1993 CHEVROLET PLYMOUTH ACCLAIM warning light

COMPONENT AND SYSTEM INDEX
Name Group-page Name Group-page
BRAKES ..................................5-1
BENDIX ANTILOCK 4 BRAKE SYSTEM ...........5-12
ABS BRAKE SYSTEM DIAGNOSTIC FEATURES.......5-24
ABS SYSTEM SELF DIAGNOSIS................ 5-24
BENDIX ANTILOCK 4 BRAKE SYSTEM DIAGNOSTICS....5-25
CONTROLLER ANTILOCK BRAKE CAB............. 5-24
LATCHING VERSUS NON-LATCHING ABS FAULTS.......5-25
START-UP CYCLE........................ 5-24
ABS COMPUTER SYSTEM SERVICE PRECAUTIONS....5-23
ABS GENERAL SERVICE PRECAUTIONS........... 5-23
ABS BRAKE SYSTEM ON VEHICLE SERVICE.........5-23
TEST DRIVING ABS COMPLAINT VEHICLES.......... 5-23
WHEEL SPEED SENSOR CABLES............... 5-23
ANTILOCK BRAKE SYSTEM COMPONENTS..........5-16
BUILD/DECAY VALVES..................... 5-16
FLUID SUMPS.......................... 5-17
HYDRAULIC SPRING ACCUMULATOR.............5-17
MODULATOR ASSEMBLY.................... 5-16
PRESSURE DIFFERENTIAL SWITCH..............5-17
PROPORTIONING VALVES................... 5-17
PUMP/MOTOR ASSEMBLY...................5-17
SHUTTLE ORIFICE........................ 5-16
WHEEL SPEED SENSORS....................5-18
ANTILOCK BRAKE SYSTEM DEFINITIONS..........5-14
ANTILOCK BRAKES OPERATION AND PERFORMANCE. . . 5-15
ANTILOCK BRAKE SYSTEM OPERATION............ 5-15
PEDAL FEEL........................... 5-15
TIRE NOISE & MARKS.....................5-15
ANTILOCK SYSTEM RELAYS AND WARNING LAMPS. . . 5-19
ANTILOCK WARNING LAMP DIODE..............5-20
Antilock Warning Lamp Off................... 5-20
Antilock Warning Lamp On...................5-20
PUMP/MOTOR RELAY...................... 5-20
SYSTEM RELAY......................... 5-19
BENDIX ANTILOCK 4 BRAKE SYSTEM DIAGNOSTICS. . . 5-22
DEFINITIONS........................... 5-23
GENERAL INFORMATION....................5-22
BLEEDING BENDIX ANTILOCK 4 BRAKE SYSTEM......5-25
BENDIX ANTILOCK 4 MODULATOR ASSEMBLY BLEEDING
PROCEDURE
......................... 5-26
HYDRAULIC BRAKE TUBE ASSEMBLY (JUNCTION BLOCK
TO MODULATOR ASSEMBLY)
................ 5-34
INSTALL............................ 5-36
REMOVE............................5-34
MASTER CYLINDER AND POWER BOOSTER.........5-38
REMOVAL AND INSTALLATION................. 5-38
MODULATOR ASSEMBLY CIRCUIT BLEEDING PROCEDURE
AND SEQUENCE
....................... 5-26
1 MODULATOR PRIMARY CHECK VALVE CIRCUIT........5-26
2 MODULATOR SECONDARY CHECK VALVE CIRCUIT......5-26
3 MODULATOR ASSEMBLY PRIMARY SUMP CIRCUIT......5-27
4 MODULATOR ASSEMBLY PRIMARY ACCUMULATOR CIRCUIT. 5-27
5 MODULATOR ASSEMBLY SECONDARY SUMP CIRCUIT....5-28
6 MODULATOR ASSEMBLY SECONDARY ACCUMULATOR
CIRCUIT
........................... 5-29
MODULATOR ASSEMBLY (FIG. 1)...............5-30
INSTALL............................ 5-32
REMOVE............................5-30
PROPORTIONING VALVES (FIG. 1)...............5-38
INSTALL............................ 5-39
REMOVAL...........................5-38
PUMP/MOTOR SERVICE....................5-29
CONTROLLER ANTILOCK BRAKE CAB.............5-18
CONTROLLER ANTILOCK BRAKE (INPUTS)..........5-19
CONTROLLER ANTILOCK BRAKE (OUTPUTS).........5-19
DIAGNOSTIC CONNECTOR.................... 5-19
ELECTRONIC COMPONENTS..................5-41
CONTROLLER ANTILOCK BRAKE CAB.............5-41
