1995 JEEP YJ warning light

(3) Cover the open end of the transmission exten-
sion housing.
4WD VEHICLESÐXJ
(1) Shift transfer case lever to NEUTRAL.
(2) Place ignition switch in the unlocked position.
4WD VEHICLESÐYJ
CAUTION: Follow these steps to be certain that the
transfer case is fully in N (NEUTRAL) and that the
axle is completely disengaged before flat towing to
prevent damage to internal parts.
(1) Shift transfer case into 2H and check that the
4WD light goes out.
(2) Start engine and drive the vehicle 3 mm (10 ft.)
rearward and then 3 mm (10 ft.) forward to make
sure the axle is disengaged.(3) Shift transmission to Neutral.
(4) Turn off engine with the ignition key in the un-
locked OFF position.
(5) Shift transfer case lever from 2H to N (NEU-
TRAL) position.
(6) Shift manual transmission into gear or auto-
matic transmission into P (PARK).
WARNING: WITH THE TRANSFER CASE IN NEU-
TRAL POSITION, THE VEHICLE COULD ROLL UN-
EXPECTEDLY. THE PARKING BRAKE SHOULD
ALWAYS BE APPLIED BEFORE THE TOW BAR IS
ATTACHED.
(7) Attach vehicle to the tow vehicle with tow bar.
CAUTION: Do not use a bumper mounted clamp-on
tow bar, damage to bumper face bar may occur.
0 - 14 LUBRICATION AND MAINTENANCEJ

DRIVETRAIN
INDEX
page page
Automatic Transmission.................... 23
Clutch and Brake Pedal Bushings............. 22
Clutch Master Cylinder..................... 22
Drive Shafts............................. 26Front and Rear Axles...................... 24
Manual Transmission...................... 22
Rubber and Plastic Hoses/Tubing............. 26
Transfer Case (4WD Vehicles)................ 24
CLUTCH AND BRAKE PEDAL BUSHINGS
If the clutch and brake pedal mechanism squeaks,
the pivot bushings should be lubricated. Use Mopar
Multi-Purpose Lubricant, or an equivalent. Refer to
Group 5, Brakes for location of bushings.
CLUTCH MASTER CYLINDER
LEVEL INSPECTION
WARNING: DO NOT ALLOW PETROLEUM OR WA-
TER BASE LIQUIDS TO CONTAMINATE CLUTCH
FLUID, SEAL DAMAGE AND CLUTCH FAILURE CAN
RESULT.
The clutch reservoir level should be inspected when
other underhood service is performed. (Fig. 1)
The fluid level is determined by its height in rela-
tion to the level indicator ring (Fig. 2) located inside
the reservoir. Add fluid until the height is level with
the indicator ring.
FLUID SPECIFICATION
Use Mopar, Brake And Hydraulic Clutch Fluid or
equivalent. Use only brake fluid conforming to DOT
3, Federal, Department of Transportation specifica-
tion. To avoid fluid contamination, use fluid from a
properly sealed container.CAUTION: Never use reclaimed brake fluid or fluid
from an unsealed container. In addition, do not use
fluid from a container that has been opened and al-
lowed to stand for an extended length of time.
Moisture in the air can be absorbed by the fluid,
which causes dilution with loss of effectiveness.
MANUAL TRANSMISSION
The manual transmission should be inspected for
oil leaks and proper oil level when other under vehi-
cle service is performed.
LUBRICANT SPECIFICATION
When it becomes necessary to add to or change the
lube oil in a Jeep manual transmission, use SAE
75W-90, API Quality Grade GL-5 gear lubricant.
LUBRICANT LEVEL
The fill-hole plug for all manual transmissions is
located on the right side of the case (Fig. 3). Deter-
mine the lubricant level according to the following
procedure.
(1) Remove the fill-hole plug (Fig. 3) from the
transmission. The lube oil should be level with the
bottom edge of the fill hole. The level can be slightly
below the bottom edge of the fill hole if the lube oil is
cold.
