low oil pressure CHEVROLET DYNASTY 1993 User Guide
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Page 243 of 2438
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
Page 252 of 2438
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
Page 258 of 2438
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
Page 271 of 2438
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
Page 276 of 2438
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
Page 289 of 2438
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
Page 290 of 2438
² Left rear wheel
² Right front wheel
(1) Pump brake pedal three or four times, then
hold a constant moderate to heavy foot pressure on
the brake pedal.
CAUTION: Just cracking the bleeder screw often re-
stricts fluid flow, and a slow, weak fluid discharge
will NOT get all the air out.
(2) Open bleeder screw (Fig. 7) at least 1 full turn.
When bleeder screw opens, brake pedal will drop to
the floor. (3) Close bleeder screw. Release brake pedal off
floor only afterbleeder screw is completely closed.
(4) Repeat steps 1 through 3, four or five times, at
each bleeder screw. This should pass a sufficient
amount of brake hydraulic fluid to expel all trapped
air. Be sure to monitor brake fluid level in master
cylinder fluid reservoir. It must stay at a level that
will not allow air to re-enter the hydraulic system
through the master cylinder. After 4 to 8 ounces of hydraulic fluid has been bled
from the bleeder screw at this wheel, and an air-free
flow has been maintained, a good bleed is indicated. Repeat above procedure at all other remaining
bleeder screws, while checking brake pedal for travel. If brake pedal travel is still excessive or has
not improved, enough brake fluid has not passed
through the hydraulic system to expel all trapped
air. Be sure to monitor brake fluid level in the mas-
ter cylinder brake fluid reservoir. It must stay at the
proper level so air will not be allowed to re-enter the
brake system through the master cylinder. Test drive vehicle to be sure brakes are operating
correctly and that pedal is not spongy.
TESTING FOR FLUID CONTAMINATION
Indications of fluid contamination are swollen or
deteriorated rubber parts. Swollen rubber parts indicate the presence of petro-
leum in the brake fluid. To test for contamination, put small amount of
drained brake fluid in clear glass jar. If fluid sepa-
rates into layers, there is mineral oil contamination. If contaminated, drain and thoroughly flush sys-
tem. Replace master cylinder, proportioning valve,
caliper seals, wheel cylinder seals and all hoses.
Fig. 6 Proper Method for Purging Air From Brake System
Fig. 7 Open Bleeder Screw at Least One Full Turn(Typical)
5 - 4 BRAKES Ä
Page 306 of 2438
ANTILOCK WARNING LAMP DIODE
The Warning Lamp Relay on the Bendix Antilock
4 Brake System has been replaced with a diode. The
diode is used to control the function of the warning
lamp and is located inside the CAB module wiring
harness. The diode is a replaceable component of the
wiring harness, and will not require replacement of
the entire wiring harness if only the diode is diag-
nosed to have failed. When the system relay is de-energized, the Anti-
lock warning lamp will be lit. This will occur because
a ground path exists for the Antilock warning lamp
through the Antilock warning lamp diode and the
system relay armature. When the system relay is en-
ergized by the CAB, the system relay armature will
no longer provide a ground and the lamp will turn
off. Thus, the lamp will be lit if either the CAB is
disconnected or a system fault causes the Antilock to
be turned off.
PUMP/MOTOR RELAY
Pump/Motor power is supplied by the Pump/Motor
Relay. The Pump/Motor Relay is either mounted on
the left front inner fender shield, or the front of the
left shock tower. The mounting location is dependent
on whether the vehicle is or is not equipped with a
power distribution center. See (Fig. 11 and 12) for
specific mounting locations.
ANTILOCK WARNING LAMP OFF
System Relay Energized
From pin 57, the CAB energizes the Antilock sys-
tem relay coil, thus the electrical current flow in the
coil closes the system relay. Then electrical current
is provided to pins 47 and 41 of the CAB to provide
power to the modulator valves. The CAB turns off the Amber Antilock Warning
Lamp by breaking the ground path through pin 15 of
the CAB.
ANTILOCK WARNING LAMP ON
System Relay De-Energized.