INSTALL............................ 5-42
REMOVE............................5-41
FRONT WHEEL SPEED SENSOR (FIG. 9)...........5-43
INSTALLATION......................... 5-44
REMOVAL........................... 5-43
REAR WHEEL SPEED SENSOR (FIGS. 10 AND 11)......5-44
INSTALLATION......................... 5-44
REMOVAL........................... 5-44
REMOVAL/INSTALLATION OF SYSTEM RELAY.........5-42
INSTALL............................ 5-43
REMOVE............................5-43
REMOVE/INSTALL PUMP MOTOR RELAY...........5-43
WHEEL SPEED SENSORS.................... 5-43
INSPECTION.......................... 5-43
GENERAL INFORMATION....................5-12
HYDRAULIC CIRCUITS AND VALVE OPERATION......5-20
ABS BRAKING-BUILD PRESSURE............... 5-20
BUILD/DECAY VALVES..................... 5-20
ABS BRAKING-DECAY PRESSURE...............5-22
BUILD/DECAY VALVES..................... 5-22
NORMAL BRAKING....................... 5-20
BUILD/DECAY VALVES.....................5-20
MAJOR COMPONENTS...................... 5-14
CONTROLLER ANTILOCK BRAKE CAB.............5-14
MASTER CYLINDER AND VACUUM BOOSTER.........5-14
MODULATOR AND PUMP MOTOR/ASSEMBLY.........5-14
WHEEL SPEED SENSORS.................... 5-14
MECHANICAL DIAGNOSTICS AND SERVICE
PROCEDURES
.......................... 5-24
INTERMITTENT FAULTS.....................5-24
SPECIAL SERVICE TOOL....................5-24
DRB DIAGNOSTIC TESTER...................5-24
NORMAL BRAKE SYSTEM FUNCTION.............5-14
ON-CAR ABS BRAKE SYSTEM SERVICE...........5-25
CHECKING BRAKE FLUID LEVEL................ 5-25
GENERAL SERVICE PRECAUTIONS...............5-25
SPECIFICATIONS......................... 5-46
SYSTEM SELF-DIAGNOSTICS..................5-15
VEHICLE PERFORMANCE.................... 5-15
WARNING SYSTEMS OPERATION...............5-16
NORMAL OPERATION OF WARNING LAMP..........5-16
GENERAL INFORMATION .....................5-1
HYDRAULIC SYSTEM CONTROL VALVES .........5-10
GENERAL INFORMATION.................... 5-10
HYDRAULIC SYSTEM SERVICE PROCEDURES........5-11
BRAKE WARNING SYSTEM................... 5-11
CHECKING BRAKE WARNING SWITCH UNIT...........5-11
TESTING ANTILOCK PROPORTIONING VALVES........5-11
PRESSURE DIFFERENTIAL WARNING LIGHT SWITCH. . . 5-10
SERVICE ADJUSTMENTS .....................5-3

The power steering pump drive belt should be in-
spected at the time and distance interval described in
the Lubrication and Maintenance Schedules. Refer to
the General Information section of this group.
POWER STEERING FLUID INSPECTION
WARNING: ENGINE MUST NOT BE RUNNING WHEN
INSPECTING POWER STEERING FLUID LEVEL,
PERSONAL INJURY CAN RESULT.
CAUTION: Do not over fill power steering reservoir
when adding fluid, seal damage and leakage can re-
sult.
TO INSPECT FLUID LEVEL:
(1) Position vehicle on a level surface with engine
at normal running temperature. (2) Turn OFF engine and remove ignition key.
(3) Using a wiping cloth, clean oil and dirt residue
from around power steering reservoir cap. (4) Remove reservoir cap or dipstick and wipe off
fluid. (5) Install cap or dipstick.
(6) Remove cap or dipstick. Holding handle or cap
above tip of dipstick, read fluid level (Fig. 4, 5, or 6).
Add fluid if reading is below cold level mark on dip-
stick.
