1988 JEEP CHEROKEE Service Repair Manual

ROD BEARING
NOTE: Crankshaft journal diameters are indicated by a color coded
mark placed on the adjacent counterweight or cheek toward
the flanged (rear) end of crankshaft. Note color code to
determine proper bearing usage. Check oil clearance after
bearing installation.
Removal
Remove oil pan. See OIL PAN REMOVAL at end of ENGINE section.
Rotate crankshaft to position rod to be serviced at bottom of stroke.
Mark bearing cap and connecting rod. Remove bearing cap with bearing.
Push piston and rod assembly up to remove upper bearing.
Installation
1) Note color code on edge of bearings removed. Install
bearings. Using Plastigage method, check bearing clearances. Replace
bearings as necessary to obtain correct clearance. Bearings are
available in standard and undersize application.
2) If required, different sized upper and lower bearings may
be installed to obtain correct oil clearance. Tighten bolts to
specification. Check rod side play. Rotate crankshaft to ensure
freedom of movement. Reverse removal procedure for remaining
components. Tighten bolts to specification.
NOTE: Avoid combining bearing inserts in excess of .001" (.02 mm)
difference in size.
MAIN BEARING
Removal
Remove oil pan. See OIL PAN REMOVAL at end of ENGINE section.
Ensure main bearing caps are marked for location. Remove bearing cap.
Rotate crankshaft to remove bearings. Note color code on edge of
bearing.
NOTE: Crankshaft main bearing journal diameters are indicated by a
color code. Color code is placed on the adjacent cheek
toward the flanged (rear) end of crankshaft for all except
the rear main. Rear main is color coded on the rear flange.
Note color code to determine proper bearing usage. Check oil
clearance after bearing installation.
Installation
1) Note color code on edge of bearings removed. Install
bearings. Ensure caps are installed in original location with arrow on
cap facing toward front of engine. Using Plastigage method, check
bearing clearances.
2) Replace bearings as necessary to obtain correct clearance.
Bearings are available in standard and undersize applications. If
required, different sized upper and lower bearings may be installed to
obtain correct oil clearance.
NOTE: If different sized bearings are used, odd sized bearings must
all be uniform in location (upper or lower). DO NOT use
bearings with a thickness difference exceeding
.001" (.02 mm).
3) Tighten bolts to specification. Check crankshaft end play.
See CRANKSHAFT END PLAY in this article. Rotate crankshaft to ensure
freedom of movement. Reverse removal procedure for remaining
components. Tighten bolts to specification.

Crankshaft End Play
1) Using dial indicator, check crankshaft end play. Inspect
crankshaft thrust surfaces or thrust bearing for wear if not within
specification. See ENGINE SPECIFICATIONS table.
2) Replace thrust bearing if required. When replacing thrust
bearing, pry crankshaft forward then reward prior to tightening main
bearing cap to specification. Recheck end play. Replace crankshaft if
not within specification.
REAR MAIN OIL SEAL
Removal
1) Remove oil pan. See OIL PAN REMOVAL in this section.
Remove rear main bearing cap. Note direction of seal lip installation.
Remove seal from bearing cap. Loosen all remaining main bearing cap
bolts.
2) Using a brass drift, tap upper seal around crankshaft
until seal protrudes enough to permit removal with pliers. Remove
seal.
Installation
1) Clean crankshaft seal surface. Coat seal-to-block contact
areas with liquid soap. Lightly coat all seal lips with engine oil.
See Fig. 7 . Install upper seal into block with lip facing toward front
of engine.
2) Apply Silicone sealer on both sides of lower seal tabs.
Ensure no sealer is applied on seal lip. Apply liquid soap on seal-to-
cap contact surfaces.
3) Install lower seal into bearing cap with lip facing toward
front of engine. Ensure seal is firmly seated in bearing cap. Apply
Silicone sealer to chamfered edges of bearing cap. See Fig. 7.
CAUTION: DO NOT apply Silicone sealer on cap-to-block contact
surfaces. Sealer should only be applied to chamfered edges
only.
4) Install rear main bearing cap. Tighten main bearing cap
bolts to specification.
Fig. 7: Installing Rear Main Bearing Oil Seal
Courtesy of Chrysler Motors.
WATER PUMP

