2002 JEEP GRAND CHEROKEE Hose

(5) Remove brake hose banjo bolt and gasket
washers. Discard gasket washers.
(6) Remove the caliper support spring by prying
the spring out of the caliper (Fig. 20).
(7) Remove the caliper slide pin bushing caps and
remove the slide pins (Fig. 21).
(8) Remove caliper from the anchor.
(9) Remove the inboard brake shoe (Fig. 22).
REMOVAL - REAR DISC BRAKE CALIPER
(1) Raise and support vehicle.
(2) Remove rear wheel and tire assembly.
(3) Drain small amount of fluid from master cylin-
der brake reservoir with acleansuction gun.
(4) Bottom caliper pistons into the caliper by pry-
ing the caliper over (Fig. 23).
Fig. 20 Caliper Support Spring
1 - SUPPORT SPRING
2 - CALIPER
Fig. 21 Slide Pins
1 - SLIDE PIN
2 - SLIDE PIN
3 - CALIPER
Fig. 22 Inboard Brake Shoe
1 - CALIPER
2 - INBOARD SHOE
Fig. 23 Bottoming Caliper Piston
1 - CALIPER
2 - CALIPER ANCHOR
WJBRAKES - BASE 5 - 15
DISC BRAKE CALIPERS (Continued)

(5) Remove brake hose banjo bolt and discard gas-
ket washers.
(6) Remove the caliper support spring by prying
the spring out of the caliper (Fig. 24).
(7) Remove the caliper slide pin bushing caps and
remove the slide pins (Fig. 25).
(8) Remove caliper from the anchor.
(9) Remove the inboard brake shoe (Fig. 26).
Fig. 24 Caliper Support Spring
1 - CALIPER
2 - ANCHOR
3 - SUPPORT SPRING
Fig. 25 Caliper Slide Pins
1 - CALIPER
2 - SLIDE PINS
Fig. 26 Inboard Brake Shoe
1 - CALIPER
2 - INBOARD SHOE
5 - 16 BRAKES - BASEWJ
DISC BRAKE CALIPERS (Continued)

DISASSEMBLY
DISASSEMBLY - FRONT DISC BRAKE CALIPER
(1) Drain the brake fluid from caliper.
(2) C-clamp a block of wood over one piston (Fig.
27).
(3) Take another piece of wood and pad it with
one-inch thickness of shop towels. Place this piece in
the outboard shoe side of the caliper in front of the
other piston. This will cushion and protect caliper
piston during removal (Fig. 28).(4) To remove the caliper piston directshort
bursts of low pressure airwith a blow gun
through the caliper brake hose port. Use only enough
air pressure to ease the piston out.
CAUTION: Do not blow the piston out of the bore
with sustained air pressure. This could result in a
cracked piston.
WARNING: NEVER ATTEMPT TO CATCH THE PIS-
TON AS IT LEAVES THE BORE. THIS COULD
RESULT IN PERSONAL INJURY.
(5) Remove the C-clamp and block of wood from
the caliper and clamp it over the dust boot of the
first piston removed. This will seal the empty piston
bore.
(6) Move the padded piece of wood in front of the
other piston.
(7) Remove the second piston using the same pro-
cedure withshort bursts of low pressure air.
(8) Remove piston dust boots with a suitable pry
tool (Fig. 29)and discard.
Fig. 27 C-Clamp One Piston
1 - BLOCK OF WOOD
2 - C-CLAMP
3 - CALIPER
Fig. 28 Protect Caliper Piston
1 - CALIPER
2 - PADDED BLOCK OF WOOD
3 - C-CLAMP
Fig. 29 Piston Dust Boot Removal
1 - CALIPER
2 - PISTON DUST BOOT
WJBRAKES - BASE 5 - 17
DISC BRAKE CALIPERS (Continued)

