2003 JEEP GRAND CHEROKEE Rear wheel bearing replacement

(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.
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BRAKES - BASE (Continued)