oil pressure CHEVROLET DYNASTY 1993 User Guide

The primary functions of the (CAB) are:
² (1) Detect wheel locking tendencies.
² (2) Control fluid modulation to the brakes while in
Anti-Lock mode.
² (3) Monitor the system for proper operation.
² (4) Provide communication to the DRB II while in
diagnostic mode. The (CAB) continuously monitors the speed of each
wheel, through the signals generated at the Wheel
Speed Sensors, to determine if any wheel is begin-
ning to lock. When a wheel locking tendency is de-
tected, the (CAB) will isolate the master cylinder
from the wheel brakes. This is done by activating the
Isolation Valves. The (CAB) then commands the ap-
propriate Build or Decay valves to modulate brake
fluid pressure in some or all of the hydraulic circuits.
The fluid used for modulation comes from the booster
servo circuit. The (CAB) continues to control pres-
sure in individual hydraulic circuits until a locking
tendency is no longer present. The (ABS) system is constantly monitored by the
(CAB) for proper operation. If the (CAB) detects a
fault, it can disable the Anti-Lock braking function.
Depending on the fault, the (CAB) will light one or
both of the brake warning lamps. The (CAB) contains a System Diagnostic Program
which triggers the brake system warning lamps
when a system fault is detected. Faults are stored in
a diagnostic program memory. There are 19 fault
codes that may be stored in the (CAB) and displayed
through the DRB II. These fault codes will remain in
the (CAB) memory even after the ignition has been
turned off. These fault codes will remain in memory
until they are cleared with the DRB II, or automati-
cally erased from the memory after (50) ignition
switch on/off cycles.
CONTROLLER ANTI-LOCK BRAKE (INPUTS)
² Four wheel speed sensors.
² Boost pressure transducer.
² Primary pressure transducer.
² Low fluid level switch.
² Differential pressure switch.
² Parking brake switch.
² Dual function pressure switch (warning pressure
only)
² Stop lamp switch.
² Ignition switch.
² System relay voltage.
² Ground.
² Low Accumulator
CONTROLLER ANTI-LOCK BRAKE (OUTPUTS)
²Ten modulator valves-3 decay, 3 build and 4 isola-
tion.
² Red Brake warning lamp.
² Amber Anti-Lock Warning Lamp.
² System relay actuation. ²
Diagnostic communication.
ABS SYSTEM DIAGNOSTIC CONNECTOR
The Bendix Anti-Lock system diagnostic connector
is located under the lower dash panel or in the area
of the fuse box (Fig. 8). The fuse box is located be-
hind the access panel that is on the bottom portion of
the dash panel, left of the steering column. The diag-
nostics connector is a blue 6 way connector.
ANTI-LOCK SYSTEM RELAYS AND WARNING
LAMPS
PUMP/MOTOR RELAY
Pump/Motor power is supplied by the Pump/Motor
Relay. The Pump/Motor relay is located inside the
Power Distribution Center (PDC). The relay coil is
energized by a ground from the Dual Function Pres-
sure Switch. See (Fig. 9) for the location of the pump/
motor relay in the (PDC).
SYSTEM RELAY
The (ABS) Modulator Valves and Anti-Lock Warn-
ing Lamp Relay are controlled through a System Re-
lay. The System relay is located on the top left inner
fender behind the headlight (Fig. 10). The system re-
lay provides power to the (CAB) for modulator valve
operation (pins 47 and 50) after the start-up cycle
when the ignition is turned on.
ANTI-LOCK WARNING LAMP RELAY
The Anti-Lock Warning Lamp is controlled by the
Yellow Light Relay. See (Fig. 10) for location behind
the left headlight. With the relay de-energized, the
lamp is lit. When the system relay is energized by
Fig. 8 A.B.S. Diagnostic Connector Location
5 - 82 ANTI-LOCK 10 BRAKE SYSTEM Ä

DRIVE-OFF CYCLE
The DRIVE-OFF CYCLE takes place when the ve-
hicle reaches about 3 miles per hour the first time af-
ter an ignition reset. During this test, the modulator
solenoid valves are activated briefly to test their
function. The DRIVE-OFF CYCLE will be bypassed
if you drive-off with the service brake pedal de-
pressed.
