1995 JEEP YJ ABS

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

(5) Remove air cleaner housing from engine com-
partment.
(6) Disconnect wire from combination valve pres-
sure differential switch (Fig. 9). Do not pull wire to
disconnect. Unsnap lock tabs on wire connecter.
(7) Disconnect canister vacuum line at manifold
fitting (Fig. 10).
(8) Disconnect brake booster vacuum hose at in-
take manifold fitting (Fig. 11). Move hose aside for
working clearance.(9) Unseat small S-clip that secures brakelines
(Fig. 12).
(10) Remove brakeline that connects master cylin-
der front port to combination valve front port (Fig.
12).
(11) Disconnect master cylinder rear brakeline at
cylinder. Then loosen line at combination valve and
swing line around to opposite side of cylinder (Fig.
13).
(12) Disconnect rear brakeline at HCU (Fig. 14).
(13) Disconnect both flex brakelines at HCU (Fig.
14).
(14) Disconnect HCU line to rear brakes at HCU
port (Fig. 14).
(15) Remove nut attaching combination valve
bracket to brake booster stud.
(16) Remove combination valve and brakelines as
assembly (Fig. 15). Work valve bracket off booster
stud. Then work brakelines around cylinder and
HCU and remove assembly.
Fig. 9 Pressure Differential Switch Wire Connection
Fig. 10 Canister Vacuum Line Location (At Manifold
Fitting)
Fig. 11 Booster Vacuum Hose Removal/Installation
(From Manifold Fitting)
Fig. 12 Master Cylinder Front Brakeline Removal/
Installation
Fig. 13 Disconnecting Master Cylinder Rear
Brakeline
5 - 18 MASTER CYLINDERÐCOMBINATION VALVEJ

(5) Remove reservoir by rocking it to one side and
pulling free of grommets (Fig. 19).
(6) Remove old grommets from cylinder body (Fig.
20).
(7) Lubricate new grommets with clean brake
fluid.
(8) Install new grommets in cylinder body (Fig.
21). Use finger pressure only to install and seat
grommets.
CAUTION: Do not use any type of tool to install the
grommets. Tools may cut, or tear the grommets cre-
ating a leak problem after installation. Install the
grommets using finger pressure only.(9) Start reservoir in grommets. Then rock reser-
voir back and forth while pressing downward to seat
it in grommets.
(10) Install pins that retain reservoir to cylinder
body (Fig. 17).
(11) Fill and bleed master cylinder on bench before
installation in vehicle.
MASTER CYLINDER AND COMBINATION VALVE
INSTALLATION (WITH ABS)
(1) Bleed master cylinder on bench before installa-
tion. Refer to procedure in this section.
(2) If new master cylinder is being installed, re-
move plastic protective sleeve from primary piston
shank.
(3) If original master cylinder is being installed,
check condition of seal at rear of master cylinder
(Fig. 22). Clean and reposition seal if dislodged. Re-
place seal if cut, or torn.
(4) Clean cylinder mounting surface of brake
booster (Fig. 23). Use shop towel wetted with brake
cleaner for this purpose. Dirt, grease, or similar ma-
terials will prevent proper cylinder seating and could
result in vacuum leak.
(5) If new master cylinder is being installed,re-
move plastic protective sleeve from piston
shank before installation.
(6) Position master cylinder on booster studs (Fig.
24). Then install and tighten cylinder attaching nuts
to 25 Nzm (220 in. lbs.) torque.
Fig. 19 Reservoir Removal
Fig. 20 Grommet Removal
Fig. 21 Grommet Installation
Fig. 22 Checking Master Cylinder Seal
Fig. 23 Cylinder Mounting Surface Of Brake Booster
5 - 20 MASTER CYLINDERÐCOMBINATION VALVEJ

POWER BRAKE BOOSTERÐBRAKE PEDALÐBRAKELIGHT SWITCH
INDEX
page page
Brake Pedal Installation..................... 31
Brake Pedal Removal...................... 31
Brakelight Switch Adjustment................. 32
Brakelight Switch Installation................. 32
Brakelight Switch Removal.................. 32
General Information....................... 22
Power Brake Booster Installation (XJ with ABS) . . . 27
Power Brake Booster Installation (XJ Without ABS).. 30
Power Brake Booster Installation (YJ).......... 30
Power Brake Booster Operation.............. 23
Power Brake Booster Removal (XJ with ABS).... 24
Power Brake Booster Removal (XJ Without ABS) . . 29
Power Brake Booster Removal (YJ)............ 30
GENERAL INFORMATION
A 205 mm (8.07 in.) dual diaphragm power brake
booster is used for all applications (Figs. 1 and 2).
The only serviceable parts on the power brake
booster (Figs. 1 and 2) are the check valve, and vac-
uum hose. The booster itself is not serviceable. Re-
place the booster as an assembly whenever diagnosis
indicates a malfunction has occurred.
Brake Pedal And Brakelight Switch
A suspended-type brake pedal is used on all mod-
els. The pedal pivots on a shaft mounted in the pedalsupport bracket. The bracket is attached to the dash
and instrument panels on all models.
A plunger-type, adjustable brakelight switch is
used on all models. The switch is attached to a flange
on the pedal support bracket.
The brake pedal is a serviceable component. The
pedal, pivot pin, sleeve, pedal bushings and spacers/
washers are all replaceable parts. The pedal bracket
can also be replaced when necessary.
Fig. 1 Brake Booster/Master Cylinder Assembly (XJ)
5 - 22 POWER BRAKE BOOSTERÐBRAKE PEDALÐBRAKELIGHT SWITCHJ