REAR WHEEL BEARINGS
INSPECTION
The rear wheel bearings should be packed with
new lubricant at the distance interval described in the Lubrication and Maintenance Schedules. Refer to
the General Information section of this group. The
bearings should be inspected for contamination and
wear before they are cleaned. Slight discoloration of
bearing rollers and race cup is normal. If metal
Fig. 3 Ball Joint Lubrication
Fig. 4 Power Steering Reservoir DipstickÐ2.2L or 2.5L Engine
Fig. 5 Power Steering Reservoir DipstickÐ3.0L Engine
Fig. 6 Power Steering Reservoir DipstickÐ3.3L or3.8L Engine
0 - 20 LUBRICATION AND MAINTENANCE Ä

BRAKE RESERVOIR LEVEL INSPECTION
WARNING: DO NOT ALLOW PETROLEUM OR WATER
BASE LIQUIDS TO CONTAMINATE BRAKE FLUID,
SEAL DAMAGE AND BRAKE FAILURE CAN RESULT.
RELIEVE PRESSURE IN ANTI-LOCK BRAKE SYS-
TEM BEFORE ADDING BRAKE FLUID TO RESER-
VOIR. IF NOT, BRAKE FLUID COULD DISCHARGED
FROM THE RESERVOIR POSSIBLY CAUSING PER-
SONAL INJURY.
The brake reservoir level should be inspected when
other under hood service is performed. It is normal
for the reservoir level to drop as disc brake pads
wear. When fluid must be added, use Mopar, Brake
Fluid or equivalent. Use only brake fluid conforming
to DOT 3, Federal, Department of Transportation
specification. To avoid brake fluid contamination, use
fluid from a properly sealed container. On vehicles with anti-lock brakes, depressurize the
system before inspecting fluid level. Turn OFF the
ignition and remove the key. Pump the brake pedal
at least 50 times to relieve the pressure in the sys-
tem.
On all vehicles, if fluid should become low after sev-
eral thousand kilometers (miles), fill the reservoir to
level marks on the side of the reservoir (Fig. 8 or 9).
HEADLAMPS
The headlamps should be inspected for intensity
and aim whenever a problem is suspected. When lug-
gage compartment is heavily loaded, the headlamp
aim should be adjusted to compensate for vehicle
height change. For proper service procedures, refer to
Group 8L, Lamps. DRIVER SUPPLEMENTAL AIRBAG SYSTEM
If the AIRBAG indicator lamp does not light at all,
stays lit or lights momentarily or continuously while
driving, a malfunction may have occurred. Prompt service is required. Refer to Group 8M, Restraint
Systems for proper diagnostic procedures.
BODY LUBRICATION
Body mechanisms and linkages should be inspected,
cleaned and lubricated as required to maintain ease of
operation and to prevent corrosion and wear. Before a component is lubricated, oil, grease and dirt
should be wiped off. If necessary, use solvent to clean
component to be lubricated. After lubrication is com-
plete, wipe off excess grease or oil. During winter season, external lock cylinders should
be lubricated with Mopar, Lock Lubricant or equiva-
lent to ensure proper operation when exposed to water
and ice. To assure proper hood latching component operation,
use engine oil to lubricate the lock, safety catch and
hood hinges when other under hood service is per-
formed. Mopar, Multi-purpose Grease or equivalent
should be applied sparingly to all pivot and slide
contact areas.
USE ENGINE OIL ON:
² Door hingesÐHinge pin and pivot points.
² Hood hingesÐPivot points.
² Luggage compartment lid hingesÐPivot points.
USE MOPAR LUBRIPLATE OR EQUIVALENT ON:
² Door check straps.
² Hood counterbalance springs.
² Luggage compartment lid latches.
² Luggage compartment lid prop rod pivots.
² Ash tray slides.
² Fuel Fill Door latch mechanism.
² Park brake mechanism.
² Front seat tracks.
Fig. 8 Anti-lock Brake Reservoir
Fig. 9 Master Cylinder Brake ReservoirÐExcept
Anti-lock
0 - 22 LUBRICATION AND MAINTENANCE Ä

WARNING: WHEN REMOVING THE REAR AXLE
PIVOT BUSHING ON VEHICLES EQUIPPED WITH EI-
THER REAR COIL SPRINGS OR AIR SUSPENSION.
THE REAR AXLE MUST BE SUPPORTED BY THE
AXLE AND TRAILING ARM TO ENSURE ADEQUATE
SUPPORT OF REAR AXLE.
(3) Support the rear axle assembly at both the axle
channel and the trailing arm (Fig. 6). Then remove
lower shock absorber to rear axle mounting bolt (Fig.
6).
(4) Remove hanger bracket to frame rail bolts (Fig.
7).