(9) Remove piston seals from caliper (Fig. 30) and
discard.
CAUTION: Do not scratch piston bore while remov-
ing the seals.
(10) Remove caliper slide pin bushings (Fig. 31).
(11) Remove caliper bleed screw.
DISASSEMBLY - REAR DISC BRAKE CALIPER
(1) Drain brake fluid out of caliper.
(2) Take a piece of wood and pad it with one-inch
thickness of shop towels. Place this piece in the out-
board shoe side of the caliper in front of the piston.This will cushion and protect caliper piston during
removal (Fig. 32).
(3) To remove caliper piston directshort bursts
of low pressure airwith a blow gun through the
caliper brake hose port (Fig. 33). Use only enough air
pressure to ease the piston out.
CAUTION: Do not blow the piston out of the bore
with sustained air pressure. This could result in a
cracked piston.
WARNING: NEVER ATTEMPT TO CATCH THE PIS-
TON AS IT LEAVES THE BORE. THIS MAY RESULT
IN PERSONAL INJURY.
Fig. 30 Piston Seal
1 - CALIPER
2 - PISTON BORE
3 - PISTON SEAL
Fig. 31 Caliper Slide Pin Bushings
1 - CALIPER
2 - BUSHING
3 - CALIPER SLIDE PIN
Fig. 32 Padding Caliper Interior
1 - SHOP TOWELS OR CLOTHS
2 - CALIPER
Fig. 33 Caliper Piston Removal
1 - CALIPER PISTON
2 - AIR GUN
3 - PADDING MATERIAL
5 - 18 BRAKES - BASEWJ
DISC BRAKE CALIPERS (Continued)

(6) Seat dust boot in caliper with Installer 8280
and Handle C-4171 (Fig. 45).
(7) Install caliper slide pin bushings into the cali-
per (Fig. 46).
(8) Install caliper bleed screw.
INSTALLATION
INSTALLATION - FRONT DISC BRAKE CALIPER
(1) Install the inboard brake shoe (Fig. 22).
(2) Lubricate the slide pins and slide pin bushings
with Dow Corningtgrease G807 or the grease pro-
vided with the caliper.
(3) Install the caliper on the anchor.(4) Install the caliper slide pin and tighten to
29-41 N´m (21-30 ft. lbs.).
(5) Install the caliper slide pin bushing caps.
(6) Install the caliper support spring in the top
end of the caliper and under the anchor. Then install
other end into the lower caliper hole. Hold the spring
into the caliper hole with your thumb while prying
the end of the spring out and down under the anchor
with a screw drive.
(7) Install brake hose to caliper withnew gasket
washersand tighten banjo bolt to 31 N´m (23 ft.
lbs.).
CAUTION: Verify brake hose is not twisted or
kinked before tightening banjo bolt.
(8) Fill and bleed brake system.
(9) Install wheel and tire assemblies.
(10) Remove supports and lower vehicle.
(11) Verify brake fluid level.
INSTALLATION - REAR DISC BRAKE CALIPER
(1) Install the inboard brake shoe (Fig. 26).
(2) Lubricate the slide pins and slide pin bushings
with Dow Corningtgrease G807 or the grease pro-
vided with the caliper.
(3) Install the caliper on the anchor.
(4) Install the caliper slide pin and tighten to
29-41 N´m (21-30 ft. lbs.).
(5) Install the caliper slide pin caps.
(6) Install the caliper support spring in the top
end of the caliper and under the anchor. Then install
other end into the lower caliper hole. Hold the spring
into the caliper hole with your thumb while prying
the end of the spring out and down under the anchor
with a screw drive.
CAUTION: Verify brake hose is not twisted or
kinked before tightening fitting bolt.
(7) Install brake hose to caliper with anewgasket
washers and tighten banjo bolt to 31 N´m (23 ft. lbs.).
(8) Fill and bleed brake system.
(9) Install wheel and tire assemblies.
(10) Remove supports and lower vehicle.
FLUID
DIAGNOSIS AND TESTING - BRAKE FLUID
CONTAMINATION
Indications of fluid contamination are swollen or
deteriorated rubber parts.
Swollen rubber parts indicate the presence of
petroleum in the brake fluid.
To test for contamination, put a small amount of
drained brake fluid in clear glass jar. If fluid sepa-
Fig. 45 Piston Dust Boot Installation
1 - HANDLE
2 - INSTALLER
3 - DUST BOOT
Fig. 46 Slide Pin And Bushing
1 - CALIPER SLIDE PIN
2 - BUSHING
5 - 22 BRAKES - BASEWJ
DISC BRAKE CALIPERS (Continued)

