1995 JEEP CHEROKEE light

DIFFERENTIAL CASE DISASSEMBLY
(1) Rotate side gears until pinion gears are located
at the differential case opening. Remove gears.
(2) Remove side gears and thrust washers.
(3) Remove differential bearings from the case
hubs with Puller C-293-PA, Adapter C-293-48 and
Plug SP-3289 (Fig. 16).
CLEANING/INSPECTION
(1) Clean all differential components in cleaning
solvent. Allow the bearings to either air dry or dry
them with a lint-free cloth. Dry the other components
with compressed air.
(2) Examine each component for wear or damage.
(3) Replace shims, bearings and cups as a set only.
Replace bearings and cups if either is galled, worn,
cracked, or damaged.
(4) Inspect the differential side and pinion gears.
Replace any gear that is worn, cracked or chipped.
(5) Inspect differential case and replace case if
cracked or damaged.
Polish each axle shaft sealing surface with
No. 600 crocus cloth. This can remove slight
surface damage. Do not reduce the diameter of
the axle shaft seal contact surface. When pol-
ishing, the crocus cloth should be moved
around the circumference of the shaft (not in-
line with the shaft).
When replacing a drive pinion gear bearing,
always replace the bearing and cup as a
matched set.
(6) Inspect the axle shaft C-clip locks for cracks or
excessive wear. Replace them if necessary.
(7) Test each threaded adjuster to determine if it
rotates freely.
(8) If an adjuster binds, repair the damaged
threads or replace the adjuster.
DIFFERENTIAL CASE ASSEMBLY
(1) Lubricate all the differential case components
with gear lubricant.
(2) Place the thrust washers on the differential
side gears. Position the gears in the differential case
counterbores.
If replacement side gears or thrust washers
are used, refer to Differential Side Gear Clear-
ance Measurement And Adjustment (Fig. 17).
(3) Position the thrust washers on the differential
pinion gears. Mesh the pinion gears with the side
gears.Ensure that the pinion gears are exactly
180 degrees opposite each other.
(4) Rotate the side gears to align the pinion gears
and thrust washers. Align these components with the
mate shaft bores in the case.
(5) If ring gear was removed, clean all contact sur-
faces. Use an Arkansas stone or fine file to remove
any sharp areas from the chamfered inside diameter.
Fig. 15 Case Flange Runout Measurement
Fig. 16 Differential Bearing Removal
Fig. 17 Side Gear Calculations
JREAR SUSPENSION AND AXLES 3 - 37

CAUTION: Never loosen pinion gear nut to decrease
pinion gear bearing preload torque and never ex-
ceed specified preload torque. If preload torque is
exceeded a new collapsible spacer must be in-
stalled. The torque sequence will have to be re-
peated.
(23) Measure pinion bearing preload torque by ro-
tating pinion shaft with a Newton-meter or an inch-
pound torque wrench. The correct bearing preload
torque is 1 to 2 Nzm (10 to 20 in. lbs.). This torque
value is with replacement bearings and pinion nut
tightened with a minimum of 285 Nzm (210 ft. lbs.)
torque (Fig. 27).
When using original pinion rear bearing and
a replacement front bearing. The correct pre-
load torque is 1 Nzm (10 in. lbs.) in addition to
the torque measured and recorded during dis-
assembly.
The bearing preload torque should be con-
stant during a complete revolution of the pin-
ion gear shaft. If preload torque varies during
rotation of the shaft, there is an internal bind-
ing that must be corrected before final assem-
bly.
(24) If the specified torque is not obtained, tighten
the nut in small increments until the preload torque
is obtained.
The differential will be unacceptable for use
if the final nut torque is less than 285 Nzm (210
ft. lbs.) torque. If the preload torque is not
within the specified range this is also unaccept-
able.
DIFFERENTIAL CASE INSTALLATION
(1) Apply a coating of hypoid gear lubricant to the
differential bearings, bearing cups and threaded ad-
justers. A dab of grease can be used to keep the ad-
justers in position. Carefully position the assembled
differential case in the housing.(2) Observe the reference marks and install the
differential bearing caps at their original locations
(Fig. 28).
(3) Install the bearing cap bolts (Fig. 28). Tighten
the upper bolts to 14 Nzm (10 ft. lbs.) torque. Tighten
the lower bolts finger-tight until the bolt head is
lightly seated.
DIFFERENTIAL BEARING PRELOAD AND RING
GEAR BACKLASH ADJUSTMENT
The following limitations must be considered when
adjusting the differential:
²The maximum ring gear backlash variation is
0.003 inch (0.076 mm).
²Mark the gears so the same teeth are meshed dur-
ing all backlash measurements.
²Maintain the specified threaded-adjuster torque
while adjusting.
²Excessive adjuster torque will introduce a high
bearing load and cause premature bearing failure.
Insufficient adjuster torque can result in excessive
differential case free-play and ring gear noise.
²Insufficient adjuster torque will not support the
ring gear correctly and can cause excessive differen-
tial case free-play and ring gear noise.
The differential bearing cups will not always
immediately follow the threaded adjusters as
they are moved during adjustment. Ensure ac-
curate bearing cup responses to the adjust-
ments. Maintain the gear teeth engaged
(meshed) as marked. The bearings must be
seated by rapidly rotating the pinion gear a
half turn back and forth. Do this five to ten
times each time the threaded adjusters are ad-
justed.
(1) Use Wrench C-4164 to adjust each threaded ad-
juster inward (Fig. 29) until the differential bearing
free-play is eliminated. Allow some ring gear back-
lash (approximately 0.01 inch/0.25 mm) between the
Fig. 27 Bearing Preload Torque Measurement
Fig. 28 Bearing Caps & Bolts
JREAR SUSPENSION AND AXLES 3 - 41