Removal
Drain cooling system. Disconnect radiator and heater hoses
from pump. Remove drive belt(s). Remove fan shroud. Remove fan
assembly. Remove electric cooling fan (if equipped). Remove power
steering bracket from water pump. Remove water pump and gasket.
Installation
Ensure gasket surfaces are clean. Install water pump. Tighten
bolts to specification. Ensure pump turns freely. Reverse removal
procedures. Fill and purge air from cooling system.
NOTE: It may be necessary to remove heater hose to remove trapped
air if system cannot be purged using following procedures.
Cooling System Air Purge (Vehicles W/Coolant Recovery)
Fill system to proper level. Place heater control to "HEAT"
position and temperature control to "WARM" or "HIGH" position. Install
coolant caps. Operate engine to normal operating temperature. Shut off
engine and allow system to cool. Add coolant to recovery bottle.
Repeat procedure to obtain correct coolant level.
Cooling System Air Purge (Vehicles W/O Coolant Recovery)
Fill system to proper level. Place heater control to "HEAT"
position and temperature control to "WARM" or "HIGH" position. Operate
engine to normal operating temperature with radiator cap removed. Add
necessary coolant and install radiator cap.
NOTE: For further information on cooling systems, see appropriate
article in the ENGINE COOLING section.
LUBRICATION
CRANKCASE CAPACITY
Crankcase capacity for 4.0L is 5 1/2 qts. (5.2L) or 5 qts.
(4.7L) for 4.2L with oil filter change.
NORMAL OIL PRESSURE
Normal oil pressure should be 37-75 psi (2.6-5.3 kg/cm)
maximum above 1600 RPM. Minimum oil pressure should be 13 psi (.9
kg/cm
) at 600 RPM.
OIL PRESSURE REGULATOR VALVE
Oil pressure regulator valve is located in pump body. Valve
is nonadjustable and serviced as an assembly.
ENGINE OILING SYSTEM
Engine lubrication is provided by the distributor driven
gear-type oil pump. Oil is supplied through the full-flow oil filter
and into an internal oil passage. Internal passage provides oil to the
lifter bores. Oil is then routed to camshaft and crankshaft bearings.
Oil is supplied to rocker arms from the hydraulic lifters and through
the push rods.
OIL PUMP
Removal
Remove oil pan. See OIL PAN REMOVAL in this section. Remove

oil pump retaining bolts.
CAUTION: DO NOT move oil pick-up pipe in pump body. If oil pick-up
pipe is moved, pick-up pipe must be replaced to ensure an
airtight seal.
Disassembly & Inspection
1) Disassemble pump. See Fig. 8. Use feeler gauge and
straightedge to check gear end clearance. Place straightedge across
gears and pump body. Using feeler gauge, determine thickness feeler
gauge which fits snugly between straightedge and gears.
2) With gears installed in pump body, insert feeler gauge
between gear tooth and inner wall of pump body to check gear-to-body
clearance. Rotate gears and measure clearance at each gear tooth.
3) Compare measurements to specification. See OIL PUMP
SPECIFICATIONS table. Repair as necessary if not within
specifications. Check pressure regulator valve for wear or binding in
pump body. Replace components if wear or binding exists.
OIL PUMP SPECIFICATIONS TABLE









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Application In. (mm)
Gear End Clearance ........... .004-.008 (.10-.20)
Gear-to-Body Clearance ....... .002-.004 (.05-.10)