Fig. 1 Clutch Reservoir LocationÐTypical
Fig. 2 Hydraulic Clutch Fluid LevelÐTypical
0 - 22 LUBRICATION AND MAINTENANCEJ

BRAKES
CONTENTS
page page
ABS BRAKE DIAGNOSIS................... 3
ABS OPERATION AND SERVICE............ 33
BRAKE FLUIDÐBRAKE BLEEDINGÐ
BRAKELINES AND HOSES............... 10
DISC BRAKES.......................... 45
DRUM BRAKES......................... 55
GENERAL INFORMATION.................. 1MASTER CYLINDERÐCOMBINATION VALVE . . 15
PARKING BRAKES....................... 60
POWER BRAKE BOOSTERÐBRAKE PEDALÐ
BRAKELIGHT SWITCH.................. 22
SERVICE BRAKE DIAGNOSIS............... 4
SPECIFICATIONS........................ 70
GENERAL INFORMATION
INDEX
page page
Antilock Brakes (ABS)....................... 1
Brake Components......................... 1
Brake Fluid/Lubricants/Cleaning Solvents......... 2
Brake Safety Precautions.................... 2Brake Warning Lights....................... 1
Brakelining Material........................ 1
Jeep Body Code Letters..................... 2
BRAKE COMPONENTS
Power assist front disc and rear drum brakes are
standard on Cherokee/Wrangler models. Disc brake
components consist of single piston calipers and ven-
tilated rotors. Rear drum brakes are dual shoe units
with cast brake drums.
The parking brake mechanism is lever and cable
operated. The cables are attached to levers on the
rear drum brake secondary shoes. The parking
brakes are operated by a foot pedal on YJ models and
a hand lever on XJ models.
A 205 mm dual diaphragm vacuum power brake
booster is used for all applications. Two master cylin-
ders are used; 4-cylinder YJ models have a one-piece
master cylinder. All other models have a two-piece
master cylinder with plastic reservoir.
All models are equipped with a combination valve.
The valve contains a pressure differential valve and
switch and a fixed rate rear proportioning valve.
BRAKELINING MATERIAL
Factory brakelining on all models consists of an or-
ganic base material combined with metallic particles.
The lining does not contain asbestos.
BRAKE WARNING LIGHTS
Cherokee/Wrangler models are equipped with one
or two brake warning lights. A red warning light is
standard on all models. An amber light is added on
models with ABS brakes. Both lights are located in
the instrument panel.
The red light is in circuit with the pressure differ-
ential switch (in the combination valve), and with the
parking brake switch. The light alerts the driver
when the parking brakes are applied, or when a
pressure differential exists between the front and
rear hydraulic systems. The light also illuminates for
a few seconds at start up as part of a bulb check.
The ABS warning light is amber in color and is lo-
cated in the same side of the instrument cluster as
the red warning light. The amber light only illumi-
nates when an ABS circuit fault occurs.
ANTILOCK BRAKES (ABS)
An antilock brake system (ABS) is available on
Cherokee/Wrangler models as an option. The system
is an electronically operated, all-wheel brake control
system. The ABS system is designed to prevent
wheel lockup during periods of high wheel slip brak-
ing. Refer to the antilock brake section for operation
and service information.
JBRAKES 5 - 1

ABS BRAKE DIAGNOSIS
INDEX
page page
ABS Diagnostic Connector................... 3
ABS Warning Light Display................... 3
Antilock ECU and Hcu Diagnosis............... 3
DRB Scan Tool............................ 3General Information........................ 3
Normal Operating Conditions.................. 3
Wheel/Tire Size and Input Signals.............. 3
GENERAL INFORMATION
The DRB scan tool is required for ABS diagnosis.
The scan tool is used to identify ABS circuit faults.
Once a faulty circuit has been identified, refer to
the appropriate chassis/body diagnostic manual for
individual component testing.
ABS WARNING LIGHT DISPLAY
The amber antilock light illuminates at startup as
part of the system self check feature. The light illu-
minates for 2-3 seconds then goes off as part of the
normal check routine.
An ABS circuit fault is indicated when the amber
light remains on after startup, or illuminates during
vehicle operation.
Verify that a fault is actually related to the ABS
system before making repairs. For example, if the
red warning illuminates but the ABS light does not,
the problem is related to a service brake component
and not the ABS system. Or, if neither light illumi-
nates but a brake problem is noted, again, the prob-
lem is with a service brake component and not with
the ABS system.
ABS DIAGNOSTIC CONNECTOR
The ABS diagnostic connector is inside the vehicle.
The connector is the access point for the DRB scan tool.
