2002 JEEP LIBERTY Jb power

REAR AXLE-81/4
TABLE OF CONTENTS
page page
REAR AXLE-81/4
DESCRIPTION.........................86
OPERATION...........................86
DIAGNOSIS AND TESTING - AXLE..........88
REMOVAL.............................91
INSTALLATION.........................91
ADJUSTMENTS........................92
SPECIFICATIONS
REAR AXLE..........................98
SPECIAL TOOLS
8 1/4 AXLE..........................98
AXLE SHAFTS
REMOVAL............................101
INSTALLATION........................101
AXLE SHAFT SEALS
REMOVAL............................101
INSTALLATION........................102
AXLE BEARINGS
REMOVAL............................102
INSTALLATION........................102PINION SEAL
REMOVAL............................102
INSTALLATION........................103
DIFFERENTIAL
REMOVAL............................104
DISASSEMBLY........................105
ASSEMBLY...........................105
INSTALLATION........................105
DIFFERENTIAL - TRAC-LOK
DIAGNOSIS AND TESTING - TRAC-LOKT....106
DISASSEMBLY........................107
CLEANING...........................109
INSPECTION.........................109
ASSEMBLY...........................109
DIFFERENTIAL CASE BEARINGS
REMOVAL............................110
INSTALLATION........................110
PINION GEAR/RING GEAR/TONE RING
REMOVAL............................110
INSTALLATION........................112
REAR AXLE-81/4
DESCRIPTION
The axle housings consist of a cast iron center sec-
tion with axle tubes extending from either side. The
tubes are pressed into and welded to the differential
housing to form a one-piece axle housing. The axles
are equipped with semi-floating axle shafts, meaning
vehicle loads are supported by the axle shaft and
bearings. The axle shafts are retained by C-locks in
the differential side gears.
The differential case is a one-piece design. The dif-
ferential pinion mate shaft is retained with a
threaded pin. Differential bearing preload and ring
gear backlash are set and maintained by threaded
adjusters at the outside of the differential housing.
Pinion bearing preload is set and maintained by the
use of a collapsible spacer.
The differential cover provides a means for inspec-
tion and service without removing the complete axlefrom the vehicle. A vent hose is used to relieve inter-
nal pressure caused by lubricant vaporization and
internal expansion.
Axles equipped with a Trac-Loktdifferential are
optional. A differential has a one-piece differential
case, and the same internal components as a stan-
dard differential, plus two clutch disc packs.
OPERATION
The axle receives power from the transmission/
transfer case through the rear propeller shaft. The
rear propeller shaft is connected to the pinion gear
which rotates the differential through the gear mesh
with the ring gear bolted to the differential case. The
engine power is transmitted to the axle shafts
through the pinion mate and side gears. The side
gears are splined to the axle shafts.
3 - 86 REAR AXLE-81/4KJ

STANDARD DIFFERENTIAL
During straight-ahead driving, the differential pin-
ion gears do not rotate on the pinion mate shaft. This
occurs because input torque applied to the gears is
divided and distributed equally between the two side
gears. As a result, the pinion gears revolve with the
pinion mate shaft but do not rotate around it (Fig. 1).
When turning corners, the outside wheel must
travel a greater distance than the inside wheel to
complete a turn. The difference must be compensated
for to prevent the tires from scuffing and skidding
through turns. To accomplish this, the differential
allows the axle shafts to turn at unequal speeds (Fig.
2). In this instance, the input torque applied to the
pinion gears is not divided equally. The pinion gears
now rotate around the pinion mate shaft in opposite
directions. This allows the side gear and axle shaft
attached to the outside wheel to rotate at a faster
speed.
TRAC-LOKTDIFFERENTIAL
This differentials clutches are engaged by two con-
current forces. The first being the preload force
exerted through Belleville spring washers within the
clutch packs. The second is the separating forces gen-
erated by the side gears as torque is applied through
the ring gear (Fig. 3).
