, automatic transmission fluid cooler pipes (if
equipped).
(5) Remove the radiator.
(6) If equipped with air conditioning:
CAUTION: DO NOT loosen or disconnect any air
conditioner system fittings. Move the condenser
and receiver/drier aside as a complete assembly.
(a) Remove the A/C compressor serpentine drive
belt idler pulley.
(b) Disconnect and remove the generator.
(c) Remove the A/C condenser attaching bolts
and move the condenser and receiver/drier assem-
bly up and out of the way.
(7) Remove the serpentine drive belt.
(8) Remove the crankshaft vibration damper.
(9) Remove the timing case cover. Clean the gas-
ket material from the cover.
(10) Remove the thrust pin and tension spring
from the preload bolt head.
(11) Rotate crankshaft until the crankshaft
sprocket timing mark is closest to and on the center
line with the camshaft sprocket timing mark (Fig.
11).
(12) Remove the camshaft sprocket preload retain-
ing bolt and washer.
(13) Remove the crankshaft oil slinger.
(14) Remove the sprockets and chain as an assem-
bly.
CAUTION: The following procedural step must be
accomplished to prevent the camshaft from damag-
ing the rear camshaft plug during pin installation.
(15) Inspect the damaged camshaft pin.
(16) If the pin is a spring-type pin, remove the bro-
ken pin by inserting a self-tapping screw into the pin
and carefully pulling the pin from the camshaft.(17) If the pin is a dowel-type pin, center-punch it.
Ensure the exact center is located when center-
punching the pin.
CAUTION: Cover the opened oil pan area to prevent
metal chips from entering the pan.
(18) Drill into the pin center witha4mm(5/32
inch) drill bit.
(19) Insert a self-tapping screw into the drilled pin
and carefully pull the pin from the camshaft.
CAMSHAFT BEARINGS
The camshaft rotates within four steel-shelled, bab-
bitt-lined bearings that are pressed into the cylinder
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) in-
crements from the front bearing (largest) to the rear
bearing (smallest). This permits easier removal and
installation of the camshaft. The camshaft bearings
are pressure lubricated.
It is not advisable to attempt to replace cam-
shaft bearings unless special removal and instal-
lation tools are available.
Camshaft end play is maintained by the load
placed on the camshaft by the sprocket preload bolt
tension spring and thrust pin.
INSTALLATION
(1) Clean the camshaft pin hole.
(2) Compress the center of the replacement spring
pin with vise grips.
(3) Carefully drive the pin into the camshaft pin
hole until it is seated.
(4) Install the camshaft sprocket, crankshaft
sprocket and timing chain with the timing marks
aligned (Fig. 11).
(5) To verify correct installation of the timing
chain, turn the crankshaft to position the camshaft
sprocket timing mark as shown in Fig. 12. Count the
Fig. 11 Timing Chain AlignmentÐTypical
J4.0L ENGINE 9 - 71