oil pressure JEEP XJ 1995 Service And Repair Manual

MAINTENANCE SCHEDULES
INTRODUCTION
There are two maintenance schedules that show
proper service intervals for Jeep Cherokee and Jeep
Wrangler vehicles. Use the schedule that best de-
scribes the conditions the vehicle is operated under.
When mileage and time is listed, follow the interval
that occurs first.
ScheduleÐAlists all the scheduled maintenance
to be performed under normal operating conditions.
ScheduleÐBis a schedule for vehicles that are
usually operated under one or more of the following
conditions.
²Frequent short trip driving less than 5 miles (8
km).
²Frequent driving in dusty conditions.
²Trailer towing or heavy load hauling.
²Frequent long periods of engine idling.
²Sustained high speed operation.
²Desert operation.
²Frequent starting and stopping.
²Cold climate operation.
²Off road driving.
²Commercial service.
²Snow plow operation.
²More than half of vehicle operation occurs in
heavy city traffic during hot weather (above 90É F).
AT EACH STOP FOR GASOLINE
²Check engine oil level and add as required.
²Check windshield washer solvent and add as re-
quired.
ONCE A MONTH
²Check tire pressure and look for unusual tire wear
or damage.
²Check fluid levels of coolant reservoir, brake mas-
ter cylinder, power steering and transmission. Add
fluid as required.
²Check all lights and other electrical items for cor-
rect operation.
²Inspect battery and clean and tighten terminals as
required.
²Check rubber seals on each side of the radiator for
proper fit.
AT EACH OIL CHANGE
²Inspect exhaust system.
²Inspect brake hoses.
²Rotate the tires at each oil change interval shown
on ScheduleÐA: (7,500 Miles) or every other interval
shown on ScheduleÐB: (6,000 Miles).
²Check engine coolant level, hoses, and clamps.
²Lubricate 4x4 steering linkage.
²Lubricate propeller shaft universal joints and slip
spline, if equipped.After completion of off-road (4WD) operation, the
underside of the vehicle should be thoroughly in-
spected. Examine threaded fasteners for looseness.
HARSH SURFACE ENVIRONMENTS
After vehicle operation in a harsh surface environ-
ment, the following components should be inspected
and cleaned as soon as possible:
²Brake drums.
²Brake linings.
²Front wheel bearings (2WD vehicles only).
²Axle coupling joints.
This will prevent wear and/or unpredictable brake
action.
EMISSION CONTROL SYSTEM MAINTENANCE
The schedule emission maintenance listed inbold
typeon the following schedules, must be done at the
mileage specified to assure the continued proper
functioning of the emission control system. These,
and all other maintenance services included in this
manual, should be done to provide the best vehicle
performance and reliability. More frequent mainte-
nance may be needed for vehicles in severe operating
conditions such as dusty areas and very short trip
driving.
SCHEDULEÐA
7,500 MILES (12 000 KM) OR AT 6 MONTHS
²Change engine oil.
²Replace engine oil filter.
²Lubricate steering linkage (4x4).
15,000 MILES (24 000 KM) OR AT 12 MONTHS
²Change engine oil.
²Replace engine oil filter.
²Lubricate steering linkage.
22,500 MILES (36 000 KM) OR AT 18 MONTHS
²Change engine oil.
²Replace engine oil filter.
²Lubricate steering linkage (4x4).
²Inspect brake linings.
30,000 MILES (48 000 KM) OR AT 24 MONTHS
²Replace air cleaner element.
²Replace spark plugs.
²Adjust belt tension on non-automatic tensioning
drive belts.
²Change engine oil.
²Replace engine oil filter.
²Lubricate steering linkage.
²Drain and refill automatic transmission.
²Drain and refill transfer case.
0 - 4 LUBRICATION AND MAINTENANCEJ

CONTAINER IDENTIFICATION
Standard engine oil identification notations have
been adopted to aid in the proper selection of engine
oil. The identifying notations are located on the label
of engine oil plastic bottles and the top of engine oil
cans (Fig. 2).
ENGINE OIL ADDITIVES
In some instances, such as infrequent operation,
short trip driving, and during break-in after a major
overhaul, addition of special materials containing an-
ti-rust and anti-scuff additives are beneficial. A suit-
able product for this purpose is MOPAR Engine Oil
Supplement.