This design provides the differential action needed
for turning corners and for driving straight ahead
during periods of unequal traction. When one wheel
looses traction, the clutch packs transfer additional
torque to the wheel having the most traction. This
differential resist wheel spin on bumpy roads and
provide more pulling power when one wheel looses
Fig. 1 Differential Operation - Straight Ahead Driving
1 - IN STRAIGHT AHEAD DRIVING EACH WHEEL ROTATES AT
100% OF CASE SPEED
2 - PINION GEAR
3 - SIDE GEAR
4 - PINION GEARS ROTATE WITH CASE
Fig. 2 Differential Operation - On Turns
1 - PINION GEARS ROTATE ON PINION SHAFT
Fig. 3 Trac-lokTLimited Slip Differential
1 - CASE
2 - RING GEAR
3 - DRIVE PINION
4 - PINION GEAR
5 - MATE SHAFT
6 - CLUTCH PACK
7 - SIDE GEAR
8 - CLUTCH PACK
KJREAR AXLE - 8 1/4 3 - 87
REAR AXLE - 8 1/4 (Continued)

traction. Pulling power is provided continuously until
both wheels loose traction. If both wheels slip due to
unequal traction, Trac-lokŸ operation is normal. In
extreme cases of differences of traction, the wheel
with the least traction may spin.
DIAGNOSIS AND TESTING - AXLE
GEAR NOISE
Axle gear noise can be caused by insufficient lubri-
cant, incorrect backlash, incorrect pinion depth, tooth
contact, worn/damaged gears, or the carrier housing
not having the proper offset and squareness.
Gear noise usually happens at a specific speed
range. The noise can also occur during a specific type
of driving condition. These conditions are accelera-
tion, deceleration, coast, or constant load.
When road testing, first warm-up the axle fluid by
driving the vehicle at least 5 miles and then acceler-
ate the vehicle to the speed range where the noise is
the greatest. Shift out-of-gear and coast through the
peak-noise range. If the noise stops or changes
greatly:
²Check for insufficient lubricant.
²Incorrect ring gear backlash.
²Gear damage.
Differential side gears and pinions can be checked
by turning the vehicle. They usually do not cause
noise during straight-ahead driving when the gears
are unloaded. The side gears are loaded during vehi-
cle turns. A worn pinion shaft can also cause a snap-
ping or a knocking noise.
BEARING NOISE
The axle shaft, differential and pinion bearings can
all produce noise when worn or damaged. Bearing
noise can be either a whining, or a growling sound.
Pinion bearings have a constant-pitch noise. This
noise changes only with vehicle speed. Pinion bearing
noise will be higher pitched because it rotates at a
faster rate. Drive the vehicle and load the differen-
tial. If bearing noise occurs, the rear pinion bearing
is the source of the noise. If the bearing noise is
heard during a coast, the front pinion bearing is the
source.
Worn or damaged differential bearings usually pro-
duce a low pitch noise. Differential bearing noise is
similar to pinion bearing noise. The pitch of differen-
tial bearing noise is also constant and varies only
with vehicle speed.
Axle shaft bearings produce noise and vibration
when worn or damaged. The noise generally changeswhen the bearings are loaded. Road test the vehicle.
Turn the vehicle sharply to the left and to the right.
This will load the bearings and change the noise
level. Where axle bearing damage is slight, the noise
is usually not noticeable at speeds above 30 mph.
LOW SPEED KNOCK
Low speed knock is generally caused by a worn
U-joint or by worn side±gear thrust washers. A worn
pinion shaft bore will also cause low speed knock.
VIBRATION
Vibration at the rear of the vehicle is usually
caused by a:
²Damaged drive shaft.
²Missing drive shaft balance weight(s).
²Worn or out-of-balance wheels.
²Loose wheel lug nuts.
²Worn U-joint(s).
²Loose/broken springs.
²Damaged axle shaft bearing(s).
²Loose pinion gear nut.
²Excessive pinion yoke run out.
²Bent axle shaft(s).
Check for loose or damaged front-end components
or engine/transmission mounts. These components
can contribute to what appears to be a rearend vibra-
tion. Do not overlook engine accessories, brackets
and drive belts.
NOTE: All driveline components should be exam-
ined before starting any repair.
DRIVELINE SNAP
A snap or clunk noise when the vehicle is shifted
into gear (or the clutch engaged), can be caused by:
²High engine idle speed.
²Transmission shift operation.
²Loose engine/transmission/transfer case mounts.
²Worn U-joints.
²Loose spring mounts.
²Loose pinion gear nut and yoke.
²Excessive ring gear backlash.
²Excessive side gear to case clearance.
The source of a snap or a clunk noise can be deter-
mined with the assistance of a helper. Raise the vehi-
cle on a hoist with the wheels free to rotate. Instruct
the helper to shift the transmission into gear. Listen
for the noise, a mechanics stethoscope is helpful in
isolating the source of a noise.