LATCHING VERSUS NON-LATCHING FAULTS
Some faults detected by the (CAB) are latching.
The fault is latched and (ABS) function is disabled
until the ignition switch is reset (turned OFF/ON).
Thus (ABS) function is disabled even if the original
fault has disappeared during the ignition cycle in
which it occurred. Other faults are non-latching; any
warning lights that are turned on are only on as long
as the fault condition exists. As soon as the condition
goes away. The Amber Anti-Lock Warning Light is
turned off. Although a fault code will be set in most
cases. (Example:low accumulator fault will not be
stored for a time of 2 minutes after the fault is de-
tected).
BENDIX ABS SYSTEMS DIAGNOSTICS
The Bendix Anti-Lock 10 Brake System diagnos-
tics. Beyond the basic mechanical diagnostics, sys-
tems and components covered earlier in this section,
is accomplished by using the DRB II diagnostic
tester. See testing procedures outlined in the Bendix
Anti-Lock 10 Diagnostics Manual for the 1993 M.Y. Please reference the above mentioned manual. For
any further diagnostic service procedures that are re-
quired on the Bendix Anti-Lock 10 Brake System, re-
quiring the use of the DRB II diagnostic tester.
ON CAR HYDRAULIC ABS COMPONENT SERVICE
WARNING: FAILURE TO FULLY DE-PRESSURIZE
THE HYDRAULIC ACCUMULATOR BEFORE PER-
FORMING HYDRAULIC SYSTEM SERVICE OPERA-
TIONS. COULD RESULT IN INJURY TO SERVICE
PERSONNEL AND OR DAMAGE TO PAINTED SUR-
FACES. SEE SECTION 2 FOR ADDITIONAL WARN-
INGS AND CAUTIONS.
GENERAL SERVICE PRECAUTIONS
The following are general precautions that should
be observed when servicing the Anti-Lock Brake Sys-
tem and/or other vehicle systems. Failure to observe
these precautions may result in Anti-Lock brake sys-
tem 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) or hydraulic assembly connector should
never be connected or disconnected with the ignition
switch in the ONposition.
Many components of the Anti-Lock brake system are
not serviceable and must be replaced as an assembly.
Do not attempt to disassemble any component
that is not designed to be a serviced component.
DE-PRESSURIZING HYDRAULIC ACCUMULA- TOR
The pump/motor assembly will keep the hydraulic
accumulator charged to approximately 11,032 and
13,790 kPa (1600 and 2000 psi) any time that the
ignition is in the ON position. The pump/motor assem-
bly cannot run if the ignition is off or if either battery
cable is disconnected. Unless otherwise specified, the hydraulic accumula-
tor should be de-pressurized before disassembling any
portion of the hydraulic system. The following proce-
dure should be used to relieve the pressure in the
hydraulic accumulator: (1) With ignition off, or either battery cable discon-
nected, pump the brake pedal a minimum of 40 times,
using approximately 222 N (50 lbs.) pedal force. A
noticeable change in pedal feel will occur, when the
accumulator is discharged. (2) When a definite increase in pedal effort is felt,
pump pedal a few additional times. This will insure
removal of all hydraulic pressure from the brake sys-
tem.
CHECKING BRAKE FLUID LEVEL
CAUTION: Use only brake fluid conforming to DOT 3
specifications such as Mopar Tor Equivalent. Do not
use any fluid in the brake hydraulic system, which
contains a petroleum base. Do not use a container
which has been used for petroleum based fluids or a
container that is wet with water. Petroleum based
fluids will cause swelling and distortion of rubber
parts in the hydraulic brake system and water will mix
with brake fluid, lowering the fluid boiling point. Keep
all brake fluid containers tightly capped to prevent
contamination.
