air condition JEEP CHEROKEE 1994 Service Owner's Guide

Excessive Oil Consumption: Although the PCM
monitors exhaust stream oxygen content through ox-
ygen sensor (closed loop), it cannot determine exces-
sive oil consumption.
Throttle Body Air Flow: The PCM cannot detect
a clogged or restricted air cleaner inlet or air filter
element.
Evaporative System: The PCM will not detect a
restricted, plugged or loaded EVAP canister.
Vacuum Assist: Leaks or restrictions in the vac-
uum circuits of vacuum assisted engine control sys-
tem devices are not monitored by the PCM. However,
a vacuum leak at the MAP sensor will be monitored
and a diagnostic trouble code (DTC) will be gener-
ated by the PCM.
Powertrain Control Module (PCM) System
Ground: The PCM cannot determine a poor system
ground. However, a DTC may be generated as a re-
sult of this condition.
Powertrain Control Module (PCM) Connector
Engagement: The PCM cannot determine spread or
damaged connector pins. However, a DTC may be
generated as a result of this condition.
HIGH AND LOW LIMITS
The powertrain control module (PCM) compares in-
put signal voltages from each input device. It will es-
tablish high and low limits that are programmed into
it for that device. If the input voltage is not within
specifications and other Diagnostic Trouble Code
(DTC) criteria are met, a DTC will be stored in mem-
ory. Other DTC criteria might include engine rpm
limits or input voltages from other sensors or
switches. The other inputs might have to be sensed
by the PCM when it senses a high or low input volt-
age from the control system device in question.
ACCESSING DIAGNOSTIC TROUBLE CODES
A stored Diagnostic Trouble Code (DTC) can be dis-
played by cycling the ignition key On-Off-On-Off-On
within three seconds and observing the Malfunction
Indicator Lamp. This lamp was formerly referred to
as the Check Engine Lamp. The lamp is located on
the instrument panel.
They can also be displayed through the use of the
Diagnostic Readout Box (DRB) scan tool. The DRB
scan tool connects to the data link connector in the
engine compartment (Figs. 45 or 46). For operation of
the DRB, refer to the appropriate Powertrain Diag-
nostic Procedures service manual.
EXAMPLES:
²If the lamp flashes 4 times, pauses and flashes 1
more time, a flashing Diagnostic Trouble Code (DTC)
number 41 is indicated.
²If the lamp flashes 4 times, pauses and flashes 6
more times, a flashing Diagnostic Trouble Code
(DTC) number 46 is indicated.After any stored DTC information has been ob-
served, the display will end with a flashing DTC
number 55. This will indicate the end of all stored
information.
Refer to the Diagnostic Trouble Code (DTC) charts
for DTC identification.
If the problem is repaired or ceases to exist, the
Powertrain Control Module (PCM) cancels the DTC
after 51 engine starts.
Diagnostic Trouble Codes indicate the results of a
failure, but never identify the failed component di-
rectly.
The circuits of the data link connector are shown
in (Fig. 47).
ERASING TROUBLE CODES
After the problem has been repaired, use the DRB
scan tool to erase a Diagnostic Trouble Code (DTC).
Refer to the appropriate Powertrain Diagnostic Pro-
cedures service manual for operation of the DRB
scan tool.
Fig. 45 Data Link ConnectorÐYJ ModelsÐTypical
Fig. 46 Data Link ConnectorÐXJ ModelsÐTypical
14 - 50 FUEL SYSTEMJ

DIAGNOSTIC TROUBLE CODE DESCRIPTIONSÐCONTINUED
Diagnostic
Trouble
CodeDRB Scan Tool
DisplayDescription of Diagnostic Trouble Code
23**..........Intake Air Temp Sensor
Voltage LowIntake air temperature sensor input below the minimum acceptable voltage.
or
Intake Air Temp Sensor
Voltage HighIntake air temperature sensor input above the maximum acceptable voltage.
24**..........Throttle Position Sensor
Voltage HighThrottle position sensor input above the maximum acceptable voltage.
or
Throttle Position Sensor
Voltage LowThrottle position sensor input below the minimum acceptable voltage.
25**..........Idle Air Control Motor
CircuitsA shorted condition detected in one or more of the idle air control motor
circuits.
