1995 JEEP CHEROKEE abs ring replace

(2) Disconnect brake lines at master cylinder and
combination valve.
(3) Remove nuts attaching master cylinder to
booster studs.
(4) Remove master cylinder.
(5) Remove cylinder cover and drain fluid.
(6) If two-piece master cylinder reservoir requires
service, refer to reservoir replacement procedure in
this section.
MASTER CYLINDER INSTALLATION (NON-ABS)
(1) Bleed master cylinder on bench before installa-
tion. Refer to procedure in this section.
(2) If new two-piece master cylinder is being in-
stalled, remove plastic protective sleeve from primary
piston shank. Also check condition of seal at rear of
cylinder body. Reposition seal if dislodged. Replace
seal if cut, or torn.
(3) Clean cylinder mounting surface of brake booster.
Use shop towel wetted with brake cleaner for this pur-
pose. Dirt, grease, or similar materials will prevent
proper cylinder seating and could result in vacuum leak.
(4) Slide master cylinder onto brake booster studs.
(5) Install nuts attaching master cylinder to booster
studs. Tighten nuts to 25 Nzm (220 in. lbs.) torque.
(6) Connect brakelines to master cylinder and com-
bination valve (Figs. 1 and 2).
(7) Fill and bleed brake system.
COMBINATION VALVE REPLACEMENT (NON-ABS)
The combination valve is not a repairable compo-
nent. The valve is serviced as an assembly whenever
diagnosis indicates replacement is necessary.
(1) Remove air cleaner cover and hose for access to
valve, if necessary.
(2) Disconnect differential pressure switch wire at
combination valve. Do not pull switch wire to discon-
nect. Unsnap connecter lock tabs to remove.
(3) Disconnect brakelines at combination valve and
remove valve.
(4) Connect brakelines to replacement valve. Start
line fittings by hand to avoid cross threading.
Tighten fittings snug but not to required torque at
this time.
(5) Connect wire to pressure differential switch.
(6) Bleed brakes.
(7) Tighten brakeline fittings to 18-24 Nzm
(160-210 in. lbs.) torque after bleeding.
MASTER CYLINDER OVERHAUL (4-CYLINDER
MODELS)
CYLINDER DISASSEMBLY
(1) Examine cylinder cover seal. Discard seal if
torn or distorted.
(2) Clamp cylinder in vise (Fig. 3).(3) Remove piston retaining snap ring. Press and
hold primary piston inward with wood dowel or sim-
ilar tool. Then remove snap ring (Fig. 4).
(4) Remove and discard primary piston (Fig. 5).
Piston is serviced only as assembly.
(5) Remove secondary piston (Fig. 6). 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.
(6) Discard secondary piston. Do not disassemble
piston as components are only serviced as assembly.
MASTER CYLINDER 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
Fig. 3 Mounting Cylinder In Vise
Fig. 4 Removing/Installing Piston Snap Ring
5 - 16 MASTER CYLINDERÐCOMBINATION VALVEJ

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.
Check the outer and inner surfaces of the cylinder
for cracks or porosity, especially if wet spots were
noted on the cylinder outer surface during removal
and disassembly.
Inspect the cylinder cover, seal and retainer spring.
Replace the seal if torn or distorted and replace the
cover and spring if either part is bent or damaged in
any way.
MASTER CYLINDER ASSEMBLY
(1) Coat cylinder bore and new piston assemblies
with brake fluid.
(2) Install secondary piston in bore with push and
turn motion (Fig. 7).Do not use any tools to start
seals into bore. Tools can cut seal and scratch
bore.
(3) Insert primary piston in bore (Fig. 5).(4) Push primary piston inward and install snap
ring (Fig. 4).
MASTER CYLINDER AND COMBINATION VALVE
REMOVAL (WITH ABS)
(1) Disconnect vent hoses at air cleaner cover.
(2) Loosen clamp securing air cleaner hose to in-
take manifold. Use screwdriver to tap clamp loose.
(3) Remove air cleaner cover and hose. Then re-
move air filter from air cleaner housing (Fig. 8).
(4) Remove two bolts and one nut that secure air
cleaner housing to body (Fig. 8).
