FLUID
DIAGNOSIS AND TESTING - BRAKE FLUID
CONTAMINATION
Indications of fluid contamination are swollen or
deteriorated rubber parts.
Swollen rubber parts indicate the presence of
petroleum in the brake fluid.
To test for contamination, put a small amount of
drained brake fluid in clear glass jar. If fluid sepa-
rates into layers, there is mineral oil or other fluid
contamination of the brake fluid.
If brake fluid is contaminated, drain and thor-
oughly flush system. Replace master cylinder, propor-
tioning valve, caliper seals, wheel cylinder seals,
Antilock Brake hydraulic unit and all hydraulic fluid
hoses.
STANDARD PROCEDURE - BRAKE FLUID
LEVEL CHECKING
Check master cylinder reservoir fluid level a mini-
mum of twice annually.
Fluid reservoirs are marked with the words FULL
and ADD to indicate proper brake fluid fill level of
the master cylinder.
If necessary, add brake fluid to bring the level to
the bottom of the FULL mark on the side of the mas-
ter cylinder fluid reservoir.
Use only Mopartbrake fluid or equivalent from a
sealed container. Brake fluid must conform to DOT 3
specifications (DOT 4 or DOT 4+ are acceptable).
DO NOTuse brake fluid with a lower boiling
point, as brake failure could result during prolonged
hard braking.
Use only brake fluid that was stored in a tightly-
sealed container.
DO NOTuse petroleum-based fluid because seal
damage will result. Petroleum based fluids would be
items such as engine oil, transmission fluid, power
steering fluid etc.
SPECIFICATIONS
BRAKE FLUID
The brake fluid used in this vehicle must conform
to DOT 3 specifications (DOT 4 and DOT 4+ are
acceptable) and SAE J1703 standards. No other type
of brake fluid is recommended or approved for usage
in the vehicle brake system. Use only MopartBrake
Fluid or equivalent from a tightly sealed container.CAUTION: Never use reclaimed brake fluid or fluid
from an container which has been left open. An
open container of brake fluid will absorb moisture
from the air and contaminate the fluid.
CAUTION: Never use any type of a petroleum-based
fluid in the brake hydraulic system. Use of such
type fluids will result in seal damage of the vehicle
brake hydraulic system causing a failure of the
vehicle brake system. Petroleum based fluids would
be items such as engine oil, transmission fluid,
power steering fluid, etc.
JUNCTION BLOCK
DESCRIPTION - NON-ABS JUNCTION BLOCK
A junction block is used on vehicles that are not
equipped with antilock brakes (ABS). The junction
block mounts in the same location as the integrated
control unit (ICU) does on vehicles equipped with
ABS. This allows for use of the same brake tube con-
figuration on all vehicles. The junction block is
located on the driver's side of the front suspension
cradle/crossmember below the master cylinder (Fig.
44).
It has six threaded ports to which the brake tubes
connect. Two are for the primary and secondary
brake tubes coming from the master cylinder. The
remaining four are for the chassis brake tubes going
to each brake assembly.
OPERATION - NON-ABS JUNCTION BLOCK
The junction block distributes the brake fluid com-
ing from the master cylinder primary and secondary
ports to the four chassis brake tubes leading to the
brakes at each wheel. Since the junction block
mounts in the same location as the ABS integrated
control unit (ICU), it allows for the common use of
brake tubes going to the brakes whether the vehicle
is equipped with or without ABS.
NOTE: Although the brake tubes coming from the
master cylinder to the junction block or ABS ICU
may appear to be the same, they are not. They are
unique to each brake system application.
RSBRAKES - BASE5-33
PROPORTIONING VALVE
DESCRIPTION - PROPORTIONING VALVE
(HEIGHT SENSING)
NOTE: Only vehicles without antilock brakes (ABS)
have a proportioning valve. Vehicles with ABS uti-
lize electronic brake distribution which is controlled
through the ABS integrated control unit.
Vehicles not equipped with ABS use a height sens-
ing proportioning valve. It is mounted to the body of
the vehicle above the rear axle (Fig. 80). It has an
actuator lever that attaches to the rear axle and
moves with the axle to help the valve sense the vehi-
cle height.