The hydraulic assembly is equipped with a plastic
fluid reservoir, with a filter/strainer located in the filler
neck of each reservoir section. The Anti-Lock brake system requires that the hy-
draulic accumulator be de-pressurized when checking
the fluid level. To check the brake fluid level, the
following procedure should be used: (1) With the ignition off, de-pressurize the hydraulic
accumulator by applying the brake pedal approxi-
mately 40 times, using a pedal force of approximately
220 N (50 lbs.). A noticeable change in pedal feel will
occur when the accumulator is de-
Ä ANTI-LOCK 10 BRAKE SYSTEM 5 - 93

(7) Install high pressure hose to hydraulic assem-
bly (Fig. 7). Tighten the hose, to hydraulic assembly
fitting to 16 N Im (145 in. lbs)
(8) Fill hydraulic assembly brake fluid reservoir to
top of screen on the reservoir filter/strainer Fig. 9.
(9) Connect all electrical connectors to the hydrau-
lic assembly. (10) Bleed the entire brake system, see Bleeding
Brake System in this section of the Service Manual. (11) Replace all fresh air intake ducts, air cleaner
and washer bottle. (12) Check that the brake fluid in the hydraulic
assembly is at the correct level before moving vehicle
(Fig. 9). (See Checking Brake Fluid Level in this sec-
tion of the service manual).
BRAKE FLUID RESERVOIR
REMOVE
(1) Fully de-pressurize the hydraulic accumulator
by pumping brake pedal a minimum of 40 times. Use
procedure described in De-Pressurizing Hydraulic Ac-
cumulator listed earlier in this section.
WARNING: FAILURE TO DE-PRESSURIZE HYDRAU-
LIC ACCUMULATOR, BEFORE PERFORMING THIS
OPERATION, MAY RESULT IN PERSONAL INJURY
AND/OR DAMAGE TO PAINTED SURFACES.
(2) Remove as much brake fluid as possible from
the fluid reservoir, using a syringe or equivalent
method. (3) Using Oil Filter Band Wrench, Special Tool
C-4065 or equivalent loosen bladder accumulator. Then remove the bladder accumulator and brake
fluid spray shield from the hydraulic assembly (Fig.
10). Remove high pressure banjo fitting from hydrau-
lic assembly.
(4) Using needle nose pliers, remove the three
fluid reservoir retaining pins from the hydraulic as-
sembly (Fig. 11). Compress the barb on the opposite
side of retaining pin to prevent pin from breaking.
(5) Remove reservoir from hydraulic assembly by
CAREFULLY prying between reservoir and hydrau-
Fig. 9 ABS Fill Level On Filter/Strainer
Fig. 10 Removing Bladder Accumulator
Fig. 11 Remove Reservoir Retaining Pins
Ä ANTI-LOCK 10 BRAKE SYSTEM 5 - 99

lic assembly with a blunt prying tool (Fig. 12). Use a
rocking motion to help disengage reservoir from
grommets while prying. BE EXTREMELY CARE-
FUL TO AVOID DAMAGING OR PUNCTURING
RESERVOIR DURING THIS PROCEDURE.
(6) Remove the brake fluid level sensor switch
from the reservoir. Remove switch by compressing
the retaining barbs (Fig. 13) on the end of the switch
and then slide switch out of the brake fluid reservoir
(Fig. 14) (7) Using fingers, remove the 3 reservoir grommets
(Fig. 14) from the hydraulic assembly or reservoir, and
discard. Grommets must not to be reused when
reservoir is installed on hydraulic assembly.
INSTALL (1) Thoroughly lubricate the new reservoir grom-
mets with clean brake fluid and install on reservoir
outlet ports (Fig. 14). The new reservoir grommets
supplied with reservoir, must ALWAYS be used. (2) Install brake fluid level switch into brake fluid
reservoir (FIG. 14). (3) Press reservoir into hydraulic assembly BY
HAND , using a rocking motion to help seat reservoir
into hydraulic assembly. Be sure that grommets are
fully seated in the hydraulic assembly. DO NOT AT-
TEMPT TO POUND RESERVOIR INTO HY-
DRAULIC ASSEMBLY, USING A HAMMER. (4) Using needle nose pliers, install the 3 brake fluid
reservoir to hydraulic assembly retaining pins (Fig.