rates into layers, there is mineral oil or other fluid
contamination of the brake fluid.
If brake fluid is contaminated, drain and thor-
oughly flush system. Replace master cylinder with
reservoir, caliper seals, HCU and all hydraulic fluid
hoses.
SPECIFICATIONS
BRAKE FLUID
The brake fluid used in this vehicle must conform
to DOT 3 specifications and SAE J1703 standards.
No other type of brake fluid is recommended or
approved for usage in the vehicle brake system. Use
only Mopar brake fluid or an equivalent from a
tightly sealed container.
CAUTION: Never use reclaimed brake fluid or fluid
from an container which has been left open. An
open container of brake fluid will absorb moisture
from the air and contaminate the fluid.
CAUTION: Never use any type of a petroleum-based
fluid in the brake hydraulic system. Use of such
type fluids will result in seal damage of the vehicle
brake hydraulic system causing a failure of the
vehicle brake system. Petroleum based fluids would
be items such as engine oil, transmission fluid,
power steering fluid, etc.
FLUID RESERVOIR
REMOVAL
(1) Remove reservoir cap and remove fluid with a
cleansuction gun.
(2) Remove the wire connector from the brake fluid
level sensor.
(3) Insert the tool (Fig. 47) provided with the res-
ervoir to release the reservoir retaining tabs.
(4) Pull the reservoir straight up out of the cylin-
der.
(5) Remove and discard grommets from the cylin-
der body.
INSTALLATION
(1) Lubricate new grommets with clean brake
fluid. Install new grommets into the cylinder body.
CAUTION: Do not use tools to install the grommets.
Tools may cut, or tear the grommets. Install the
grommets using finger pressure only.(2) Start reservoir in grommets then press the res-
ervoir straight down to seat the reservoir into the
cylinder grommets.
CAUTION: Do not rock the reservoir during installa-
tion.
(3) Verify retaining tabs are seated.
(4) Install the wire connector to the brake fluid
level sensor.
(5) Fill master cylinder.
MASTER CYLINDER
DESCRIPTION
The master cylinder body is made of aluminum
and contains a primary and secondary piston assem-
bly. The cylinder body including the piston assem-
blies are not serviceable. If diagnosis indicates an
internal problem with the cylinder body, it must be
replaced as an assembly. The master cylinder has a
removable reservoir and fluid level indicator. The res-
ervoir, reservoir grommets, reservoir cap and fluid
level switch are the only replaceable parts on the
master cylinder.
Fig. 47 Release Tool
1 - RESERVOIR
2 - RELEASE TOOL
3 - RETAINING TABS
WJBRAKES - BASE 5 - 23
FLUID (Continued)

