warning CHEVROLET DYNASTY 1993 Repair Manual

ABS BRAKING-DECAY PRESSURE
ISOLATION VALVES Closed, isolating the wheel brakes from the master
cylinder primary and secondary fluid supplies (Fig.
3)
BUILD/DECAY VALVES
Open, allowing release of fluid pressure through
decay valve to the fluid reservoir. Which gets
pumped into the accumulator for the build pressure
cycle (Fig. 3).
ABS BRAKE SYSTEM DIAGNOSIS
GENERAL INFORMATION
WARNING: SOME OPERATIONS IN THIS SECTION
REQUIRE THAT HYDRAULIC TUBES, HOSES AND
FITTINGS BE DISCONNECTED FOR INSPECTION
OR TESTING PURPOSES.
CAUTION: REVIEW THIS ENTIRE SECTION PRIOR
TO PERFORMING ANY MECHANICAL WORK ON A
VEHICLE EQUIPPED WITH THE BENDIX ANTI-LOCK
6 BRAKE SYSTEM. THIS SECTION CONTAINS IN-
FORMATION ON PRECAUTIONS PERTAINING TO
POTENTIAL COMPONENT DAMAGE, VEHICLE DAM- AGE AND PERSONAL INJURY WHICH COULD RE-
SULT WHEN SERVICING AN ABS EQUIPPED
VEHICLE.
CAUTION: Certain components of the Anti-Lock
Brake System (ABS) are not intended to be serviced
individually. Attempting to remove or disconnect
certain system components, may result in personal
injury and/or improper system operation. Only
those components with approved removal and in-
stallation procedures in this manual should be ser-
viced.
This section contains information necessary to di-
agnosis mechanical conditions which can affect oper-
ation of the Bendix Anti-Lock 6 Brake System.
Specifically, this section should be used to help diag-
nose mechanical conditions which result in any of
the following: (1) Anti-Lock Warning Lamp turned on.
(2) Brakes Lock on Hard Application
Diagnosis of conditions which are obviously me-
chanical in nature. Such as brake noise, brake pulsa-
tion, lack of power assist, turning on of the Red
Brake Warning Lamp or vehicle vibration during
normal braking. Should be directed to Group 5
Brakes in this service manual. This also pertains to
problems involving the parking brake system.
Fig. 3 Decay Pressure - Hydraulic Control
Ä ANTI-LOCK 6 BRAKE SYSTEM 5 - 123

In order to effectively diagnose an Anti-Lock Brake
System (ABS) condition. It is important to read Anti-
Lock Brake System Description. And to follow the
diagnostic procedures outlined in this section. Many conditions that generate customer complaints
may be normal operating conditions, but are judged to
be a problem due to not being familiar with the ABS
system. These conditions can be recognized without
performing extensive diagnostic work. Given adequate
understanding of the operating principles and perfor-
mance characteristics of the ABS system. See Section 1
of this manual to familiarize yourself with the operat-
ing principles of the ABS system.
DEFINITIONS
Several abbreviations are used in this manual. They
are presented here for reference.
² CABÐController Anti-Lock Brake
² ABSÐAnti-Lock Brake System
² PSIÐPounds per Square Inch (pressure)
² WSSÐWheel Speed Sensor
ABS COMPUTER SYSTEM SERVICE PRECAUTIONS
The ABS system uses an electronic control module,
the (CAB). This module is designed to withstand nor-
mal current draws associated with vehicle operation.
However care must be taken to avoid overloading the
(CAB) circuits. In testing for open or short circuits,
do not ground or apply voltage to any of the
circuits unless instructed to do so by the appro-
priate diagnostic procedure. These circuits should
only be tested using a high impedance multi-meter,
special tools or the DRB II tester as described in this
section. Power should never be removed or applied to
any control module with the ignition in the ON posi-
tion. Before removing or connecting battery cables,
fuses, or connectors, always turn the ignition to the
OFF position.