3 - 88 REAR AXLE-81/4KJ
REAR AXLE - 8 1/4 (Continued)

BRAKES
TABLE OF CONTENTS
page page
BRAKES - BASE........................... 1BRAKES - ABS........................... 32
BRAKES - BASE
TABLE OF CONTENTS
page page
BRAKES - BASE
DESCRIPTION..........................2
WARNING.............................2
DIAGNOSIS AND TESTING - BASE BRAKE
SYSTEM.............................3
STANDARD PROCEDURE
STANDARD PROCEDURE - PRESSURE
BLEEDING............................5
STANDARD PROCEDURE - MANUAL
BLEEDING............................6
SPECIFICATIONS
BRAKE COMPONENTS..................6
TORQUE.............................7
SPECIAL TOOLS
BASE BRAKES........................7
BRAKE LINES
DESCRIPTION..........................8
DIAGNOSIS AND TESTING - BRAKE LINE
AND HOSES..........................8
STANDARD PROCEDURE
STANDARD PROCEDURE - DOUBLE
INVERTED FLARING....................8
STANDARD PROCEDURE - ISO FLARING . . . 8
REMOVAL
REMOVAL - FRONT HOSE...............9
REMOVAL - REAR BRAKE HOSE..........9
INSTALLATION
INSTALLATION - FRONT BRAKE HOSE....10
INSTALLATION - REAR BRAKE HOSE......10
BRAKE PADS / SHOES
DESCRIPTION - REAR DRUM BRAKE.......10
OPERATION - REAR DRUM BRAKE.........11
REMOVAL
REMOVAL - FRONT BRAKE PADS.........11
REMOVAL - DRUM BRAKE SHOES........11
INSTALLATION
INSTALLATION - FRONT BRAKE PADS.....11INSTALLATION - DRUM BRAKE SHOES....11
ADJUSTMENTS
ADJUSTMENT - REAR DRUM BRAKE......12
DISC BRAKE CALIPERS
DESCRIPTION.........................13
OPERATION...........................14
REMOVAL.............................14
DISASSEMBLY.........................14
CLEANING............................16
INSPECTION..........................16
ASSEMBLY............................16
INSTALLATION.........................17
DISC BRAKE CALIPER ADAPTER
REMOVAL.............................18
INSTALLATION.........................18
ROTORS
DIAGNOSIS AND TESTING - DISC BRAKE
ROTOR .............................18
STANDARD PROCEDURE - DISC BRAKE
ROTOR .............................19
REMOVAL.............................19
INSTALLATION.........................19
JUNCTION BLOCK
DESCRIPTION.........................20
OPERATION...........................20
DIAGNOSIS AND TESTING -
PROPORTIONING VALVE...............20
REMOVAL.............................20
INSTALLATION.........................20
PEDAL
DESCRIPTION.........................20
OPERATION...........................20
REMOVAL.............................20
INSTALLATION.........................20
POWER BRAKE BOOSTER
DESCRIPTION.........................21
OPERATION...........................21
KJBRAKES 5 - 1

DIAGNOSIS AND TESTING - MASTER
CYLINDER/POWER BOOSTER...........21
REMOVAL.............................22
INSTALLATION.........................23
MASTER CYLINDER
DESCRIPTION.........................24
OPERATION...........................24
DIAGNOSIS AND TESTING - MASTER
CYLINDER/POWER BOOSTER...........24
STANDARD PROCEDURE - MASTER
CYLINDER BLEEDING..................24
REMOVAL.............................25
INSTALLATION.........................25
FLUID RESERVOIR
REMOVAL.............................26
INSTALLATION.........................26
FLUID
DIAGNOSIS AND TESTING - BRAKE FLUID
CONTAMINATION.....................26
STANDARD PROCEDURES - MASTER
CYLINDER FLUID LEVEL................26
SPECIFICATIONS
BRAKE FLUID........................27
DRUM
DIAGNOSIS AND TESTING - BRAKE DRUM . . . 27
STANDARD PROCEDURES - BRAKE DRUM
MACHINING..........................27SUPPORT PLATE
REMOVAL
REMOVAL - 198 RBI AXLE..............27
REMOVAL - 8 1/4 AXLE.................27
INSTALLATION
INSTALLATION - 198 RBI AXLE...........28
INSTALLATION - 8 1/4 AXLE.............28
WHEEL CYLINDERS
REMOVAL.............................28
DISASSEMBLY.........................28
CLEANING............................28
INSPECTION..........................29
ASSEMBLY............................29
INSTALLATION.........................29
PARKING BRAKE
DESCRIPTION.........................29
OPERATION...........................29
ADJUSTMENTS
ADJUSTMENT - LOCK OUT.............30
CABLES
REMOVAL.............................30
INSTALLATION.........................30
LEVER
REMOVAL.............................31
INSTALLATION.........................31
BRAKES - BASE
DESCRIPTION
Power assist front disc and rear drum brakes are
standard equipment. Disc brake components consist
of single piston calipers and ventilated 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 hand lever.