11). Make sure that pins are fully installed with barbs
extending past reservoir on opposite side. (5) Reinstall the high pressure hose, banjo fitting
onto the hydraulic assembly and torque the fitting to
13 N Im (10.0 ft.lbs).
(6) Install the brake fluid spray shield and bladder
accumulator onto the hydraulic assembly. Install the
bladder accumulator by hand to be sure it does not bet
cross threaded. Be sure that the O-Ring on the
bladder accumulator is fully seated into the hy-
draulic assembly. (7) Using Oil Filter Band Wrench, Special Tool C-
4065 or equivalent, (Fig. 10) torque the bladder accu-
mulator to 48 N Im (35 ft. lbs.)
Fig. 12 Remove Reservoir From Hydraulic Assembly
Fig. 13 Fluid Switch Retaining Barbs
Fig. 14 Remove Brake Fluid Level Switch
5 - 100 ANTI-LOCK 10 BRAKE SYSTEM Ä

WARNING: FAILURE TO DE-PRESSURIZE HYDRAU-
LIC ASSEMBLY/ACCUMULATOR PRIOR PERFORM-
ING THIS OPERATION. MAY RESULT IN PERSONAL
INJURY AND/OR DAMAGE TO PAINTED SURFACES
OF THE VEHICLE.
(2) Using Oil Filter Band Wrench, Special Tool
C-4065 or equivalent loosen bladder accumulator.
Then remove the bladder accumulator and brake
fluid shield from the hydraulic assembly (Fig. 17).
INSTALL
(1) Install the brake fluid spray shield onto the hy-
draulic accumulator (Fig. 1). (2) Install the bladder accumulator onto the hy-
draulic assembly by hand. Be sure that the O-Ring
on the bladder accumulator is fully seated into the
hydraulic assembly. (3) Using Oil Filter Band Wrench, Special Tool
C-4065 or equivalent, (Fig. 17) torque the bladder ac-
cumulator to 48 N Im (35 ft. lbs.)
(4) Turn ignition switch to the run position to en-
ergize the pump/motor assembly and pressurize hy-
draulic system. Check for leakage at the hydraulic
assembly to hydraulic bladder accumulator fitting. (5) Again de-pressurize accumulator by pumping
brake pedal a minimum of 40 times. Use procedure
described in De-Pressurizing Hydraulic Accumulator
in this section of the service manual. (6) Then check the brake fluid level in the hydrau-
lic assembly reservoir. If brake fluid level is low, fill
reservoir to proper level (Fig. 15) with Mopar tbrake
fluid or equivalent conforming to DOT 3 require-
ments.PROPORTIONING VALVES (FIG. 18)
CAUTION: Proportioning valves should never be dis-
assembled or repaired in any way, repair is by re-
placement only.
REMOVE (1) Fully de-pressurize the hydraulic accumulator by
pumping brake pedal a minimum of 40 times. Use
procedure described in De-Pressurizing Hydraulic Ac-
cumulator listed earlier in this section.
WARNING: FAILURE TO FULLY DE-PRESSURIZE THE
HYDRAULIC ASSEMBLY/ACCUMULATOR PRIOR TO
REMOVING THE PROPORTIONING VALVE. MAY RE-
SULT IN PERSONAL INJURY AND/OR DAMAGE TO
PAINTED SURFACES OF THE VEHICLE.
(2) Remove fresh air intake ducts and air cleaner.
(3) Remove pressure and return hose (Fig. 5) from
hydraulic unit. (See Pressure and Return Hose Section
For Proper Removal Procedure). (4) Remove brake tube from the proportioning valve
that requires servicing. (5) Remove proportioning valve requiring service
from the hydraulic assembly (Fig. 19).
INSTALL (1) Install proportioning valve on hydraulic assem-
bly and tighten to 40 N Im (30 ft. lbs.) torque.