ABS GENERAL SERVICE PRECAUTIONS
TEST DRIVING ABS COMPLAINT VEHICLES
Most ABS complaints will require a test drive as a
part of the diagnostic procedure. The purpose of the
test drive is to duplicate the condition. Remember conditions that result in the turn-
ing on of the Red Brake Warning Lamp may
indicate reduced braking ability. The following
procedure should be used to test drive an ABS
complaint vehicle. Before test driving a brake complaint vehicle, note
whether the Red or Amber Brake Warning Lamp is
turned on. If it is the Red Brake Warning Lamp, refer
to the standard brake, Control Valves Section in the
brake group of this manual. If the Amber Anti-Lock
Warning light was/is on, read record and erase the
fault. While the Amber ABS Warning Lamp is on the
ABS system is not functional. When the Am- ber Anti-Lock Warning Lamp is on only the Anti-Lock
function of the brake system if affected. The standard
brake system and the ability to stop the car is not be
affected if only the Amber Anti-Lock Warning Lamp is
on. (1) Turn the key to the off position and then back to
the on position. Note whether the Amber ABS Warning
Lamp continues to stay on. If it does refer to the 1993
M.Y. Bendix Anti-Lock 6 Diagnostic Manual for the
required test procedures. (2) If the Amber ABS Warning Lamp goes out, shift
into gear and drive the car to a speed of 5 mph to
complete the ABS start up cycle. If at this time the
Amber ABS Warning Lamp goes on refer to the Bendix
Anti-Lock 6 Diagnostic Manual. (3) If the Amber ABS Warning Lamp remains OUT,
drive the vehicle a short distance. During this test
drive be sure that the vehicle achieves at least 25 mph.
Brake to at least one complete stop and again acceler-
ate to 25 mph. (4) If a functional problem with the A.B.S. system is
determined while test driving a vehicle. Refer to the
Bendix Anti-Lock 6 Diagnostics Manual for required
test procedures and proper use of the DRB II tester.
ABS BRAKE SYSTEM ON VEHICLE SERVICE
The following are general precautions which
should be observed when servicing and diagnos-
ing the ABS system and/or other vehicle systems.
Failure to observe these precautions may result
in ABS system damage. (1) If welding work is to be performed on a vehicle
using an arc welder, the (CAB) should be disconnected
before the welding operation begins. (2) The (CAB) and modulator assembly 10 way con-
nector should never be connected or disconnected with
the ignition in the on position. (3) Some components of the ABS system are not
serviced separately and must be serviced as complete
assemblies. Do not disassemble any component which
is designated as non-serviceable.
CAUTION: Brake fluid will damage painted surfaces.
If brake fluid is spilled on any painted surfaces, wash
off with water immediately.
WHEEL SPEED SENSOR CABLES
Proper installation of the Wheel Speed Sensor Cables
is critical to continued system operation. Be sure that
cables are installed, routed and clipped properly. Fail-
ure to install speed sensor cables as shown in the on
car service section of this manual. May result in
contact with moving parts or over extension of cables,
resulting in component failure and an open circuit.
5 - 124 ANTI-LOCK 6 BRAKE SYSTEM Ä

MECHANICAL DIAGNOSTICS AND SERVICE
PROCEDURES
SPECIAL SERVICE TOOL
Some diagnostic procedures in this section require
the use of the DRB II diagnostics tester. The proper
application and procedures for the use of this tool are
described below.
DRB II DIAGNOSTIC TESTER Some of the diagnostic procedures that are ex-
plained in this section require the use of the DRB II
Diagnostics Tester to insure that proper diagnostics
are performed. Refer to those sections for proper test-
ing procedures and the DRB II operators manual for
its proper operational information.
INTERMITTENT FAULTS
As with virtually any electronic system, intermit-
tent faults in the ABS system may be difficult to ac-
curately diagnose. Most intermittent faults are caused by faulty elec-
trical connections or wiring. When an intermittent
fault is encountered, check suspect circuits for: (1) Poor mating of connector halves or terminals
not fully seated in the connector body. (2) Improperly formed or damaged terminals. All
connector terminals in a suspect circuit should be
carefully reformed to increase contact tension. (3) Poor terminal to wire connection. This requires
removing the terminal from the connector body to in-
spect. (4) Pin presence in the connector assembly
If a visual check does not find the cause of the
problem, operate the car in an attempt to duplicate
the condition and record the Fault code. Most failures of the ABS system will disable Anti-
Lock function for the entire ignition cycle even if the
fault clears before key-off. There are some failure
conditions, however, which will allow ABS operation
to resume during the ignition cycle in which a fail-
ure occurred. If the failure conditions are no longer
present. The following conditions may result in inter-
mittent illumination of the Amber Anti-Lock Warn-
ing Lamp. All other failures will cause the lamp to
remain on until the ignition switch is turned off. Cir-
cuits involving these inputs to the (CAB) should be
investigated if a complaint of intermittent warning
system operation is encountered. (1) Low system voltage. If Low System Voltage is
detected by the (CAB), the (CAB) will turn on the
Amber Anti-Lock Warning Lamp until normal sys-
tem voltage is achieved. Once normal voltage is seen
at the (CAB), normal operation resumes. (2) Anti-Lock relay. If the relay fails to make the
ground circuit connection or is an intermittent
ground. The (CAB) will turn on the Amber Anti-Lock
Warning Light. (3) Excess decay, an extended pressure decay pe-
riod, will turn on the Amber Anti-Lock Warning
Light until the vehicle comes to a complete stop. Additionally, any condition which results in inter-
ruption of electrical current to the (CAB) or modula-
tor assembly. May cause the Amber Anti-Lock
Warning Lamp to turn on intermittently.