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

pedal. The proper course of action is to bleed the sys-
tem, or replace thin drums and suspect quality brake
lines and hoses.
HARD PEDAL OR HIGH PEDAL EFFORT
A hard pedal or high pedal effort may be due to lin-
ing that is water soaked, contaminated, glazed, or
badly worn. The power booster or check valve could
also be faulty. Test the booster and valve as described
in this section.
BRAKE DRAG
Brake drag occurs when the lining is in constant
contact with the rotor or drum. Drag can occur at one
wheel, all wheels, fronts only, or rears only. It is a
product of incomplete brakeshoe release. Drag can be
minor or severe enough to overheat the linings, ro-
tors and drums. A drag condition also worsens as
temperature of the brake parts increases.
Brake drag also has a direct effect on fuel economy.
If undetected, minor brake drag can be misdiagnosed
as an engine or transmission/torque converter prob-
lem.
Minor drag will usually cause slight surface char-
ring of the lining. It can also generate hard spots in
rotors and drums from the overheat/cool down pro-
cess. In most cases, the rotors, drums, wheels and
tires are quite warm to the touch after the vehicle is
stopped.
Severe drag can char the brake lining all the way
through. It can also distort and score rotors and
drums to the point of replacement. The wheels, tires
and brake components will be extremely hot. In se-
vere cases, the lining may generate smoke as it chars
from overheating.
An additional cause of drag involves the use of in-
correct length caliper mounting bolts. Bolts that are
too long can cause a partial apply condition. The cor-
rect caliper bolts have a shank length of 67 mm
(2.637 in.), plus or minus 0.6 mm (0.0236 in.). Refer
to the Disc Brake service section for more detail on
caliper bolt dimensions and identification.
Some common causes of brake drag are:
²loose or damaged wheel bearing
²seized or sticking caliper or wheel cylinder piston
²caliper binding on bolts or slide surfaces
²wrong length caliper mounting bolts (too long)
²loose caliper mounting bracket
²distorted rotor, brake drum, or shoes
²brakeshoes binding on worn/damaged support
plates
²severely rusted/corroded components
²misassembled components.
If brake drag occurs at all wheels, the problem may
be related to a blocked master cylinder compensatorport or faulty power booster (binds-does not release).
The condition will worsen as brake temperature in-
creases.
The brakelight switch can also be a cause of drag.
An improperly mounted or adjusted brakelight
switch can prevent full brake pedal return. The re-
sult will be the same as if the master cylinder com-
pensator ports are blocked. The brakes would be
partially applied causing drag.
BRAKE FADE
Brake fade is a product of overheating caused by
brake drag. However, overheating and subsequent
fade can also be caused by riding the brake pedal,
making repeated high deceleration stops in a short
time span, or constant braking on steep roads. Refer
to the Brake Drag information in this section for
causes.
PEDAL PULSATION (NON-ABS BRAKES ONLY)
Pedal pulsation is caused by parts that are loose,
or beyond tolerance limits. This type of pulsation is
constant and will occur every time the brakes are ap-
plied.
Disc brake rotors with excessive lateral runout or
thickness variation, or out of round brake drums are
the primary causes of pulsation.
On vehicles with ABS brakes, remember that pedal
pulsation is normal during antilock mode brake
stops. If pulsation occurs during light to moderate
brake stops, a standard brake part is either loose, or
worn beyond tolerance.
BRAKE PULL
A front pull condition could be the result of:
²contaminated lining in one caliper
²seized caliper piston
²binding caliper
²wrong caliper mounting bolts (too long)
²loose caliper
²loose or corroded mounting bolts
²improper brakeshoes
²damaged rotor
²incorrect wheel bearing adjustment (at one wheel)
A worn, damaged wheel bearing or suspension com-
ponent are further causes of pull. A damaged front
tire (bruised, ply separation) can also cause pull.
Wrong caliper bolts (too long) will cause a partial ap-
ply condition and pull if only one caliper is involved.
A common and frequently misdiagnosed pull condi-
tion is where direction of pull changes after a few
stops. The cause is a combination of brake drag fol-
lowed by fade at the dragging brake unit.
As the dragging brake overheats, efficiency is so re-
duced that fade occurs. If the opposite brake unit is
still functioning normally, its braking effect is magni-
5 - 6 SERVICE BRAKE DIAGNOSISJ

