2003 JEEP GRAND CHEROKEE piston

INSTALLATION.........................23
MASTER CYLINDER
DESCRIPTION.........................23
OPERATION...........................24
DIAGNOSIS AND TESTING - MASTER
CYLINDER/POWER BOOSTER...........24
STANDARD PROCEDURE - MASTER
CYLINDER BLEEDING PROCEDURE......25
REMOVAL.............................25
INSTALLATION.........................25
PEDAL
DESCRIPTION
DESCRIPTION - STANDARD PEDAL.......25
DESCRIPTION - ADJUSTABLE PEDALS....25
OPERATION...........................26
REMOVAL
REMOVAL - NON-ADJUSTABLE PEDAL....26
REMOVAL - ADJUSTABLE PEDALS........27
INSTALLATION
INSTALLATION - NON-ADJUSTABLE PEDAL . 28
INSTALLATION - ADJUSTABLE PEDALS....28
PEDAL MOTOR
REMOVAL.............................28
INSTALLATION.........................28
POWER BRAKE BOOSTER
DESCRIPTION.........................29
OPERATION...........................29
REMOVAL.............................31
INSTALLATION.........................31
ROTORS
DIAGNOSIS AND TESTING
DIAGNOSIS AND TESTING - FRONT DISC
BRAKE ROTOR.......................31DIAGNOSIS AND TESTING - REAR DISC
BRAKE ROTOR.......................32
STANDARD PROCEDURE - DISC ROTOR
MACHINING..........................33
REMOVAL
REMOVAL - FRONT DISC BRAKE ROTOR . . 33
REMOVAL - REAR DISC BRAKE ROTOR . . . 33
INSTALLATION
INSTALLATION - FRONT DISC BRAKE
ROTOR .............................34
INSTALLATION - REAR DISC BRAKE
ROTOR .............................34
PARKING BRAKE
OPERATION...........................34
DIAGNOSIS AND TESTING - PARKING BRAKE . 34
CABLES
REMOVAL
REMOVAL - FRONT PARKING BRAKE
CABLE..............................35
REMOVAL - REAR PARKING BRAKE
CABLES............................36
INSTALLATION
INSTALLATION - FRONT PARKING BRAKE
CABLE..............................37
INSTALLATION - REAR PARKING BRAKE
CABLES............................37
LEVER
REMOVAL.............................38
INSTALLATION.........................39
SHOES
REMOVAL.............................39
INSTALLATION.........................39
ADJUSTMENTS - PARKING BRAKE SHOE....40
BRAKES - BASE
DESCRIPTION
Dual piston disc brake calipers are used on the
front. Single piston disc brake calipers are used on
the rear. Ventilated disc brake rotors are used on the
front and solid rotors are used on the rear.
Power brake assist is supplied by a vacuum oper-
ated, dual diaphragm power brake booster. The mas-
ter cylinder used for all applications has an
aluminum body and nylon reservoir with single filler
cap. A fluid level indicator is mounted to the side of
the reservoir.
The braking force of the rear wheels is controlled
by electronic brake distribution (EBD). The EBD
functions like a rear proportioning valve. The EBD
system uses the ABS system to control the slip of the
rear wheels in partial braking range. The braking
force of the rear wheels is controlled electronically by
using the inlet and outlet valves located in the HCU.
Factory installed brake linings on all models con-
sists of organic base material combined with metallic
particles.
DIAGNOSIS AND TESTING - BASE BRAKE
SYSTEM
Base brake components consist of the brake shoes,
calipers, rear park brake drums/rotors, front brake
rotors, brake lines, master cylinder, booster, HCU
and parking brake shoes.
Brake diagnosis involves determining if the prob-
lem is related to a mechanical, hydraulic, electrical
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.
5 - 2 BRAKES - BASEWJ

(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, brake lines, master cyl-
inder, and HCU.
(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,
cups, hoses, master cylinder, and HCU will also
have to be replaced after flushing. Use clean brake
fluid to flush the system.
(4) Check parking brake operation. Verify free
movement and full release of cables and lever. 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 (do not exceed 25 mph) 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. 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 system may also be
the problem with no visual fluid leak.
LOW PEDAL
If a low pedal is experienced, pump the pedal sev-
eral times. If the pedal comes back up, the most
likely causes are worn linings, rotors, or calipers are
not sliding on the slide pins. The proper course of
action is to inspect and replace all worn component.
SPONGY PEDAL
A spongy pedal is most often caused by air in the
system. However substandard brake hoses can cause
a spongy pedal. The proper course of action is to
bleed the system, and replace 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, check valve, check
valve seal/grommet or vacuum leak could also cause
a hard pedal or high pedal effort.
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. Other causes are loose wheel bearings or cali-
pers 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 release.
Drag can be minor or severe enough to overheat the
linings, rotors and park brake drums.
Minor drag will usually cause slight surface charring
of the lining. It can also generate hard spots in rotors
and park brake drums from the overheat-cool down pro-
cess. In most cases, the rotors, 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 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 over-
heating.
WJBRAKES - BASE 5 - 3
BRAKES - BASE (Continued)