ABS BRAKE SYSTEM DIAGNOSTIC FEATURES
ABS SYSTEM SELF DIAGNOSIS
The ABS system is equipped with a self diagnostic
capability which may be used to assist in isolation of
ABS faults. The features of the self diagnostics sys-
tem are described below.
START-UP CYCLE
The self diagnostic ABS start up cycle begins when
the ignition switch is turned to the on position. An
electrical check is completed on the ABS components.
Such as Wheel Speed Sensor Continuity and System
and other Relay continuity. During this check the
Amber Anti-Lock Light is turned on for approxi-
mately 1- 2 seconds. Further Functional testing is accomplished once
the vehicle is set in motion.
² The solenoid valves and the pump/motor are acti-
vated briefly to verify function.
² The voltage output from the wheel speed sensors is
verified to be within the correct operating range. If the vehicle is not set in motion within 3 minutes
from the time the ignition switch is set in the on po-
sition. The solenoid test is bypassed but the pump/
motor is activated briefly to verify that it is
operating correctly.
CONTROLLER ANTI-LOCK BRAKE (CAB)
Fault codes are kept in a Non-Volatile memory un-
til either erased by the technician using the DRB II
or erased automatically after 50 ignition cycles (key
ON-OFF cycles). The only fault that will not be
erased after 50 (KEY CYCLES) is the (CAB) fault. A
(CAB) fault can only be erased by the technician us-
ing the DRB II diagnostic tester. More than one fault
can be stored at a time. The number of key cycles
since the most recent fault was stored is also dis-
played. Most functions of the (CAB) and ABS system
can be accessed by the technician for testing and di-
agnostic purposes by using the DRB II.
LATCHING VERSUS NON-LATCHING ABS FAULTS
Some faults detected by the (CAB) are latching; the
fault is latched and (ABS) is disabled until the igni-
tion switch is reset. Thus ABS is disabled even if the
original fault has disappeared. Other faults are non-
latching; any warning lights that are turned on, are
only turned on as long as the fault condition exists.
Ä ANTI-LOCK 6 BRAKE SYSTEM 5 - 125

As soon as the condition goes away, the Anti-Lock
Warning Light is turned off. Although a fault code
will be set in most cases.
BENDIX ABS SYSTEMS DIAGNOSTICS
Bendix Anti-Lock 6 Brake System Diagnostics, be-
yond basic mechanical diagnostics, covered earlier in
this section. Are accomplished by using the DRB II
scan tool. See testing procedures outlined in the Ben-
dix Anti-Lock 6 Diagnostics Manual for the 1992
M.Y. vehicles. Please refer to the above mentioned manual for
any further electronic diagnostics and service proce-
dures that are required on the Bendix Anti-Lock 6
Brake System.
ON-CAR ABS BRAKE SYSTEM SERVICE
GENERAL SERVICE PRECAUTIONS
The following are general cautions which should be
observed when servicing the Anti-Lock brake system
and/or other vehicle systems. Failure to observe
these precautions may result in Anti-Lock Brake
System component damage. If welding work is to be performed on the vehicle,
using an electric arc welder, the (CAB) connector
should be disconnected during the welding operation. The (CAB) connector should never be connected or
disconnected with the ignition switch in the ON po-
sition. Many components of the Anti-Lock Brake System
are not serviceable and must be replaced as an as-
sembly. Do not disassemble any component which is
not designed to be serviced.
CHECKING BRAKE FLUID LEVEL
CAUTION: Only use brake fluid conforming to DOT
3 specifications, such as Mopar or Equivalent. Do
not use any fluid which contains a petroleum base.
