JEEP CHEROKEE 1994 Service Repair Manual

CLEANING
Clean the cylinder bores thoroughly. Apply a light
film of clean engine oil to the bores with a clean lint-
free cloth.
INSTALLATION
(1) Install the piston rings on the pistons if re-
moved.
(2) Lubricate the piston and rings with clean en-
gine oil.
CAUTION: Ensure that connecting rod bolts do not
scratch the crankshaft journals or cylinder walls.
Short pieces of rubber hose slipped over the con-
necting rod bolts will provide protection during in-
stallation.
(3) Use a piston ring compressor to install the con-
necting rod and piston assemblies through the top of
the cylinder bores (Fig. 18).
(4) Ensure the arrow on the piston top points to
the front of the engine (Fig. 18).
(5) Raise the vehicle.
Each bearing insert is fitted to its respective jour-
nal to obtain the specified clearance between the
bearing and the journal. In production, the select fit
is obtained by using various-sized, color-coded bear-
ing inserts as listed in the Connecting Rod Bearing
Fitting Chart. The color code appears on the edge of
the bearing insert. The size is not stamped on inserts
used for production of engines.
The rod journal is identified during the engine pro-
duction by a color-coded paint mark on the adjacent
cheek or counterweight toward the flange (rear) end
of the crankshaft. The color codes used to indicate
journal sizes are listed in the Connecting Rod Bear-
ing Fitting Chart.
When required, upper and lower bearing inserts of
different sizes may be used as a pair (refer to Con-
necting Rod Bearing Fitting Chart). A standard sizeinsert is sometimes used in combination with a 0.025
mm (0.001 inch) undersize insert to reduce clearance
0.013 mm (0.0005 inch).
CAUTION: DO NOT intermix bearing caps. Each
connecting rod and bearing cap are stamped with
the cylinder number. The stamp is located on a ma-
chined surface adjacent to the oil squirt hole that
faces the camshaft side of the cylinder block.
(6) Install the connecting rod bearing caps and in-
serts in the same positions as removed.
CAUTION: Verify that the oil squirt holes in the rods
face the camshaft and that the arrows on the pis-
tons face the front of the engine.
(7) Install the oil pan and gaskets as outlined in
the installation procedure.
(8) Lower the vehicle.
(9) Install the engine cylinder head, push rods,
rocker arms, bridges, pivots and engine cylinder head
cover.
(10) Fill the crankcase with engine oil.
CRANKSHAFT MAIN BEARINGS
REMOVAL
(1) Disconnect negative cable from battery.
(2) Remove the spark plugs.
(3) Raise the vehicle.
(4) Remove the oil pan and oil pump.
(5) Remove only one main bearing cap and lower
insert at a time (Fig. 1).
Fig. 18 Rod and Piston Assembly Installation
Fig. 1 Removing Main Bearing Caps and Lower Inserts
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(6) Remove the lower insert from the bearing cap.
(7) Remove the upper insert by LOOSENING (DO
NOT REMOVE) all of the other bearing caps. Now
insert a small cotter pin tool in the crankshaft jour-
nal oil hole. Bend the cotter pin as illustrated to fab-
ricate the tool (Fig. 2). With the cotter pin tool in
place, rotate the crankshaft so that the upper bear-
ing insert will rotate in the direction of its locking
tab. Because there is no hole in the No.3 main jour-
nal, use a tongue depressor or similar soft-faced tool
to remove the bearing insert (Fig. 2). After moving
the insert approximately 25 mm (1 inch), it can be
removed by applying pressure under the tab.
(8) Using the same procedure described above, re-
move the remaining bearing inserts one at a time for
inspection.
INSPECTION
Wipe the inserts clean and inspect for abnormal
wear patterns and for metal or other foreign material
imbedded in the lining. Normal main bearing insert
wear patterns are illustrated (Fig. 3).
If any of the crankshaft journals are scored,
remove the engine for crankshaft repair.
Inspect the back of the inserts for fractures, scrap-
ings or irregular wear patterns.
Inspect the upper insert locking tabs for damage.
Replace all damaged or worn bearing inserts.
FITTING (CRANKSHAFT INSTALLED)
The main bearing caps, numbered (front to rear)
from 1 through 5 have an arrow to indicate the for-
ward position. The upper main bearing inserts are
grooved to provide oil channels while the lower in-
serts are smooth.Each bearing insert pair is selectively fitted to its
respective journal to obtain the specified operating
clearance. In production, the select fit is obtained by
using various-sized color-coded bearing insert pairs
as listed in the Main Bearing Fitting Chart. The
bearing color code appears on the edge of the insert.
The size is not stamped on bearing inserts used
for engine production.
The main bearing journal size (diameter) is identi-
fied by a color-coded paint mark on the adjacent
cheek. The rear main journal, is identified by a color-
coded paint mark on the crankshaft rear flange.
When required, upper and lower bearing inserts of
different sizes may be used as a pair. A standard size
insert is sometimes used in combination with a 0.025
mm (0.001 inch) undersize insert to reduce the clear-
ance by 0.013 mm (0.0005 inch).Never use a pair
of bearing inserts with greater than a 0.025 mm
(0.001 inch) difference in size (Fig. 4).
When replacing inserts, the odd size inserts
must be either all on the top (in cylinder block)
or all on the bottom (in main bearing cap).
Once the bearings have been properly fitted, pro-
ceed to Crankshaft Main BearingÐInstallation.
Fig. 2 Removing Upper Inserts
Fig. 3 Main Bearing Wear Patterns
Fig. 4 Bearing Insert Pairs
J2.5L ENGINE 9 - 41