CAUTION: The height sensing proportioning valve
is not adjustable. No attempt should be made to
adjust it. It is replaced as a complete assembly.
CAUTION: The use of after-market load leveling or
load capacity increasing devices on this vehicle are
prohibited. Using air shock absorbers or helper
springs on this vehicle will cause the height sens-
ing proportioning valve to inappropriately reduce
the hydraulic pressure to the rear brakes. This inap-
propriate reduction in hydraulic pressure potentially
could result in increased stopping distance of the
vehicle.
OPERATION - PROPORTIONING VALVE
(HEIGHT SENSING)
Vehicles not equipped with ABS use a height sens-
ing proportioning valve.
The height sensing proportioning valve operates
similarly to a standard proportioning valve in the fol-
lowing way. As hydraulic pressure is applied to the
valve, full input hydraulic pressure is supplied to the
rear brakes up to a certain pressure point, called the
split point. Beyond the split point, the proportioning
valve reduces the amount of hydraulic pressure to
the rear brakes according to a given ratio. Thus, on
light brake applications, approximately equal
hydraulic pressure will be transmitted to both the
front and rear brakes. Upon heavier brake applica-
tions, the hydraulic pressure transmitted to the rear
brakes will be lower than the front brakes. This will
prevent premature rear wheel lockup and skid.
Here is how the height sensing proportioning valve
differs from a standard proportioning valve. As the
height of the rear suspension changes, the height
sensing portion of the proportioning valve changes
the split point of the proportioning valve. When the
height of the rear suspension is low, the proportion-
ing valve interprets this as extra load and the split
point of the proportioning valve is raised to a higher
pressure to allow for more rear braking. When the
height of the rear suspension is high, the proportion-
ing valve interprets this as a light load and the split
point of the proportioning valve is lowered to a lower
pressure and rear braking is reduced.
The height sensing proportioning valve regulates
the pressure by sensing the load condition of the
vehicle through the movement of the proportioning
valve actuator lever (Fig. 80). As the position of the
rear axle changes, depending on the load the vehicle
is carrying, the movement is transferred to the pro-
portioning valve. The proportioning valve adjusts the
hydraulic pressure accordingly.
The height sensing proportioning valve allows the
brake system to maintain the optimal front to rear
brake balance regardless of the vehicle load condi-
tion. Under a light load condition, hydraulic pressure
to the rear brakes is minimized. As the rear load con-
dition increases, so does the hydraulic pressure to
the rear brakes.
Fig. 80 HEIGHT SENSING PROPORTIONING VALVE
1 - PROPORTIONING VALVE
2 - ACTUATOR LEVER
3 - AXLE BRACKET
4 - REAR AXLE
RSBRAKES - BASE5-53
PROPORTIONING VALVE SPECIFICATIONS
WHEEL
BASEDRIVE
TRAINSALES
CODEBRAKE
SYSTEMSPLIT
POINTSLOPEINLET
PRESSURE
PSIOUTLET
PRESSURE
PSI
SWB FWD BRB-BGF159DISC/
DRUM W/O
ANTILOCKVAR. 0.59 1000 PSI 675-875 PSI
REMOVAL - PROPORTIONING VALVE (HEIGHT
SENSING)
(1) Using a brake pedal depressor, move and lock
the brake pedal to a position past its first 1 inch of
travel. This will prevent brake fluid from draining
out of the master cylinder when the brake tubes are
removed from the proportioning valve.
(2) Raise vehicle. (Refer to LUBRICATION &
MAINTENANCE/HOISTING - STANDARD PROCE-
DURE).
CAUTION: Before removing the brake tubes from
the proportioning valve, the proportioning valve and
the brake tubes must be thoroughly cleaned. This is
required to prevent contamination from entering the
proportioning valve or the brake tubes.
(3) Remove the four brake tubes from the inlet and
outlet ports of the proportioning valve (Fig. 81).
(4) Remove the two bolts attaching the proportion-
ing valve and bracket to the vehicle (Fig. 81).
(5) Slide the bracket out from under rear track bar
bracket. Lower the valve down enough to pull itsactuator rod out of the axle bracket and remove the
proportioning valve from the vehicle.INSTALLATION - PROPORTIONING VALVE
(HEIGHT SENSING)
(1) Install the end of the actuator rod through the
axle bracket grommet and slide the proportioning
valve bracket under the rear track bar body bracket
(Fig. 81).