Do not use a container which has been used for pe-
troleum based fluids or a container which is wet
with water. Petroleum based fluids will cause swell-
ing and distortion of rubber parts in the hydraulic
brake system. Water will mix with brake fluid, low-
ering the fluid boiling point. Keep all brake fluid
containers capped to prevent contamination. Re-
move the front cap of the master cylinder reservoir
and fill to the bottom of the split ring.
For the specific procedure for the inspection of
brake fluid level and adding of brake to the reser-
voir. Refer to the Service Adjustments Section in this
group of the service manual.
BLEEDING BENDIX ANTI-LOCK 6 BRAKE SYSTEM
The Anti-Lock Brake System must be bled anytime
air is permitted to enter the hydraulic system, due to
disconnection of brake lines, hoses of components. If the Modulator Assembly is removed from the ve-
hicle, both the Base Brake System and the Anti-Lock
Brake System must be bled using the appropriate
procedures. It is important to note that excessive air
in the brake system will cause a soft or spongy feel-
ing brake pedal. During bleeding operations, be sure that the brake
fluid level remains close to the FULL level in the
reservoir. Check the fluid level periodically during
the bleeding procedure and add DOT 3 brake fluid as
required. The Bendix Anti-Lock 6 Brake System must be
bled as two independent braking systems. The non
ABS portion of the brake system is to be bled the
same as any non ABS system. Refer to the Service
Adjustments section in this manual for the proper
bleeding procedure to be used. This brake system can
be either pressure bled or manually bled. The Anti-Lock portion of brake system MUST be
bled separately. This bleeding procedure requires the
use of the DRB II Diagnostic tester and the bleeding
sequence procedure outlined below.
ABS BLEEDING PROCEDURE (FIG. 1)
(1) Assemble and install all brake system compo-
nents on vehicle making sure all hydraulic fluid
lines are installed and properly torqued. (2) Bleed the base brake system. Using the stan-
dard pressure or manual bleeding procedure as out-
lined in the Service Adjustments section of this
service manual. To perform the bleeding procedure on the ABS
unit. The battery and acid shield must be removed
from the vehicle. Reconnect the vehicles battery, to
the vehicles positive and negative battery cables us-
ing jumper cables. This is necessary to allow access
to the 4 bleeder screws located on the top of the Mod-
ulator assembly. (3) Connect the DRB II Diagnostics Tester to the
diagnostics connector. Located behind the Fuse Panel
access cover on the lower section of the dash panel to
the left of the steering column. (It is a blue 6 way
connector). (4) Using the DRB II check to make sure the
(CAB) does not have any fault codes stored. If it does
remove them using the DRB II.
5 - 126 ANTI-LOCK 6 BRAKE SYSTEM Ä

WARNING: WHEN BLEEDING THE MODULATOR
ASSEMBLY WEAR SAFETY GLASSES. A CLEAR
BLEED TUBE MUST BE ATTACHED TO THE
BLEEDER SCREWS AND SUBMERGED IN A CLEAR
CONTAINER FILLED PART WAY WITH CLEAN
BRAKE FLUID. DIRECT THE FLOW OF BRAKE
FLUID AWAY FROM THE PAINTED SURFACES OF
THE VEHICLE. BRAKE FLUID AT HIGH PRESSURE
MAY COME OUT OF THE BLEEDER SCREWS,
WHEN OPENED.
When bleeding the Modulator Assembly. The fol-
lowing bleeding sequence MUSTbe followed to in-
sure complete and adequate bleeding of the brakes
hydraulic system. The Modulator Assembly can be
bled using a Manual bleeding procedure or standard
Pressure Bleeding Equipment. If the brake system is to be bled using pressure
bleeding equipment. Refer to Bleeding Brake System,
in the Service Adjustments section at the beginning
of this group, for proper equipment usage and proce-
dures.
MODULATOR ASSEMBLY BLEEDING SEQUENCE
1 SECONDARY SUMP
(1) Put a bleeder tube on the Secondary Sump
bleeder screw (Fig. 1). (2) Use a pressure bleeder, or have an assistant,
apply light and constant pressure on the brake pedal.