On XJ models, the connector is located under the
instrument panel to the right of the steering column.
On some models, the connecter may be tucked under
the carpeting on the transmission tunnel. The con-
necter is a black, 6-way type.
On YJ models, the connector is under the instru-
ment panel by the the driver side kick panel. The
connecter is a black, 6 or 8-way type.
The DRB scan tool kit contains adapter cords for
both types of connecter. Use the appropriate cord for
test hookup.
DRB SCAN TOOL
ABS diagnosis is performed with the DRB scan tool.
Refer to the DRB scan tool manual for test hookup and
procedures. Diagnosis information is provided in the ap-
propriate chassis/body diagnostic manual.
WHEEL/TIRE SIZE AND INPUT SIGNALS
Antilock system operation is dependant on accurate
signals from the wheel speed sensors. Ideally, the ve-
hicle wheels and tires should all be the same size
and type. However, the Jeep ABS system is designed
to operate with a compact spare tire installed.
NORMAL OPERATING CONDITIONS
Sound Levels
The hydraulic control unit pump and solenoid valves
may produce some sound as they cycle on and off. This
is a normal condition and should not be mistaken for
faulty operation. Under most conditions, pump and so-
lenoid valve operating sounds will not be audible.
Vehicle Response In Antilock Mode
During antilock braking, the hydraulic control unit
solenoid valves cycle rapidly in response to antilock
electronic control unit signals.
The driver will experience a pulsing sensation
within the vehicle as the solenoids decrease, hold, or
increase pressure as needed. Brake pedal pulsing will
also be noted and is anormal condition.
Steering Response
A modest amount of steering input is required dur-
ing extremely high deceleration braking, or when
braking on differing traction surfaces. An example of
differing traction surfaces would be when the left
side wheels are on ice and the right side wheels are
on dry pavement.
Owner Induced Faults
Driving away with the parking brakes still applied
will cause warning light illumination. Pumping the
brake pedal will also generate a system fault and in-
terfere with ABS system operation.
ANTILOCK ECU AND HCU DIAGNOSIS
An ECU or HCU fault can only be determined
through testing with the DRB scan tool. Do not re-
place either component unless a fault is actually in-
dicated.
JABS BRAKE DIAGNOSIS 5 - 3

SERVICE BRAKE DIAGNOSIS
INDEX
page page
Brake Drag............................... 6
Brake Fade.............................. 6
Brake Fluid Contamination................... 7
Brake Noise.............................. 7
Brake Pull............................... 6
Brake Warning Light Operation................ 5
Brakes Do Not Hold After Driving Through Deep
Water Puddles........................... 7
Component Inspection...................... 5
Contaminated Brakelining.................... 7
Diagnosing Parking Brake Malfunctions.......... 8
Diagnosis Procedures....................... 4
General Information........................ 4Hard Pedal or High Pedal Effort............... 6
Low Pedal............................... 5
Master Cylinder/Power Booster Test............ 8
Pedal Falls Away.......................... 5
Pedal Pulsation (Non-ABS Brakes Only)......... 6
Power Booster Check Valve Test............... 9
Power Booster Vacuum Test.................. 9
Preliminary Brake Check..................... 4
Rear Brake Grab.......................... 7
Road Testing............................. 5
Spongy Pedal............................. 5
Wheel and Tire Problems.................... 7
GENERAL INFORMATION
The diagnosis information in this section covers
service brake components which include:
²disc brake calipers
²disc brakeshoes
²drum brake wheel cylinders
²drum brakeshoes and brake drums
²drum brake support plates
²parking brake mechanism
²master cylinder/combination valve
²vacuum power brake booster
²brake pedal and brakelight switch
²brake warning light
DIAGNOSIS PROCEDURES
Service brake diagnosis involves determining if a
problem is related to a mechanical, hydraulic or vac-
uum operated component. A preliminary brake check,
followed by road testing and component inspection
are needed to determine a problem cause.
Road testing will either verify proper brake opera-
tion or confirm the existence of a problem. Compo-
nent inspection will, in most cases, identify the
actual part responsible for a problem.
The first diagnosis step is the preliminary brake
check. This involves inspecting fluid level, parking
brake action, wheel and tire condition, checking for
obvious leaks or component damage and testing
brake pedal response. A road test will confirm or
deny the existence of a problem. The final diagnosis
procedure involves road test analysis and a visual in-
spection of brake components.
