
engine and connecting rod oil squirt hole should face camshaft side of
engine.
3) Install bearings. Check oil clearance and connecting rod
side play clearance. Reverse removal procedures for remaining
components. Tighten bolts to specification.
Fitting Pistons
1) Determine cylinder taper, wear and out-of-roundness and
piston clearance. For cylinder specifications, see CYLINDER, PISTON &
CONNECTING ROD SPECIFICATIONS table. If taper or out-of-roundness are
not within specification, hone or bore cylinders for installation of
new pistons.
2) Measure piston at right angle of the piston pin at the
center line of the pin. Compare reading to cylinder bore to determine
clearance. Mark fitted piston for cylinder location.
CYLINDER, PISTON & CONNECTING ROD SPECIFICATIONS TABLE
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Application In. (mm)
Connecting Rod
Crankshaft Bore .......... 2.2080-2.2085 (56.083-56.095)
Pin Bore ................... .9288-.9298 (23.591-23.616)
Cylinder Bore
Diameter ................. 3.8751-3.8775 (98.427-98.488)
Out-of-Round ................................ .001 (.02)
Taper ....................................... .001 (.02)
Piston Pin Bore Diameter ..... .9308-.9313 (23.642-23.655)
Piston Pin Diameter .......... .9304-.9309 (23.632-23.644)
Piston-to-Cylinder Clearance ..... .0009-.0017 (.022-.043)
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PISTON PIN REPLACEMENT
NOTE: Note direction of arrow on piston and oil squirt hole in
connecting rod prior to removal.
Removal
Position piston on Support (J-21872-1), Pin Pilot (J-21872-2\
)
and Driver (J-21872-3) on an arbor press. See Fig. 6. Press piston pin
from piston.
NOTE: Piston and pin must be at standard room temperature when
measuring fit. Piston pin should gravity-fall through the
piston at room temperature. Piston pin cannot be reused
after removal.
Inspection
Measure piston pin diameter, piston bore and connecting rod
bores. Replace components if not within specification. See CYLINDER,
PISTON & CONNECTING ROD SPECIFICATIONS table.
NOTE: Connecting rod must be positioned on the piston so the oil
squirt hole faces the camshaft side of the engine with
piston installed with arrow toward the front of the engine.
Installation
1) Insert pin pilot through piston and connecting rod. Place
assembly on support. Insert piston pin through the upper piston pin
bore and into connecting rod pin bore. See Fig. 6.

1) Drain cooling system. Remove fan shroud and drive belts.
Remove fan assembly.
2) Disconnect heater hoses and lower radiator hose at water
pump. Remove water pump retaining bolts. Remove water pump.
Installation
Clean all gasket surfaces. 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 With 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 Without 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 system capacities and
other cooling system components, see ENGINE COOLING SYSTEMS
article.
ENGINE OILING
CRANKCASE CAPACITY
Crankcase capacity is 4 qts. (3.8 L) with oil filter change.
NORMAL OIL PRESSURE
Normal oil pressure should be 13 psi (.91 kg/cm) at 600 RPM
or 37-75 psi (2.6-5.3 kg/cm) at 1600 RPM.
OIL PRESSURE REGULATOR VALVE
Oil pressure regulator valve is located in oil pump body and
is nonadjustable.
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 runs along right
side of block and intersects 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. By-pass valves are located in oil filter mounting and oil
pump.
OIL PUMP
Removal
Remove oil pan. See OIL PAN REMOVAL article. Remove oil pump