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CAUTION: If pressure regulator valve is replaced, ensure replacement
valve is the same diameter as that removed. Different
diameter valves may be used.
Reassembly & Installation
1) Reverse procedures for reassembly and installation. Apply
Permatex No. 2 to pick-up pipe prior to installation. Using Pipe
Installer (J-21882), install pick-up pipe. Ensure pick-up pipe support\
bracket is aligned with pump cover bolt.
2) Fill gear cavity with petroleum jelly prior to installing
cover. Apply Loctite on pump cover area. Install cover and bolts.
Tighten bolts to specification. Check pump gears for freedom of
rotation.
3) Install oil pump and new gasket. Tighten retaining bolts
to specification.
Fig. 8: Exploded View of Oil Pump Assembly
Courtesy of Chrysler Motors.
TORQUE SPECIFICATIONS TABLE

TORQUE SPECIFICATIONS TABLE








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Application Ft. Lbs. (N.m)
Camshaft Sprocket Bolt .......................... 80 (109)
Connecting Rod Cap Nut ........................... 33 (45)
Crankshaft Pulley-to-Damper Bolt ................. 20 (27)
Cylinder Head Bolt
4.0L
No. 11 .................................... 100 (135)
All Others ................................. 110 (149)
4.2L
No. 11 ..................................... 75 (102)
All Others .................................. 85 (115)
Exhaust Pipe-to-Manifold Bolt .................... 20 (27)
Fan & Hub Bolt ................................... 18 (24)
Flywheel-to-Crankshaft Bolt .................... 105 (142)
Fuel Rail Bolt ................................... 20 (27)
Intake & Exhaust Manifold Bolt
4.0L
Exhaust Manifold Bolts 1-5 ................... 23 (31)
Exhaust Manifold Bolts 6-7 .................. 17 (23)
Exhaust Manifold Bolts 8-11 ................. 23 (31)
Exhaust Manifold Bolts 12-13 ................ 30 (41)
4.2L ........................................... 23 (31)
Main Bearing Cap Bolt
Step 1 ......................................... 40 (54)
Step 2 ......................................... 70 (95)
Step 3 ........................................ 80 (109)
Oil Pump Attaching Bolt
Short .......................................... 10 (14)
Long ........................................... 17 (23)
Oxygen Sensor .................................... 35 (47)
Rocker Arm Bolt .................................. 19 (26)
Vibration Damper Bolt ....................... (1) 80 (109)
Water Pump Bolts ................................. 13 (18)
INCH Lbs. (N.m)
Engine Front Cover
Bolt ............................................ 60 (7)
Studs ......................................... 192 (22)
Oil Pan Bolt
1/4" X 20 ....................................... 84 (9)
5/16" X 18 .................................... 132 (15)
Oil Pump Cover Bolt ............................... 70 (8)
Valve Cover Bolt .................................. 55 (5)
( 1) - Clean and lubricate with oil prior to tightening.









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ENGINE SPECIFICATIONS
GENERAL ENGINE SPECIFICATIONS
GENERAL SPECIFICATIONS TABLE








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Application In. (mm)
4.0L
Displacement

Cu. In. .......................................... 242
Liters ........................................... 4.0
Fuel System ........................................ MPI
HP@RPM ...................................... 173 @ 2500
Torque Ft. Lbs.@RPM ......................... 220 @ 2500
Compression Ratio ................................ 9.2:1
Bore ....................................... 3.88 (98.4)
Stroke ..................................... 3.44 (87.4)
4.2L
Displacement
Cu. In. .......................................... 258
Liters ........................................... 4.2
Fuel System ..................................... 2-Bbl.
HP@RPM ...................................... 112 @ 3000
Torque Ft. Lbs.@RPM ......................... 210 @ 2000
Compression Ratio ................................ 9.2:1
Bore ....................................... 3.75 (95.3)
Stroke ..................................... 3.90 (98.9)









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VALVE SPECIFICATIONS
VALVES SPECIFICATIONS TABLE








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Application In. (mm)
4.0L
Intake
Head Diameter ........................... 1.91 (48.51)
Face Angle ....................................... 45