OIL LEVEL INDICATOR (DIPSTICK)
The engine oil level indicator (Dipstick) is located
at the right rear of both 2.5L engines and 4.0L en-
gines (Fig. 3).
CRANKCASE OIL LEVEL INSPECTION
CAUTION: Do not overfill crankcase with engine oil,
oil foaming and oil pressure loss can result.
Inspect engine oil level approximately every 800 ki-
lometers (500 miles). Unless the engine has exhibited
loss of oil pressure, run the engine for about five
minutes before checking oil level. Checking engine oil
level on a cold engine is not accurate.
To ensure proper lubrication of an engine, the en-
gine oil must be maintained at an acceptable level.
The acceptable levels are indicated between the ADD
and SAFE marks on the engine oil dipstick (Fig. 4
and 5).
(1) Position vehicle on level surface.
(2) With engine OFF, allow approximately ten min-
utes for oil to settle to bottom of crankcase, remove
engine oil dipstick.
(3) Wipe dipstick clean.
(4) Install dipstick and verify it is seated in the
tube.
(5) Remove dipstick, with handle held above the
tip, take oil level reading (Figs.4 and 5).
(6) Add oil only if level is below the ADD mark on
dipstick.
ENGINE OIL CHANGE AND FILTER REPLACEMENT
ENGINE OIL CHANGE
Change engine oil at mileage and time intervals
described in Maintenance Schedules.
TO CHANGE ENGINE OIL
Run engine until achieving normal operating tem-
perature.
(1) Position the vehicle on a level surface and turn
engine off.
(2) Hoist and support vehicle on safety stands. Re-
fer to Hoisting and Jacking Recommendations in this
group.
Fig. 2 API Certification Mark
Fig. 3 Engine Oil Dipstick LocationÐTypical
Fig. 4 Engine Oil DipstickÐ2.5L Engine
0 - 16 LUBRICATION AND MAINTENANCEJ

USED ENGINE OIL DISPOSAL
Care should be exercised when disposing used en-
gine oil after it has been drained from a vehicle en-
gine. Refer to the WARNING listed above.
ENGINE COOLING SYSTEM
WARNINGS AND PRECAUTIONS
WARNING: ANTIFREEZE IS AN ETHYLENE GLYCOL
BASE COOLANT AND IS HARMFUL IF SWAL-
LOWED OR INHALED. IF SWALLOWED, DRINK
TWO GLASSES OF WATER AND INDUCE VOMIT-
ING. IF INHALED, MOVE TO FRESH AIR AREA.
SEEK MEDICAL ATTENTION IMMEDIATELY. DO NOT
STORE IN OPEN OR UNMARKED CONTAINERS.
WASH SKIN AND CLOTHING THOROUGHLY AFTER
COMING IN CONTACT WITH ETHYLENE GLYCOL.
KEEP OUT OF REACH OF CHILDREN.
DISPOSE OF GLYCOL BASE COOLANT PROP-
ERLY, CONTACT YOUR DEALER OR GOVERNMENT
AGENCY FOR LOCATION OF COLLECTION CENTER
IN YOUR AREA.
DO NOT OPEN A COOLING SYSTEM WHEN THE
ENGINE IS AT RUNNING TEMPERATURE, PER-
SONAL INJURY CAN RESULT.
AVOID RADIATOR COOLING FAN WHEN ENGINE
COMPARTMENT RELATED SERVICE IS PER-
FORMED, PERSONAL INJURY CAN RESULT.
CAUTION: Do not use straight antifreeze as engine
coolant, inadequate engine running temperatures
can result.
Do not operate vehicle without proper concentra-
tion of recommended ethylene glycol coolant, high
running temperatures and cooling system corrosion
can result.
The engine cooling system will develop internal
pressure of 97 to 123 kPa (14 to 18 psi) at normal op-
erating temperature. Allow the vehicle approximately
one half hour to cool off before opening the cooling
system. As an indicator of pressure, squeeze the up-
per radiator hose between index finger and thumb. If
it collapses with little effort the system would have
low internal pressure and should be safe to open to
the first safety notch of the radiator cap. Refer to
Group 7, Cooling System.
