Content .. 46 47 48 49 ..

Jeep Grand Cherokee WJ. Manual - part 48

Holder—6958

Holder—6963-A

Remover—7794-A

Splitter, Bearing—1130

Installer, Gear/Bearing—7913-A

3 - 138

226 RBA AXLE

SPECIAL TOOLS (Continued)

BRAKES

TABLE OF CONTENTS

page

BASE BRAKE SYSTEM . . . . . . . . . . . . . . . . . . . . . . 1

ANTILOCK BRAKES . . . . . . . . . . . . . . . . . . . . . . . 38

BASE BRAKE SYSTEM

TABLE OF CONTENTS

page

DESCRIPTION AND OPERATION

DIAGNOSIS AND TESTING

SERVICE PROCEDURES

BASE BRAKE BLEEDING. . . . . . . . . . . . . . . . . . . 12
BRAKE FLUID LEVEL . . . . . . . . . . . . . . . . . . . . . 12
MASTER CYLINDER BLEEDING . . . . . . . . . . . . . 12
BRAKE TUBE FLARING . . . . . . . . . . . . . . . . . . . . 13
DISC ROTOR MACHINING. . . . . . . . . . . . . . . . . . 13
FRONT BRAKE ROTOR MATCH MOUNTING . . . . 13

REMOVAL AND INSTALLATION

DISASSEMBLY AND ASSEMBLY

FRONT DISC BRAKE CALIPER . . . . . . . . . . . . . . 31
REAR DISC BRAKE CALIPER . . . . . . . . . . . . . . . 33

CLEANING AND INSPECTION

CALIPER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

ADJUSTMENTS

BRAKE LAMP SWITCH . . . . . . . . . . . . . . . . . . . . 36
PARKING BRAKE SHOE . . . . . . . . . . . . . . . . . . . 36

SPECIFICATIONS

BRAKE FLUID . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
BRAKE COMPONENTS . . . . . . . . . . . . . . . . . . . . 37
TORQUE CHART . . . . . . . . . . . . . . . . . . . . . . . . . 37

SPECIAL TOOLS

BASE BRAKES . . . . . . . . . . . . . . . . . . . . . . . . . . 37

BRAKES

5 - 1

DESCRIPTION AND OPERATION

BRAKE SYSTEM

DESCRIPTION

Dual piston disc brake calipers are used on the

front. Single piston disc brake calipers are used on
the rear. Ventilated disc brake rotors are used on the
front and solid rotors are used on the rear.

Power brake assist is supplied by a vacuum oper-

ated, dual diaphragm power brake booster. The mas-
ter

cylinder

used

for

all

applications

has

aluminum body and nylon reservoir with single filler
cap. A fluid level indicator is mounted to the side of
the reservoir.

The braking force of the rear wheels is controlled

by electronic brake distribution (EBD). The EBD
functions like a rear proportioning valve. The EBD
system uses the ABS system to control the slip of the
rear wheels in partial braking range. The braking
force of the rear wheels is controlled electronically by
using the inlet and outlet valves located in the HCU.

Factory installed brake linings on all models con-

sists of organic base material combined with metallic
particles.

SERVICE WARNINGS & CAUTIONS

WARNING: DUST AND DIRT ACCUMULATING ON
BRAKE PARTS DURING NORMAL USE MAY CON-
TAIN ASBESTOS FIBERS FROM AFTERMARKET
LININGS. BREATHING EXCESSIVE CONCENTRA-
TIONS OF ASBESTOS FIBERS CAN CAUSE SERI-
OUS

BODILY

HARM.

EXERCISE

CARE

WHEN

SERVICING

BRAKE

PARTS.