Fig. 8 Air Cleaner Components
Fig. 5 Removing/Installing Primary Piston
Fig. 6 Removing Secondary Piston Assembly
Fig. 7 Installing Secondary Piston
JMASTER CYLINDERÐCOMBINATION VALVE 5 - 17

WHEEL SPEED SENSOR OPERATION
Wheel speed input signals are generated by a sen-
sor and tone ring at each wheel. The sensors, which
are connected directly to the ECU, are mounted on
brackets attached to the front steering knuckles and
rear brake support plates.
The sensor triggering devices are the tone rings
which are similar in appearance to gears. The tone
rings are located on the outboard end of each front/rear axle shaft. The speed sensors generate a signal
whenever a tone ring tooth rotates past the sensor
pickup face.
The wheel speed sensors provide the input signal
to the ECU. If input signals indicate ABS mode brak-
ing, the ECU causes the HCU solenoids to decrease,
hold, or increase fluid apply pressure as needed.
The HCU solenoid valves are activated only when
wheel speed input signals indicate that a wheel is
approaching a high slip, or lockup condition. At this
point, the ECU will cycle the appropriate wheel con-
trol channel solenoid valves to prevent lockup.
The wheel sensors provide speed signals whenever
the vehicle wheels are rotating. The ECU examines
these signals for degree of deceleration and wheel
slip. If signals indicate normal braking, the solenoid
valves are not activated. However, when incoming
signals indicate the approach of wheel slip, or lockup,
the ECU cycles the solenoid valves as needed.
ACCELERATION SWITCH OPERATION
The ECU monitors the acceleration switch at all
times. The switch assembly contains three mercury
switches that monitor vehicle ride height and decel-
eration rates (G-force). Sudden, rapid changes in ve-
hicle and wheel deceleration rate, triggers the switch
sending a signal to the ECU. The switch assembly
provides three deceleration rates; two for forward
braking and one for rearward braking.
ECU OPERATION
The antilock ECU controls all phases of antilock
operation. It monitors and processes input signals
from the system sensors.
It is the ECU that activates the solenoid valves to
modulate apply pressure during antilock braking.
The ECU program is able to determine which wheel
control channel requires modulation and which fluid
pressure modulation cycle to use. The ECU cycles the
solenoid valves through the pressure decrease, hold
and increase phases.
ABS COMPONENT SERVICEABILITY
The ECU, acceleration sensor, wheel sensors, and
wire harnesses are serviced as assemblies only. The
axle shaft tone wheels are also not serviceable. If a
tone wheel becomes damaged, it will be necessary to
replace the axle shaft, or disc brake rotor and hub
assembly.
SPEED SENSOR AIR GAP
Front sensor air gap is fixed and not adjustable.
Only rear sensor air gap is adjustable.
Although front air gap is not adjustable, it can be
checked if diagnosis indicates this is necessary. Front
Fig. 7 Pressure Hold Cycle
Fig. 8 Pressure Increase Cycle
JABS OPERATION AND SERVICE 5 - 37

air gap should be 0.40 to 1.3 mm (0.0157 to 0.051
in.). If gap is incorrect, the sensor is either loose, or
damaged.
A rear sensor air gap adjustment is only needed
when reinstalling an original sensor. Replacement
sensors have an air gap spacer attached to the sensor
pickup face. The spacer establishes correct air gap
when pressed against the tone ring during installa-
tion. As the tone ring rotates, it peels the spacer off
the sensor to create the required air gap. Rear sensor
air gap is 0.92-1.45 mm (0.036-0.057 in.).
Sensor air gap measurement, or adjustment proce-
dures are provided in this section. Refer to the front,
or rear sensor removal and installation procedures as
required.
FRONT WHEEL SENSOR REMOVAL
(1) Raise vehicle and turn wheel outward for easier
access to sensor.
(2) Remove sensor wire from mounting brackets.
(3) Clean sensor and surrounding area with shop
towel before removal.
(4) Remove bolt attaching sensor to steering
knuckle and remove sensor.
(5) remove sensor wire from brackets on body and
steering knuckle.
(6) Unseat sensor wire grommet in wheel house
panel.
(7) In engine compartment, disconnect sensor wire
connector at harness plug. Then remove sensor and
wire.
FRONT WHEEL SENSOR INSTALLATION
(1) Iforiginalsensor will be installed, wipe all
traces of old spacer material off sensor pickup face.
Use a dry shop towel for this purpose.
(2) Apply Mopar Lock N' Seal or Loctite 242 to bolt
that secures sensor in steering knuckle. Use new
sensor bolt if original bolt is worn or damaged.