COOLING SYSTEM INSPECTION
Coolant level should be inspected when other en-
gine compartment service is performed or when cool-
ant leak is suspected. With the engine at normal
operating temperature, observe the coolant level in
thecoolant recovery bottle. The coolant level mustbe at least above the ADD mark and preferably at
the FULL mark. Add coolant to the coolant recovery
bottleonly, if necessary.
Cooling system freeze protection should be tested
at the onset of the winter season or every 12 months.
Service is required if coolant is low, contaminated,
rusty or freeze protection is inadequate. To properly
test cooling system, see Group 7, Cooling System.
The cooling system factory fill is a mixture of 50%
Ethylene Glycol based antifreeze and 50% water. Us-
ing a suitable hydrometer, measure antifreeze con-
centration in the radiator when the engine is cool. If
the cooling system has recently been serviced, allow
coolant to circulate for at least 20 minutes before
taking hydrometer reading. Properly mixed coolant
will protect the cooling system to -37ÉC (-35ÉF). If the
freeze protection is above -28ÉC (-20ÉF), drain enough
coolant from the cooling system to allow room to add
antifreeze to achieve adequate protection. A mix table
on the coolant container indicates the amount of an-
tifreeze required to winterize the cooling system
based on the capacity, see Capacity Chart in General
Information section of this group.
ANTIFREEZE SPECIFICATION
Chrysler Corporation recommends the use of Mo-
par Antifreeze/Coolant or a high quality, ethylene
glycol base antifreeze/coolant, with a silicate inhibi-
tor.
COOLING SYSTEM SERVICE
The cooling system should be drained, flushed and
filled with the proper coolant mixture at the inter-
vals described in the Lubrication and Maintenance
Schedules. Refer to General Information section of
this group. For proper service instructions see Group
7, Cooling System.
AIR CLEANER ELEMENT
The air cleaner element should be serviced at the
intervals described in the Lubrication and Mainte-
nance Schedules sections of this group. Additional in-
formation can be found in Group 14, Fuel System
and Group 25, Emission System. Inspect all air
cleaner hoses or tubes for damage or leaks when
other engine compartment service is performed. Re-
place faulty components.
FILTER ELEMENT SERVICE/REPLACEMENT
CAUTION: The air cleaner cover must be installed
properly for the emissions system and engine con-
troller to function correctly.
Do not immerse paper air filter element in clean-
ing solvents, damage can result.
(1) Remove the air cleaner cover from the body/
housing (Fig. 9).
0 - 18 LUBRICATION AND MAINTENANCEJ

(2) Note any indication of drum/rotor overheating,
wheel dragging or the vehicle pulling to one side
when the brakes are applied.
(3) Evaluate any performance complaints received
from the owner/operator.
(4) Repair the brake system as necessary. Refer to
Group, 5 Brakes for additional information and ser-
vice procedures.
TIRES
RECOMMENDED MAINTENANCE
The general condition of the tires and the inflation
pressures should be inspected at the same time the
engine oil is changed and the oil filter is replaced.
In addition, the tires/wheels should be rotated at
the intervals described in the Maintenance Schedules
section of this group.
INSPECTION
Inspect the tires for excessive wear, damage, etc.
Test the tires for the recommended inflation pres-sure. Refer to the tire inflation pressure decal located
on the inside of the glove box door, and also to Group
22, Tires And Wheels.
ROTATION
Refer to Group 22, Tires And Wheels for the recom-
mended method of tire/wheel rotation for a Jeep ve-
hicle.
BODY COMPONENTS
LUBRICATION REQUIREMENTS
All Jeep operating mechanisms and linkages
should be lubricated when necessary. The door
weatherstrip seals should be lubricated to prolong
their life as well as to improve door sealing.
LUBRICANT SPECIFICATIONS
All applicable exterior and interior vehicle operat-
ing mechanisms should be:
²Inspected
²Cleaned
²Pivot/sliding contact areas on the mechanisms
should then be lubricated.
Multi-purpose NLGI GC-LB MOPAR Multi-Mileage
Lubricant or an equivalent, should be used to lubri-
cate the mechanisms. The door weatherstrip seals
should be lubricated with silicone lubricant spray.
Refer to the Body Lubricant Specifications chart be-
low for additional lubricant applications.