PRELIMINARY BRAKE CHECK
(1) If amber ABS light is illuminated, refer to ABS
Brake System Diagnosis. If red warning light is illu-
minated, or if neither warning light is illuminated,
continue with brake check.(2) Inspect condition of tires and wheels. Damaged
wheels and worn, damaged, or underinflated tires
can cause pull, shudder, tramp and a condition simi-
lar to grab.
(3) If complaint was based on noise when braking,
check suspension components. Jounce front and rear
of vehicle and listen for noise that might be caused
by loose, worn, or damaged suspension or steering
components.
(4) Inspect brake fluid level:
(a) If vehicle has one-piece master cylinder, fluid
level should be within 6 mm (1/4 in.) of reservoir
rim.
(b) If vehicle has nylon reservoir with single
filler cap, correct level is to FULL mark on side of
reservoir. Acceptable level is between FULL and
ADD marks.
(c) Remember that fluid level in the reservoir
compartments will decrease in proportion to nor-
mal lining wear. However, if fluid level is abnor-
mally low, look for leaks at calipers, wheel
cylinders, brakelines and master cylinder.
(5) Inspect brake fluid condition:
(a) Fluid should be free of foreign material.Note
that brake fluid tends to darken over time.
This is normal and should not be mistaken for
contamination. If fluid is clear of foreign ma-
terial, it is OK.
(b) If fluid is highly discolored, or appears to con-
tain foreign material, drain out a sample with a
clean suction gun. Pour sample in a glass container
and note condition described in step (c).
(c) If fluid separates into layers, obviously con-
tains oil, or a substance other than brake fluid,
system seals and cups will have to be replaced and
hydraulic system flushed.
(6) Check parking brake operation. Verify free
movement and full release of cables and foot pedal or
5 - 4 SERVICE BRAKE DIAGNOSISJ

hand lever. Also note if vehicle was being operated
with parking brake partially applied (this will cause
red light to remain on).
(7) Check brake pedal operation. Verify that pedal
does not bind and has adequate free play. If pedal
lacks free play, check pedal and power booster for be-
ing loose or for bind condition. Do not road test until
condition is corrected.
(8) If components inspected look OK, road test ve-
hicle.
ROAD TESTING
(1) If amber warning light is on, problem is with
antilock system component. Refer to antilock diagno-
sis section.
(2) If red warning light is not on, proceed to step
(4).
(3) If red warning light is on, proceed as follows:
(a) See if parking brakes are applied. If brakes
are applied, release them and proceed to step (4).
(b) Note if brake pedal is abnormally low. If
pedal is definitely low and red light is still on,
check front/rear hydraulic circuits for leak.Do not
road test. Inspect and repair as needed.
(4) Check brake pedal response with transmission
in Neutral and engine running. Pedal should remain
firm under steady foot pressure. If pedal falls away,
do not road test as problem is in master cylinder, or
HCU on ABS models. If pedal holds firm, proceed to
next step.
(5) During road test, make normal and firm brake
stops in 25-35 mph range. Note faulty brake opera-
tion such as hard pedal, pull, grab, drag, noise, fade,
etc.
(6) Return to shop and inspect brake components.
Refer to inspection and diagnosis information.
COMPONENT INSPECTION
Fluid leak points and dragging brake units can
usually be located without removing any components.
The area around a leak point will be wet with fluid.
The components at a dragging brake unit (wheel,
tire, rotor) will be quite warm or hot to the touch.
Other brake problem conditions will require compo-
nent removal for proper inspection. Raise the vehicle
and remove the necessary wheels for better visual ac-
cess.
During component inspection, pay particular atten-
tion to heavily rusted/corroded brake components
(e.g. rotors, caliper pistons, brake return/holddown
springs, support plates, etc.).
Heavy accumulations of rust may be covering se-
vere damage to a brake component. It is wise to re-
move surface rust in order to accurately determine
the depth of rust penetration and damage. Light sur-
face rust is fairly normal and not a major concern (as
long as it is removed). However, heavy rust buildup,especially on high mileage vehicles may cover struc-
tural damage to such important components as
brakelines, rotors, support plates, and brake boost-
ers. Refer to the wheel brake service procedures in
this group for more information.