Common causes of brake drag are:
²Parking brake partially applied.
²Loose/worn wheel bearing.
²Seized caliper.
²Caliper binding.
²Loose caliper mounting.
²Mis-assembled components.
²Damaged brake lines.
If brake drag occurs at the front, rear or all
wheels, the problem may be related to a blocked mas-
ter cylinder return port, faulty power booster (binds-
does not release) or the ABS system.
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
²Wheel alignment.
²Tire pressure.
A worn, damaged wheel bearing or suspension compo-
nent 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 DRAG OR PULL
Rear drag or pull may be caused by improperly
adjusted park brake shoes or seized parking brake
cables, contaminated lining, bent or binding shoes or
improperly assembled components. This is particu-
larly true when only one rear wheel is involved.However, when both rear wheels are affected, the
master cylinder or ABS system could be at fault.
BRAKES DO NOT HOLD AFTER DRIVING THROUGH DEEP
WATER PUDDLES
This condition is generally caused by water soaked
lining. If the lining is only wet, it can be dried by
driving with the brakes very lightly applied for a
mile or two. However, if the lining is both soaked and
dirt contaminated, cleaning and or replacement will
be necessary.
BRAKE LINING CONTAMINATION
Brake lining contamination is mostly a product of
leaking calipers or worn seals, driving through deep
water puddles, or lining that has become covered with
grease and grit during repair. Contaminated lining
should be replaced to avoid further brake problems.
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.
NOTE: Propshaft angle can also cause vibration/
shudder.
Severely worn tires with very little tread left can
produce a grab-like condition as the tire loses and
recovers traction. Flat-spotted tires can cause vibra-
tion and generate shudder during brake operation.
Tire damage such as a severe bruise, cut, ply separa-
tion, low air pressure can cause pull and vibration.
BRAKE NOISES
Some brake noise is common on some disc brakes
during the first few stops after a vehicle has been
parked overnight or stored. This is primarily due to
the formation of trace corrosion (light rust) on metal
surfaces. This light corrosion is typically cleared from
the metal surfaces after a few brake applications
causing the noise to subside.
BRAKE SQUEAK/SQUEAL
Brake squeak or squeal may be due to linings that
are wet or contaminated with brake fluid, grease, or oil.
Glazed linings and rotors with hard spots can also con-
tribute to squeak. Dirt and foreign material embedded
in the brake lining will also cause squeak/squeal.
A very loud squeak or squeal is frequently a sign of
severely worn brake lining. If the lining has worn
through to the brake shoes in spots, metal-to-metal
contact occurs. If the condition is allowed to continue,
rotors may become so scored that replacement is nec-
essary.
5 - 4 BRAKES - BASEWJ
BRAKES - BASE (Continued)

SPECIFICATIONS
BRAKE COMPONENTS
SPECIFICATIONS
DESCRIPTION SPECIFICATION
Front Disc Brake Caliper
TypeFloating
Front Disc Brake Caliper
Piston48 mm (1.889 in.)
Front Disc Brake Rotor
TypeVentilated
Front Disc Brake Rotor
Diameter305 mm (12 in.)
Front Disc Brake Rotor
Max. Runout0.05 mm (0.002 in.)
Front Disc Brake Rotor
Max. Thickness Variation0.0127 mm (0.0005 in.)
Front Disc Brake Rotor
Min. Thickness24.5 mm (0.9646 in.)
Rear Disc Brake Caliper
TypeFloatingDESCRIPTION SPECIFICATION
Rear Disc Brake Caliper
Piston48 mm (1.889 in.)
Rear Disc Brake Rotor
Type DiameterSolid
Rear Disc Brake Rotor
Diameter305 mm (12 in.)
Rear Disc Brake Rotor
Max. Runout0.76 mm (0.003 in.)
Rear Disc Brake Rotor
Max. Thickness Variation0.0127 mm (0.0005 in.)
Rear Disc Brake Rotor
Min. Thickness8.5 mm (0.335 in.)
Rear Disc Brake Rotor
Drum Max. Diameter196 mm (7.7166 in.)
Brake Booster Type Dual Diaphragm
TORQUE CHART
TORQUE SPECIFICATIONS
DESCRIPTION N´m Ft. Lbs. In. Lbs.
Brake Pedal Support Bolt 23-24 17-25 Ð
Brake Pedal Pivot Nut 27-35 20-26 Ð
Brake Pedal Bracket
Adjustable pedals28 21 250
Brake Pedal Bracket To Dash 12 9 105
Brake Booster Mounting Nuts 39 29 Ð
Master Cylinder Mounting Nuts 25 18 Ð
Master Cylinder Primary Brake Line 16 Ð 144
Master Cylinder Secondary Brake Line 16 Ð 144
Front Caliper Slide Pins 29-41 21-30 Ð
Front Caliper Anchor Bolts 90-115 66-85 Ð
Front Caliper Brake Hose Banjo Bolt 31 23 Ð
Front Caliper Bleed Screw 16 Ð 144
Rear Caliper Slide Pins 29-41 21-30 Ð
Rear Caliper Anchor Bolts 90-115 66-85 Ð
Rear Caliper Brake Hose Banjo Bolt 31 23 Ð
Rear Caliper Bleed Screw 16 Ð 144
5 - 6 BRAKES - BASEWJ
BRAKES - BASE (Continued)