(2) Install brake tube on proportioning valve.
Tighten tube nut to 16 N Im (145 in. lbs.) torque.
(3) Install hydraulic pressure and return hoses.
Torque pressure hose to hydraulic assembly fitting to
16 N Im (145 in. lbs). Torque return hose to metal tube
hose clamp to 1 N Im (10 in. lbs.).
(4) Install fresh air intake duct and air cleaner.
(5) Bleed the affected brake line, see Bleeding Brake
System in this section.
Fig. 17 Remove And Install Bladder Accumulator
Fig. 18 ABS Proportioning Valve
5 - 102 ANTI-LOCK 10 BRAKE SYSTEM Ä

CAUTION: Do not insert dual function pressure
switch into hydraulic assembly using the socket
and ratchet. Cross threading of the switch may oc-
cur. (1) Install the dual function pressure switch into
the hydraulic assembly by hand until the O-ring
seals are seated. (2) Using Socket, Special Tool 6607, (Fig. 10)
torque the dual function pressure switch into the hy-
draulic assembly to 12 N Im (9 ft. lbs.).
(3) Connect the wiring harness connectors (Fig. 9)
onto the dual function pressure switch and the boost
pressure transducer. Be sure the locking tabs on the
connectors are fully engaged on the switches. (4) Lower the vehicle.
(5) Turn the ignition switch to the on position and
let the system pressurize. Check for any leaks at the
dual function pressure switch. (6) Fully de-pressurize the hydraulic assembly a
second time. This will purge any air out that may
have entered hydraulic assembly when the switch
was removed. Turn the ignition switch to the on po-
sition and let the system pressurize again. (7) Road test vehicle to insure that the brake sys-
tem is performing correctly.
PRIMARY PRESSURE TRANSDUCER
REMOVE
WARNING: FAILURE TO FULLY DE-PRESSURIZE
THE HYDRAULIC BLADDER ACCUMULATOR PRIOR
TO REMOVING PRIMARY PRESSURE TRANS-
DUCER. WILL RESULT IN PERSONAL INJURY
AND/OR DAMAGE TO PAINTED SURFACES OF THE
VEHICLE.
To remove primary pressure transducer (Fig. 11),
from hydraulic assembly, removal of hydraulic as-
sembly from vehicle is notrequired.
(1) Fully de-pressurize the hydraulic accumulator
by pumping brake pedal a minimum of 40 times. Use
procedure described in De-Pressurizing Hydraulic Ac-
cumulator listed earlier in this section. (2) Remove as much brake fluid as possible from
the brake fluid reservoir, using a syringe or equiva-
lent method. (3) Using oil filter band wrench, Special Tool
C-4065 or equivalent, (Fig. 12) loosen bladder accu-
mulator. Then remove bladder accumulator and
brake fluid spray shield from hydraulic assembly. (4) Remove high pressure banjo fitting (Fig. 13)
from hydraulic assembly. (5) Using needle nose pliers, remove the 3 fluid
reservoir retaining pins from the hydraulic assembly
(Fig. 14). Compress barb on opposite side of retaining
pin, to prevent pin from breaking. CAUTION: Be extremely careful during the following
procedure to avoid damaging or puncturing brake
fluid reservoir during its removal.
(6) Remove brake fluid reservoir from hydraulic
assembly by carefullyprying between reservoir and
hydraulic assembly using a blunt pry bar (Fig. 15).
Use a rocking motion to help disengage reservoir
from grommets while prying. (7) Remove brake fluid level sensor from reservoir
and remove fluid reservoir from vehicle. (8) Remove hydraulic assembly wiring harness
connector from the primary pressure transducer (Fig.
16).
Fig. 11 Primary Pressure Transducer Location On Hydraulic Assembly
Fig. 12 Removing Bladder Accumulator
5 - 108 ANTI-LOCK 10 BRAKE SYSTEM Ä

(7) Using needle nose pliers, install the 3 brake fluid
reservoir to hydraulic assembly retaining pins (Fig.