A dual diaphragm vacuum power brake booster is
used for all applications. All models have an alumi-
num 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.
Factory brake lining on all models consists of an
organic base material combined with metallic parti-
cles. The original equipment linings do not contain
asbestos.
WARNING
WARNING: DUST AND DIRT ACCUMULATING ON
BRAKE PARTS DURING NORMAL USE MAY CON-
TAIN ASBESTOS FIBERS FROM AFTERMARKET
LININGS. BREATHING EXCESSIVE CONCENTRA-
TIONS OF ASBESTOS FIBERS CAN CAUSE SERI-
OUS BODILY HARM. EXERCISE CARE WHEN
SERVICING BRAKE PARTS. DO NOT CLEAN
BRAKE PARTS WITH COMPRESSED AIR OR BY
DRY BRUSHING. USE A VACUUM CLEANER SPE-
CIFICALLY DESIGNED FOR THE REMOVAL OF
ASBESTOS FIBERS FROM BRAKE COMPONENTS.
IF A SUITABLE VACUUM CLEANER IS NOT AVAIL-
ABLE, CLEANING SHOULD BE DONE WITH A
WATER DAMPENED CLOTH. DO NOT SAND, OR
GRIND BRAKE LINING UNLESS EQUIPMENT USED
IS DESIGNED TO CONTAIN THE DUST RESIDUE.
DISPOSE OF ALL RESIDUE CONTAINING ASBES-
TOS FIBERS IN SEALED BAGS OR CONTAINERS
TO MINIMIZE EXPOSURE TO YOURSELF AND OTH-
ERS. FOLLOW PRACTICES PRESCRIBED BY THE
OCCUPATIONAL SAFETY AND HEALTH ADMINIS-
TRATION AND THE ENVIRONMENTAL PROTECTION
AGENCY FOR THE HANDLING, PROCESSING, AND
DISPOSITION OF DUST OR DEBRIS THAT MAY
CONTAIN ASBESTOS FIBERS.
5 - 2 BRAKES - BASEKJ

CAUTION: Never use gasoline, kerosene, alcohol,
motor oil, transmission fluid, or any fluid containing
mineral oil to clean the system components. These
fluids damage rubber cups and seals. Use only
fresh brake fluid or Mopar brake cleaner to clean or
flush brake system components. These are the only
cleaning materials recommended. If system contam-
ination is suspected, check the fluid for dirt, discol-
oration, or separation into distinct layers. Also
check the reservoir cap seal for distortion. Drain
and flush the system with new brake fluid if con-
tamination is suspected.
CAUTION: Use Mopar brake fluid, or an equivalent
quality fluid meeting SAE/DOT standards J1703 and
DOT 3. Brake fluid must be clean and free of con-
taminants. Use fresh fluid from sealed containers
only to ensure proper antilock component opera-
tion.
CAUTION: Use Mopar multi-mileage or high temper-
ature grease to lubricate caliper slide surfaces,
drum brake pivot pins, and shoe contact points on
the backing plates. Use multi-mileage grease or GE
661 or Dow 111 silicone grease on caliper slide pins
to ensure proper operation.
DIAGNOSIS AND TESTING - BASE BRAKE
SYSTEM
Base brake components consist of the brake shoes,
calipers, wheel cylinders, brake drums, rotors, brake
lines, master cylinder, booster, and parking brake
components.
Brake diagnosis involves determining if the prob-
lem is related to a mechanical, hydraulic, or vacuum
operated component.
The first diagnosis step is the preliminary check.