BEARING-TO-JOURNAL CLEARANCE (CRANKSHAFT
INSTALLED)
When using Plastigage, check only one bearing
clearance at a time.
Install the grooved main bearings into the cylinder
block and the non-grooved bearings into the bearing
caps.
Install the crankshaft into the upper bearings dry.
Place a strip of Plastigage across full width of the
crankshaft journal to be checked.
Install the bearing cap and tighten the bolts to 108
Nzm (80 ft. lbs.) torque.
DO NOT rotate the crankshaft. This will cause
the Plastigage to shift, resulting in an inaccurate
reading. Plastigage must not be permitted to
crumble. If brittle, obtain fresh stock.
Remove the bearing cap. Determine the amount of
clearance by measuring the width of the compressed
Plastigage with the scale on the Plastigage envelope
(Fig. 5). Refer to Engine Specifications for the proper
clearance.
Plastigage should indicate the same clearance
across the entire width of the insert. If clearance var-
ies, it may indicate a tapered journal or foreign ma-
terial trapped behind the insert.
If the specified clearance is indicated and there are
no abnormal wear patterns, replacement of the bear-
ing inserts is not necessary. Remove the Plastigage
from the crankshaft journal and bearing insert. Pro-
ceed to Crankshaft Main BearingÐInstallation.
If the clearance exceeds specification, install a pair
of 0.025 mm (0.001 inch) undersize bearing inserts
and measure the clearance as described in the previ-
ous steps.
The clearance indicated with the 0.025 mm (0.001
inch) undersize insert pair installed will determine if
this insert size or some other combination will pro-
vide the specified clearance.FOR EXAMPLE:If the clearance was 0.0762 mm
(0.003 inch) originally, a pair of 0.0254 mm (0.001
inch) undersize inserts would reduce the clearance by
0.0254 mm (0.001 inch). The clearance would then be
0.0508 mm (0.002 inch) and within the specification.
A 0.051 mm (0.002 inch) undersize bearing insert
and a 0.0254 mm (0.001 inch) undersize insert would
reduce the original clearance an additional 0.0127
mm (0.0005 inch). The clearance would then be
0.0381 mm (0.0015 inch).
CAUTION: Never use a pair of inserts that differ
more than one bearing size as a pair.
FOR EXAMPLE:DO NOT use a standard size up-
per insert and a 0.051 mm (0.002 inch) undersize
lower insert.
If the clearance exceeds specification using a pair
of 0.051 mm (0.002 inch) undersize bearing inserts,
measure crankshaft journal diameter with a mi-
crometer. If the journal diameter is correct, the
crankshaft bore in the cylinder block may be mis-
aligned, which requires cylinder block replacement
or machining to true bore.
If journals 1 through 5 diameters are less than
63.4517 mm (2.4981 inches), replace crankshaft or
grind crankshaft down to accept the appropriate un-
dersize bearing inserts.
Once the proper clearances have been obtained,
proceed to Crankshaft Main BearingÐInstallation.
MAIN BEARING JOURNAL DIAMETER (CRANKSHAFT
REMOVED)
Remove the crankshaft from the cylinder block (re-
fer to Cylinder Block - Disassemble).
Clean the oil off the main bearing journal.
Determine the maximum diameter of the journal
with a micrometer. Measure at two locations 90É
apart at each end of the journal.
The maximum allowable taper and out of round is
0.013 mm (0.0005 inch). Compare the measured di-
ameter with the journal diameter specification (Main
Bearing Fitting Chart). Select inserts required to ob-
tain the specified bearing-to-journal clearance.
Once the proper clearances have been obtained,
proceed to Crankshaft Main BearingÐInstallation.
INSTALLATION
(1) Lubricate the bearing surface of each insert
with engine oil.
(2) Loosen all the main bearing caps. Install the
main bearing upper inserts.
(3) Install the lower bearing inserts into the main
bearing caps.
(4) Install the main bearing cap(s) and lower in-
sert(s).
(5) Clean the rear main bearing cap (No.5) mating
surfaces.
Fig. 5 Measuring Bearing Clearance with Plastigage
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MAIN BEARING FITTING CHART
J2.5L ENGINE 9 - 43