14). Be sure retaining pins are fully installed with
barbs extending out past reservoir on opposite
side. (8) Install high pressure hose banjo fitting onto
hydraulic assembly and install banjo fitting attaching
bolt. Torque banjo fitting to hydraulic assembly banjo
bolt to 13 N Im (10 ft. lbs.).
(9) Install brake fluid spray shield onto hydraulic
assembly. Install bladder accumulator into hydraulic
assembly by hand (using care not to cross thread
accumulator) until O-ring seal is fully seated into
hydraulic assembly. (10) Using Oil Filter Band Wrench, Special Tool
C-4065 or equivalent, (Fig. 12) torque bladder accumu-
lator to 48 N Im (35 ft. lbs.).
(11) Fill hydraulic assembly fluid reservoir to the top
of the screen on the filter rainer. Use only fresh clean
brake fluid conforming to DOT 3 requirements, such as
Mopar tor equivalent.
(12) Bleed the brake hydraulic system using proce-
dure shown in Bleeding Brake System in this section of
the service manual.
DIFFERENTIAL PRESSURE SWITCH
REMOVE
WARNING: FAILURE TO FULLY DE-PRESSURIZE THE
HYDRAULIC BLADDER ACCUMULATOR PRIOR TO
REMOVING DIFFERENTIAL PRESSURE SWITCH.
WILL RESULT IN PERSONAL INJURY AND/OR DAM-
AGE TO PAINTED SURFACES OF THE VEHICLE.
To remove the differential pressure switch (Fig. 18),
from the hydraulic assembly, removal of the hydraulic
assembly from the vehicle is notrequired. (1) De-pressurize hydraulic bladder accumulator on
hydraulic assembly by pumping the brake pedal a
minimum of 40 times. Refer to the procedure as de-
scribed in De-Pressurizing Hydraulic Accumulator
listed earlier in this section. (2) Disconnect the hydraulic assembly wiring har-
ness connector from the primary pressure transducer
(Fig. 19).
(3) Disconnect differential pressure switch wiring
harness connector from hydraulic assembly wiring
harness (Fig. 19). Do not attempt to remove wiring
harness from differential pressure switch. (4) Raise vehicle on a frame contact type hoist. See
Hoisting in the Lubrication And Maintenance section
of this manual, for the required lifting procedure to be
used for this vehicle. (5) Using a long extension and Socket, Special Tool
6684 loosen and remove differential pressure switch
from bottom of hydraulic assembly (Fig. 20)
Fig. 18 Differential Pressure Switch Location
Fig. 19 Primary Pressure Transducer And Differen- tial Pressure Switch Wiring Harness Connectors
Fig. 17 Primary Pressure Transducer Removal And Replacement
5 - 110 ANTI-LOCK 10 BRAKE SYSTEM Ä

Lamp Relay opens the Anti-Lock Warning Lamp Re-
lay switch. This breaks the ground path to the Am-
ber Anti-Lock Warning Lamp and the light is turned
off. The (CAB) by itself, also has the ability to turn on
the Amber Anti-Lock Warning Lamp. The (CAB) can
turn on the Amber Anti-Lock Warning Lamp by pro-
viding a ground at pin 15.
ANTI-LOCK WARNING LAMP ON
System Relay and Anti-Lock Warning Lamp
Relay De-Energized. When the Amber Anti-Lock Warning Lamp is on,
there is no electrical current flow from the (CAB) at
pin 57. The System Relay coil is NOT energized. No
electrical current flows to pin 47 and 41 (modulator
valve power), or to the Anti-Lock Warning Lamp Re-
lay coil. Thus, the Amber Anti-Lock Warning Lamp
is not energized. The Amber Anti-Lock Warning Lamp is grounded through the Anti-Lock Warning
Lamp Relay contacts. The Amber Anti-Lock Warning
Lamp is turned on.