PRELIMINARY BRAKE CHECK
(1) Check condition of tires and wheels. Damaged
wheels and worn, damaged, or underinflated tires
can cause pull, shudder, vibration, and a condition
similar to grab.
(2) 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.
(3) Inspect brake fluid level and condition. Note
that the brake reservoir fluid level will decrease in
proportion to normal lining wear.Also note that
brake fluid tends to darken over time. This is
normal and should not be mistaken for contam-
ination.(a) If fluid level is abnormally low, look for evi-
dence of leaks at calipers, wheel cylinders, brake
lines, and master cylinder.
(b) If fluid appears contaminated, drain out a
sample to examine. System will have to be flushed
if fluid is separated into layers, or contains a sub-
stance other than brake fluid. The system seals
and cups will also have to be replaced after flush-
ing. Use clean brake fluid to flush the system.
(4) Check parking brake operation. Verify free
movement and full release of cables and pedal. Also
note if vehicle was being operated with parking
brake partially applied.
(5) 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
being loose or for bind condition. Do not road test
until condition is corrected.
(6) Check booster vacuum check valve and hose.
(7) If components checked appear OK, road test
the vehicle.
ROAD TESTING
(1) If complaint involved low brake pedal, pump
pedal and note if it comes back up to normal height.
(2) Check brake pedal response with transmission
in Neutral and engine running. Pedal should remain
firm under constant foot pressure.
(3) During road test, make normal and firm brake
stops in 25-40 mph range. Note faulty brake opera-
tion such as low pedal, hard pedal, fade, pedal pulsa-
tion, pull, grab, drag, noise, etc.
(4) Attempt to stop the vehicle with the parking
brake only and note grab, drag, noise, etc.
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 brake line, fitting, hose, or
caliper/wheel cylinder. If leakage is severe, fluid will
be evident at or around the leaking component.
Internal leakage (seal by-pass) in the master cylin-
der caused by worn or damaged piston cups, may
also be the problem cause.
An internal leak in the ABS or RWAL system may
also be the problem with no physical evidence.
LOW PEDAL
If a low pedal is experienced, pump the pedal sev-
eral times. If the pedal comes back up worn linings,
rotors, drums, or rear brakes out of adjustment are
the most likely causes. The proper course of action is
to inspect and replace all worn component and make
the proper adjustments.
KJBRAKES - BASE 5 - 3
BRAKES - BASE (Continued)

SPONGY PEDAL
A spongy pedal is most often caused by air in the
system. However, thin brake drums or substandard
brake lines and hoses can also cause a spongy pedal.
The proper course of action is to bleed the system,
and replace thin drums and substandard quality
brake hoses if suspected.
HARD PEDAL OR HIGH PEDAL EFFORT
A hard pedal or high pedal effort may be due to
lining that is water soaked, contaminated, glazed, or
badly worn. The power booster or check valve could
also be faulty.
PEDAL PULSATION
Pedal pulsation is caused by components that are
loose, or beyond tolerance limits.
The primary cause of pulsation are disc brake
rotors with excessive lateral runout or thickness vari-
ation, or out of round brake drums. Other causes are
loose wheel bearings or calipers and worn, damaged
tires.
NOTE: Some pedal pulsation may be felt during
ABS activation.
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.
Drag is a product of incomplete brake shoe release.
Drag can be minor or severe enough to overheat the
linings, rotors and drums.
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
severe cases, the lining may generate smoke as it
chars from overheating.
Common causes of brake drag are:
²Seized or improperly adjusted parking brake
cables.
²Loose/worn wheel bearing.
²Seized caliper or wheel cylinder piston.
²Caliper binding on corroded bushings or rusted
slide surfaces.
²Loose caliper mounting.
²Drum brake shoes binding on worn/damaged
support plates.
²Mis-assembled components.²Long booster output rod.
If brake drag occurs at all wheels, the problem
may be related to a blocked master cylinder return
port, or faulty power booster (binds-does not release).
BRAKE FADE
Brake fade is usually a product of overheating
caused by brake drag. However, brake overheating
and resulting 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
mountain roads. Refer to the Brake Drag information
in this section for causes.
BRAKE PULL
Front brake pull condition could result from:
²Contaminated lining in one caliper
²Seized caliper piston
²Binding caliper
²Loose caliper
²Rusty caliper slide surfaces
²Improper brake shoes
²Damaged rotor
A worn, damaged wheel bearing or suspension
component are further causes of pull. A damaged
front tire (bruised, ply separation) can also cause
pull.