(6) Apply Loctite 515, or equivalent on the rear
bearing cap (Fig. 6). The bead should be 3 mm (0.125
in) thick. DO NOT apply Loctite 515, or equivalent
to the lip of the seal.
(7) Install the rear main bearing cap. DO NOT
strike the cap more than twice for proper engage-
ment.
(8) Tighten the bolts of caps 1, 3, 4 and 5 to 54
Nzm (40 ft. lbs.) torque. Now tighten these bolts to 95
Nzm (70 ft. lbs.) torque. Finally, tighten these bolts
to 108 Nzm (80 ft. lbs.) torque.
(9) Push the crankshaft forward and backward.
Load the crankshaft front or rear and tighten cap
bolt No.2 to 54 Nzm (40 ft. lbs.) torque. Then tighten
to 95 Nzm (70 ft. lbs.) torque and finally tighten to
108 Nzm (80 ft. lbs.) torque.
(10) Rotate the crankshaft after tightening each
main bearing cap to ensure the crankshaft rotates
freely.
(11) Check crankshaft end play. Crankshaft end
play is controlled by the thrust bearing which is
flange and installed at the No.2 main bearing posi-
tion.
(a) Attach a magnetic base dial indicator to the
cylinder block at either the front or rear of the en-
gine.
(b) Position the dial indicator rod so that it is
parallel to the center line of the crankshaft.
(c) Pry the crankshaft forward, position the dial
indicator to zero.
(d) Pry the crankshaft forward and backward.
Note the dial indicator readings. End play is the
difference between the high and low measurements
(Fig. 7). Correct end play is 0.038-0.165 mm(0.0015-0.0065 inch). The desired specifications are
0.051-0.064 mm (0.002-0.0025 inch).
(e) If end play is not within specification, inspect
crankshaft thrust faces for wear. If no wear is ap-
parent, replace the thrust bearing and measure end
play. If end play is still not within specification, re-
place the crankshaft.
If the crankshaft was removed, install the crank-
shaft into the cylinder block (refer to Cylinder Block -
Assemble).
(12) Install the oil pan.
(13) Install the drain plug. Tighten the plug to 34
Nzm (25 ft. lbs.) torque.
(14) Lower the vehicle.
(15) Install the spark plugs. Tighten the plugs to
37 Nzm (27 ft. lbs.) torque.
(16) Fill the oil pan with engine oil to the full
mark on the dipstick level.
(17) Connect negative cable to battery.
REAR MAIN OIL SEALS
REMOVAL
(1) Remove the flywheel or converter drive plate.
Discard the old bolts.
(2) Pry out the seal from around the crankshaft
flange (Fig. 8).
INSTALLATION
(1) Coat the outer lip of the replacement rear main
bearing seal with engine oil.
(2) Carefully position the seal into place. Use rear
main Seal Installer Tool 6271 to install the seal flush
with the cylinder block.
CAUTION: The felt lip must be located inside the
flywheel mounting surface. If the lip is not posi-
tioned correctly the flywheel could tear the seal.
Fig. 6 Location of Loctite 515 (or equivalent)
Fig. 7 Crankshaft End Play Measurement
9 - 44 2.5L ENGINEJ