(5) Lower axle assembly down enough to remove
pivot bolt and hanger bracket (Fig. 7). Right side
trailing arm shown.
PIVOT BUSHING REMOVAL FROM AXLE AS- SEMBLY
Remove bushing with Remover/Installer Spe-
cial Tool C-4212-L (Press) and 3 piece set, Spe- cial Tool 6122 (Receiver Support Bridge, Bushing
Remover/Installer and Bushing Remover). (1) Install receiver (support) bridge into base of
press C-4212-L and bushing Remover/Installer disc
onto screw. (2) Position assembly with receiver bridge support-
ing trailing arm while turning screw to begin bushing
removal. (3) After bushing has begun to move replace bushing
remover/installer (round disc) with bushing remover
(oval shaped disc). Use this assembly to finish pressing
bushing out of trailing arm (Fig. 8).
PIVOT BUSHING INSTALLATION
(1) Align the bushing with the bushing mounting
hole in the trailing arm bracket (Fig. 9). Tap bushing in
slightly to hold position. (2) Assemble bushing installer Tool onto press screw
and support bridge into press base. Position assem-
bly as shown in (Fig. 10) and press bushing into
arm to depth shown in (Fig. 9). (3) Position hanger bracket on pivot bushing, and
install through bolt, loose assemble nut (Fig. 11). Right
side trailing arm shown. (4) Position hanger to frame rail (a suitable drift will
aid in guiding hanger bracket into position). Install
and tighten screws to 75 N Im (55 ft. lbs.) torque (Fig.
12). Install lower shock absorber mounting bolt, but
do not tighten. (5) Position brake hose mounting bracket to trailing
arm, install and tighten retaining screw to 11 N Im (95
in. lbs.) torque (Fig. 13). (6) Attach park brake cable housing to hanger
bracket and cable to connector.
Fig. 8 Tools Installed To Remove Bushing
Fig. 6 Remove Pivot Bushing Hanger Bracket Bolts
Fig. 7 Remove Hanger Bracket
Ä SUSPENSION AND DRIVESHAFTS 2 - 53

PIVOT BUSHING AC AG AJ AP BODY
REMOVE FROM VEHICLE
(1) Raise vehicle (see Hoisting, Group 0). Remove
brake hose mounting bracket screw (Fig. 1). (2) Detach park brake cable at connector and from
hanger bracket (Fig. 1).
WARNING: WHEN REMOVING THE REAR AXLE
PIVOT BUSHING ON VEHICLES EQUIPPED WITH EI-
THER REAR COIL SPRINGS OR AIR SUSPENSION.
THE REAR AXLE MUST BE SUPPORTED BY THE
AXLE AND TRAILING ARM TO ENSURE ADEQUATE
SUPPORT OF REAR AXLE. (3) Support the rear axle assembly at both the axle
channel and the trailing arm with jack stands (Fig.
2). Then remove lower shock absorber to rear axle
mounting bolt (Fig. 2).
(4) Remove hanger bracket to frame rail bolts (Fig.
3). (5) Lower axle assembly down enough to remove
pivot bolt and hanger bracket (Fig. 3). Right side
trailing arm shown.
PIVOT BUSHING REMOVAL FROM AXLE AS- SEMBLY
Remove bushing with Remover/Installer Spe-
cial Tool C-4702-7 Press. And 3 piece set, Special
Tool C-4212 and C-4366-1 (Receiver Support
Bridge, Bushing Remover/Installer and Bushing
Remover). (1) Install receiver (support) cup C-4366-1 into base
of press C-4212 and Bushing Remover Cup C-4702-7
onto screw. (2) Position assembly with receiver bridge support-
ing trailing arm while turning screw to begin bushing
removal. (3) After bushing has begun to move replace bushing
remover/installer (round disc) with bushing remover
(oval shaped disc). Use this assembly to finish pressing
bushing out of trailing arm (Fig. 4).