BRAKE PADS / SHOES
DESCRIPTION
DESCRIPTION - FRONT DISC BRAKE SHOES
The calipers are twin piston type. The calipers are
free to slide laterally on the anchor, this allows con-
tinuous compensation for lining wear.
DESCRIPTION - REAR DISC BRAKE SHOES
The rear disc brakes consist of single piston float-
ing-type calipers and solid rotors. The rear caliper is
mounted on an anchor attached to an adapter
attached the rear axle tube flange. The anchors are
secured to the adapters with mounting bolts. The
disc brake rotor splash shield is part of the adaptor.
The disc brake rotor has a built in brake drum used
for the parking brakes (Fig. 6). The parking brake
shoes are mounted to the adaptor.
OPERATION
OPERATION - FRONT DISC BRAKE SHOES
When the brakes are applied fluid pressure is
exerted against the caliper pistons. The fluid pres-
sure is exerted equally and in all directions. This
means pressure exerted against the caliper pistons
and within the caliper bores will be equal (Fig. 7).
Fluid pressure applied to the pistons is transmit-
ted directly to the inboard brake shoe. This forces the
shoe lining against the inner surface of the disc
brake rotor. At the same time, fluid pressure within
the piston bores forces the caliper to slide inward on
the slide pins. This action brings the outboard brake
shoe lining into contact with the outer surface of the
disc brake rotor.
Fluid pressure acting simultaneously on the pis-
tons and caliper to produces a strong clamping
action. When sufficient force is applied, friction will
stop the rotors from turning and bring the vehicle to
a stop.Application and release of the brake pedal gener-
ates only a very slight movement of the caliper and
pistons. Upon release of the pedal, the caliper and
pistons return to a rest position. The brake shoes do
not retract an appreciable distance from the rotor. In
fact, clearance is usually at, or close to zero. The rea-
sons for this are to keep road debris from getting
between the rotor and lining and in wiping the rotor
surface clear each revolution.
The caliper piston seals control the amount of pis-
ton extension needed to compensate for normal lining
wear.
During brake application, the seals are deflected
outward by fluid pressure and piston movement (Fig.
8). When the brakes (and fluid pressure) are
released, the seals relax and retract the pistons.
The front outboard brake shoes have wear indica-
tors.
OPERATION - REAR DISC BRAKE SHOES
When the brakes are applied fluid pressure is
exerted against the caliper pistons. The fluid pres-
sure is exerted equally and in all directions. This
means pressure exerted against the caliper pistons
and within the caliper bores will be equal (Fig. 7).
Fluid pressure applied to the pistons is transmit-
ted directly to the inboard brake shoe. This forces the
Fig. 6 Rear Disc Brake Rotor
1 - PARKING BRAKE DRUM SURFACE
2 - REAR DISC BRAKE ROTOR
Fig. 7 Brake Caliper Operation
1 - CALIPER
2 - PISTON
3 - PISTON BORE
4 - SEAL
5 - INBOARD SHOE
6 - OUTBOARD SHOE
5 - 10 BRAKES - BASEWJ