(3) Position sensor on steering knuckle. Seat sen-
sor locating tab in hole in knuckle and install sensor
attaching bolt finger tight.
(4) Tighten sensor attaching bolt to 14 Nzm (11 ft.
lbs.) torque.
(5) If original sensor has been installed, check sen-
sor air gap. Air gap should be 0.40 to 1.3 mm (0.0157
to 0.051 in.). If gap is incorrect, sensor is either loose,
or damaged.
(6) Secure sensor wire to steering knuckle and
body brackets.
(7) Route sensor wire forward and behind shock
absorber. Then attach sensor wire to spring seat
bracket with grommets on sensor wire.
(8) Route sensor wire to outer sill bracket. Remove
all twists or kinks from wire.
(9) Attach sensor wire to sill bracket with grom-
met. Be sure wire is free of twists and kinks.(10) Verify sensor wire routing. Wire should loop
forward and above sill bracket. Loose end of wire
should be below sill bracket and towards brake hose.
(11) Seat sensor wire grommet in body panel and
clip wire to brake line at grommet location.
(12) Connect sensor wire to harness in engine com-
partment.
REAR WHEEL SENSOR REMOVAL
(1) On XJ models, raise and fold rear seat forward
for access to rear sensor connectors (Fig. 9).
(2) Disconnect sensors at rear harness connectors.
(3) Push sensor grommets and sensor wires
through floorpan.
(4) Raise vehicle.
(5) Disconnect sensor wires at rear axle connectors.
(6) Remove wheel and tire assembly.
(7) Remove brake drum.
(8) Remove clips securing sensor wires to brake-
lines, rear axle and, brake hose.
(9) Unseat sensor wire support plate grommet.
(10) Remove bolt attaching sensor to bracket and
remove sensor.
REAR WHEEL SENSOR INSTALLATION AND
ADJUSTMENT
(1) Iforiginal sensoris being installed, remove
any remaining pieces of cardboard spacer from sen-
sor pickup face. Use dry shop towel only to remove
old spacer material.
(2) Insert sensor wire through support plate hole.
Then seat sensor grommet in support plate.
(3) Apply Mopar Lock N' Seal or Loctite 242 to
Fig. 9 Acceleration Switch And Rear Sensor
Connections (XJ)
5 - 38 ABS OPERATION AND SERVICEJ

CAUTION: The mercury switch (inside the accelera-
tion switch), will not function properly if the switch
is mispositioned. Verify that the switch locating ar-
row is pointing to the front of the vehicle.
(2) Position switch in mounting bracket.
(3) Install and tighten switch attaching screws to
2-4 Nzm (17-32 in. lbs.) torque.
(4) Connect harness to switch. Be sure harness
connecter is firmly seated.
(5) Move seat back to normal position.
ECU REMOVAL (XJ MODELS)
On left hand drive models, the ECU is located to
the right of the steering column near the heater duct
(Fig. 13). On right hand drive models, the ECU is lo-
cated near the right side cowl panel adjacent to the
dash (Fig. 14).
(1) Turn ignition key to Off position.
(2) Remove lower finish panel from instrument
panel for added working clearance if necessary.
(3) Remove ECU mounting bracket attaching bolts/
nuts.
(4) Release strap that secures ECU harness con-
nector to pin terminals (Fig. 15). Use tool such as
small flat blade screwdriver to lift and release strap.(5) Disconnect harness connector from ECU. Tilt
connector upward to disengage it from ECU pin ter-
minals. Then slide it out of retaining tangs in ECU.
(6) Remove ECU and mounting bracket as assem-
bly.
ECU INSTALLATION (XJ MODELS)
(1) If ECU is being replaced, install it on mounting
bracket and tighten fasteners to 10-14 Nzm (85-125
in. lbs.) torque
Fig. 13 Antilock ECU Mounting (Left Hand Drive XJ)
Fig. 14 Antilock ECU Mounting (Right Hand Drive XJ)
Fig. 15 ECU Harness Connector Attachment (XJ)
5 - 40 ABS OPERATION AND SERVICEJ

WARNING: HOT, PRESSURIZED COOLANT CAN
CAUSE INJURY BY SCALDING.
Carefully remove the radiator pressure cap from
the filler neck and check the coolant level. Push
down on the cap to disengage it from the stop tabs.