PIVOT BUSHING INSTALLATION
(1) Align the bushing with the bushing mounting
hole in the trailing arm bracket (Fig. 5). Tap bushing in
slightly to hold it in position on trailing arm. (2) Assemble Bushing Installer Special Tool
C-4702-2 onto press screw and Support Cup Special
Fig. 1 Remove Brake Hose Mounting Bracket Screw and Park Brake Cable
Fig. 2 Remove Pivot Bushing Hanger Bracket Bolts
Fig. 3 Remove Hanger Bracket
Fig. 4 Tools Installed To Remove Bushing
Ä SUSPENSION AND DRIVESHAFTS 2 - 55

BRAKES
CONTENTS
page page
ANTI-LOCK BRAKE SYSTEMÐBENDIX ANTI-LOCK 10 AC/Y BODY ............. 72
ANTI-LOCK BRAKE SYSTEMÐBENDIX ANTI-LOCK 6 AA,AG,AJ,AP BODY ....... 113
BRAKE DISC (ROTOR) ................... 53
BRAKE SUPPORT ASSEMBLY ............. 25
FRONT DISC BRAKES ................... 31
GENERAL INFORMATION .................. 1
HYDRAULIC SYSTEM CONTROL VALVES . . . 26
KELSEY HAYES DOUBLE PIN FAMILY CALIPER ............................ 35 KELSEY HAYES DOUBLE PIN NON-FAMILY
CALIPER ............................ 38
MASTER CYLINDER ..................... 66
PARKING BRAKES ...................... 57
POWER BRAKES ....................... 68
REAR DISC BRAKES .................... 45
REAR WHEEL DRUM BRAKES ............ 18
SERVICE ADJUSTMENTS .................. 4
WHEEL BEARINGS ...................... 70
WHEEL CYLINDERS ..................... 23
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 Anti-Lock 10 braking system, uses the
standard power brake system caliper assemblies,
braking discs, pedal assembly, brake lines and hoses.
The unique parts of the Bendix Anti-Lock 10 braking
system consists of the following components. Propor-
tioning valves, wheel speed sensors, tone wheels,
electronic control unit, modulator assembly and hy-
draulic assembly. These components replace the con-
ventional master cylinder and power booster. The
components will be described in detail in the Bendix
Anti-Lock 10 brake section in this group of the ser-
vice manual. The Bendix Anti-Lock 6 braking system, uses the
following standard brake system components. Master
cylinder, power booster, caliper assemblies, braking
discs, pedal assembly, brake lines and hoses. The
unique parts of the Bendix Anti-Lock 6 braking sys-
tem consists of the following components. Modulator
assembly, unique proportioning valves, wheel speed
sensors, tone wheels, and electronic control unit.
These components will be described in detail in the
Bendix Anti-Lock 6 brake section in this group of the
service manual. The front disc brake shoes have semi-metallic lin-
ings. The hydraulic brake system (Fig .123and4)is
diagonally split on both the Non-ABS and ABS brak-
ing system. With the left front and right rear brakes
on one hydraulic system and the right front and left
rear on the other. The Non-ABS and ABS brake system may use dif-
ferent types of brake line fittings and tubing flares.
The Non-ABS brake system uses double wall tubing
flares and fittings at all tubing joint locations. Some
ABS brake systems use both ISO style tubing flares
and double wall tubing flares and corresponding fit-
tings at different joint locations. See (Figs . 2 3 and 4)
for specific joint locations and type of tubing flare. The front disc brakes consist of two different types
of caliper assemblies. A double pin Kelsey-Hayes cal-
iper (family caliper) with a bolt-on adapter attached
to the steering knuckle. Or a double pin Kelsey-
Hayes caliper (non-family caliper) which mounts di-
rectly to rails on the steering knuckle. The non-
family caliper is only used on the AY Body
(Imperials).
CAUTION: Caliper pistons, boots and seals for the
different caliper assemblies used on the front and
rear disc brake assemblies are not interchangeable.
Misusage could result in a complete brake system
failure. Be sure that the parts are replaced with the
correct replacement parts, refer to the parts book
for the type and model year of the vehicle being
worked on.
The master cylinder is anodized, lightweight alu-
minum, with a bore size of 24.0mm, 21.0mm or 7/8
inch.
Ä BRAKES 5 - 1

HYDRAULIC SYSTEM CONTROL VALVES INDEX
page page
ABS Brake Proportioning Valve Operation ...... 27
General Information ....................... 26
Hydraulic System Service Procedures ......... 27 Non-ABS Proportioning Unit Operation
........ 26
Pressure Differential Warning Light Switch ...... 26
Testing ABS Proportioning Valves ............ 29
GENERAL INFORMATION
Most models not equipped with an Anti-Lock brak-
ing system have a combination hydraulic system con-
trol valve in the brake hydraulic system (Fig. 1). The
valve is attached to the frame rail below the master
cylinder.
