JEEP YJ 1995 Service And Repair Manual

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 41 Nzm (30 ft. lbs.) torque.
INSPECTIONÐCYLINDER BORE
(1) It is mandatory to use a dial bore gauge to
measure each cylinder bore diameter (Fig. 12). To
correctly select the proper size piston, a cylinder bore
gauge, Special Tool 6879, capable of reading in .00019
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 readings.
(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 di-
ameter 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 con-
dition exceeds these maximum limits, the cylinder
must be bored and then honed to accept an oversizepiston. 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 oil pump.
(4) Install the oil pan and gasket.
(5) Install the camshaft.
(6) Install the sprockets and chain as an assembly.
(7) Install the oil slinger from the crankshaft.
(8) Install the timing case cover seal.
(9) Install the timing case cover.
(10) Install the vibration damper.
(11) Install the water pump. Tighten the mounting
bolts to 31 Nzm (270 in. lbs.) torque.
(12) Lubricate the oil filter seal with clean engine
oil. Tighten oil filter to 18 Nzm (13 ft. lbs.) torque.
(13) Install the engine into the vehicle.
(14) Fill the engine with clean lubrication oil (refer
to Group 0, Lubrication and Maintenance).
(15) Fill the cooling system (refer to Group 7, Cool-
ing System for the proper procedures).
Fig. 12 Cylinder Bore Measurement
9 - 92 4.0L ENGINEJ

SPECIFICATIONS
ENGINE SPECIFICATIONS
J4.0L ENGINE 9 - 93

ENGINE SPECIFICATIONS (CONT.)
9 - 94 4.0L ENGINEJ

ENGINE SPECIFICATIONS (CONT.)
TORQUE SPECIFICATIONS
J4.0L ENGINE 9 - 95

EXHAUST SYSTEM AND INTAKE MANIFOLD
CONTENTS
page page
EXHAUST SYSTEM....................... 1
EXHAUST SYSTEM DIAGNOSIS............. 2SERVICE PROCEDURES................... 3
TORQUE SPECIFICATIONS................ 10
EXHAUST SYSTEM
GENERAL INFORMATION
The basic exhaust system consists of an engine ex-
haust manifold, exhaust pipe with oxygen sensor, cat-
alytic converter, exhaust heat shield(s), muffler and
exhaust tailpipe (Fig. 1).
The exhaust system uses a single muffler with a
single monolithic-type catalytic converter.
The 4.0L engines use a seal between the engine ex-
haust manifold and exhaust pipe to assure a tight
seal and strain free connections.
The exhaust system must be properly aligned to
prevent stress, leakage and body contact. If the sys-
tem contacts any body panel, it may amplify objec-tionable noises originating from the engine or body.
When inspecting an exhaust system, critically in-
spect for cracked or loose joints, stripped screw or
bolt threads, corrosion damage and worn, cracked or
broken hangers. Replace all components that are
badly corroded or damaged. DO NOT attempt to re-
pair.
When replacement is required, use original equip-
ment parts (or their equivalent). This will assure
proper alignment and provide acceptable exhaust
noise levels.
CAUTION: Avoid application of rust prevention com-
pounds or undercoating materials to exhaust sys-
tem floor pan exhaust heat shields. Light overspray
near the edges is permitted. Application of coating
will result in excessive floor pan temperatures and
objectionable fumes.
CATALYTIC CONVERTER
The stainless steel catalytic converter body is de-
signed to last the life of the vehicle. Excessive heat
can result in bulging or other distortion, but exces-
sive heat will not be the fault of the converter. If un-
burned fuel enters the converter, overheating may
occur. If a converter is heat-damaged, correct the
cause of the damage at the same time the converter
is replaced. Also, inspect all other components of the
exhaust system for heat damage.
Unleaded gasoline must be used to avoid contami-
nating the catalyst core.
EXHAUST HEAT SHIELDS
Exhaust heat shields are needed to protect both the
vehicle and the environment from the high tempera-
tures developed by the catalytic converter. The cata-
lytic converter releases additional heat into the
exhaust system. Under severe operating conditions,
the temperature increases in the area of the con-
Fig. 1 Typical Exhaust System
JEXHAUST SYSTEM AND INTAKE MANIFOLD 11 - 1