BRAKE WARNING LIGHT OPERATION
The red brake warning light will illuminate under
the following conditions:
²for 2-3 seconds at startup as part of normal bulb
check
²when parking brakes are applied
²low pedal caused by leak in front/rear brake hy-
draulic circuit
If the red light remains on after startup, first ver-
ify that the parking brakes are fully released. Then
check pedal action and fluid level. A red light plus
low pedal indicates the pressure differential switch
and valve have been actuated due to a system leak.
On models with ABS brakes, the amber warning
light only illuminates when an ABS malfunction has
occurred. The ABS light operates independently of
the red warning light.
PEDAL FALLS AWAY
A brake pedal that falls away under steady foot
pressure is generally the result of a system leak. The
leak point could be at a brakeline, fitting, hose,
wheel cylinder, or caliper. Internal leakage in the
master cylinder caused by worn or damaged piston
cups, may also be the problem cause.
If leakage is severe, fluid will be evident at or
around the leaking component. However internal
leakage in the master cylinder will not be physically
evident. Refer to the cylinder test procedure at the
end of this section.
LOW PEDAL
If a low pedal is experienced, pump the pedal sev-
eral times. If the pedal comes back up, worn lining
and worn rotors or drums are the most likely causes.
However, if the pedal remains low and the red warn-
ing light is on, the likely cause is a leak in the hy-
draulic system.
A decrease in master cylinder fluid level may only
be the result of normal lining wear. Fluid level will
drop somewhat as lining wear occurs. It is a result of
the outward movement of caliper and wheel cylinder
pistons to compensate for normal wear.
SPONGY PEDAL
Air in the system is the usual cause of a spongy
pedal. Brake drums machined way beyond allowable
limits (too thin), or substandard brake lines and
hoses can also cause a condition similar to a spongy
JSERVICE BRAKE DIAGNOSIS 5 - 5

produce a condition similar to grab as the tire loses
and recovers traction.
Flat-spotted tires can cause vibration and wheel
tramp and generate shudder during brake operation.
A tire with internal damage such as a severe bruise
or ply separation can cause vibration and pull. The
pull will be magnified when braking.
DIAGNOSING PARKING BRAKE MALFUNCTIONS
Adjustment Mechanism
Parking brake adjustment is controlled by a ca-
ble tensioner mechanism. The cable tensioner,
once adjusted at the factory, will not need further
attention under normal circumstances. There are
only two instances when adjustment is required.
The first is when a new tensioner, or cables have
been installed. And the second, is when the ten-
sioner and cables are disconnected for access to
other brake components.
Parking Brake Switch And Warning Light Illumination
The parking brake switch on the lever, or foot
pedal, is in circuit with the red warning light. The
switch will illuminate the red light only when the
parking brakes are applied. If the light remains on
after parking brake release, the switch or wires are
faulty, or cable tensioner adjustment is incorrect.
If the red light comes on while the vehicle is in mo-
tion and brake pedal height decreases, a fault has oc-
curred in the front or rear brake hydraulic system.
Parking Brake problem Causes
In most cases, the actual cause of an improperly
functioning parking brake (too loose/too tight/wont
hold), can be traced to a drum brake component.
The leading cause of improper parking brake
operation, is excessive clearance between the
brakeshoes and the drum surface. Excessive
clearance is a result of: lining and/or drum
wear; oversize drums; or inoperative shoe ad-
juster components.
Excessive parking brake lever travel (sometimes de-
scribed as a loose lever or too loose condition), is the re-
sult of worn brakeshoes/drums, improper brakeshoe
adjustment, or incorrectly assembled brake parts.
A ``too loose'' condition can also be caused by inop-
erative brakeshoe adjusters. If the adjusters are mis-
assembled, they will not function. In addition, since
the adjuster mechanism only works during reverse
stops, it is important that complete stops be made.
The adjuster mechanism does not operate when roll-
ing stops are made in reverse. The vehicle must be
brought to a complete halt before the adjuster lever
will turn the adjuster screw.
A condition where the parking brakes do not hold, will
most probably be due to a wheel brake component.
