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 red warning light alerts the driver if a pres-
sure differential exists between the front and rear
hydraulic systems or the parking brakes are applied.
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.
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. The diaphragms are connected to
the booster primary push rod.
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 has a removable nylon reser-
voir. The cylinder body is made of aluminum and
contains a primary and secondary piston assembly.
The cylinder body including the piston assemblies
are not serviceable. If diagnosis indicates an internal
problem with the cylinder body, it must be replaced
as an assembly. The reservoir and grommets 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.
COMBINATION VALVE
DESCRIPTION
The combination valve contains a pressure differ-
ential valve and switch and a rear brake proportion-
ing valve. The valve is not repairable and must be
replaced as an assembly if diagnosis indicates this is
necessary.
OPERATION
PRESSURE DIFFERENTIAL VALVE
The pressure differential switch is connected to the
brake warning light. The switch is actuated by move-
ment of the switch valve. The switch monitors fluid
pressure in the separate front/rear brake hydraulic
circuits.
A decrease or loss of fluid pressure in either
hydraulic circuit will cause the switch valve to shut-
tle to the low pressure side. Movement of the valve
pushes the switch plunger upward. This action closes
the switch internal contacts completing the electrical
circuit to the red warning light. The switch valve will
remain in an actuated position until repairs to the
brake system are made.
PROPORTIONING VALVE
The proportioning valve is used to balance front-
rear brake action at high decelerations. The valve
allows normal fluid flow during moderate braking.
The valve only controls fluid flow during high decel-
erations brake stops.
XJ
BRAKES
5 - 3
DESCRIPTION AND OPERATION (Continued)
Summary of Contents for 200 Cherokee
Page 5: ...FASTENER IDENTIFICATION 4 INTRODUCTION XJ DESCRIPTION AND OPERATION Continued ...
Page 6: ...FASTENER STRENGTH XJ INTRODUCTION 5 DESCRIPTION AND OPERATION Continued ...
Page 8: ...METRIC CONVERSION CHART XJ INTRODUCTION 7 DESCRIPTION AND OPERATION Continued ...
Page 9: ...TORQUE SPECIFICATIONS 8 INTRODUCTION XJ DESCRIPTION AND OPERATION Continued ...
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Page 107: ...Fig 105 Gear Tooth Contact Patterns 3 60 TUBE 181 AND 186 FBI AXLE XJ ADJUSTMENTS Continued ...
Page 111: ...Installer D 144 Installer W 262 3 64 TUBE 181 AND 186 FBI AXLE XJ SPECIAL TOOLS Continued ...
Page 145: ...Fig 79 Gear Tooth Contact Patterns 3 98 194 RBI AXLE XJ ADJUSTMENTS Continued ...
Page 177: ...Fig 59 Gear Tooth Contact Patterns 3 130 8 1 4 REAR AXLE XJ ADJUSTMENTS Continued ...
Page 230: ...Fig 8 Clutch Components And Inspection XJ CLUTCH 6 5 DIAGNOSIS AND TESTING Continued ...
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Page 1074: ...Fig 18 4 0L Engine XJ 8W 90 CONNECTOR LOCATIONS 8W 90 27 DESCRIPTION AND OPERATION Continued ...
Page 1087: ...Fig 31 Liftgate 8W 90 40 8W 90 CONNECTOR LOCATIONS XJ DESCRIPTION AND OPERATION Continued ...
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Page 1912: ...Fig 3 Hood Components XJ BODY 23 25 REMOVAL AND INSTALLATION Continued ...
Page 1955: ...WELD LOCATIONS UPPER COWL 23 68 BODY XJ SPECIFICATIONS Continued ...
Page 1956: ...UPPER COWL XJ BODY 23 69 SPECIFICATIONS Continued ...
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Page 1974: ...REINFORCEMENT XJ BODY 23 87 SPECIFICATIONS Continued ...
Page 1975: ...FRONT INNER FENDER 23 88 BODY XJ SPECIFICATIONS Continued ...
Page 1976: ...FRONT INNER FENDER AND RADIATOR CLOSURE PANEL XJ BODY 23 89 SPECIFICATIONS Continued ...
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Page 2000: ...COWL AND DASH PANEL XJ BODY 23 113 SPECIFICATIONS Continued ...
Page 2001: ...DASH PANEL AND FLOOR PAN 23 114 BODY XJ SPECIFICATIONS Continued ...
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Page 2003: ...REAR INNER WHEELHOUSE 23 116 BODY XJ SPECIFICATIONS Continued ...
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Page 2010: ...LIFTGATE OPENING XJ BODY 23 123 SPECIFICATIONS Continued ...
Page 2011: ...STRUCTURAL ADHESIVE LOCATIONS LEFT QUARTER PANEL 23 124 BODY XJ SPECIFICATIONS Continued ...
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