verter. Such conditions can exist when the engine
misfires or otherwise does not operate at peak effi-
ciency.
DO NOT remove spark plug wires from plugs or by
any other means short out cylinders. Failure of the
catalytic converter can occur due to a temperature
increase caused by unburned fuel passing through
the converter.DO NOT allow the engine to operate at fast idle for
extended periods (over 5 minutes). This condition
may result in excessive temperatures in the exhaust
system and on the floor pan.
EXHAUST SYSTEM DIAGNOSIS
11 - 2 EXHAUST SYSTEM AND INTAKE MANIFOLDJ

SERVICE PROCEDURES
INDEX
page page
Catalytic Converter......................... 4
Engine Exhaust ManifoldÐ2.5L Engine.......... 7
Engine Exhaust ManifoldÐ4.0L Engine.......... 7
Exhaust PipeÐXJ Vehicles................... 3
Exhaust PipeÐYJ Vehicles................... 4Intake ManifoldÐ2.5L Engine................. 7
Intake ManifoldÐ4.0L Engine................. 8
Muffler and Exhaust TailpipeÐXJ Vehicles........ 5
Muffler and Exhaust TailpipeÐYJ Vehicles........ 6
EXHAUST PIPEÐXJ VEHICLES
WARNING: IF TORCHES ARE USED WHEN WORK-
ING ON THE EXHAUST SYSTEM, DO NOT ALLOW
THE FLAME NEAR THE FUEL LINES.
REMOVAL
(1) Raise and support the vehicle.
(2) Saturate the bolts and nuts with heat valve lu-
bricant (Fig. 1). Allow 5 minutes for penetration.
(3) Remove the oxygen sensor from the exhaust
pipe (Fig. 2).
(4) Disconnect the exhaust pipe from the engine
exhaust manifold. Discard the seal (4.0L engine,
only).(5) Support the transmission and remove the rear
crossmember.
(6) Remove the clamp nuts and clamp (Fig. 3). To
remove the exhaust pipe from the catalytic converter,
apply heat until the metal becomes cherry red. Dis-
connect the exhaust pipe from the catalytic converter
(Fig. 3). Remove the exhaust pipe.
Fig. 1 Exhaust Pipe-to-Engine Exhaust Manifold
Nuts
Fig. 2 Oxygen Sensor
Fig. 3 Exhaust Pipe-to-Catalytic Converter
Connection
JEXHAUST SYSTEM AND INTAKE MANIFOLD 11 - 3