LUBRICATION
All pivoting and sliding contact areas, should be lu-
bricated periodically to ensure quiet, easy operation
and to protect against wear and corrosion. Areas in-
clude:
²Seat tracks.
²Door hinges/latches/strikers.
²Liftgate/tailgate/hood hinges (Fig. 11).
(1) As required, lubricate the body components
with the specified lubricants.
(2) Apply silicone lubricant to a cloth and wipe it
on door seals to avoid over-spray that can soil pas-
senger clothing.
(3) Before applying lubricant, the component
should be wiped clean. After lubrication, any excess
lubricant should be removed.
(4) The door lock cylinders should be lubricated 2
times each year (preferably autumn and spring):
²Spray a small amount of lock cylinder lubricant di-
rectly into the lock cylinder.
²Apply a small amount to the key and insert it into
the lock cylinder.
²Rotate it to the locked position and then back to
the unlocked position several times.
²Remove the key. Wipe the lubricant from it with a
clean cloth to avoid soiling of clothing.
Fig. 9 Park Brake Equalizer (XJ)ÐTypical
Fig. 10 Park Brake Equalizer (YJ)ÐTypical
0 - 32 LUBRICATION AND MAINTENANCEJ

MODEL 30 AXLE AND TUBE AXLE (2WD)
INDEX
page page
Axle Bushing Replacement.................. 34
Axle ShaftÐCardan U-Joint.................. 26
Backlash and Contact Pattern Analysis......... 45
Cleaning/Inspection........................ 37
Differential and Pinion Measurement........... 40
Differential Assembly....................... 38
Differential Disassembly.................... 35
Differential Installation...................... 44
Differential Removal....................... 34
Differential Shim Pack Measurement and
Adjustment............................ 43
Drive Axle Assembly ReplacementÐXJ Vehicles . . 23
Drive Axle Assembly ReplacementÐYJ Vehicles . . 24Final Assembly........................... 46
Hub Bearing and Axle Shaft................. 25
Information.............................. 22
Inner Axle Shaft Oil Seal Replacement......... 35
Lubricant Change......................... 23
Lubricant Specifications..................... 22
Pinion Gear Assembly/Installation............. 42
Pinion Gear Depth Information............... 39
Pinion Removal/Disassembly................. 36
Pinion Seal Replacement................... 25
Steering Knuckle and Ball Studs.............. 32
Vacuum Disconnect AxleÐYJ Vehicles......... 27
INFORMATION
The Model 30 front axles consists of a cast iron dif-
ferential housing with axle shaft tubes extending
from either side. The tubes are pressed into the dif-
ferential housing and welded.
The integral type housing, hypoid gear design has
the centerline of the pinion set above the centerline
of the ring gear.
The axle has a fitting for a vent hose used to re-
lieve internal pressure caused by lubricant vaporiza-
tion and internal expansion.
The axles are equipped with semi-floating axle
shafts, meaning that loads are supported by the hub
bearings. The axle shafts are retained by nuts at the
hub bearings. The hub bearings are bolted to the
steering knuckle at the outboard end of the axle tube
yoke. The hub bearings are serviced as an assembly.
The axles are equipped with ABS brake sensors.
The sensors are attached to the knuckle assemblies
and tone rings are pressed on the axle shaft.Use
care when removing axle shafts as NOT to dam-
age the tone wheel or the sensor.
The stamped steel cover provides a means for in-
spection and servicing the differential.
The Model 30 axle has the assembly part number
and gear ratio listed on a tag. The tag is attached to
the housing cover. Build date identification codes are
stamped on the axle shaft tube cover side.
The differential case is a one-piece design. The dif-
ferential pinion mate shaft is retained with a roll
pin. Differential bearing preload and ring gear back-
lash is adjusted by the use of shims (select thick-
ness). The shims are located between the differential
bearing cones and case. Pinion bearing preload is set
and maintained by the use of collapsible spacer.
COMMAND-TRACÐYJ VEHICLES
The Command-Trac system is a vacuum disconnect
axle. The system has a two-piece axle shaft coupled
together by a shift collar. For two-wheel drive opera-
tion, the vacuum motor and shift fork disengages the
axle shaft splines. For four-wheel drive operation, the
vacuum motor and shift fork engages the axle
splines.