engine.
3) Install bearings. Check oil clearance and connecting rod
side play clearance. Reverse removal procedure for remaining
components. Tighten bolts to specification.
Fitting Pistons
1) Determine cylinder taper, wear and out-of-roundness and
piston clearance. For cylinder specifications, see CYLINDER, PISTON &
ROD SPECIFICATIONS table. If taper or out-of-roundness are not within
specification, hone or bore cylinders for installation of new pistons.
2) Measure piston at right angle of the piston pin at the
center line of the pin. Compare reading to cylinder bore to determine
clearance. Mark fitted piston for cylinder location.
CYLINDER, PISTON & ROD SPECIFICATIONS TABLE
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Application In. (mm)
Connecting Rod
Crankshaft Bore ................ 2.2080-2.2085 (56.083-56.095)
Pin Bore ......................... .9288-.9298 (23.591-23.616)
Cylinder Bore
Diameter
4.0L ......................... 3.8751-3.8775 (98.427-98.488)
4.2L ......................... 3.7501-3.7533 (95.252-95.334)
Out-of-Round ...................................... .001 (.02)
Taper ............................................. .001 (.02)
Piston Pin Bore Diameter ........... .9308-.9313 (23.642-23.655)
Piston Pin Diameter ................ .9304-.9309 (23.632-23.644)
Piston-to-Cylinder Clearance ..... .0009-.0017 (.022-.043)
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PISTON PIN
NOTE: Note direction of arrows on piston and oil squirt hole in
connecting rod location prior to removal.
Removal
Position piston on Support (J-21872-1), Pin Pilot (J-21872-2\
)
and Driver (J-21872-3) on an arbor press. See Fig. 6. Note location of
piston pin through gauge window. Press piston pin from piston.
NOTE: Piston and pin must be at standard room temperature when
measuring fit. Piston pin should gravity-fall through the
piston at room temperature. Piston pin cannot be reused
after removal.
Inspection
Measure piston pin diameter, piston bore and connecting rod
bores. Replace components if not within specification. See CYLINDER,
PISTON & ROD SPECIFICATIONS table.
NOTE: Rod must be positioned on the piston so the oil squirt hole
faces the camshaft side of the engine when piston is
installed with arrow toward the front of the engine.
Installation
1) Insert pin pilot through piston and connecting rod. Place
assembly on support. Insert piston pin through the upper piston pin
bore and into connecting rod pin bore. See Fig. 6.

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

of the scale, a symbol for defroster indicates defrost position. In
"BI-LEVEL" position, a mixture of floor heat and defroster air is
obtained.
The lower temperature control lever operates blend-air door
in heater core housing. At full right position, all air is directed
through heater core, providing maximum heat flow. At full left
position, all air is directed around heater core providing fresh air.
Control can be set in any intermediate position to provide a blend of
heated and unheated air. Heater must be in heat or defrost mode before
any air can enter vehicle.
TROUBLE SHOOTING
See JEEP TROUBLE SHOOTING at the end of this article.
REMOVAL & INSTALLATION
CONDENSER
Removal (Cherokee, Comanche & Wagoneer) NOTE: On these
models, condenser and receiver-drier are replaced
as a unit.
1) Drain radiator. Disconnect fan shroud and radiator hoses.
Disconnect automatic transmission cooler lines (if equipped).
Discharge A/C system using approved refrigerant recovery/recycling
equipment.
2) Disconnect A/C hoses from condenser. Unplug low pressure
switch. Remove radiator and condenser as an assembly. Detach condenser
retaining bolts. Separate condenser from radiator. Remove receiver-
drier from condenser.
NOTE: Plug receiver-drier openings whenever unit is removed from
condenser. Add 1 oz. of refrigerant oil (AMC No. 8132400) to
system when replacing condenser.
Installation
To install, reverse removal procedure. Fill radiator.
Evacuate, leak test, recharge and check A/C system operation.
Removal (Wrangler)
1) Discharge system (slowly to prevent loss of compressor
oil) using approved refrigerant recovery/recycling equipment. Drain
coolant. Remove fan shroud and radiator. Disconnect pressure line at
condenser. Remove condenser mounting screws. Tilt bottom of condenser
toward engine.
2) From underside of vehicle, disconnect hose attaching
receiver-drier to evaporator. Plug all openings to prevent entry of
dirt or moisture. Remove receiver-drier and condenser assembly. Remove
receiver-drier from condenser.
Installation
To install, reverse removal procedure. Fill radiator.
Evacuate, leak test, recharge and check A/C system operation.
RECEIVER-DRIER
NOTE: On Cherokee, Comanche and Wagoneer, receiver-drier is
removed with condenser and radiator as an assembly.
Removal (Wrangler)

Carefully remove thermostat and capillary tube.
NOTE: On Wrangler models, servicing temperature control thermostat
requires disassembly of evaporator core housing.
Installation
To install, insert capillary tube into evaporator coil a
minimum of 2" (51 mm). See Fig. 4. Install thermostat and evaporator
housing lower cover.
Fig. 3: Capillary Tube & Temperature Control Thermostat Locations
Cherokee, Comanche and Wagoneer locations are shown.