27* ..........Injector #1 Control Circuit Injector #1 output driver does not respond properly to the control signal.
or
Injector #2 Control Circuit Injector #2 output driver does not respond properly to the control signal.
or
Injector #3 Control Circuit Injector #3 output driver does not respond properly to the control signal.
or
Injector #4 Control Circuit Injector #4 output driver does not respond properly to the control signal.
or
Injector #5 Control Circuit Injector #5 output driver does not respond properly to the control signal.
or
Injector #6 Control Circuit Injector #6 output driver does not respond properly to the control signal.
33* .......... A/CClutch Relay Circuit An open or shorted condition detected in the A/C clutch relay circuit.
34* ..........Speed Control Solenoid
CircuitsAn open or shorted condition detected in the Speed Control vacuum or vent
solenoid circuits.
or
Speed Control Switch
Always LowSpeed Control switch input below the minimum acceptable voltage.
or
Speed Control Switch
Always HighSpeed Control switch input above the maximum acceptable voltage.
35* (XJ Only).... RadFanControl Relay
CircuitsAn open or shorted condition detected in the radiator fan relay circuit.
* Check Engine Lamp will not illuminate at all times if this Diagnostic Trouble Code was recorded. Cycle Ignition key as
described in manual and observe code flashed by Check Engine lamp.
** Check Engine Lamp will illuminate during engine operation if this Diagnostic Trouble Code was recorded.
14 - 52 FUEL SYSTEMJ

DIAGNOSTIC TROUBLE CODE DESCRIPTIONSÐCONTINUED
Diagnostic
Trouble
CodeDRB Scan Tool
DisplayDescription of Diagnostic Trouble Code
41**..........Generator Field Not
Switching ProperlyAn open or shorted condition detected in the generator field control circuit.
42* ..........Auto Shutdown Relay
Control CircuitAn open or shorted condition detected in the auto shutdown relay circuit.
44* ..........Battery Temp Sensor
Volts out of LimitAn open or shorted condition exists in the engine coolant temperature sensor
circuit or a problem exists in the PCM's battery temperature voltage circuit.
46**..........Charging System Voltage
Too HighBattery voltage sense input above target charging voltage during engine
operation.
47**..........Charging System Voltage
Too LowBattery voltage sense input below target charging during engine operation.
Also, no significant change detected in battery voltage during active test of
generator output.
51**.......... O2SSignal Stays Below
Center (Lean)Oxygen sensor signal input indicates lean air/fuel ratio condition during
engine operation.
52**.......... O2SSignal Stays Above
Center (Rich)Oxygen sensor signal input indicates rich air/fuel ratio condition during
engine operation.
53* ..........Internal PCM Failure PCM Internal fault condition detected.
or
PCM Failure SPI
CommunicationsPCM Internal fault condition detected.
54* .......... NoCamSync Signal at
PCMNo fuel sync (camshaft signal) detected during engine cranking.
55* .......... N/ACompletion of diagnostic trouble code display on the Malfunction Indicator
Lamp (Check Engine Lamp).
62* .......... PCMFailure SPI miles not
storedUnsuccessful attempt to update SPI miles in the PCM EEPROM.
63* .......... PCMFailure EEPROM
Write DeniedUnsuccessful attempt to write to an EEPROM location by the PCM.
* Check Engine Lamp will not illuminate at all times if this Diagnostic Trouble Code was recorded. Cycle Ignition key as
described in manual and observe code flashed by Check Engine lamp.