When the Amber Antilock Warning Lamp is on,
there is no electrical current flow from the CAB at
pin 57 and the System Relay coil is NOT energized.
No electrical current flows to pin 47 and 41 (modula-
tor valve power), or to the Antilock Warning Lamp
diode. Thus, the Amber Antilock Warning Lamp is
not energized. The Amber Antilock Warning Lamp is
now grounded through the Antilock Warning Lamp
diode and pin 15 of the CAB turning on the Amber
Antilock Warning Lamp.
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 Antilock 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
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
master cylinder primary and secondary circuits flows
through the build/decay valves to the wheel brakes.
ABS BRAKING-BUILD PRESSURE
BUILD/DECAY VALVES
Open (Fig. 2)
Fig. 11 Pump Motor Relay Location On AA Body W/O Power Distribution Center
Fig. 12 Pump Motor Relay Location On AJ BodyWith Power Distribution Center
5 - 20 ANTILOCK 4 BRAKE SYSTEM Ä
Page 311 of 2438
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.
As soon as the condition goes away, the Antilock
Warning Light is turned off. Although a fault code
will be set in most cases.
BENDIX ANTILOCK 4 BRAKE SYSTEM DIAGNOSTICS
Bendix Antilock 4 Brake System Diagnostics, be-
yond basic mechanical diagnostics, covered earlier in
this section, are accomplished by using the DRB scan
tool. See testing procedures outlined in the 1994 Ben-
dix Antilock 4 Diagnostics Manual. Please refer to the above mentioned manual for
any further electronic diagnostics and service proce-
dures that are required on the Bendix Antilock 4
Brake System.
ON-CAR ABS BRAKE SYSTEM SERVICE
GENERAL SERVICE PRECAUTIONS
The following are general cautions which should be
observed when servicing the Bendix Antilock 4
Brake System and other vehicle electronic systems.
Failure to observe these precautions may result in
Antilock Brake System component damage. If welding work is to be performed on a vehicle us-
ing an electric arc welder, disconnect the 60 way wir-
ing harness connector from the CAB, prior to
performing the welding operation. The wiring harness connector should never be con-
nected or disconnected from the CAB with the igni-
tion key in the ON or Run position. (3) Most components making up the assemblies of
the Bendix Antilock 4 Brake System can not be ser-
viced separately from those assemblies. This will re-
quire replacement of the complete assembly for the
servicing of these components. Do not disassemble
any component from an assembly which is desig-
nated as non-serviceable.
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 boiling point of the brake fluid, possibly causing brake fluid to boil resulting in brake fade.
Keep all brake fluid containers capped to prevent
contamination. Remove 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 ANTILOCK 4 BRAKE SYSTEM
The base brakes and Antilock Brake System must
be bled anytime air is permitted to enter the hydrau-
lic system, due to disconnection of brake lines, hoses
or components. If the Antilock Modulator Assembly is removed
from the vehicle, both the Base Brake System and
the Antilock Brake System must be bled using the
appropriate procedure. It is important to note that
excessive air in the brake system will cause a soft or
spongy feeling brake pedal. During brake bleeding operations, ensure that
brake fluid level remains close to the FULL level in
the reservoir. Check brake fluid level periodically
during bleeding procedure, adding DOT 3 brake fluid
as required.
CAUTION: The base brake and Antilock brake hy-
draulic systems, on the Bendix Antilock 4 Brake
System, can NOT be bled using any type of brake
pressure bleeding equipment. This type of bleeding
equipment does not develop the pressure required
in the brake hydraulic system, to adequately bleed
all trapped air. The only approved method for bleed-
ing air out of the hydraulic system on vehicles
equipped with the Bendix Antilock 4 Brake System,
is the manual procedure of pressurizing the hydrau-
lic system using constant, moderate to heavy foot
pressure on the brake pedal.
The Bendix Antilock 4 Brake System must be bled
as two independent brake systems. The non ABS por-
tion of the brake system is to be bled the same as
any non ABS system. Refer to the Service Adjust-
ments section in this manual for the proper bleeding
procedure to be used. The Bendix Antilock 4 Brake
System can only be bled using a manual method of
pressurizing the brakes hydraulic system. The Antilock portion of brake system MUST be
bled separately. This bleeding procedure requires the
use of the DRB Diagnostic tester and the bleeding se-
quence procedure outlined below.