2000 ....................... 27.82 ........................... 2.1
3000 ....................... 26.82 ........................... 3.1
4000 ....................... 25.82 ........................... 4.1
5000 ....................... 24.92 ........................... 5.0
6000 ....................... 23.92 ........................... 6.0
7000 ....................... 23.02 ........................... 6.9
8000 ....................... 22.22 ........................... 7.7
9000 ....................... 21.32 ........................... 8.6
10,000 ..................... 20.52 ........................... 9.4
(1) - Add correction shown to gauge readings
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OPERATIONAL TEST GAUGE READINGS
Normal System Operating Pressures (PSI) ( 1)
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Low Side High Side
Gauge Gauge
Application (Suct.) (Disc.\
)
Jeep 1980-87
(Thermostatic Switch) ........ 5-24 ................... 208-250\
1988
(Accumulator Type) ........... 24-50 .................. 160-250\
( 1) - Pressure readings given are for a system in good operating
condition, at sea level and an ambient temperature of 80
F
(27C). \
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AIR CONDITIONING SYSTEM PERFORMANCE CHECK TABLE \
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PERFORM TESTS: SHOULD BE: IF: \
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Temperature Check Temperature Check is
* Switch to LOW
blower
* Close doors Too warm-Check control lever
* Check outlet 35-45
F (1.7-7.2C) operation, heater water valve,
temperature. cooling system and gauge
readings.
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Visual Check Visual Check Shows:
* Compressor Quiet, no leaks Noisy-Check belts, oil level,
seals, gaskets, reed valves.
* Condenser Free of Blocked-Clean off. Plugged-
obstructions Flush or replace.
* Receiver- Dry and warm to Frosty-Check for restriction,
Drier touch. replace desiccant.
* Sight Glass Clear or few Bubbly, foamy or streaks-
bubbles Check gauge readings.
* High Side Dry and warm to Frosty or very hot-Check for
touch. restriction or overcharge.
* Low Side Dry and cool to Frosty or warm-Check for
Lines touch. restriction, low charge or
bad valve.

* Switch to LOW
blower.
* Close doors. Too warm - Check control
lever operation, heater
water valve, cooling
system and gauge readings.
* Check outlet
temperature. 35-45
F (1.7-7.2 C)\
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Visual Check Visual Check Shows:
* Compressor Quiet, No Leaks Noisy - Check belts, oil
level, seals, gaskets,
reed valves.
* Condenser Free of Obstructions Blocked - Clean off.
Plugged - Flush or
replace.
* Receiver-Drier Dry and warm to Frosty - Check for re-
touch striction, replace
Desicant.
* Sight Glass Clear or few bubbles Bubbly, foamy or streaks -
Check gauge readings.
* High Side Lines Dry and warm to Frosty or very hot - Check
touch for restriction or
overcharge.
* Low Side Lines Dry and cool to Frosty or warm - Check for
touch restriction, low charge or
bad valve.
* Expansion Valve Dry Frosty - Check for moisture
or restriction. Check
sensing bulb.
* STV Dry and cool to Frosty or warm - Check
touch gauge readings for valve
malfunction.
* Evaporator Dry and cold to Freezing or warm - Check
touch expansion valve, STV or
thermo switch.
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Gauge Readings Gauge Readings are:
* High Side Gauge See Pressure Chart Above or below normal - See
A/C DIAGNOSIS.
* Low Side Gauge See Pressure Chart Above or below normal - See
A/C DIAGNOSIS.
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PRESSURE CHARTS