OPERATION
The master cylinder bore contains a primary and
secondary piston. The primary piston supplies
hydraulic pressure to the front brakes. The secondary
piston supplies hydraulic pressure to the rear brakes.
The master cylinder reservoir stores reserve brake
fluid for the hydraulic brake circuits.
DIAGNOSIS AND TESTING - MASTER
CYLINDER/POWER BOOSTER
NOTE: Inspect and repair any external fluid leaks
before performing test.
(1) Start engine and check booster vacuum hose
connections. A hissing noise indicates vacuum leak.
Correct any vacuum leak before proceeding.
(2)
Stop engine and shift transmission into Neutral.
(3) Pump brake pedal until all vacuum reserve in
booster is depleted.
(4) Press and hold brake pedal under light foot
pressure. The pedal should hold firm, if the pedal
falls away the master cylinder or HCU may be faulty
(internal leakage).
(5) Start engine and note pedal action. It should
fall away slightly under light foot pressure then hold
firm. If no pedal action is discernible, power booster,
vacuum supply, or vacuum check valve is faulty. Pro-
ceed to the POWER BOOSTER VACUUM TEST.
(6) If the POWER BOOSTER VACUUM TEST
passes, rebuild booster vacuum reserve as follows:
Release brake pedal. Increase engine speed to 1500
rpm, close the throttle and turn off the engine.
(7) Wait a minimum of 90 seconds and try brake
action again. Booster should provide two or more vac-
uum assisted pedal applications. If vacuum assist is
not provided, some component of the booster is faulty.
POWER BOOSTER VACUUM TEST
(1) Connect vacuum gauge to booster check valve
with short length of hose and T-fitting (Fig. 48).
(2) Start and run engine at curb idle speed for one
minute.
(3) Observe the vacuum supply. If vacuum supply
is not adequate, repair vacuum supply.
(4) Clamp hose shut between vacuum source and
check valve.
(5) Stop engine and observe vacuum gauge.
(6) If vacuum drops more than one inch HG (33
millibars) within 15 seconds, booster diaphragm,
check valve or check valve seal/grommet is faulty.
POWER BOOSTER CHECK VALVE TEST
(1) Disconnect vacuum hose from check valve.
(2)
Remove check valve and valve seal from booster.
(3) Use a hand operated vacuum pump for test.(4) Apply 51-67 kPa (15-20 in.) vacuum at large
end of check valve (Fig. 49).
(5) Vacuum should hold steady. If gauge on pump
indicates vacuum loss the check valve and seal
should be replaced.
Fig. 48 Typical Booster Vacuum Test Connections
1 - TEE FITTING
2 - SHORT CONNECTING HOSE
3 - CHECK VALVE
4 - CHECK VALVE HOSE
5 - CLAMP TOOL
6 - INTAKE MANIFOLD
7 - VACUUM GAUGE
Fig. 49 Vacuum Check Valve And Seal
1 - BOOSTER CHECK VALVE
2 - APPLY TEST VACUUM HERE
3 - VALVE SEAL
5 - 24 BRAKES - BASEWJ
MASTER CYLINDER (Continued)

(5) Install the cluster bezel (Refer to 23 - BODY/
INSTRUMENT PANEL/CLUSTER BEZEL -
INSTALLATION).
(6) Reconnect the negative battery cable.
POWER BRAKE BOOSTER
DESCRIPTION
The booster assembly consists of a housing divided
into separate chambers by two internal diaphragms.
The outer edge of each diaphragm is attached to the
booster housing.
Two push rods are used in the booster. The pri-
mary push rod connects the booster to the brake
pedal. The secondary push rod connects the booster
to the master cylinder to stroke the cylinder pistons.
OPERATION
The atmospheric inlet valve is opened and closed
by the primary push rod. Booster vacuum supply is
through a hose attached to an intake manifold fittingat one end and to the booster check valve at the
other. The vacuum check valve in the booster housing
is a one-way device that prevents vacuum leak back.
Power assist is generated by utilizing the pressure
differential between normal atmospheric pressure
and a vacuum. The vacuum needed for booster oper-
ation is taken directly from the engine intake mani-
fold. The entry point for atmospheric pressure is
through a filter and inlet valve at the rear of the
housing (Fig. 59) .
The chamber areas forward of the booster dia-
phragms are exposed to vacuum from the intake
manifold. The chamber areas to the rear of the dia-
phragms, are exposed to normal atmospheric pres-
sure of 101.3 kilopascals (14.7 pounds/square in.).
Brake pedal application causes the primary push
rod to open the atmospheric inlet valve. This exposes
the area behind the diaphragms to atmospheric pres-
sure. The resulting pressure differential provides the
extra apply force for power assist.
The booster check valve, check valve grommet and
booster seals are serviceable.
WJBRAKES - BASE 5 - 29
PEDAL MOTOR (Continued)