Loosen the Secondary Sump bleeder screw (Fig. 1). (3) Using the DRB II select the Actuate Valves
test mode. Then actuate the LF Build/Decay Valve. (4) Bleed the Secondary Sump. Until a clear air
free flow of brake fluid is evident in the clear hose
and no air bubbles appear in the container, or the
brake pedal bottoms. (5) Tighten the bleeder screw and release the
brake pedal. (6) Repeat steps 2 through 5 until a clear air free
flow of brake fluid is coming out of the Secondary
Sump bleeder screw. (7) Next select and actuate the RR Build/Decay
Valve. Again repeat steps 2 through 5 until a clean
air free flow of brake fluid is coming out of the Sec-
ondary Sump bleeder screw.
2 PRIMARY SUMP
(1) Put a bleeder tube on the Primary Sump
bleeder screw (Fig. 1). (2) Use a pressure bleeder, or have an assistant,
apply light and constant pressure on the brake pedal.
Loosen the Primary Sump bleeder screw (Fig. 1). (3) Using the DRB II select the Actuate Valves
test mode. Then actuate the RF Build/Decay Valve. (4) Bleed the Primary Sump. Until a clear air free
flow of brake fluid is evident in the clear hose and no
air bubbles appear in the container, or the brake
pedal bottoms. (5) Tighten the bleeder screw and release the
brake pedal. (6) Repeat steps 2 through 5 until a clear air free
flow of brake fluid is coming out of the Primary
Sump bleeder screw. (7) Next select and actuate the LR Build/Decay
Valve. Again repeat steps 2 through 5 until a clean
air free flow of brake fluid is coming out of the Pri-
mary Sump bleeder screw.
3 PRIMARY ACCUMULATOR
(1) Put a bleeder tube on the Primary Accumulator
bleeder screw. (Fig. 1) (2) Use a pressure bleeder, or have an assistant,
apply light and constant pressure on the brake pedal.
Loosen the Primary Accumulator bleeder screw (Fig.
1). (3) Using the DRB II select the Actuate Valves
test mode. Then actuate the RF/LR Isolation Valve. (4) Bleed the Primary Accumulator. Until a clear
air free flow of brake fluid is evident in the clear
hose and no air bubbles appear in the container, or
the brake pedal bottoms. (5) Tighten the bleeder screw and release the
brake pedal.
Fig. 1 Bleeding ABS Modulator Assembly
Ä ANTI-LOCK 6 BRAKE SYSTEM 5 - 127

junction block. Torque both lower mounting bracket
bolts to 28 N Im (250 in. lbs.)
(4) Reinstall the 4 hydraulic brake tubes to the
Modulator Assembly and torque the fittings to 16
N Im (145 in. lbs.).
(5) Reconnect the 10 way Modulator assembly con-
nector, and the delta P switch connector. (6) Lower the vehicle and install the 2 master cyl-
inder supply tubes to the Modulator Assembly.
Torque the Modulator Assembly fittings and the
master cylinder fittings to 16 N Im (145 in.lbs.).
(7) Torque the Modulator to fender splash shield
attaching bolt to 28 N Im (250 in. lbs.)
(8) Bleed the brake system. Refer to the Bleeding
Bendix Anti 6 Brake System in this section of the
manual for proper bleeding procedure. (9) Reinstall the acid shield and battery tray. Re-
install battery and connect battery cables.
MASTER CYLINDER AND POWER BOOSTER
REMOVAL AND INSTALLATION
If the Master Cylinder or the Power Booster need
to be serviced or replaced. Refer to Master Cylinder
or Power Brake Service section in this group of the
service manual. After servicing the Master Cylinder. Refer back to
this section of the service manual. For the appropri-
ate procedure and sequence, used to bleed the base
and ABS portion of the brake system
PROPORTIONING VALVES (FIG. 5)
CAUTION: Proportioning valves should never be
disassembled.
REMOVAL (1) Remove brake tube and fitting from proportion-
ing valve. (2) Remove proportioning valve from Modulator
Assembly.
INSTALLATION (1) Install proportioning valve on Modulator As-
sembly and tighten to 40 N Im (30 ft. lbs.) torque.
(2) Install brake tube on proportioning valve.
Tighten tube nut to 15 N Im (11 ft. lbs.) torque.
(3) Bleed the affected brake line, see Bleeding Ben-
dix Anti Lock 6 Brake System in this section of the
manual.