(2) Install the proportioning valve attaching bolts
(Fig. 81). Tighten the attaching bolts to a torque of
54 N´m (40 ft. lbs.).
(3) Install the four chassis brake lines into the
inlet and outlet ports of the proportioning valve (Fig.
81). Tighten all tube nuts to a torque of 17 N´m (145
in. lbs.).
CAUTION: The height sensing proportioning valve
is not adjustable. No attempt should be made to
adjust it.
(4) Bleed the brake system thoroughly to ensure
that all air has been expelled from the hydraulic sys-
tem. (Refer to 5 - BRAKES - BASE - STANDARD
PROCEDURE).
(5) Lower the vehicle to the ground.
(6) Road test the vehicle to verify proper operation
of the brake system.
ROTOR
DIAGNOSIS AND TESTING - BRAKE ROTOR
Any servicing of the rotor requires extreme care to
maintain the rotor within service tolerances to
ensure proper brake action.
Excessive runout or wobble in a rotor can increase
pedal travel due to piston knock-back. This increases
guide pin sleeve wear due to the tendency of the cal-
iper to follow the rotor wobble.
When diagnosing a brake noise or pulsation, the
machined disc braking surface should be checked and
inspected.
Fig. 81 PROPORTIONING VALVE MOUNTING
1 - LEFT REAR OUTLET TUBE
2 - RIGHT REAR OUTLET TUBE
3 - RIGHT REAR INLET TUBE
4 - MOUNTING BOLTS
5 - LEFT REAR INLET TUBE
RSBRAKES - BASE5-55
PROPORTIONING VALVE (Continued)
BRAKING SURFACE INSPECTION
Light braking surface scoring and wear is accept-
able. If heavy scoring or warping is evident, the rotor
must be refaced or replaced. (Refer to 5 - BRAKES/
HYDRAULIC/MECHANICAL/ROTORS - STAN-
DARD PROCEDURE).
Excessive wear and scoring of the rotor can cause
improper lining contact on the rotor's braking sur-
face. If the ridges on the rotor are not removed before
new brake shoes are installed, improper wear of the
shoes will result.
If a vehicle has not been driven for a period of
time, the rotor's braking surface will rust in the
areas not covered by the brake shoes at that time.
Once the vehicle is driven, noise and chatter from
the disc brakes can result when the brakes are
applied.
Some discoloration or wear of the rotor surface is
normal and does not require resurfacing when lin-
ings are replaced. If cracks or burned spots are evi-
dent, the rotor must be replaced.
ROTOR MINIMUM THICKNESS
Measure rotor thickness at the center of the brake
shoe contact surface. Replace the rotor if it is worn
below minimum thickness or if machining the rotor
will cause its thickness to fall below specifications.
CAUTION: Do not machine the rotor if it will cause
the rotor to fall below minimum thickness.
Minimum thickness specifications are cast on the
rotor's unmachined surface (Fig. 82). Limits can also
be found in this section's specification table. (Refer to
5 - BRAKES/HYDRAULIC/MECHANICAL/ROTOR -
SPECIFICATIONS)
ROTOR THICKNESS VARIATION
Thickness variation in a rotor's braking surface
can result in pedal pulsation, chatter and surge. This
can be caused by excessive runout in the rotor or the
hub.
Rotor thickness variation measurements should be
made in conjunction with measuring runout. Mea-
sure thickness of the brake rotor at 12 equal points
around the rotor braking surface with a micrometer
at a radius approximately 25 mm (1 inch) from edge
of rotor (Fig. 83). If thickness measurements vary
beyond the specification listed in the specifaction
table (Refer to 5 - BRAKES/HYDRAULIC/MECHAN-
ICAL/ROTOR - SPECIFICATIONS), the rotor should
be refaced or replaced. (Refer to 5 - BRAKES/HY-
DRAULIC/MECHANICAL/ROTORS - STANDARD
PROCEDURE).