NOT

CLEAN

BRAKE PARTS WITH COMPRESSED AIR OR BY
DRY BRUSHING. USE A VACUUM CLEANER SPE-
CIFICALLY DESIGNED FOR THE REMOVAL OF
ASBESTOS FIBERS FROM BRAKE COMPONENTS.
IF A SUITABLE VACUUM CLEANER IS NOT AVAIL-
ABLE, CLEANING SHOULD BE DONE WITH A
WATER DAMPENED CLOTH. DO NOT SAND, OR
GRIND BRAKE LINING UNLESS EQUIPMENT USED
IS DESIGNED TO CONTAIN THE DUST RESIDUE.
DISPOSE OF ALL RESIDUE CONTAINING ASBES-
TOS FIBERS IN SEALED BAGS OR CONTAINERS
TO MINIMIZE EXPOSURE TO YOURSELF AND OTH-
ERS. FOLLOW PRACTICES PRESCRIBED BY THE
OCCUPATIONAL SAFETY AND HEALTH ADMINIS-
TRATION AND THE ENVIRONMENTAL PROTECTION
AGENCY FOR THE HANDLING, PROCESSING, AND
DISPOSITION OF DUST OR DEBRIS THAT MAY
CONTAIN ASBESTOS FIBERS.

CAUTION: Never use gasoline, kerosene, alcohol,
motor oil, transmission fluid, or any fluid containing
mineral oil to clean the system components. These
fluids damage rubber cups and seals. Use only
fresh brake fluid or Mopar brake cleaner to clean or
flush brake system components. These are the only
cleaning materials recommended. If system contam-
ination is suspected, check the fluid for dirt, discol-
oration, or separation into distinct layers. Also
check the reservoir cap seal for distortion. Drain
and flush the system with new brake fluid if con-
tamination is suspected.

CAUTION: Use Mopar brake fluid, or an equivalent
quality fluid meeting SAE/DOT standards J1703 and
DOT 3. Brake fluid must be clean and free of con-
taminants. Use fresh fluid from sealed containers
only to ensure proper antilock component opera-
tion.

CAUTION: Use Mopar multi-mileage grease or Dow
G807 silicone grease on caliper slide pins to ensure
proper operation.

BRAKE PEDAL

DESCRIPTION

A suspended-type brake pedal is used, the pedal

pivots on a shaft mounted in the pedal support
bracket. The bracket is attached to the dash panel.

The brake pedal assembly and pedal pad are the

only serviceable component.

OPERATION

The brake pedal is attached to the booster push

rod. When the pedal is depressed, the primary
booster push rod is depressed which moves the
booster secondary rod. The booster secondary rod
depresses the master cylinder piston.

BRAKE LAMP SWITCH

DESCRIPTION

The plunger type brake lamp switch is mounted on

a bracket attached to the brake pedal support. The
switch can be adjusted when necessary.

OPERATION

The brake lamp switch is used for the brake lamp,

speed control and brake sensor circuits.

5 - 2

BRAKES

ELECTRONIC BRAKE DISTRIBUTION

DESCRIPTION

The electronic brake distribution (EBD) functions

like a rear proportioning valve. The EBD system uses
the ABS system to control the slip of the rear wheels
in partial braking range. The braking force of the
rear wheels is controlled electronically by using the
inlet and outlet valves located in the HCU.

OPERATION

Upon entry into EBD the inlet valve for the rear

brake circuit is switched on so that the fluid supply
from the master cylinder is shut off. In order to
decrease the rear brake pressure the outlet valve for
the rear brake circuit is pulsed. This allows fluid to
enter the low pressure accumulator (LPA) in the
HCU resulting in a drop in fluid pressure to the rear
brakes. In order to increase the rear brake pressure
the outlet valve is switched off and the inlet valve is
pulsed. This increases the pressure to the rear
brakes. This will continue until the required slip dif-
ference is obtained. At the end of EBD braking (no
brake application) the fluid in the LPA drains back to
the master cylinder by switching on the outlet valve
and draining through the inlet valve check valve. At
the same time the inlet valve is switched on to pre-
vent a hydraulic short circiut in case of another
brake application.

The EBD will remain functional during many ABS

fault modes. If the red and amber warning lamps are
illuminated the EBD may have a fault.

RED BRAKE WARNING LAMP

DESCRIPTION

A red warning lamp is used for the service brake

portion of the hydraulic system. The lamp is located
in the instrument cluster.

OPERATION

The lamp is turned on momentarily when the igni-

tion switch is turn to the on position. This is a self
test to verify the lamp is operational.

The red warning light alerts the driver if the fluid

level is low or the parking brakes are applied. A red
warning lamp with an amber warning lamp may
indicate a electronic brake distribution fault.

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 fitting
at 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. 1).

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.

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.

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.

BRAKES

5 - 3

DESCRIPTION AND OPERATION (Continued)

Content .. 46 47 48 49 ..