SELEC-TRACÐXJ VEHICLES
The Selec-Trac system is a non-disconnect axle.
Shifting from two-wheel to four-wheel drive is done
at the transfer case.
For XJ vehicles equipped withSelec-Tracand
ABS brake system, refer to Group 5ÐBrakes for ad-
ditional service information.
LUBRICANT SPECIFICATIONS
Multi-purpose, hypoid gear lubricant should be
used for Model 30 axles. The lubricant should have
MIL-L-2105C and API GL 5 quality specifications.
MOPARtHypoid Gear Lubricant conforms to both of
these specifications.
²The factory fill for the Model 30 axle is SAE Ther-
mally Stable 80W-90 gear lubricant.Do not use
heavier weight lubricant, this will cause axle
engagement difficulties.
²The factory installed lubricant quantity for the
NON-DISCONNECT TYPE AXLE is 1.48 L (3.13
pts.).
²The factory installed lubricant quantity for the
VACUUM-DISCONNECT TYPE AXLE is 1.65 L (3.76
pts.).
Refer to Group 0, Lubrication and Maintenance for
additional information regarding temperature range,
viscosity and fluid level.
2 - 22 FRONT SUSPENSION AND AXLEJ

BRAKE FLUIDÐBRAKE BLEEDINGÐBRAKELINES AND HOSES
INDEX
page page
Brake Bleeding (With ABS Brakes)............ 11
Brake Bleeding (With Standard Brakes)......... 11
Brake Bleeding Recommendations............ 10
Brake Fluid Contamination.................. 10Brake Fluid Level......................... 10
Brakeline Charts.......................... 12
Brakelines and Hoses...................... 12
Recommended Brake Fluid.................. 10
RECOMMENDED BRAKE FLUID
Recommended brake fluid for Jeep vehicles is Mo-
par brake fluid, or an equivalent fluid meeting SAE
J1703 and DOT 3 standards. The recommendation
applies to models with standard or ABS brakes.
Use new brake fluid to top off the master cyl-
inder or refill the system. Never use reclaimed
fluid, fluid not meeting the SAE/DOT standards
or fluid from an unsealed container. Do not use
fluid from any container that has been left
open for any length of time. Fluid in open con-
tainers can absorb moisture.
BRAKE FLUID LEVEL
Always clean the master cylinder reservoir and
cover or cap before adding fluid. This avoids having
dirt from the cap or reservoir exterior fall into the
fluid.
If the vehicle has a one piece master cylinder, cor-
rect fluid level is to within 6 mm (1/4 in.) of the res-
ervoir rim (Fig. 1).
If the vehicle has a plastic reservoir with a single
cap, preferred fluid level is to the FULL mark (Fig.
2).
CAUTION: Do not allow brake fluid to contact
painted surfaces. Fluid spills must be cleaned up
immediately as brake fluid can loosen and lift paint.
BRAKE FLUID CONTAMINATION
Oil in the fluid will cause brake system rubber
seals to soften and swell. The seals may also become
porous and begin to deteriorate.If fluid contamination is suspected, drain off a sam-
ple from the master cylinder. A suction gun or similar
device can be used for this purpose.
Empty the drained fluid into a glass container.
Contaminants in the fluid will cause the fluid to sep-
arate into distinct layers. If contamination has oc-
curred, the system rubber seals, hoses and cups must
be replaced and the system thoroughly flushed with
clean brake fluid.
BRAKE BLEEDING RECOMMENDATIONS
²Use Mopar DOT 3 brake fluid, or an equivalent
meeting SAE/DOT standards J1703-F and DOT 3, to
fill and bleed the system.
²Bleeding can be performed manually, or with vac-
uum or pressure equipment. Vacuum and pressure
bleeding equipment are both available. Both types
are effective but should be used only as described in
the manufacturers instructions.
²Do not allow the master cylinder to run out of
fluid when bleeding the brakes. An empty cylinder
will allow additional air to be drawn into the system.
Check fluid level frequently during bleed operations.