Fig. 82 Minimum Brake Rotor Thickness Markings
(Typical)
1 - ROTOR MINIMUM THICKNESS MARKING
2 - ROTOR
Fig. 83 Checking Rotor For Thickness
1 - CALIPER
5 - 56 BRAKES - BASERS
ROTOR (Continued)
ROTOR RUNOUT
On-vehicle rotor runout is the combination of the
individual runout of the hub face and the runout of
the rotor. (The hub and rotor runouts are separable).
To measure rotor runout on the vehicle, first remove
the tire and wheel assembly. Reinstall the wheel
mounting nuts on the studs, tightening the rotor to
the hub. Mount the Dial Indicator, Special Tool
C-3339, with Mounting Adaptor, Special Tool SP-
1910 on steering arm. The dial indicator plunger
should contact braking surface of rotor approximately
ten millimeters from edge of rotor (Fig. 84). Check
lateral runout on both sides of the rotor, marking the
low and high spots on both. Runout limits can be
found in the specification table in this section. (Refer
to 5 - BRAKES/HYDRAULIC/MECHANICAL/RO-
TOR - SPECIFICATIONS)
If runout is in excess of the specification, check the
lateral runout of the hub face. Before removing the
rotor from the hub, place a chalk mark across both
the rotor and the one wheel stud closest to where the
high runout measurement was taken. This way, the
original mounting spot of the rotor on the hub is
indexed (Fig. 85).
Remove the rotor from the hub.
NOTE: Clean the hub face surface before checking
runout. This provides a clean surface to get an
accurate indicator reading.
Mount Dial Indicator, Special Tool C-3339, and
Mounting Adaptor, Special Tool SP-1910, to the steer-
ing knuckle. Position the indicator stem so it contacts
the hub face near the outer diameter. Care must be
taken to position stem outside of the stud circle, but
inside of the chamfer on the hub rim (Fig. 86).Hub runout should not exceed 0.03 mm (0.0012
inch). If runout exceeds this specification, the hub
must be replaced. (Refer to 2 - SUSPENSION/
FRONT/HUB / BEARING - REMOVAL)(Refer to 2 -
SUSPENSION/REAR/HUB / BEARING - REMOVAL)
Fig. 84 Checking Rotor Runout
1 - SPECIAL TOOL SP-1910
2 - 10 MILLIMETERS FROM EDGE
3 - DISC SURFACE
4 - SPECIAL TOOL C-3339
Fig. 85 Marking Rotor and Wheel Stud
1 - CHALK MARK
Fig. 86 Checking Hub Runout
1 - HUB SURFACE
2 - SPECIAL TOOL C-3339
3 - SPECIAL TOOL SP-1910
RSBRAKES - BASE5-57
ROTOR (Continued)
SPECIFICATIONS
BRAKE ROTOR
When refacing a rotor, the required TIR (Total
Indicator Reading) and thickness variation limitsMUST BE MAINTAINED. Extreme care in the oper-
ation of rotor turning equipment is required.
LIMITS/SPECIFICATIONS
Braking Rotor Rotor ThicknessMinimum Rotor
ThicknessRotor Thickness
VariationRotor Runout*
Front - TRW27.87±28.13 mm
1.097-1.107 in.25.3 mm
0.996 in.0.009 mm
0.0004 in.0.075 mm
0.0030 in.
Front - Continental
Teves27.90±28.10 mm
1.098-1.106 in.25.3 mm
0.996 in.0.008 mm
0.0003 in.0.100 mm
0.0039 in.
Rear12.4±12.6 mm
0.488 -0.496 in.11.25 mm
0.443 in.0.013 mm
0.0005 in.0.14 mm
0.0055 in.
*
TIR Total Indicator Reading (Measured On Vehicle)
BRAKE ROTOR - EXPORT
NOTE: Use the following information on all 4 wheel
disc brake vehicles that are equipped with BR3
sales code.When refacing a rotor, the required TIR (Total
Indicator Reading) and thickness variation limits
MUST BE MAINTAINED. Extreme care in the oper-
ation of rotor turning equipment is required.
LIMITS/SPECIFICATIONS
Brake Rotor Rotor ThicknessMinimum Rotor
ThicknessRotor Thickness
VariationRotor Runout*
Front27.9-28.1 mm
1.098 -1.106 in.26.5 mm
1.043 in0.010 mm
0.0004 in.0.080 mm
0.0031 in.