The control valve assembly combines a warning
switch with a dual proportioning valve (Fig. 2) Proportioning valves balance front to rear braking
by controlling at a given ratio, the increase in rear
system hydraulic pressure above a preset level. Un-
der light pedal application, the valve allows full hy-
draulic pressure to the rear brakes. There is only one valve assembly in each vehicle,
see Valve Application Chart. During any service pro-
cedures identify valve assemblies by part number as
well as split point (PSI) and slope.
PRESSURE DIFFERENTIAL WARNING LIGHT
SWITCH
The hydraulic brake system, on non-ABS vehicles,
is split diagonally. The left front and right rear
brakes are part of one system. And the right front and left rear are part of another. Both systems are
routed through, but hydraulically separated by a Pres-
sure Differential Switch. The function of the Pressure
Differential Switch is to alert the driver of a malfunc-
tion in the brake system. If hydraulic pressure is lost in one system, the
warning light switch will activate a red light on the
instrument panel, when the brake pedal is depressed.
At this point the brakes require 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. The instrument panel bulb can be checked each time
the ignition switch is turned to the start position or the
parking brake is set.
NON-ABS PROPORTIONING UNIT OPERATION
The proportioning valve section operates by trans-
mitting full input pressure to the rear brakes up to a
certain point. This is called the split point. Beyond this
point it reduces the amount of pressure increase to the
rear brakes according to a certain ratio. On light pedal applications equal brake pressure will
be transmitted to the front and rear brakes. On heavier
pedal applications the pressure transmitted
Fig. 1 Brake Combination Valve And Warning Switch Location
Fig. 2 Switch and Valve Assembly
5 - 26 BRAKES Ä

to the rear will be lower than the front brakes. This will
prevent premature rear wheel lock-up and skid. If
hydraulic pressure is lost in one half of the diagonally
split system, the operation of the proportioning valve
in the remaining half is not effected.
ABS BRAKE PROPORTIONING VALVE OPERATION
On vehicles using the ABS braking system, screw in
proportioning valves are used in place of the conven-
tional differential pressure/proportioning valve. Each rear brake circuit has its own screw-in propor-
tioning valve which is attached to the rear brake outlet
ports of the hydraulic assembly. These valves limit
brake pressure to the rear brakes after a certain
pressure is reached. This improves front to rear brake
balance during normal braking.
Screw in proportioning valves can be identified by
the numbers stamped on the body of the valve. The
first digit represents the slope, the second digit repre-
sents the split (cut-in) point, and the arrow represents
the flow direction of the valve. Be sure that the
numbers listed on the replacement valve are the
same as on the valve that is being removed. See
(Fig. 3) for detail of the valve identification.
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 sys-
tems fail.
CAUTION:Make sure air does not enter the hydrau-
lic system during this test procedure. See bleeding
without a pressure bleeder at the beginning of this
section for master cylinder fluid level checking pro-
cedures.
To test the service brake warning system lamp.
Raise the vehicle on a hoist and open a wheel cylin-
der bleeder while a helper depresses the brake pedal
and observes the warning light. If the light fails to light, inspect for a burned out
bulb, disconnected socket, or a broken or discon-
nected wire at the switch. If the bulb is not burned
out and the wire continuity is uninterrupted. 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 correction has been made, if
necessary.
PROPORTIONING VALVES
TESTING PROPORTIONING VALVE UNIT
If premature rear wheel skid occurs on hard brake
application, it could be an indication that a malfunc-
tion has occurred with the proportioning valve unit. The proportioning valve is designed with two sep-
arate systems. One half controls the right rear
brake, and the other half controls the left rear brake.
Therefore, a road test to determine which rear brake
slides first is essential.
RIGHT REAR WHEEL SLIDES FIRST To test the proportioning valve when the right rear
wheel slides first, leave the front brakes connected to
the valve, proceed as follows: (1) Install one gauge and (TEE) of set C-4007-A
between the brake line from the master cylinder sec-
ondary port and the brake valve assembly. (2) Install the second gauge of set C-4007-A to the
right rear brake outlet port (Fig. 4). Using an
adapter tube, made from a short piece of brake tube
and (2) 3/8 x 24 tube nuts. Connect the hose to the
valve. Bleed the hose and gauge. (3) Have a helper exert pressure on the brake
pedal (holding pressure) to get a reading on the valve
inlet gauge and check the reading on the outlet
Fig. 3 ABS PROPORTIONING VALVE IDENTIFICA- TION
Ä BRAKES 5 - 27