Jeep Cherokee 2000 Service Manual - page 183
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
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. A
tire with internal damage such as a severe bruise,
cut, or ply separation can cause pull and vibration.
BRAKE NOISES
Some brake noise is common with rear drum
brakes and 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 contribute 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 and drums can become so scored that replace-
ment is necessary.
BRAKE CHATTER
Brake chatter is usually caused by loose or worn
components, or glazed/burnt lining. Rotors with hard
spots can also contribute to chatter. Additional causes
of chatter are out-of-tolerance rotors, brake lining not
securely attached to the shoes, loose wheel bearings
and contaminated brake lining.
THUMP/CLUNK NOISE
Thumping or clunk noises during braking are fre-
quently not caused 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,
improperly adjusted, or improperly assembled rear
brake shoes can also produce a thump noise.
BRAKE LAMP SWITCH
The brake lamp switch operation can be tested
with an ohmmeter. The ohmmeter is used to check
continuity between the pin terminals (Fig. 6).
SWITCH CIRCUIT IDENTIFICATION
•
Terminals 1 and 2: brake sensor circuit
•
Terminals 3 and 4: speed control circuit if
equipped
•
Terminals 5 and 6: brake lamp circuit
SWITCH CONTINUITY TEST
NOTE: Disconnect switch harness before testing
switch continuity.
With the switch plunger retracted, attach test
leads to terminal pins 1 and 2. Replace switch if
meter indicates no continuity.
With the switch plunger retracted, attach test
leads to terminal pins 3 and 4. Replace switch if
meter indicates no continuity.
With the switch plunger extended, attach test
leads to terminal pins 5 and 6. Replace switch if
meter indicates no continuity.
RED BRAKE WARNING LAMP
The red brake warning lamp will illuminate under
the following conditions:
•
Self test at start-up.
•
Parking brakes are applied.
•
Leak in front/rear brake hydraulic circuit.
If the red light remains on after start-up, first ver-
ify that the parking brakes are fully released. Then
check pedal action and fluid level. If the lamp on and
the brake pedal is low this indicates the pressure dif-
Fig. 6 Brake Lamp Switch Terminal Identification
1 – TERMINAL PINS
2 – PLUNGER TEST POSITIONS
XJ
BRAKES
5 - 9
DIAGNOSIS AND TESTING (Continued)