** Check Engine Lamp will illuminate during engine operation if this Diagnostic Trouble Code was recorded.
JFUEL SYSTEM 14 - 53

MULTI-PORT FUEL INJECTION (MFI)ÐCOMPONENT REMOVAL/INSTALLATION
INDEX
page page
Accelerator Pedal and Throttle Cable......... 54
Air Cleaner Housing...................... 54
Air Conditioning (A/C) Clutch Relay........... 54
Air Filter............................... 54
Automatic Shut Down (ASD) Relay........... 54
Brake Switch............................ 54
Camshaft Position Sensor.................. 54
Crankshaft Position Sensor................. 55
Engine Coolant Temperature Sensor.......... 55
Fuel Filter.............................. 55
Fuel Injector............................ 55
Fuel Pump Module....................... 56
Fuel Pump Relay........................ 56
Fuel Rail Assembly....................... 56
Fuel System Pressure Release Procedure...... 56
Fuel Tank Pressure Relief/Rollover Valve...... 56
Fuel Tanks............................. 56Fuel Tubes/Lines/Hoses and Clamps.......... 56
Idle Air Control (IAC) Motor................. 56
Ignition Coil............................. 57
Intake Air Temperature Sensor.............. 54
Intake Manifold.......................... 57
Manifold Absolute Pressure (MAP) Sensor..... 57
Oxygen (O2S) Sensor..................... 57
Park Neutral Switch....................... 58
Power Steering Pressure SwitchÐ2.5L
Engine Only........................... 58
Powertrain Control Module (PCM)............ 58
Quick-Connect Fittings..................... 59
Throttle Body............................ 59
Throttle Position Sensor (TPS).............. 59
Torque Converter Clutch Relay.............. 60
Vehicle Speed Sensor..................... 60
ACCELERATOR PEDAL AND THROTTLE CABLE
Refer to the Accelerator Pedal and Throttle Cable
section of this group for removal/installation proce-
dures.
AIR CONDITIONING (A/C) CLUTCH RELAY
The A/C clutch relay is located in the Power Dis-
tribution Center (PDC) (Figs. 1 or 2). For location of
this relay within the PDC, refer to label on PDC
cover.
AIR CLEANER HOUSING
Refer to Group 25, Emission Control System.
AIR FILTER
Refer to Group 25, Emission Control System.
AUTOMATIC SHUT DOWN (ASD) RELAY
The ASD relay is located in the Power Distribution
Center (Figs. 1 or 2) (PDC). For location of this relay
within the PDC, refer to label on PDC cover.
BRAKE SWITCH
Refer to Group 5, Brakes for removal/installation
procedures.
CAMSHAFT POSITION SENSOR
For removal/installation procedures, refer to Group
8D, Ignition System. See Camshaft Position Sensor.
INTAKE AIR TEMPERATURE SENSOR
The intake manifold air temperature sensor is in-
stalled into the intake manifold plenum (Figs. 3 or
4).
Fig. 1 PDCÐYJ Models
Fig. 2 PDCÐXJ Models
14 - 54 FUEL SYSTEMJ

ABS BRAKE DIAGNOSIS
INDEX
page page
ABS Fault Diagnosis....................... 4
ABS System Wiring and Electrical Circuits...... 4
ABS Warning Light Display.................. 3
Brake Warning Light Display................. 4
Diagnosis Procedures...................... 3
ECU Diagnosis........................... 4
HCU Diagnosis........................... 4Loss of Sensor Input....................... 3
Operating Sound Levels.................... 3
Rear Speed Sensor Air Gap................. 3
Steering Response........................ 3
Vehicle Response in Antilock Mode............ 3
Wheel/Tire Size and Input Signals............. 3
DIAGNOSIS PROCEDURES
ABS diagnosis involves three basic steps. First is
observation of the warning light display. Second is a
visual examination for low fluid level, leaks, parking
brakes applied, or obvious damage to system compo-
nents or wires. The third step involves using the
DRB II scan tool to identify a faulty component.
The visual examination requires a check of reser-
voir fluid level and all system components. Things to
look for are leaks, loose connections, or obvious com-
ponent damage.
The final diagnosis step involves using the DRB II
scan tool to determine the specific circuit or compo-
nent at fault. The tester is connected to the ABS di-
agnostic connector in the passenger compartment.
The connector is at the driver side of the center con-
sole under the instrument panel. Refer to the DRB II
scan tool Manual for tester procedures. Also refer to
the ABS Fault Diagnosis charts at the end of this
section for additional diagnosis information.
Initial faults should be cleared and the vehicle road
tested to reset any faults that remain in the system.
Faults can be cleared with the DRB II scan tool.
REAR SPEED SENSOR AIR GAP
The front wheel sensors are fixed and cannot be ad-
justed. Only the rear sensor air gap is adjustable. Air
gap must be set with a brass feeler gauge.
Correct air gap is important to proper signal gen-
eration. An air gap that is too large may cause com-
plete loss of sensor input. Or, a gap that is too small
could produce a false input signal, or damaging con-
tact between the sensor and tone ring.