Seat Angle ..................................... 44.5
Seat Width ..................... .040-.060 (1.02-1.52)
Stem Diameter ............................ .312 (7.92)
Stem Clearance ................... .001-.003 (.03-.08)
Valve Lift .............................. .424 (10.76)
Exhaust
Head Diameter ........................... 1.50 (38.10)
Face Angle ....................................... 45

Seat Angle ..................................... 44.5
Seat Width ..................... .040-.060 (1.02-1.52)
Stem Diameter ............................ .312 (7.92)
Stem Clearance .................. .001-.003 (.03-.003)
Valve Lift .............................. .424 (10.76)
Valve Spring Height Installed ............ 1.625 (41.29)
4.2L
Intake
Head Diameter .................. 1.78-1.79 (45.3-45.5)
Face Angle ....................................... 29

Seat Angle ....................................... 30
Seat Width ..................... .040-.060 (1.02-1.52)
Stem Diameter ................ .3715-.3725 (9.44-9.46)
Stem Clearance ................... .001-.003 (.03-.08)
Valve Lift .............................. .405 (10.29)
Exhaust
Head Diameter .................. 1.40-1.41 (35.6-35.8)
Face Angle ....................................... 44

Seat Angle ..................................... 44.5
Seat Width ..................... .040-.060 (1.02-1.52)
Stem Diameter ................ .3715-.3725 (9.44-9.46)
Stem Clearance ................... .001-.003 (.03-.08)
Valve Lift .............................. .405 (10.29)
Valve Spring Height Installed ...................... ( 1)

(1) - Specification not provided from manufacturer.








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PISTON/PIN/RING SPECIFICATIONS
PISTONS, PINS & RINGS TABLE








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Application In. (mm)
Piston Clearance ................. .0009-.0017 (.023-.043)
Pins
Piston Fit ..................... .0003-.0005 (.008-.013)
Rod Fit ...................................... Press Fit
Rings
Ring No. 1 & No. 2
End Gap .......................... .010-.020 (.25-.51)
Side Clearance ............... .0017-.0032 (.043-.081)
Ring No. 3
End Gap .......................... .010-.025 (.25-.64)
Side Clearance .................. .001-.008 (.03-.020)









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BEARING SPECIFICATIONS
CRANKSHAFT MAIN & CONNECTING ROD BEARINGS TABLE








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Application In. (mm)
Main Bearings
Journal Diameter ........... 2.4996-2.5001 (63.49-63.50)
Clearance ....................... .0010-.0025 (.03-.064)
Thrust Bearing ................................... No. 3
Crankshaft End Play ............ .0015-.0065 (.038-1.65)
Connecting Rod Bearings
Journal Diameter ........... 2.0934-2.0955 (53.17-53.23)
Clearance .......................... .001-.003 (.03-.08)
Side Play .......................... .010-.019 (.25-.48)









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CAMSHAFT SPECIFICATIONS
CAMSHAFT TABLE








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Application In. (mm)
Clearance ............................ .001-.003 (.03-.08)
Lobe Lift .................................... .253 (6.43)
Journal Diameter
No. 1 ........................ 2.029-2.030 (51.54-51.56)
No. 2 ........................ 2.019-2.020 (51.28-51.31)
No. 3 ........................ 2.009-2.010 (51.03-51.05)
No. 4 ........................ 1.999-2.000 (50.77-50.80)









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VALVE SPRING SPECIFICATIONS
VALVE SPRINGS TABLE








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Application In. (mm)
4.0L
Pressure ( 1)

Valve Closed ............ 66-74 @ 1.625 (30-34 @ 45.5)
Valve Open ........... 205-220 @ 1.20 (91-100 @ 30.48)
Free Length ............................... 1.82 (46.23)
4.2L
Pressure (1)
Valve Closed ............. 64-72 @ 1.79 (29-33 @ 45.5)
Valve Open ............. 188-202 @ 1.41 (85-92 @ 35.8)
Free Length ................................ 1.99 (50.5)
( 1) - Lbs. @ In. (Kg @ mm).









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