fied. This causes pull to switch direction in favor of
the brake unit that is functioning normally.
When diagnosing a change in pull condition, re-
member that pull will return to the original direction
if the dragging brake unit is allowed to cool down
(and is not seriously damaged).
REAR BRAKE GRAB
Rear grab (or pull) is usually caused by contami-
nated lining, bent or binding shoes and support
plates, or improperly assembled components. This is
particularly true when only one rear wheel is in-
volved. However, when both rear wheels are affected,
the master cylinder could be at fault.
BRAKES DO NOT HOLD AFTER DRIVING THROUGH
DEEP WATER PUDDLES
This condition is caused by water soaked lining. If
the lining is only wet, it can be dried by driving with
the brakes lightly applied for a mile or two. However,
if the lining is both wet and dirty, disassembly and
cleaning will be necessary.
CONTAMINATED BRAKELINING
Brakelining contaminated by water is salvageable.
The lining can either be air dried or dried using heat.
In cases where brakelining is contaminated by oil,
grease, or brake fluid, the lining should be replaced.
Replacement is especially necessary when fluids/lu-
bricants have actually soaked into the lining mate-
rial. However, grease or dirt that gets onto the lining
surface (from handling) during brake repairs, can be
cleaned off. Spray the lining surface clean with Mo-
par brake cleaner.
BRAKE FLUID CONTAMINATION
There are two basic causes of brake fluid contami-
nation. The first involves allowing dirt, debris, or
other materials to enter the cylinder reservoirs when
the cover is off. The second involves adding non-rec-
ommended fluids to the cylinder reservoirs.
Brake fluid contaminated with only dirt, or debris
usually retains a normal appearance. In some cases,
the foreign material will remain suspended in the
fluid and be visible. The fluid and foreign material
can be removed from the reservoir with a suction gun
but only if the brakes have not been applied. If the
brakes are applied after contamination, system flush-
ing will be required. The master cylinder may also
have to be disassembled, cleaned and the piston seals
replaced. Foreign material lodged in the reservoir
compensator/return ports can cause brake drag by re-
stricting fluid return after brake application.
Brake fluid contaminated by a non-recommended
fluid may appear discolored, milky, oily looking, or
foamy. However, remember that brake fluid will
darken in time and occasionally be cloudy in appear-ance. These are normal conditions and should not be
mistaken for contamination.
If some type of oil has been added to the system,
the fluid will separate into distinct layers. To verify
this, drain off a sample with a clean suction gun.
Then pour the sample into a glass container and ob-
serve fluid action. If the fluid separates into distinct
layers, it is definitely contaminated.
The only real correction for contamination by non-
recommended fluid is to flush the entire hydraulic
system and replace all the seals.
BRAKE NOISE
Squeak/Squeal
Factory installed brakelining is made from as-
bestos free materials. These materials have dif-
ferent operating characteristics than previous
lining material. Under certain conditions, as-
bestos free lining may generate some squeak,
groan or chirp noise. This noise is considered
normal and does not indicate a problem. The
only time inspection is necessary, is when noise
becomes constant or when grinding, scraping
noises occur.
Constant brake squeak or squeal may be due to lin-
ings that are wet or contaminated with brake fluid,
grease, or oil. Glazed linings, rotors/drums with hard
spots, and dirt/foreign material embedded in the
brake lining also cause squeak. Loud squeak, squeal,
scraping, or grinding sounds are a sign of severely
worn brake lining. If the lining has worn completely
through in spots, metal-to-metal contact occurs.
Thump/Clunk
Thumping or clunk noises during braking are fre-
quentlynotcaused by brake components. In many
cases, such noises are caused by loose or damaged
steering, suspension, or engine components. However,
calipers that bind on the slide surfaces can generate
a thump or clunk noise. In addition, worn out, im-
properly adjusted, or improperly assembled rear
brakeshoes can also produce a thump noise.
Chatter/Shudder
Brake chatter, or shudder is usually caused by
loose or worn components, or glazed/burnt lining. Ro-
tors with hard spots can also contribute to chatter.
Additional causes of chatter are out of tolerance ro-
tors, brake lining not securely attached to the shoes,
loose wheel bearings and contaminated brake lining.
WHEEL AND TIRE PROBLEMS
Some conditions attributed to brake components
may actually be caused by a wheel or tire problem.
A damaged wheel can cause shudder, vibration and
pull. A worn or damaged tire can also cause pull.
Severely worn tires with very little tread left can
JSERVICE BRAKE DIAGNOSIS 5 - 7