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 function with a compact spare tire installed.
OPERATING SOUND LEVELS
The ABS 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 oper-
ation.
VEHICLE RESPONSE IN ANTILOCK MODE
During antilock braking, the HCU solenoid valves
cycle rapidly in response to ECU inputs.
The driver will experience a pulsing sensation
within the vehicle as the solenoids decrease, hold, or
increase pressure as needed. A pulsing brake pedal
will also be noted.
The pulsing sensation occurs as the solenoids cycle
during antilock mode braking. A slight pulse in the
brake pedal may also be noted during the dynamic
self check part of system initialization.
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.
LOSS OF SENSOR INPUT
Sensor malfunctions will most likely be due to
loose connections, damaged sensor wires, incorrect
rear sensor air gap, or a malfunctioning sensor. Ad-
ditional causes of sensor faults would be sensor and
tone ring misalignment or damage.
ABS WARNING LIGHT DISPLAY
ABS Light Illuminates At Startup
The amber ABS 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 self check routine.
ABS Light Remains On After Startup
An ABS system fault is indicated when the light
remains on after startup. Diagnosis with the DRB II
JBRAKES 5 - 3

scan tool will be necessary to determine which ABS
component has malfunctioned.
ABS Light Illuminates During Brake Stop
A system fault such as loss of speed sensor signal
or solenoid failure, will cause the amber warning
light to illuminate. The most effective procedure here
is to check for obvious damage first. Then check the
electronic components with the DRB II scan tool.
BRAKE WARNING LIGHT DISPLAY
The red brake warning light and the ABS light op-
erate independently. If the red light remains on after
startup or illuminates during a brake stop, refer to
the standard brake system diagnosis section. Either
the parking brakes are applied, or a wheel brake
malfunction has occurred.
ECU DIAGNOSIS
The ECU controls all phases of antilock system op-
eration. It also differentiates between normal and an-
tilock mode braking.
The ECU monitors and processes the signals gen-
erated from all of the system sensors at all times.
The ECU program includes a self check routine
that tests each of the system components. The self
check occurs during both phases of the initialization
program. A failure of the self check program will
cause the immediate illumination of the amber warn-
ing light. The light will also illuminate if a solenoid
or other system component fails during the dynamic
phase of initialization.
If a system malfunction should occur, do not imme-
diately replace the ECU. A blown system fuse, bad
chassis ground, or loss of feed voltage will each cause
a system malfunction similar to an ECU failure.
Never replace the ECU unless diagnosis with the
DRB II scan tool indicates this is necessary.
HCU DIAGNOSIS
The HCU pump and motor and solenoid valve body
are serviced only as an assembly. The HCU assembly
should not be replaced unless a fault has actually
been confirmed. Verify fault conditions with the DRB
II scan tool before proceeding with repair.
ABS SYSTEM WIRING AND ELECTRICAL CIRCUITS
Location of the ABS fuse (in the fuse panel) is
shown in Figure 1. The engine compartment harness
routing for the ABS components is shown in Figure 2.
ABS FAULT DIAGNOSIS
The fault diagnosis chart provides additional infor-
mation on potential ABS system faults. Use the
chart as a guide when diagnosing a system problem.
Fig. 1 ABS Fuse Location
5 - 4 BRAKESJ

(2) If red warning light is illuminated, or if neither
warning light is illuminated, make several stops and
note pedal action and brake response.
(3) Check brake pedal response with transmission
in Neutral and engine running. Pedal should remain
firm under steady foot pressure. If pedal falls away,
problem is either in vacuum booster or master cylin-
der.
(4) During road test, make normal and firm brake
stops in 25-40 mph range. Note faulty brake opera-
tion such as pull, grab, drag, noise, fade, pedal pul-
sation, etc.
(5) Inspect suspect brake components and refer to
problem diagnosis information for causes of various
brake conditions.
COMPONENT INSPECTION
Fluid leak points and dragging brake units can
usually be located without removing any compo-
nents. 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 boosters.
Refer to the wheel brake service procedures in this
group for more information.