Wipe the inner part of the filler neck and examine
the lower inside sealing seat for nicks, cracks, paint,
dirt and solder residue. Inspect the reserve/overflow
tank tube for internal obstructions. Insert a wire
through the tube to be sure it is not obstructed.
Inspect the cams on the outside part of the filler
neck. If the cams are bent, seating of pressure cap
valve and tester seal will be affected. Replace cap if
cams are bent.
Attach pressure tester 7700 (or an equivalent) to
the radiator filler neck (Fig. 21).Operate the tester pump to apply 124 kPa (18 psi)
pressure to the system. If the hoses enlarge exces-
sively or bulge while testing, replace as necessary.
Observe the gauge pointer and determine the condi-
tion of the cooling system according to the following
criteria:
²Holds Steady: If the pointer remains steady for
two minutes, there are no serious coolant leaks in
the system. However, there could be an internal leak
that does not appear with normal system test pres-
sure. Inspect for interior leakage or do the Internal
Leakage Test. Do this if it is certain that coolant is
being lost and no leaks can be detected.
²Drops Slowly: Shows a small leak or seepage is oc-
curring. Examine all connections for seepage or slight
leakage with a flashlight. Inspect the radiator, hoses,
gasket edges and heater. Seal any small leak holes
with a Sealer Lubricant or equivalent. Repair leak
holes and reinspect the system with pressure ap-
plied.
²Drops Quickly: Shows that a serious leakage is oc-
curring. Examine the system for serious external
leakage. If no leaks are visible, inspect for internal
leakage. Large radiator leak holes should be repaired
by a reputable radiator repair shop.
INTERNAL LEAKAGE INSPECTION
Remove the engine oil pan drain plug and drain a
small amount of engine oil. Coolant, being heavier
than engine oil, will drain first. Another way of test-
ing is to operate the engine and check for water glob-
ules on the engine oil dipstick. Also inspect the
automatic transmission oil dipstick for water glob-
ules. Inspect the automatic transmission fluid cooler
for leakage. Operate the engine without the pressure
cap on the radiator until thermostat opens.
Attach a pressure tester to the filler neck. If pres-
sure builds up quickly, a leak exists as a result of a
faulty cylinder head gasket or crack in the engine.
Repair as necessary.
WARNING: DO NOT ALLOW PRESSURE TO EX-
CEED 124 KPA (18 PSI). TURN THE ENGINE OFF.
TO RELEASE THE PRESSURE, ROCK THE TESTER
FROM SIDE TO SIDE. WHEN REMOVING THE
TESTER, DO NOT TURN THE TESTER MORE THAN
1/2 TURN IF THE SYSTEM IS UNDER PRESSURE.
If there is no immediate pressure increase, pump
the pressure tester until the indicated pressure is
within the system range. Vibration of the gauge
pointer indicates compression or combustion leakage
into the cooling system.
WARNING: DO NOT DISCONNECT THE SPARK
PLUG WIRES WHILE THE ENGINE IS OPERATING.
Fig. 20 Leak Detection Using Black LightÐTypical
Fig. 21 Pressurizing SystemÐTypical
JCOOLING SYSTEM SERVICE PROCEDURES 7 - 23

CAUTION: Do not operate the engine with a spark
plug shorted for more than a minute. The catalytic
converter may be damaged.
Isolate the compression leak by shorting each
spark plug to the cylinder block. The gauge pointer
should stop or decrease vibration when spark plug
for leaking cylinder is shorted. This happens because
of the absence of combustion pressure.
COMBUSTION LEAKAGE TEST (WITHOUT
PRESSURE TESTER)
DO NOT WASTE reusable coolant. If the solution
is clean, drain the coolant into a clean container for
reuse.
WARNING: DO NOT REMOVE THE CYLINDER
BLOCK DRAIN PLUGS OR LOOSEN THE RADIATOR
DRAINCOCK WITH THE SYSTEM HOT AND UNDER
PRESSURE. SERIOUS BURNS FROM COOLANT
CAN OCCUR.
Drain sufficient coolant to allow for thermostat re-
moval. Refer to Thermostat Replacement. Disconnect
the water pump drive belt.
Disconnect the upper radiator hose from the ther-
mostat housing. Remove the housing and thermostat.
Install the thermostat housing.
Add coolant to the radiator to bring the level to
within 6.3 mm (1/4 in) of the top of the thermostat
housing.