INSTALLATION
(1) Assemble exhaust pipe to manifold and cata-
lytic converter loosely to permit proper alignment of
all parts.
(2) Use a new clamp and tighten the nuts to 61
Nzm (45 ft. lbs.) torque.
(3) Connect the exhaust pipe to the engine exhaust
manifold. Install a new seal between the exhaust
manifold and the exhaust pipe (4.0L engine, only).
Tighten the nuts to 31 Nzm (23 ft. lbs.) torque (Fig.
1).
(3) Install the rear crossmember. Tighten the
crossmember-to-sill bolts to 41 Nzm (30 ft. lbs.)
torque. Remove the support from the transmission.
(4) Coat the oxygen sensor with anti-seize com-
pound. Install the sensor and tighten the nut to 48
Nzm (35 ft. lbs.) torque.
(5) Lower the vehicle.
(6) Start the engine and inspect for exhaust leaks
and exhaust system contact with the body panels.
Adjust the alignment, if needed.
EXHAUST PIPEÐYJ VEHICLES
WARNING: IF TORCHES ARE USED WHEN WORK-
ING ON THE EXHAUST SYSTEM, DO NOT ALLOW
THE FLAME NEAR THE FUEL LINES.
REMOVAL
(1) Raise and support the vehicle.
(2) Saturate the bolts and nuts with heat valve lu-
bricant (Fig. 4). Allow 5 minutes for penetration.(3) Remove the oxygen sensor from the exhaust
pipe (Fig. 2).
(4) Disconnect the exhaust pipe from the engine
exhaust manifold.
(5) Disconnect the exhaust pipe from the catalytic
converter and slide the pipe out of the transmission
torque arm insulator (Fig. 5). Remove the exhaust
pipe.
INSTALLATION
(1) Slide the exhaust pipe into the transmission
torque arm insulator and onto the catalytic converter
(Fig. 5).
(2) Clean the mating surface of the engine exhaust
manifold flange.
(3) Connect the exhaust pipe to the engine exhaust
manifold using new nuts. DO NOT tighten the nuts.
(4) Align the exhaust pipe.
(5) Use a new clamp at the exhaust pipe to cata-
lytic converter connection and tighten the nuts to 61
Nzm (45 ft. lbs.) torque.
(6) Tighten the exhaust pipe-to-engine exhaust
manifold nuts to 31 Nzm (23 ft. lbs.) torque.
(7) Coat the oxygen sensor with anti-seize com-
pound. Install the sensor and tighten the nut to 48
Nzm (35 ft. lbs.) torque.
(8) Lower the vehicle.
(9) Start the engine and inspect for exhaust leaks
and exhaust system contact with the body panels.
Adjust the alignment, if needed.
CATALYTIC CONVERTER
WARNING: IF TORCHES ARE USED WHEN WORK-
ING ON THE EXHAUST SYSTEM, DO NOT ALLOW
THE FLAME NEAR THE FUEL LINES.
REMOVAL
(1) Raise and support the vehicle.
Fig. 4 Exhaust Pipe-to-Engine Exhaust Manifold
Bolts and Nuts
Fig. 5 Exhaust Pipe-to-Catalytic Converter
ConnectionÐYJ Vehicles
11 - 4 EXHAUST SYSTEM AND INTAKE MANIFOLDJ

(2) Remove the clamp from the catalytic converter
and muffler connection (Fig. 6).
(3) Heat the catalytic converter and muffler con-
nection with an oxyacetylene torch until the metal
becomes cherry red.
(4) While the metal is still cherry red, twist the
muffler assembly back and forth to separate it from
the catalytic converter.
(5) Disconnect the exhaust pipe from the catalytic
converter (Figs. 3 and 5). If needed, heat up the pipes
to separate.
INSTALLATION
(1) Connect the catalytic converter to the exhaust
pipe (Figs. 3 and 5). Use a new clamp and tighten
the nuts to 61 Nzm (45 ft. lbs.) torque.
(2) Install the muffler onto the catalytic converter
until the alignment tab is inserted into the align-
ment slot.
(3) Install a new clamp at the muffler and catalytic
converter connection (Fig. 6). Tighten the clamp nuts
to 61 Nzm (45 ft. lbs.) torque.
(4) Lower the vehicle.
(5) Start the engine and inspect for exhaust leaks
and exhaust system contact with the body panels.
Adjust the alignment, if needed.
MUFFLER AND EXHAUST TAILPIPEÐXJ VEHICLES
All original equipment exhaust systems are manu-
factured with the exhaust tailpipe welded to the muf-
fler. Service replacement mufflers and exhaust
tailpipes are either clamped together or welded to-
gether.
WARNING: IF TORCHES ARE USED WHEN WORK-
ING ON THE EXHAUST SYSTEM, DO NOT ALLOW
THE FLAME NEAR THE FUEL LINES.
REMOVAL
(1) Raise and support the vehicle.
(2) Remove the front muffler clamp from the cata-
lytic converter and muffler connection (Fig. 6).
(3) Remove the rear exhaust tailpipe hanger clamp
(Fig. 7) and remove the exhaust tailpipe from the
front exhaust tailpipe hanger (Fig. 8).
(4) Heat the catalytic converter-to-muffler connec-
tion with an oxyacetylene torch until the metal be-
comes cherry red.
(5) While the metal is still cherry red, remove the
exhaust tailpipe/muffler assembly from the catalytic
converter.
(6) Remove the exhaust tailpipe from the muffler:
Fig. 6 Catalytic Converter-to-Muffler Connection
Fig. 7 Rear Exhaust Tailpipe Hanger Clamp
Fig. 8 Front Exhaust Tailpipe Hanger
JEXHAUST SYSTEM AND INTAKE MANIFOLD 11 - 5