shoe lining against the inner surface of the disc
brake rotor. At the same time, fluid pressure within
the piston bores forces the caliper to slide inward on
the slide pins. This action brings the outboard brake
shoe lining into contact with the outer surface of the
disc brake rotor.
Fluid pressure acting simultaneously on the pis-
tons and caliper to produces a strong clamping
action. When sufficient force is applied, friction will
stop the rotors from turning and bring the vehicle to
a stop.
Application and release of the brake pedal gener-
ates only a very slight movement of the caliper and
pistons. Upon release of the pedal, the caliper and
pistons return to a rest position. The brake shoes do
not retract an appreciable distance from the rotor. In
fact, clearance is usually at, or close to zero. The rea-
sons for this are to keep road debris from getting
between the rotor and lining and in wiping the rotor
surface clear each revolution.
The caliper piston seals control the amount of pis-
ton extension needed to compensate for normal lining
wear.
During brake application, the seals are deflected
outward by fluid pressure and piston movement (Fig.
8). When the brakes (and fluid pressure) are
released, the seals relax and retract the pistons.
The front outboard brake shoes have wear indica-
tors.
REMOVAL
REMOVAL- FRONT DISC BRAKE SHOES
(1) Raise and support vehicle.
(2) Remove wheel and tire assembly.(3) Drain small amount of fluid from master cylin-
der brake reservoir withcleansuction gun.
(4) Bottom caliper pistons into the caliper by pry-
ing the caliper over (Fig. 9).
(5) Remove the caliper support spring by prying
the spring out of the caliper (Fig. 10).
(6) Remove the caliper slide pin bushing caps and
remove the slide pins (Fig. 11).
(7) Remove caliper from the anchor.
Fig. 8 Lining Wear Compensation By Piston Seal
1 - PISTON
2 - CYLINDER BORE
3 - PISTON SEAL BRAKE PRESSURE OFF
4 - CALIPER HOUSING
5 - DUST BOOT
6 - PISTON SEAL BRAKE PRESSURE ON
Fig. 9 Bottoming Caliper Piston
1 - ROTOR
2 - CALIPER
Fig. 10 Caliper Support Spring
1 - SUPPORT SPRING
2 - CALIPER
WJBRAKES - BASE 5 - 11
BRAKE PADS / SHOES (Continued)

(8) Secure caliper to nearby suspension part with
wire.Do not allow brake hose to support caliper
weight.
(9) Remove the inboard brake shoe from the cali-
per (Fig. 12).
(10) Remove the outboard brake shoe (Fig. 13)
from the caliper anchor.REMOVAL - REAR DISC BRAKE SHOES
(1) Raise and support vehicle.
(2) Remove rear wheel and tire assembly.
(3) Drain small amount of fluid from master cylin-
der brake reservoir with acleansuction gun.
(4) Bottom caliper pistons into the caliper by pry-
ing the caliper over (Fig. 14).
Fig. 11 Caliper Slide
1 - SLIDE PIN
2 - SLIDE PIN
3 - CALIPER
Fig. 12 Inboard Brake Shoe
1 - CALIPER
2 - INBOARD SHOE
Fig. 13 Outboard Brake Shoe
1 - CALIPER ANCHOR
2 - OUTBOARD BRAKE SHOE
Fig. 14 Bottoming Caliper Piston
1 - CALIPER
2 - CALIPER ANCHOR
5 - 12 BRAKES - BASEWJ
BRAKE PADS / SHOES (Continued)

(8) Install wheel and tire assembly.
(9) Remove support and lower vehicle.
(10) Pump brake pedal until caliper pistons and
brake shoes are seated and a firm brake pedal is
obtained.
(11) Fill brake fluid.
INSTALLATION - REAR DISC BRAKE SHOES
(1) Install the inboard brake shoe onto the caliper
(Fig. 17).
(2) Install the outboard brake shoe onto the caliper
anchor (Fig. 18).
(3) Lubricate the slide pins and slide pin bushings
with Dow Corningtgrease G807 or the grease pro-
vided with the brake shoes.
(4) Install caliper on the anchor.
(5) Install the caliper slide pin and tighten to
29-41 N´m (21-30 ft. lbs.).
(6) Install the caliper slide pin bushing caps.
(7) Install the caliper support spring in the top
end of the caliper and under the anchor. Then installother end into the lower caliper hole. Hold the spring
into the caliper hole with your thumb while prying
the end of the spring out and down under the anchor
with a screw drive.
(8) Install wheel and tire assembly.
(9) Remove support and lower vehicle.
(10) Pump brake pedal until caliper piston and
brake shoes are seated and a firm brake pedal is
obtained.
(11) Fill brake fluid level if necessary.
DISC BRAKE CALIPERS
REMOVAL
REMOVAL - FRONT DISC BRAKE CALIPER
(1) Raise and support vehicle.
(2) Remove front wheel and tire assembly.
(3) Drain small amount of fluid from master cylin-
der brake reservoir withcleansuction gun.
(4) Bottom caliper pistons into the caliper by pry-
ing the caliper over (Fig. 19).
Fig. 18 Outboard Brake Shoe
1 - OUTBOARD BRAKE SHOE
2 - CALIPER ANCHOR
3 - ROTOR
Fig. 19 Bottoming Caliper Piston
1 - ROTOR
2 - CALIPER
5 - 14 BRAKES - BASEWJ
BRAKE PADS / SHOES (Continued)