Items to look for when diagnosing a parking brake
problem, are:
²rear brakeshoe wear or adjuster problem
²rear brake drum wear
²brake drums machined beyond allowable diameter
(oversize)
²parking brake front cable not secured to lever
²parking brake rear cable seized
²parking brake strut reversed
²parking brake strut not seated in both shoes
²parking brake lever not seated in secondary shoe
²parking brake lever or brakeshoe bind on support
plate
²brakeshoes reversed
²adjuster screws seized
²adjuster screws reversed
²holddown or return springs misassembled or lack
tension
²wheel cylinder pistons seized
Brake drums that are machined oversize are diffi-
cult to identify without inspection. If oversize drums
are suspected, diameter of the braking surface will
have to be checked with an accurate drum gauge.
Oversize drums will cause low brake pedal and lack
of parking brake holding ability.
Improper parking brake strut and lever installation
will result in unsatisfactory parking brake operation.
Intermixing the adjuster screws will cause drag, bind
and pull along with poor parking brake operation.
Parking brake adjustment and parts replacement pro-
cedures are described in the Parking Brake section.
MASTER CYLINDER/POWER BOOSTER TEST
(1) Start engine and check booster vacuum hose
connections. Hissing noise indicates vacuum leak.
Correct any vacuum leak before proceeding.
(2) Stop engine and shift transmission into Neu-
tral.
(3) Pump brake pedal until all vacuum reserve in
booster is depleted.
(4) Press and hold brake pedal under light foot
pressure.
(a) If pedal holds firm, proceed to step (5).
(b) If pedal does not hold firm and falls away,
master cylinder is faulty due to internal leakage.
Overhaul or replace cylinder.
(5) Start engine and note pedal action.
(a) If pedal falls away slightly under light foot
pressure then holds firm, proceed to step (6).
(b) If no pedal action is discernible, or hard pedal
is noted, power booster or vacuum check valve is
faulty. Install known good check valve and repeat
steps (2) through (5).
(6) Rebuild booster vacuum reserve as follows: Re-
lease brake pedal. Increase engine speed to 1500
rpm, close throttle and immediately turn off ignition.
5 - 8 SERVICE BRAKE DIAGNOSISJ

MASTER CYLINDERÐCOMBINATION VALVE
INDEX
page page
Combination Valve Replacement (Non-ABS)..... 16
General Service Information................. 15
Master Cylinder and Combination Valve Installation
(With ABS)............................. 20
Master Cylinder and Combination Valve Removal
(With ABS)............................. 17Master Cylinder Bench Bleeding.............. 21
Master Cylinder Installation (Non-ABS)......... 16
Master Cylinder Overhaul (4-Cylinder Models).... 16
Master Cylinder Removal (Non-ABS)........... 15
Reservoir Replacement (2-Piece Master Cylinder) . 19
GENERAL SERVICE INFORMATION
Master Cylinder
Two different master cylinders are used. A one-piece
cast aluminum cylinder is used on 4-cylinder YJ models
(Fig. 1). All other models have a two-piece master cylin-
der with removable nylon reservoir (Fig. 2).
The two master cylinders are serviced differently.
The reservoir and grommets are the only replaceable
parts on the two-piece master cylinder. The one-piece
master cylinder can be overhauled when necessary.
Combination Valve
A combination valve is used in all models. The
valve contains a pressure differential valve and
switch and a rear brake proportioning valve. The
valve is not repairable. It must be replaced if diagno-
sis indicates this is necessary.
The pressure differential switch is connected to the
brake warning light. The switch is actuated by move-
ment of the switch valve. The switch monitors fluid
pressure in the separate front/rear brake hydraulic cir-
cuits.
A decrease or loss of fluid pressure in either hydraulic
circuit will cause the switch valve to shuttle to the low
pressure side. Movement of the valve pushes the switch
plunger upward. This action closes the switch internal
contacts completing the electrical circuit to the red
warning light. The switch valve will remain in an actu-
ated position until repairs are made.
The rear proportioning valve is used to balance front-
rear brake action. The valve allows normal fluid flow
during moderate effort brake stops. The valve only con-
trols (meters) fluid flow during high effort brake stops.
MASTER CYLINDER REMOVAL (NON-ABS)
(1) Remove air cleaner hose, cover and housing.
Fig. 1 Master Cylinder And Combination Valve
(4-Cyl. YJ Models)
Fig. 2 Master Cylinder And Combination Valve (All
Except 4-Cyl. YJ Models)
JMASTER CYLINDERÐCOMBINATION VALVE 5 - 15