²Do not pump the brake pedal at any time while
bleeding. Air in system will be compressed into small
Fig. 1 Correct Fluid Level (4-Cylinder Models)
Fig. 2 Correct Fluid Level (All Except 4-Cylinder
Models)
5 - 10 BRAKE FLUIDÐBRAKE BLEEDINGÐBRAKELINES AND HOSESJ

CLUTCH DIAGNOSIS
INDEX
page page
Clutch Contamination....................... 3
Clutch Cover and Disc Runout................ 3
Clutch Housing Misalignment................. 4
Clutch Misalignment........................ 3Flywheel Runout........................... 3
General Diagnosis Information................ 3
Inspection and Diagnosis Charts............... 4
Installation Methods and Parts Usage........... 4
GENERAL DIAGNOSIS INFORMATION
Unless the cause of a clutch problem is obvious, ac-
curate problem diagnosis will usually require a road
test to confirm a problem. Component inspection will
then be required to determine the actual problem
cause.
During a road test, drive the vehicle at normal
speeds. Shift the transmission through all gear
ranges and observe clutch action. If chatter, grab,
slip, or improper release is experienced, remove and
inspect the clutch components. However, if the prob-
lem is noise or hard shifting, further diagnosis may
be needed as the transmission or another driveline
component may be at fault. Careful observation dur-
ing the test will help narrow the problem area.
CLUTCH CONTAMINATION
Fluid contamination is a frequent cause of clutch
malfunctions. Oil, water, or clutch fluid on the clutch
disc and pressure plate surfaces will cause chatter,
slip and grab.
During inspection, note if any components are con-
taminated with oil, hydraulic fluid, or water/road
splash.
Oil contamination indicates a leak at either the
rear main seal or transmission input shaft. Oil leak-
age produces a residue of oil on the housing interior
and on the clutch cover and flywheel. Heat buildup
caused by slippage between the cover, disc and fly-
wheel, can sometimes bake the oil residue onto the
components. The glaze-like residue ranges in color
from amber to black.
Road splash contamination means dirt/water is en-
tering the clutch housing due to loose bolts, housing
cracks, or through hydraulic line openings. Driving
through deep water puddles can force water/road
splash into the housing through such openings.
Clutch fluid leaks are usually from damaged slave
cylinder push rod seals. This type of leak can only be
confirmed by visual inspection.
CLUTCH MISALIGNMENT
Clutch components must be in proper alignment
with the crankshaft and transmission input shaft.Misalignment caused by excessive runout or warpage
of any clutch component will cause grab, chatter and
improper clutch release.
FLYWHEEL RUNOUT
Check flywheel runout whenever misalignment is
suspected. Flywheel runout should not exceed 0.08
mm (0.003 in.). Measure runout at the outer edge of
the flywheel face with a dial indicator. Mount the in-
dicator on a stud installed in place of one of the fly-
wheel bolts.
Common causes of runout are:
²heat warpage
²improper machining
²incorrect bolt tightening
²improper seating on crankshaft flange shoulder
²foreign material on crankshaft flange
Flywheel machining is not recommended. The fly-
wheel clutch surface is machined to a unique contour
and machining will negate this feature. However, mi-
nor flywheel scoring can be cleaned up by hand with
180 grit emery, or with surface grinding equipment.
Remove only enough material to reduce scoring (ap-
proximately 0.001 - 0.003 in.). Heavy stock removal
isnot recommended.Replace the flywheel if scor-
ing is severe and deeper than 0.076 mm (0.003 in.).
Excessive stock removal can result in flywheel crack-
ing or warpage after installation; it can also weaken
the flywheel and interfere with proper clutch release.
Clean the crankshaft flange before mounting the
flywheel. Dirt and grease on the flange surface may
cock the flywheel causing excessive runout. Use new
bolts when remounting a flywheel and secure the
bolts with Mopar Lock And Seal. Tighten flywheel
bolts to specified torque only. Overtightening can dis-
tort the flywheel hub causing runout.
CLUTCH COVER AND DISC RUNOUT
Check the clutch disc before installation. Axial
(face) runout of anewdisc should not exceed 0.50
mm (0.020 in.). Measure runout about 6 mm (1/4 in.)
from the outer edge of the disc facing. Obtain an-
other disc if runout is excessive.