(3) Install the flywheel or converter drive plate.
New bolts MUST be used when installing the fly-
wheel or converter plate. Tighten the new bolts to 68
Nzm (50 ft. lbs.) torque. Turn the bolts an additional
60É.
CYLINDER BLOCK
Remove the Engine Assembly from the vehicle.
DISASSEMBLY
Refer to the applicable sections for detailed instruc-
tions.
(1) Drain the engine oil. Remove and discard the
oil filter.
(2) Remove the water pump from the cylinder
block.
(3) Remove the distributor from the cylinder block.
(4) Remove the vibration damper.
(5) Remove the timing case cover and lay the cover
upside down.
(6) Position a drift punch into the slot in the back
of the cover and tap the old seal out.
(7) Remove the timing chain bumper.
(8) Remove the oil slinger from crankshaft.
(9) Remove the camshaft retaining bolt and re-
move the sprockets and chain as an assembly.
(10) Remove the camshaft.
(11) Remove the oil pan and gasket.
(12) Remove the timing chain tensioner.
(13) Remove the front and rear oil galley plugs.
(14) Remove the connecting rods and the pistons.
Remove the connecting rod and piston assemblies
through the top of the cylinder bores.
(15) Remove the crankshaft.
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, the filter
bypass hole (Fig. 9).
²The front and rear oil galley holes (Figs. 10 and
11).
Fig. 8 Replacement of Rear Crankshaft Oil SealFig. 9 Oil Filter Adaptor Hole
Fig. 10 Front Oil Galley Hole
Fig. 11 Rear Oil Galley Hole
J2.5L ENGINE 9 - 45

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 41 Nzm (30 ft. lbs.) torque.
INSPECTIONÐCYLINDER BORE
(1) Use a bore gauge to measure each cylinder bore
diameter (Fig. 12). If a bore gauge is not available,
use an inside micrometer.
(2) Measure the cylinder bore diameter crosswise
to the cylinder block near the top of the bore. Repeat
the measurement near the bottom of the bore.
(3) Determine taper by subtracting the smaller di-
ameter from the larger diameter.
(4) Rotate measuring device 120É and repeat steps
above. Finally, rotate the device another 120É and re-
peat measurements.
(5) Determine out-of-roundness by comparing the
difference between each 120É measurement.(6) 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 con-
dition 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.
HONINGÐCYLINDER BORE
The honing operation should be closely coordinated
with the fitting of pistons and rings. This will ensure
specified clearances are maintained.
Refer to Standard Service Procedures in the begin-
ning of this Group for the proper honing of cylinder
bores.
ASSEMBLY
Refer to the applicable sections for detailed instruc-
tions.
(1) Install the crankshaft.
(2) Install the connecting rods and the pistons
through the top of the cylinder bores.
(3) Install the front and rear oil galley plugs.
(4) Install the timing chain tensioner.
(5) Install the camshaft.
(6) Install the sprockets and chain as an assembly.
(7) Install the oil slinger to the crankshaft.
(8) Install the timing chain bumper.
(9) Install the timing case cover seal.
(10) Install the timing case cover.
(11) Install the oil pan gasket and oil pan.
(12) Install the vibration damper.
(13) Install the water pump. Tighten the mounting
bolts to 31 Nzm (270 in. lbs.) torque.
(14) Remove the distributor from the cylinder
block.
(15) Lubricate the oil filter seal with clean engine
oil. Tighten oil filter to 18 Nzm (13 ft. lbs.) torque.
(16) Install the engine into the vehicle.
(17) Fill the engine with clean lubrication oil (re-
fer to Group 0, Lubrication and Maintenance).
(18) Fill the cooling system (refer to Group 7, Cool-
ing System for the proper procedures).
Fig. 12 Cylinder Bore Measurement
9 - 46 2.5L ENGINEJ

SPECIFICATIONS
ENGINE SPECIFICATIONS
J2.5L ENGINE 9 - 47

ENGINE SPECIFICATIONS (CONT.)
9 - 48 2.5L ENGINEJ

ENGINE SPECIFICATIONS (CONT.)
TORQUE SPECIFICATIONS
J2.5L ENGINE 9 - 49