HYDRAULIC CIRCUITS AND VALVE OPERATION
Through the following operation descriptions and
diagrams. The function of the various hydraulic con-
trol valves in the ABS system will be described. The
fluid control valves mentioned below, control the flow
of pressurized brake fluid to the wheel brakes during
the different modes of Anti-Lock braking. For explanation purposes we will assume all speed
sensors are sending the same wheel speed informa-
tion, requiring the same hydraulic fluid modulation
at the same rate.
NORMAL BRAKING
ISOLATION VALVES
Open to primary and secondary master cylinder
fluid supply (Fig. 1)
BUILD/DECAY VALVES Closed (Fig. 1)
The brake pedal is applied. The travel of the brake
pedal closes primary and secondary circuits from the
master cylinder fluid supply. Brake fluid from the
primary and secondary circuits flows through the
open isolation valves, through the build/decay valves
to the wheel brakes.
ABS BRAKING-BUILD PRESSURE
ISOLATION VALVES
Closed, isolating wheel brakes from master cylin-
der primary and secondary fluid supply. Through
open build valves (Fig. 2).
BUILD/DECAY VALVES Open (Fig. 2)
Fig. 11 Pump Motor Relay W/O Power Distribution Center
Ä ANTI-LOCK 6 BRAKE SYSTEM 5 - 121

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

SERVICE ADJUSTMENTS INDEX
page page
Bleeding Bendix Antilock 4 Brake System ....... 3
Master Cylinder Fluid Level .................. 3 Testing for Fluid Contamination
............... 4
MASTER CYLINDER FLUID LEVEL
Check master cylinder reservoir brake fluid level a
minimum of two times a year. Master cylinder reservoirs are marked with the
words fill to bottom of rings indicating proper fluid
level (Fig. 4). Use only Mopar tbrake fluid or an equivalent from
a sealed container. Brake fluid must conform to DOT
3, specifications. Use only brake fluid that was stored in a tightly-
sealed container.
CAUTION: DO NOT use petroleum-based fluid be-
cause seal damage in the brake system will result.
CAUTION: DO NOT use brake fluid with a lower
boiling point, as brake failure could result during
prolonged hard braking.
If necessary add only an approved brake fluid to
master cylinder fluid reservoir until filled to the
proper level. Correct master cylinder fluid reservoir
fill level is to the bottom of the primary reservoir
split ring.
BLEEDING BENDIX ANTILOCK 4 BRAKE SYSTEM
CAUTION: When bleeding the Bendix Antilock 4
Brake System hydraulic circuits, refer to the Bendix
Antilock 4 Brake System bleeding procedure in this
service manual supplement.
BASE BRAKE SYSTEM BLEEDING PROCEDURE
CAUTION: The base brakes hydraulic system, on a
vehicle equipped with a Bendix Antilock 4 Brake
System, can NOT be bled using a brake hydraulic
system pressure bleeder. This type of pressure
bleeding equipment, does not develop the pressure
required in the brake hydraulic system, to ade-
quately bleed all trapped air. The only approved
method of bleeding the base brakes hydraulic sys-
tem, on vehicles equipped with a Bendix Antilock 4
Brake System, is the manual procedure of pressur-
izing the hydraulic system using constant moderate
to heavy foot pressure on the brake pedal.
When bleeding brake hydraulic systems, some air
may be trapped in brake lines or valves as far as ten
feet from the bleeder screw (Fig. 5). Therefore, it is
essential to have a fast flow of a large volume of
brake fluid when bleeding the brakes. This will en-
sure all trapped air is completely bled out of the
brakes hydraulic system.
To bleed the base brake hydraulic system. Attach a
clear plastic hose to the bleeder screw starting at the
right rear wheel and feed the hose into a clear jar
containing fresh brake fluid (Fig. 6). The following wheel sequence when bleeding the
base brakes hydraulic system should be used. This
sequence will ensure adequate removal of all trapped
air from the hydraulic system.
² Right rear wheel
² Left front wheel
Fig. 4 Master Cylinder Fluid Level
Fig. 5 Trapped Air in Brake Line
Ä BRAKES 5 - 3