DIAGNOSING SERVICE BRAKE PROBLEMS
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
²parking brakes applied
²low pedal caused by malfunction in front/rear
brake hydraulic circuit (differential switch valve ac-
tuated)
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 indi-
cates that the valve in the differential pressureswitch has been actuated. If a problem is confirmed,
inspect the hydraulic system and wheel brake compo-
nents.
On models with ABS brakes, the amber warning
light only illuminates when an ABS component has
malfunctioned. The ABS light operates indepen-
dently of the red warning light. Refer to the antilock
brake section for more detailed diagnosis informa-
tion.
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 in 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/or the warn-
ing light illuminates, the problem is in the master
cylinder, wheel cylinders, or calipers.
A decrease in master cylinder fluid level may only
be the result of normal lining wear. Fluid level will
decrease as lining wear occurs. It is a result of the
outward movement of caliper and wheel cylinder pis-
tons to compensate for normal wear.
SPONGY PEDAL
A spongy pedal is most often caused by air in the
system. However, thin drums or substandard brake
lines and hoses will also cause a condition similar to
a spongy pedal. The proper course of action is to
bleed the system, 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
lining 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 de-
scribed 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,
rotors and drums.
5 - 8 BRAKESJ

when the cover is off. The second involves adding to,
or filling the cylinder reservoirs with a non-recom-
mended fluid.
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
flushing will be required. The master cylinder may
also have to be disassembled, cleaned and the piston
seals replaced. Foreign material lodged in the reser-
voir compensator/return ports can cause brake drag
by restricting fluid return after brake application.
Brake fluid contaminated by a non-recommended
fluid will usually be discolored, milky, oily looking,
or foamy. In some cases, it may even appear as if the
fluid contains sludge.However, remember that
brake fluid will darken in time and occasionally
be cloudy in appearance. These are normal con-
ditions and should not be mistaken for contami-
nation.
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
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 brakeshoes in spots, metal-to-metal
contact occurs. If the condition is allowed to continue,
rotors can become so scored that replacement is nec-
essary.
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. How-
ever, calipers that bind on the slide surfaces can gen-
erate a thump or clunk noise. In addition, worn out,
improperly 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.
BRAKELINING CONTAMINATION
Brakelining contamination is usually a product of
leaking calipers or wheel cylinders, driving through
deep water puddles, or lining that has become cov-
ered with grease and grit during repair.
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 condition similar to grab as the tire loses
and recovers traction.
Flat-spotted tires can cause vibration and wheel
tramp and generate shudder during brake operation.
A tire with internal damage such as a severe
bruise or ply separation can cause pull and vibration.
DIAGNOSING PARKING BRAKE PROBLEMS
Adjustment Mechanism
Parking brake adjustment is controlled by a
cable tensioner mechanism. This applies to 1991
through 1994 YJ models and 1992 and later XJ
models. The cable tensioner, once adjusted at
the factory, will not need further adjustment un-
der normal circumstances. There are only two
instances when adjustment is required. The first
is when a new tensioner, or cables have been in-
stalled. And the second, is when the tensioner
and cables are disconnected for access to other
brake components.
Parking Brake problem Causes
In most cases, the actual cause of an improperly
functioning parking brake (too loose/too tight/wont
hold), can be traced to a drum brake component.
The leading cause of improper parking brake
operation, is excessive clearance between the
brakeshoes and the drum surface. Excessive
clearance is a result of: lining and/or drum wear;
oversize drums; or inoperative shoe adjuster
components.
Excessive parking brake lever travel (sometimes
described as a loose lever or too loose condition), is
the result of worn brakeshoes/drums, improper
brakeshoe adjustment, or mis-assembled brake parts.
A ``too loose'' condition can also be caused by inop-
erative brakeshoe adjusters. If the adjusters are mis-
5 - 10 BRAKESJ

STANDARD MASTER CYLINDER
INDEX
page page
General Service Information................ 20
Master Cylinder Installation................. 20Master Cylinder Overhaul.................. 20
Master Cylinder Removal.................. 20
GENERAL SERVICE INFORMATION
The service information in this section covers the
standard (non-ABS) master cylinder only. The center
feed master cylinder used with the ABS system is
covered in the antilock brake component service sec-
tion.
MASTER CYLINDER REMOVAL
(1) Disconnect brake lines at master cylinder.