Ä ANTILOCK 4 BRAKE SYSTEM 5 - 25
Page 333 of 2438
MANUAL TRANSAXLE CLUTCH
CONTENTS
page page
CLEANING PRECAUTIONS ................. 6
CLUTCH CABLE MECHANISM .............. 1
CLUTCH CABLE REPLACEMENT ............ 2
CLUTCH CHATTER COMPLAINTS ........... 1
CLUTCH DISC REPLACEMENT ............. 5
CLUTCH PEDAL NOISE/POP ............... 2 CLUTCH PEDAL POSITION SWITCH
......... 4
EXCESSIVE CLUTCH SPIN TIME/CLASH INTO REVERSE COMPLAINTS ............ 1
GENERAL INFORMATION .................. 1
RELEASE BEARING AND FORK ............. 6
GENERAL INFORMATION
Throughout this group, references may be made to
a particular vehicle by letter or number designation.
A chart showing the breakdown of these designations
is included in the Introduction Section at the front of
this service manual. The clutch used in all models are a single, dry disc
type with no adjustment for wear being provided in
the clutch itself. The clutch pedal is connected to the release shaft
through a cable and lever. The upper end of the clutch pedal pivots in the
pedal bracket on two nylon bushings. These bushings
do not require periodic lubrication.
CLUTCH CHATTER COMPLAINTS
For all clutch chatter complaints, do the following:
(1) Check for loose, misaligned, or broken engine
and transmission mounts. If present, they should be
corrected at this time. Test vehicle for chatter. If
chatter is gone, there is no need to go any further. If
chatter persists: (2) Check to see if clutch cable routing is correct
and operates smoothly. (3) Check for loose connections in drive train. Cor-
rect any problems and determine if clutch chatter
complaints has been satisfied. If not, (4) Remove transaxle. See Group 21, Manual Tran-
saxle, for procedure. (5) Check to see if the release bearing is sticky or
binding. Replace bearing, if needed. (6) Check linkage for excessive wear on bushings.
Replace all worn parts. A small amount of bearing
grease between the release shaft bushings and the
shaft is beneficial, but not required. (7) Check flywheel and clutch pressure plate for
contamination (dirt, oil) or scored. Replace flywheel
and/or pressure plate, if required. (8) Check to see if the clutch disc hub splines are
damaged. Replace with new disc. (9) Check input shaft splines for damage. Replace
if necessary. (10) Check for uneven wear on clutch fingers.
EXCESSIVE CLUTCH SPIN TIME/CLASH INTO
REVERSE COMPLAINTS
For all excessive clutch spin time/clash into reverse
complaints, do the following: (1) Depress clutch pedal to floor and hold. After
three seconds, shift to reverse. If clash is present,
clutch has excessive spin time. (2) Remove transaxle. See Group 21, Manual Tran-
saxle, for procedure. (3) Check the input shaft spline, clutch disc splines
and release bearing for dry rust. If present, clean
rust off and apply a light coat of bearing grease to
the input shaft splines. Apply grease on the input
shaft splines only where the clutch disc slides. (4) Check to see if the clutch disc hub splines are
damaged, replace with new disc if required. (5) Check the input shaft for damaged splines. Re-
place as necessary. (6) Check for excessive clutch disc runout or
warpage. (7) Install clutch assembly and transaxle.
CLUTCH CABLE MECHANISM
The manual transaxle clutch release system has a
unique self-adjusting mechanism to compensate for
clutch disc wear. This adjuster mechanism is located
within the clutch pedal. The preload spring main-
tains tension on the cable. This tension keeps the
clutch release bearing continuously loaded against
the fingers of the clutch cover assembly. When the pedal is depressed, teeth on the adjuster
and the positioner engage and pull the release cable.
A spring located behind the adjuster ensures proper
tooth engagement. When the pedal is released, the adjuster contacts
the bumper. This separates the adjuster and posi-
tioner teeth, allowing the preload spring to function.
Ä MANUAL TRANSAXLE CLUTCH 6 - 1