POWER BRAKE BOOSTER REMOVAL
(XJ WITH ABS)
(1) Disconnect vacuum and 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. 4).
(4) Remove two bolts and one nut that secure air
cleaner housing to body (Fig. 4).
(5) Remove air cleaner housing from engine com-
partment (Fig. 4).
(6) Disconnect wire at combination valve pressure
differential switch (Fig. 5). Do not pull on wires to
disconnect. Unsnap lock tabs on connecter to remove
wires.
(7) Disconnect canister vacuum line at manifold
fitting (Fig. 6).(8) Disconnect brake booster vacuum hose at in-
take manifold fitting (Fig. 7). Move hose aside for
working clearance.
(9) Unseat small S-clip that secures brakelines
(Fig. 8).
(10) Remove front brakeline that connects master
cylinder front port to combination valve front port
(Fig. 8).
Fig. 3 Power Brake Booster Internal Components
5 - 24 POWER BRAKE BOOSTERÐBRAKE PEDALÐBRAKELIGHT SWITCHJ

POWER BRAKE BOOSTER INSTALLATION (XJ WITH
ABS)
(1) If new booster is being installed, install new
check valve and vacuum hose (Fig. 17). Also install
dash seal and spacer on new booster, if equipped.
(2) Position booster on dash panel (Fig. 17) seat
booster studs in dash panel holes.
(3) Working inside vehicle, install nuts on booster
mounting studs. Tighten nuts just enough to hold
booster in place.
(4) Attach booster push rod to brake pedal. Secure
push rod with retainer clip.
(5) Tighten booster attaching nuts to 41 Nzm (30 ft.
lbs.) on XJ and 34 Nzm (25 ft. lbs.) on YJ.
(6) If necessary, bleed master cylinder on bench be-
fore installation. Refer to procedure in master cylin-
der section.
(7) If new master cylinder is being installed,re-
move plastic protective sleeve from primary
piston shank.
Fig. 13 Disconnecting HCU Solenoid Harness
Fig. 14 Disconnecting HCU Pump Harness
Fig. 15 HCU Front/Rear Brakeline Connections
Fig. 16 Push Rod Attachment At Brake Pedal
Fig. 17 Brake Booster Positioned On Dash Panel
JPOWER BRAKE BOOSTERÐBRAKE PEDALÐBRAKELIGHT SWITCH 5 - 27

(16) Install combination valve as follows:
(a) Work combination valve and brakelines into
position.
(b) Slide combination valve bracket onto booster
stud closest to driver side fender (Fig. 25). Then in-
stall bracket attaching nut but do not fully tighten
nut at this time.
(c) Connect flex lines to HCU. Start lines by
hand to avoid cross threading.
(17) Swing rear brakeline around and connect it to
master cylinder. Then install and connect front
brakeline to combination valve and master cylinder.
Start brakelines by hand to avoid cross threading.
(18) Tighten combination valve bracket attaching
nut to 25 Nzm (220 in. lbs.) torque.
(19) Install clip on lines from master cylinder to
combination valve.
(20) Connect wire to pressure differential switch
on combination valve.
(21) Connect flex lines to HCU (Fig. 10). Start line
fittings by hand to avoid cross threading. Then
tighten fittings snug but not to required torque at
this time.(22) Bleed brakes. Refer to procedure in Brake
Fluid-Brake Bleeding-Brakelines And Hoses section.
(23) Tighten brakeline fittings to 15-18 Nzm (130-
160 in. lbs.) at HCU and master cylinder, and 18-24
Nzm (160-210 in. lbs.) at combination valve.
(24) Install air cleaner assembly.
(25) Connect vacuum lines to manifold fittings.
(26) Check brake pedal action before moving vehi-
cle. Bleed brakes again if pedal is not firm (feels soft/
spongy).POWER BRAKE BOOSTER REMOVAL (XJ WITHOUT
ABS)
(1) Disconnect vent and vacuum hose from engine
air cleaner cover.
(2) Remove engine air cleaner cover, filter, housing
and hoses (Fig. 4).
(3) Disconnect brakelines at master cylinder.
(4) Disconnect wire at combination valve differen-
tial pressure switch.
(5) If combination valve does not have an integral
bracket, disconnect brakelines at combination valve
and remove valve.
(6) If combination valve has integral bracket, re-
move nut attaching valve bracket to booster studs
and remove valve.
(7) Remove nuts attaching master cylinder to
booster studs and remove cylinder.
(8) Disconnect vacuum hose from booster check
valve.
(9) In passenger compartment, remove instrument
panel lower trim cover.
(10) Remove retaining clip that secures booster
push rod to brake pedal (Fig. 5).
Fig. 23 HCU And Bracket Mounting (RHD Models)
Fig. 24 Starting Brakelines In HCU
Fig. 25 Combination Valve Installation
JPOWER BRAKE BOOSTERÐBRAKE PEDALÐBRAKELIGHT SWITCH 5 - 29