Check condition of the clutch before installation. A
warped cover or diaphragm spring will cause grab
and incomplete release or engagement. Be careful
JCLUTCH DIAGNOSIS 6 - 3

COOLING SYSTEM
CONTENTS
page page
DIAGNOSIS............................. 4
ENGINE ACCESSORY DRIVE BELTS......... 38
ENGINE BLOCK HEATER.................. 44GENERAL INFORMATION.................. 1
SERVICE PROCEDURES.................. 13
SPECIFICATIONS........................ 45
GENERAL INFORMATION
Throughout this group, references are made to par-
ticular vehicle models by alphabetical designation
(XJ or YJ) or by the particular vehicle nameplate. A
chart showing a breakdown of alphabetical designa-
tions is included in the Introduction section at the
beginning of this manual.
COOLING SYSTEM
The cooling system regulates engine operating tem-
perature. It allows the engine to reach normal oper-
ating temperature as quickly as possible, maintains
normal operating temperature and prevents over-
heating.
The cooling system also provides a means of heat-
ing the passenger compartment and cooling the auto-
matic transmission fluid (if equipped). The cooling
system is pressurized and uses a centrifugal water
pump to circulate coolant throughout the system.
An optional factory installed heavy duty cooling
package is available on most models. The package
consists of a radiator that has an increased number
of cooling fins. XJ models equipped with a 4.0L 6-cyl-inder engine and heavy duty cooling and/or air con-
ditioning also have an auxiliary electric cooling fan.
COOLING SYSTEM COMPONENTS
The cooling system consists of:
²A radiator
²Cooling fan (mechanical and/or electrical)
²Thermal viscous fan drive
²Fan shroud
²Radiator pressure cap
²Thermostat
²Coolant reserve/overflow system
²Transmission oil cooler (if equipped with an auto-
matic transmission)
²Coolant
²Water pump
²Hoses and hose clamps
SYSTEM COOLANT ROUTING
For cooling system flow routings, refer to Figs. 1, 2,
3or4.
JCOOLING SYSTEM 7 - 1

SERVICE PROCEDURES
INDEX
page page
Auxiliary Electric Cooling FanÐXJ Models with 4.0L
6-Cylinder Engine....................... 35
Coolant................................. 20
Coolant Reserve/Overflow System............. 24
Cooling System Cleaning/Reverse Flushing...... 22
Cooling System Fans...................... 32
Cooling System Hoses..................... 32
Draining Cooling System.................... 21
Radiator Pressure Cap..................... 25
Radiators............................... 26Refilling Cooling System.................... 21
Testing Cooling System for Leaks............. 22
Thermostat.............................. 17
Transmission Oil Coolers.................... 36
Viscous Fan Drive......................... 34
Water Pump Tests......................... 13
Water PumpsÐGeneral Information............ 13
Water PumpsÐRemoval/Installation........... 14
WATER PUMPSÐGENERAL INFORMATION
A centrifugal water pump circulates coolant
through the water jackets, passages, intake manifold,
radiator core, cooling system hoses and heater core.
The pump is driven from the engine crankshaft by a
drive belt on all engines.
The water pump impeller is pressed onto the rear
of a shaft that rotates in bearings pressed into the
housing. The housing has a small hole to allow seep-
age to escape. The water pump seals are lubricated
by the antifreeze in the coolant mixture. No addi-
tional lubrication is necessary.
CAUTION: All engines are equipped with a reverse
(counter-clockwise) rotating water pump and vis-
cous fan drive assembly. REVERSE is stamped or
imprinted on the cover of the viscous fan drive and
inner side of the fan. The letter R is stamped into
the back of the water pump impeller (Fig. 1).
Engines from previous model years, depending
upon application, may have been equipped with a for-
ward (clockwise) rotating water pump. Installation of
the wrong water pump will cause engine overheating.
A quick test to determine if the pump is working is
to check if the heater warms properly. A defective wa-
ter pump will not be able to circulate heated coolant
through the long heater hose to the heater core.
WATER PUMP TESTS
LOOSE IMPELLER
DO NOT WASTE reusable coolant. If solution is
clean, drain coolant into a clean container for reuse.
WARNING: DO NOT REMOVE THE CYLINDER
BLOCK DRAIN PLUGS OR LOOSEN THE RADIATOR
DRAINCOCK WITH THE SYSTEM HOT AND UNDER
PRESSURE. SERIOUS BURNS FROM THE COOL-
ANT CAN OCCUR.(1) Drain the cooling system.