(2) Remove cylinder mounting nuts and remove
master cylinder.
(3) Remove cylinder cover and drain fluid.
MASTER CYLINDER INSTALLATION
(1) Bleed master cylinder on bench before installa-
tion. Refer to overhaul assembly procedure in this
section for bleeding method.
(2) Install cylinder on brake booster studs and in-
stall cylinder attaching nuts. Tighten nuts to 21 NIm
(15 ft. lbs.).
(3) Connect brakelines to cylinder.
(4) Fill and bleed brake system.
MASTER CYLINDER OVERHAUL
CYLINDER DISASSEMBLY
(1) Remove cylinder cover and drain fluid.
(2) Examine cylinder cover seal. Discard seal if
torn or distorted.
(3) Clamp cylinder in vise (Fig. 1).
(4) Press primary piston inward with wood dowel
or phillips screwdriver and remove snap ring (Fig. 2).
(5) Remove and discard primary piston (Fig. 3).
Piston is serviced only as an assembly.
(6) Remove secondary piston (Fig. 4). Apply air
pressure through rear outlet port to ease piston out
of bore. Cover small ports at bottom of rear reservoir
with towel to prevent air leakage.
(7) Discard secondary piston. Do not disassemble
piston as components are only serviced as assembly.
CLEANING AND INSPECTION
Clean the cylinder with Mopar brake cleaning sol-
vent or clean brake fluid. Remove cleaning residue
with compressed air.
Inspect the cylinder bore. A light discoloration of
the bore surface is normal and acceptable but only if
the surface is in good condition.Replace the cylinder if the bore is scored, corroded,
or pitted.Do not hone the cylinder bore in an at-
tempt to restore the surface. Replace the cylin-
der if the bore is corroded or if doubt exists
about cylinder bore condition.
Fig. 1 Cylinder Mounted In Vise
Fig. 2 Removing/Installing Piston Snap Ring
5 - 20 BRAKESJ

(9) Remove inboard shoe. Grasp ends of shoe and
tilt shoe outward to release springs from caliper pis-
ton (Fig. 8). Then remove shoe from caliper.
(10) Support caliper on box, mechanics stool, or se-
cure it to nearby suspension part with wire.Do not
allow brake hose to support caliper weight.
(11) Wipe caliper off with shop rags or towels.Do
not use compressed air. Compressed air can un-
seat dust boot and force dirt into piston bore.
(12) Inspect condition of caliper piston dust boot
(Fig. 9). Overhaul caliper if there is evidence of leak-
age past piston and dust boot. Then inspect caliper
bushings and boots (Fig. 9). Replace boots if torn or
cut. If bushings or boots are damaged, replace them.
DISC BRAKESHOE INSTALLATION
(1) Clean brakeshoe mounting ledge slide surfaces
of steering knuckle with wire brush. Then apply
light coat of Mopar multi-mileage grease to slide sur-
faces (Fig. 10).
(2) Lubricate caliper mounting bolts and bushings
(Fig. 10). Use GE 661 or Dow 111 silicone grease.(3) Keep new or original brakeshoes in sets.Do
not interchange them.
(4) Install inboard shoe in caliper (Fig. 11). Be
sure shoe retaining springs are fully seated in caliper
piston.
(5) Install outboard shoe in caliper (Fig. 12). Start
one end of shoe in caliper. Rotate shoe downward and
into place until shoe locating lugs and shoe spring
are seated.
(6) Verify that locating lugs on outboard shoe are
seated in caliper (Fig. 6).
(7) Install caliper. Position notches at lower end of
brakeshoes on bottom mounting ledge (Fig. 13). Then
install caliper over rotor and seat upper ends of
brakeshoes on top mounting ledge (Fig. 11).
CAUTION: Before securing the caliper, be sure the
caliper brake hose is not twisted, kinked or touch-
ing any chassis components. Also be sure the hose
is clear of all suspension and steering components.
Loosen and reposition the hose if necessary.
Fig. 7 Removing Outboard Brakeshoe
Fig. 8 Removing Inboard Brakeshoe
Fig. 9 Caliper Dust Boots And Bushing Locations
Fig. 10 Caliper Lubrication Points
5 - 26 BRAKESJ