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 one of the brake units.
As the dragging brake overheats, efficiency is so
reduced that fade occurs. Since the opposite brake
unit is still functioning normally, its braking effect is
magnified. This causes pull to switch direction in
favor of the normally functioning brake unit.
An additional point when diagnosing a change in
pull condition concerns brake cool down. Remember
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 OR PULL
Rear grab or pull is usually caused by improperly
adjusted or seized parking brake cables, contami-
nated lining, bent or binding shoes and support
plates, or improperly assembled components. This is
particularly true when only one rear wheel is
involved. However, when both rear wheels are
affected, the master cylinder or proportioning valve
could be at fault.
5 - 4 BRAKES - BASEKJ
BRAKES - BASE (Continued)

POWER BRAKE BOOSTER
DESCRIPTION
The booster assembly consists of a housing divided
into separate chambers by two internal diaphragms.
The outer edge of each diaphragm is attached to the
booster housing. The diaphragms are connected to
the booster primary push rod.
Two push rods are used in the booster. The pri-
mary push rod connects the booster to the brake
pedal. The secondary push rod connects the booster
to the master cylinder to stroke the cylinder pistons.
OPERATION
The atmospheric inlet valve is opened and closed
by the primary push rod. Booster vacuum supply is
through a hose attached to an intake manifold fitting
at one end and to the booster check valve at the
other. The vacuum check valve in the booster housing
is a one-way device that prevents vacuum leak back.
Power assist is generated by utilizing the pressure
differential between normal atmospheric pressure
and a vacuum. The vacuum needed for booster oper-
ation is taken directly from the engine intake mani-
fold. The entry point for atmospheric pressure is
through a filter and inlet valve at the rear of the
housing (Fig. 33).
The chamber areas forward of the booster dia-
phragms are exposed to vacuum from the intake
manifold. The chamber areas to the rear of the dia-
phragms, are exposed to normal atmospheric pres-
sure of 101.3 kilopascals (14.7 pounds/square in.).Brake pedal application causes the primary push
rod to open the atmospheric inlet valve. This exposes
the area behind the diaphragms to atmospheric pres-
sure. The resulting pressure differential provides the
extra apply force for power assist.
The booster check valve, check valve grommet and
booster seals are serviceable.
DIAGNOSIS AND TESTING - MASTER
CYLINDER/POWER BOOSTER
(1) Start engine and check booster vacuum hose
connections. A 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. The pedal should hold firm, if the pedal
falls away master cylinder is faulty (internal leak-
age).
(5) Start engine and note pedal action. It should
fall away slightly under light foot pressure then hold
firm. If no pedal action is discernible, power booster,
vacuum supply, or vacuum check valve is faulty. Pro-
ceed to the POWER BOOSTER VACUUM TEST.
(6) If the POWER BOOSTER VACUUM TEST
passes, rebuild booster vacuum reserve as follows:
Release brake pedal. Increase engine speed to 1500
rpm, close the throttle and immediately turn off igni-
tion to stop engine.
(7) Wait a minimum of 90 seconds and try brake
action again. Booster should provide two or more vac-
uum assisted pedal applications. If vacuum assist is
not provided, booster is faulty.
POWER BOOSTER VACUUM TEST
(1) Connect vacuum gauge to booster check valve
with short length of hose and T-fitting (Fig. 34).
(2) Start and run engine at curb idle speed for one
minute.
(3) Observe the vacuum supply. If vacuum supply
is not adequate, repair vacuum supply.
(4) Clamp hose shut between vacuum source and
check valve.
(5) Stop engine and observe vacuum gauge.
(6) If vacuum drops more than one inch Hg (33
millibars) within 15 seconds, booster diaphragm or
check valve is faulty.
POWER BOOSTER CHECK VALVE TEST
(1) Disconnect vacuum hose from check valve.
(2) Remove check valve and valve seal from
booster.
(3) Use a hand operated vacuum pump for test.
Fig. 32 BOOSTER PUSH ROD
1 - MASTER CYLINDER ASSEMBLY
2 - BRAKE BOOSTER
3 - CLIP
4 - BRAKE PEDAL
5 - BOOSTER ROD
KJBRAKES - BASE 5 - 21
PEDAL (Continued)