(2) Loosen the fan belt(s).
(3) Disconnect the lower radiator hose from the
water pump.
(4) Bend a stiff clothes hanger or welding rod as
shown in (Fig. 2).
(5) Position the rod in the water pump inlet and
attempt to hold the impeller while turning the fan
blades. If equipped with a viscous fan drive, turn the
water pump shaft with a breaker bar and socket at-
tached to a mounting flange nut. If the impeller is
loose and can be held with the rod while the fan
blades are turning, the pump is defective. If the im-
peller turns, the pump is OK.
Connect the hose and install the coolant, or proceed
with repairs.
Fig. 1 Reverse Rotating Water PumpÐTypical
JCOOLING SYSTEM SERVICE PROCEDURES 7 - 13

WARNING: HOT, PRESSURIZED COOLANT CAN
CAUSE INJURY BY SCALDING.
Carefully remove the radiator pressure cap from
the filler neck and check the coolant level. Push
down on the cap to disengage it from the stop tabs.
Wipe the inner part of the filler neck and examine
the lower inside sealing seat for nicks, cracks, paint,
dirt and solder residue. Inspect the reserve/overflow
tank tube for internal obstructions. Insert a wire
through the tube to be sure it is not obstructed.
Inspect the cams on the outside part of the filler
neck. If the cams are bent, seating of pressure cap
valve and tester seal will be affected. Replace cap if
cams are bent.
Attach pressure tester 7700 (or an equivalent) to
the radiator filler neck (Fig. 21).Operate the tester pump to apply 124 kPa (18 psi)
pressure to the system. If the hoses enlarge exces-
sively or bulge while testing, replace as necessary.
Observe the gauge pointer and determine the condi-
tion of the cooling system according to the following
criteria:
²Holds Steady: If the pointer remains steady for
two minutes, there are no serious coolant leaks in
the system. However, there could be an internal leak
that does not appear with normal system test pres-
sure. Inspect for interior leakage or do the Internal
Leakage Test. Do this if it is certain that coolant is
being lost and no leaks can be detected.
²Drops Slowly: Shows a small leak or seepage is oc-
curring. Examine all connections for seepage or slight
leakage with a flashlight. Inspect the radiator, hoses,
gasket edges and heater. Seal any small leak holes
with a Sealer Lubricant or equivalent. Repair leak
holes and reinspect the system with pressure ap-
plied.
²Drops Quickly: Shows that a serious leakage is oc-
curring. Examine the system for serious external
leakage. If no leaks are visible, inspect for internal
leakage. Large radiator leak holes should be repaired
by a reputable radiator repair shop.
INTERNAL LEAKAGE INSPECTION
Remove the engine oil pan drain plug and drain a
small amount of engine oil. Coolant, being heavier
than engine oil, will drain first. Another way of test-
ing is to operate the engine and check for water glob-
ules on the engine oil dipstick. Also inspect the
automatic transmission oil dipstick for water glob-
ules. Inspect the automatic transmission fluid cooler
for leakage. Operate the engine without the pressure
cap on the radiator until thermostat opens.
Attach a pressure tester to the filler neck. If pres-
sure builds up quickly, a leak exists as a result of a
faulty cylinder head gasket or crack in the engine.
Repair as necessary.
WARNING: DO NOT ALLOW PRESSURE TO EX-
CEED 124 KPA (18 PSI). TURN THE ENGINE OFF.
TO RELEASE THE PRESSURE, ROCK THE TESTER
FROM SIDE TO SIDE. WHEN REMOVING THE
TESTER, DO NOT TURN THE TESTER MORE THAN
1/2 TURN IF THE SYSTEM IS UNDER PRESSURE.
If there is no immediate pressure increase, pump
the pressure tester until the indicated pressure is
within the system range. Vibration of the gauge
pointer indicates compression or combustion leakage
into the cooling system.
WARNING: DO NOT DISCONNECT THE SPARK
PLUG WIRES WHILE THE ENGINE IS OPERATING.
Fig. 20 Leak Detection Using Black LightÐTypical
Fig. 21 Pressurizing SystemÐTypical
JCOOLING SYSTEM SERVICE PROCEDURES 7 - 23