ELECTRONIC COMPONENTS
CONTROLLER ANTI-LOCK BRAKE (CAB)
REMOVAL
(1) Turn vehicle ignition off. (2) Disconnect the wiring harness connectors from
the Anti-Lock relays (Fig. 6). Relays will be removed
as part of the (CAB) bracket. (3) Disconnect the wiring harness 60 way connec-
tor (Fig. 6) from the Controller Anti-Lock Brake
Module (CAB). VERIFY THAT THE VEHICLE
IGNITION IS OFF BEFORE REMOVING THE
60 WAY CONNECTOR. (4) Remove the 2 (CAB) module bracket, to frame
rail mounting bolts (Fig. 6) (5) Remove the (CAB) module from the vehicle.
(6) Remove the 3 (CAB) to bracket mounting
screws and remove the (CAB) from the mounting
bracket (Fig. 7).
INSTALLATION
The Controller Anti-Lock Brake (CAB) module in-
stallation is done in the reverse order of removal.
REMOVAL/INSTALLATION OF SYSTEM AND WARNING LAMP RELAY
The System and Warning Lamp relay are both ser-
viced together as an assembly, with the mounting
bracket. They are mounted to a separate bracket that
is attached to the (CAB) bracket assembly (Fig. 8).
Fig. 5 ABS Proportioning Valve Identification
5 - 130 ANTI-LOCK 6 BRAKE SYSTEM Ä

REMOVE (1) Hold the relays with one hand, while pulling
strait down on the wiring harness connector. Until
the connectors are free from the relays (do not twist
the connectors). (2) Remove the screw (Fig. 9) holding the relay
bracket to the (CAB) bracket. Remove the relays and
bracket assembly
INSTALL
(1) Mount the relay and bracket assembly to the
(CAB) bracket, with the mounting screw (Fig. 9). (2) Holding the relays with one hand, push the
wiring harness connector strait onto the terminals of
the relay. Make sure the connector is fully seated
onto the terminals of the relay.
Fig. 6 Location Controller Anti-Lock Brake (CAB)
Fig. 7 (CAB) Removal From Mounting Bracket
Fig. 8 System Relay/Warning Lamp Relay Location
Fig. 9 Relay And Bracket Removal
Ä ANTI-LOCK 6 BRAKE SYSTEM 5 - 131

BRAKES
CONTENTS
page page
BENDIX ANTILOCK 4 BRAKE SYSTEM ...... 12
GENERAL INFORMATION .................. 1 HYDRAULIC SYSTEM CONTROL VALVES . . . 10
SERVICE ADJUSTMENTS
.................. 3
GENERAL INFORMATION
Throughout this group, references may be made to
a particular vehicle by letter or number designation.
A chart showing the break down of these designa-
tions is included in the Introduction Section at the
front of this service manual. Standard brake equipment consists of:
² Double pin floating caliper disc front brakes.
² Rear automatic adjusting drum brakes.
² Differential valve with a brake warning switch.
² Master cylinder.
² Vacuum power booster.
² Double pin floating caliper rear disc brakes are
available on some models. The Bendix Antilock 4 Brake System, uses the fol-
lowing standard brake system components. Master
cylinder, power booster, caliper assemblies, braking
discs, pedal assembly, brake lines and hoses. The
unique parts of the Bendix Antilock 4 Brake System
consists of the following components, modulator as-
sembly, unique proportioning valves, unique junction
block, wheel speed sensors, tone wheels, and elec-
tronic control unit. These components will be de-
scribed in detail in the Bendix Antilock 4 Brake
System section in this service manual supplement. The hydraulic system, (Fig. 1) on the Bendix Anti-
lock 4 brake system is diagonally split. Diagonally
split hydraulic brake systems, have the left front and
right rear brakes on one hydraulic system and the
right front and left rear on the other. A diagonally
split hydraulic brake system, will maintain half of
the vehicles braking capability if there is a failure in
either half of the hydraulic system. The Bendix Antilock 4 Brake System uses two
types of brake line fittings and tubing flares on the
modulator assembly (Fig. 1). The different types are
the ISO style and double wall style with their corre-
sponding fittings at different joint locations. See (Fig.
2) for specific joint locations and type of tubing
flares. CAUTION: When servicing a vehicle, sheet metal
screws, bolts or other metal fastener cannot be in-
stalled in a shock tower to take the place of any
original plastic clip. Also, NO holes can be drilled
into the front shock tower in the area shown in (Fig.
3), for installation of any metal fasteners into the
shock tower.
Because of minimum clearance in this area, (Fig.