(11) Remove nuts attaching booster to passenger
compartment side of dash panel.
(12) In engine compartment, slide booster studs
out of dash panel, tilt booster upward, and remove
booster from engine compartment.
(13) Remove dash seal from booster.
(14) If booster is only being removed for access to
other components, cover booster front opening with
clean shop towel.
POWER BRAKE BOOSTER INSTALLATION (XJ
WITHOUT ABS)
(1) If original booster is being installed, test check
valve with vacuum tool before booster installation.
Replace check valve if it will not hold vacuum.
(2) Install dash seal on booster.
(3) Align and position booster on dash panel (Fig.
17).
(4) In passenger compartment, install nuts that at-
tach booster to dash panel. Tighten nuts just enough
to hold booster in place.
(5) Slide booster push rod onto brake pedal. Then
secure push rod to pedal pin with retaining clip.
(6) Tighten booster attaching nuts to 41 Nzm (30 ft.
lbs.) on XJ and 34 Nzm (25 ft. lbs.) on YJ.
(7) Install instrument panel lower trim cover.
(8) If original master cylinder is being installed,
check condition of seal at rear of master cylinder
(Fig. 18). Clean and reposition seal if dislodged. Re-
place seal if cut, or torn.
(9) Clean cylinder mounting surface of brake
booster. Use shop towel wetted with brake cleaner for
this purpose. Dirt, grease, or similar materials will
prevent proper cylinder seating and could result in
vacuum leak.
(10) Align and install master cylinder on booster
studs. Tighten cylinder attaching nuts to 13-25 Nzm
(115-220 in. lbs.) torque.
(11) Connect vacuum hose to booster check valve.
(12) Connect and secure brakelines to combination
valve and master cylinder. Start all brakeline fittings
by hand to avoid cross threading.
(13) If combination valve has integral bracket, po-
sition bracket on booster studs. Then install and
tighten bracket attaching nuts to 13-25 Nzm (115-220
in. lbs.) torque.
(14) Connect wire to combination valve switch.
(15) Top off master cylinder fluid level.
(16) Bleed brakes. Refer to procedures in section
on brake bleeding.
(17) Install engine air cleaner and hoses.
(18) Verify proper brake operation before moving
vehicle.
POWER BRAKE BOOSTER REMOVAL (YJ)
(1) Disconnect brakelines at master cylinder. Then
loosen lines at combination valve and move lines
away from cylinder.
(2) Remove nuts master cylinder to booster studs.
(3) If combination valve has integral bracket, slide
bracket off studs and move valve aside.
(4) Remove master cylinder. Slide cylinder off
studs and remove it from engine compartment.
(5) Working under instrument panel, remove re-
tainer clip that secures booster push rod to brake
pedal.
(6) Disconnect vacuum hose at booster check valve.
(7) On non-ABS models, remove nuts attaching
brake booster spacer to dash panel and remove
booster (Fig. 26).
(8) On ABS models, remove nuts attaching booster
to spacer and remove booster (Fig. 27).
POWER BRAKE BOOSTER INSTALLATION (YJ)
(1) Install seal on booster spacer, if equipped.
(2) Position booster on dash panel, or on spacer.
(3) Secure booster push rod to brake pedal with re-
taining clip.
(4) Install and tighten booster attaching nuts to
27-47 Nzm (20-35 ft. lbs.) torque. Nut torque applies
to both styles of booster.
Fig. 26 Booster Mounting (4-Cyl. Models)
Fig. 27 Booster Mounting (With ABS)
5 - 30 POWER BRAKE BOOSTERÐBRAKE PEDALÐBRAKELIGHT SWITCHJ