CAUTION: Avoid overheating. Do not operate the
engine for an excessive period of time. Open the
draincock immediately after the test to eliminate
boil over of coolant.
Start the engine and accelerate rapidly three times
(to approximately 3000 rpm) while observing the
coolant. If internal engine combustion gases are leak-
ing into the cooling system, bubbles will appear in
the coolant. If bubbles do not appear, there is no in-
ternal combustion gas leakage.
COOLANT RESERVE/OVERFLOW SYSTEM
The system works along with the radiator pressure
cap. This is done by using thermal expansion and
contraction of the coolant to keep the coolant free of
trapped air. It provides:
²A volume for coolant expansion and contraction.
²A convenient and safe method for checking/adjust-
ing coolant level at atmospheric pressure. This is
done without removing the radiator pressure cap.
²Some reserve coolant to the radiator to cover mi-
nor leaks and evaporation or boiling losses.
As the engine cools, a vacuum is formed in the
cooling system of both the radiator and engine. Cool-ant will then be drawn from the coolant tank and re-
turned to a proper level in the radiator.
The coolant reserve/overflow system consists of a
radiator mounted pressurized cap, a plastic reserve/
overflow tank (Figs. 22, 23 or 24), a tube (hose) con-
necting the radiator and tank, and an overflow tube
on the side of the tank.
Fig. 22 Reserve/Overflow TankÐYJ Models
Fig. 23 Reserve/Overflow TankÐXJ ModelsÐExcept
Right Hand Drive
7 - 24 COOLING SYSTEM SERVICE PROCEDURESJ

nostic Procedures manual for diagnostic information
and operation of the DRB scan tool.
To test operation of the fan relay only, refer to Re-
laysÐOperation/Testing. This can be found in Group
14, Fuel Systems.
REMOVAL
The auxiliary cooling fan is attached to the radia-
tor upper crossmember behind the radiator.
(1) Remove the two fan mounting bolts from radi-
ator upper crossmember (Fig. 43).
(2) Disconnect the electric fan connector.
(3) Lift fan straight up and out of vehicle.
INSTALLATION
(1) Align lower retaining tabs of fan shroud with
slots in bracket at bottom of radiator. Push fan down
into position.
(2) Tighten the mounting bolts to 4 Nzm (31 in.
lbs.) torque.
(3) Connect auxiliary cooling fan electrical connec-
tor.
TRANSMISSION OIL COOLERS
WATER-TO-OIL COOLER
All models equipped with an automatic transmis-
sion are equipped with a transmission oil cooler
mounted internally within the radiator tank. This in-
ternal cooler is supplied as standard equipment on
all models equipped with an automatic transmission.
Transmission oil is cooled when it passes through
this separate cooler. In case of a leak in the internalradiator mounted transmission oil cooler, engine cool-
ant may become mixed with transmission fluid or
transmission fluid may enter engine cooling system.
Both cooling system and transmission should be
drained and inspected if the internal radiator
mounted transmission cooler is leaking.
Also refer to the section on Transmission Air-to-Oil
Coolers. This auxiliary air-to-oil cooler is an option
on most engine packages.
REPLACING WATER-TO-OIL COOLER IN
RADIATOR SIDE TANK
The internal transmission oil cooler located within
the radiator is not serviceable. If it requires service,
the radiator must be replaced.
Once the repaired or replacement radiator has
been installed, fill the cooling system and inspect for
leaks. Refer to the Refilling Cooling System and Test-
ing Cooling System For Leaks sections in this group.
If the transmission operates properly after repairing
the leak, drain the transmission and remove the
transmission oil pan. Inspect for sludge and/or rust.
Inspect for a dirty or plugged inlet filter. If none of
these conditions are found, the transmission and
torque convertor may not require reconditioning. Re-
fer to Group 21 for automatic transmission servicing.
AIR-TO-OIL COOLER
An auxiliary air-to-oil transmission oil cooler is
available with most engine packages.
On XJ and YJ models, the cooler is located in front
of the radiator or A/C condenser (if equipped) and be-
hind the grill (Figs. 44, 45 or 46). It is mounted to
the front frame crossmember.
Fig. 43 Auxiliary Cooling FanÐRemove/InstallÐ
Typical
Fig. 44 Auxiliary Air-To-Oil CoolerÐYJ Models
7 - 36 COOLING SYSTEM SERVICE PROCEDURESJ