3) installation of metal fasteners could damage the
coil spring coating and lead to a corrosion failure of
the spring. If a plastic clip is missing, lost or broken
during servicing a vehicle, replace only with the
equivalent part listed in the Mopar parts catalog.
Fig. 1 Identifying Hydraulic Brake Tubing Flares
Ä BRAKES 5 - 1

HYDRAULIC SYSTEM CONTROL VALVES INDEX
page page
General Information ....................... 10
Hydraulic System Service Procedures ......... 11 Pressure Differential Warning Light Switch
...... 10
GENERAL INFORMATION
All models equipped with a Bendix Antilock 4 Brake
System have 2 screw-in type proportioning valves.
There is 1 valve for each individual rear wheel hydrau-
lic brake line. The proportioning valves are mounted
directly into the rear brake outlet ports of the modula-
tor assembly (Fig. 1).
The proportioning valves limit brake pressure to the
rear brakes after a certain pressure (split point) is
reached. This improves front to rear brake balance
during normal braking. Screw-in proportioning valves can be identified by
numbers stamped on the body of the valve. The first
digit represents the slope, the second digit represents
the split (cut-in) point, and the arrow represents the
flow direction of the valve. Be sure numbers listed
on a replacement valve are the same as on the
valve that is being removed. See (Fig. 2) for detail of
the valve identification.
PRESSURE DIFFERENTIAL WARNING LIGHT
SWITCH
The hydraulic brake system, on vehicles equipped
with the Bendix Antilock 4 Brake System is split
diagonally. The left front and right rear brakes are on
one hydraulic system, and the right front and left
rear are on another. Both systems are routed
through, and hydraulically separated by the Pressure
Differential Switch (Fig. 3) mounted in the hydraulic brake tube junction block. The function of the Pressure
Differential Switch is to alert the driver of a malfunc-
tion in the brake hydraulic system.
If hydraulic pressure is lost in one system, the
warning light switch will activate the RED brake
warning light on the instrument panel, when the brake
pedal is depressed. At this point the brakes hydraulic
system requires immediate service. However, since the
brake systems are split diagonally the vehicle will
retain 50% of its stopping capability in the event of a
failure in either half. The warning light switch is the latching type. It
will automatically center itself after the repair is
made and the brake pedal is depressed.
Fig. 1 Rear Brake Proportioning Valve Location On Modulator Assembly
Fig. 2 ABS PROPORTIONING VALVE IDENTIFICA- TION
Fig. 3 Pressure Differential Warning Light Switch InJunction Block.
5 - 10 BRAKES Ä

The instrument panel bulb can be checked each
time the ignition switch is turned to the start posi-
tion or the parking brake is set.
HYDRAULIC SYSTEM SERVICE PROCEDURES
BRAKE WARNING SYSTEM
CHECKING BRAKE WARNING SWITCH UNIT
The Red Brake Warning light will come on when the
parking brake is applied with the ignition key turned
ON. The same light will also illuminate should one of
the two service brake hydraulic systems fail.
CAUTION:Make sure air does not enter the hydraulic
system during this test procedure. See bleeding with-
out a pressure bleeder at the beginning of this section
for master cylinder fluid level checking procedures.
To test the service brake warning system lamp.
Raise vehicle on a hoist and open a wheel cylinder
bleeder while a helper depresses the brake pedal and
observes the warning light.
If light fails to come on, inspect for a burned out bulb,
disconnected socket, or a broken or disconnected wire at
the switch. If the bulb is not burned out and the wire
continuity is not interrupted. Check the service brake
warning switch operation with a test lamp between the
switch terminal and a known good ground. Be sure to
fill master cylinder and bleed brake system after correc-
tion has been made, if necessary.
TESTING ANTILOCK PROPORTIONING VALVES
(1) Install one gauge and (TEE) between modula-
tor assembly and male end (Inlet) of proportioning
valve (Fig. 4). (2) Install second gauge at female end (Outlet) of
proportioning valve (Fig. 4).
(3) Have a helper exert pressure on brake pedal to
obtain and hold required pressure reading on the
valve inlet gauge. (4) Check reading on outlet gauge. If inlet and out-
let pressures do not agree with the following chart,
replace the valve. See (Fig. 3) for proportioning valve
identification.
BENDIX ANTILOCK 4 PROPORTIONING VALVE APPLICATIONS
BENDIX ANTILOCK 4 PROPORTIONING VALVE PRESSURES
Fig. 4 Tube Connections for ABS
Ä BRAKES 5 - 11