Rear12.4-12.6 mm
0.488-0.496 in.11.25 mm
0.443 in.0.013 mm
0.0005 in.0.14 mm
0.0055 in.
* TIR Total Indicator Reading (Measured On Vehicle)
5 - 60 BRAKES - BASERS
ROTOR (Continued)
BRAKES - ABS
TABLE OF CONTENTS
page page
BRAKES - ABS
DESCRIPTION
DESCRIPTION - ANTILOCK BRAKE
SYSTEM............................87
DESCRIPTION - ANTILOCK BRAKE
SYSTEM (EXPORT)....................87
DESCRIPTION - ELECTRONIC VARIABLE
BRAKE PROPORTIONING...............88
DESCRIPTION - TRACTION CONTROL
SYSTEM............................88
OPERATION
OPERATION - ANTILOCK BRAKE SYSTEM . . 88
OPERATION - ELECTRONIC VARIABLE
BRAKE PROPORTIONING...............89
OPERATION - TRACTION CONTROL
SYSTEM............................89
CAUTION.............................90
STANDARD PROCEDURE - ANTILOCK BRAKE
SYSTEM BLEEDING...................90
SPECIFICATIONS
ABS FASTENER TORQUE...............91
TONE WHEEL RUNOUT................91
WHEEL SPEED SENSOR AIR GAP........91
FRONT WHEEL SPEED SENSOR
REMOVAL.............................91
INSTALLATION.........................92
REAR WHEEL SPEED SENSOR - AWD
REMOVAL.............................92INSTALLATION.........................92
REAR WHEEL SPEED SENSOR - FWD
REMOVAL.............................93
INSTALLATION.........................93
TONE WHEEL
INSPECTION - TONE WHEEL..............94
TRACTION CONTROL SWITCH
DIAGNOSIS AND TESTING - TRACTION
CONTROL SWITCH....................94
REMOVAL.............................95
INSTALLATION.........................95
HYDRAULIC/MECHANICAL
OPERATION - HYDRAULIC CIRCUITS AND
VALVES .............................95
HCU (HYDRAULIC CONTROL UNIT)
DESCRIPTION........................100
OPERATION..........................101
ICU (INTEGRATED CONTROL UNIT)
DESCRIPTION........................102
OPERATION..........................102
REMOVAL
REMOVAL - LHD.....................102
REMOVAL - RHD.....................104
DISASSEMBLY - ICU...................105
ASSEMBLY - ICU......................106
INSTALLATION
INSTALLATION - LHD.................106
INSTALLATION - RHD.................107
BRAKES - ABS
DESCRIPTION
DESCRIPTION - ANTILOCK BRAKE SYSTEM
This section covers the physical and operational
descriptions and the on-car service procedures for the
Mark 20e Antilock Brake System and the Mark 20e
Antilock Brake System with traction control.
The purpose of the antilock brake system (ABS) is
to prevent wheel lockup under braking conditions on
virtually any type of road surface. Antilock braking is
desirable because a vehicle that is stopped without
locking the wheels retains directional stability and
some steering capability. This allows the driver to
retain greater control of the vehicle during braking.
DESCRIPTION - ANTILOCK BRAKE SYSTEM
(EXPORT)
Four-wheel disc antilock brakes are standard on all
models. The Mark 20e antilock brake system is used
on all models. Depending on whether the vehicle is a
left-hand drive (LHD) or right-hand drive (RHD)
model, the integrated control unit (ICU) is located in
one of two locations. On LHD models, the ICU is
mounted above the front suspension cradle/cross-
member below the master cylinder. On RHD models,
the ICU is located behind the front suspension cra-
dle/crossmember on the left side of the vehicle.
RSBRAKES - ABS5-87
DESCRIPTION - ELECTRONIC VARIABLE
BRAKE PROPORTIONING
Vehicles equipped with ABS use electronic variable
brake proportioning (EVBP) to balance front-to-rear
braking. The EVBP is used in place of a rear propor-
tioning valve. The EVBP system uses the ABS system
to control the slip of the rear wheels in partial brak-
ing range. The braking force of the rear wheels is con-
trolled electronically by using the inlet and outlet
valves located in the integrated control unit (ICU).
EVBP activation is invisible to the customer since
there is no pump motor noise or brake pedal feedback.
DESCRIPTION - TRACTION CONTROL SYSTEM
Traction control reduces wheel slip and maintains
traction at the driving wheels at speeds below 56
km/h (35 mph) when road surfaces are slippery. The
traction control system reduces wheel slip by braking
the wheel that is losing traction.
HYDRAULIC SHUTTLE VALVES
Two pressure relief hydraulic shuttle valves are
included on vehicles with traction control. These
valves are located inside the HCU and cannot be ser-
viced separately from the HCU.
TRACTION CONTROL LAMP
The traction control function lamp is located in the
transmission range indicator display of the instru-
ment cluster, displaying TRAC, TRAC OFF or nei-
ther depending on system mode.
The TRAC OFF lamp is controlled by a Traction
Control Off switch that is a momentary contact type
switch. The Traction Control Off switch is located on
the steering column upper shroud.
OPERATION
OPERATION - ANTILOCK BRAKE SYSTEM
There are a few performance characteristics of the
Mark 20e Antilock Brake System that may at first
seem abnormal, but in fact are normal. These char-
acteristics are described below.
NORMAL BRAKING
Under normal braking conditions, the ABS func-
tions the same as a standard base brake system with
a diagonally split master cylinder and conventional
vacuum assist.
ABS BRAKING
ABS operation is available at all vehicle speeds above
3±5 mph. If a wheel locking tendency is detected during
a brake application, the brake system enters the ABS
mode. During ABS braking, hydraulic pressure in thefour wheel circuits is modulated to prevent any wheel
from locking. Each wheel circuit is designed with a set of
electric solenoids to allow modulation, although for vehi-
cle stability, both rear wheel solenoids receive the same
electrical signal. Wheel lockup may be perceived at the
very end of an ABS stop and is considered normal.
During an ABS stop, the brakes hydraulic system
is still diagonally split. However, the brake system
pressure is further split into three control channels.
During antilock operation of the vehicle's brake sys-
tem, the front wheels are controlled independently
and are on two separate control channels, and the
rear wheels of the vehicle are controlled together.
The system can build and release pressure at each
wheel, depending on signals generated by the wheel
speed sensors (WSS) at each wheel and received at
the controller antilock brake (CAB).
NOISE AND BRAKE PEDAL FEEL
During ABS braking, some brake pedal movement
may be felt. In addition, ABS braking will create
ticking, popping, or groaning noises heard by the
driver. This is normal and is due to pressurized fluid
being transferred between the master cylinder and
the brakes. If ABS operation occurs during hard
braking, some pulsation may be felt in the vehicle
body due to fore and aft movement of the suspension
as brake pressures are modulated.
At the end of an ABS stop, ABS is turned off when
the vehicle is slowed to a speed of 3±4 mph. There may
be a slight brake pedal drop anytime that the ABS is
deactivated, such as at the end of the stop when the
vehicle speed is less than 3 mph or during an ABS stop
where ABS is no longer required. These conditions exist
when a vehicle is being stopped on a road surface with
patches of ice, loose gravel, or sand on it. Also, stopping
a vehicle on a bumpy road surface activates ABS
because of the wheel hop caused by the bumps.
TIRE NOISE AND MARKS
Although the ABS system prevents complete wheel
lockup, some wheel slip is desired in order to achieve
optimum braking performance. Wheel slip is defined
as follows: 0 percent slip means the wheel is rolling
freely and 100 percent slip means the wheel is fully
locked. During brake pressure modulation, wheel slip
is allowed to reach up to 25±30 percent. This means
that the wheel rolling velocity is 25±30 percent less
than that of a free rolling wheel at a given vehicle
speed. This slip may result in some tire chirping,
depending on the road surface. This sound should not
be interpreted as total wheel lockup.
Complete wheel lockup normally leaves black tire
marks on dry pavement. The ABS will not leave dark
black tire marks since the wheel never reaches a
fully locked condition. However, tire marks may be
noticeable as light patched marks.
5 - 88 BRAKES - ABSRS
BRAKES - ABS (Continued)