Brake lines DODGE RAM 1500 1998 2.G User Guide

(7) Remove the mounting bolt for the brake hose
at the axle (Fig. 8).
(8) Remove the hose.
REMOVAL - REAR TUBE / HOSE ASSEMBLY
(1) Install prop rod on the brake pedal to keep
pressure on the brake system.
(2) Raise and support the vehicle.
(3) Remove the brake line located at the axle.
(4) Remove the mounting bolt for the brake hose
at the axle (Fig. 9).
(5) Remove the banjo bolt at the caliper (Fig. 9).
(6) Remove the hose.
REMOVAL - FRONT HOSE
(1) Install a prop rod on the brake pedal to keep
pressure on the brake system.
(2) Raise and support vehicle.
(3) Remove the tire and wheel assembly.
(4) Remove the brake hose from the brake line
located at the frame (Fig. 10).
(5) Remove the brake hose banjo bolt at the caliper
(Fig. 10).
(6) Remove the mounting bolt securing the brake
hose to the frame and remove the wheel speed sensor
wire from the brake hose (Fig. 10).
(7) Remove the hose.
INSTALLATION
INSTALLATION - REAR BRAKE HOSE
(1) Install the hose.
(2) Install the mounting bolt for the brake hose at
the axle (Fig. 8).
(3) Install the two brake lines at the bottom of the
hose located at the axle (Fig. 8).
(4) Install the vent tube (Fig. 8).
(5) Install the brake hose clip at the top of the
hose located at the frame (Fig. 7).
(6) Install the brake line to the hose at the frame
(Fig. 7).
(7) Lower the vehicle and remove the support.
(8) Remove the prop rod.
(9) Bleed the brake system (Refer to 5 - BRAKES -
STANDARD PROCEDURE).
Fig. 8 REAR HOSE
1 - BRAKE HOSE
2 - VENT HOSE
3 - BRAKE LINES
Fig. 9 BRAKE LINE WITH RUBBER HOSE
1 - BANJO BOLT
2 - MOUNTING BOLT
3 - REAR TUBE / HOSE ASSEMBLY
Fig. 10 BRAKE HOSE MOUNTED PASSENGER SIDE
1 - MOUNTING BOLT
2 - BRAKE HOSE
3 - BANJO BOLT
4 - WHEEL SPEED SENSOR WIRE
5 - 12 BRAKES - BASEDR
BRAKE LINES (Continued)

INSTALLATION - REAR TUBE / HOSE
ASSEMBLY
(1) Install the hose.
(2) Install the banjo bolt at the caliper (Fig. 9) and
tighten fitting bolt to 27 N´m (245 in. lbs.).
(3) Install the mounting bolt for the brake hose at
the axle (Fig. 9).
(4) Install the brake line located at the axle.
(5) Lower the vehicle and remove the support.
(6) Remove the prop rod.
(7) Bleed the brake system (Refer to 5 - BRAKES -
STANDARD PROCEDURE).
INSTALLATION - FRONT BRAKE HOSE
(1) Install the hose.
(2) Install the mounting bolt for the brake hose at
the frame (Fig. 11).
(3) Install the brake hose banjo bolt at the caliper
(Fig. 10).
(4) Reinstall the wheel speed sensor wire to the
brake hose (Fig. 10).
(5) Remove the support and lower the vehicle.
(6) Remove the prop rod from the brake pedal.
(7) Bleed the brake system (Refer to 5 - BRAKES -
STANDARD PROCEDURE).
BRAKE PADS/SHOES
REMOVAL
REMOVAL - FRONT
(1) Raise and support vehicle.
(2) Remove the wheel and tire assemblies.(3) Compress the caliper.
(4) Remove the caliper, (Refer to 5 - BRAKES/HY-
DRAULIC/MECHANICAL/DISC BRAKE CALIPERS
- REMOVAL).
(5) Remove the caliper by tilting the top up and off
the caliper adapter (Fig. 12).
NOTE: Do not allow brake hose to support caliper
assembly.
(6) Support and hang the caliper. (Fig. 13)
(7) Remove the inboard brake shoe from the cali-
per adapter (Fig. 14).
Fig. 11 BRAKE HOSE MOUNT DRIVERS SIDE
1 - MOUNTING BOLT
2 - WHEEL SPEED SENSOR WIRE
3 - BRAKE HOSE
Fig. 12 Caliper
1 - CALIPER
2 - CALIPER ADAPTER
Fig. 13 DISC BRAKE CALIPER - FRONT
1 - STEERING KNUCKLE
2 - DISC BRAKE CALIPER
3 - CALIPER MOUNTING ADAPTER
4 - DISC BRAKE ROTOR
DRBRAKES - BASE 5 - 13
BRAKE LINES (Continued)

(5) Remove the reservoir from the master cylinder
by pulling upwards.
(6) Remove old grommets from cylinder body (Fig.
42).
INSTALLATION
CAUTION: Do not use any type of tool to install the
grommets. Tools may cut, or tear the grommets cre-
ating a leak problem after installation. Install the
grommets using finger pressure only.
(1) Lubricate the new grommets with clean brake
fluid and Install new grommets in cylinder body. Use
finger pressure to install and seat grommets.
(2) Start the reservoir in grommets. Then rock the
reservoir back and forth while pressing downward to
seat it into the grommets.
(3) Install the mounting bolt for the reservoir to
the master cylinder.
(4) Reconnect the electrical connector to the fluid
reservoir level switch.
(5) Remove the prop rod from the vehicle.
(6) Fill and bleed base brake system,(Refer to 5 -
BRAKES - STANDARD PROCEDURE).
BRAKE JUNCTION BLOCK
REMOVAL
(1) Remove the brake lines from the junction block
(Fig. 43).
(2) Remove the junction block mounting bolt and
remove the junction block from the bracket (Fig. 43).
INSTALLATION
(1) Position the junction block on the bracket and
install the mounting bolt. Tighten the mounting bolt
to 23 N´m (210 in. lbs.) (Fig. 43).
(2) Install the brake lines into the junction block
and tighten to 19-23 N´m (170-200 in. lbs.) (Fig. 43).
(3) Bleed the base brake system, (Refer to 5 -
BRAKES/HYDRAULIC/MECHANICAL - STAN-
DARD PROCEDURE).
MASTER CYLINDER
DESCRIPTION
A two-piece master cylinder is used on all models.
The cylinder body containing the primary and sec-
ondary pistons is made of aluminum. The removable
fluid reservoir is made of nylon reinforced with glass
fiber. The reservoir stores reserve brake fluid for the
hydraulic brake circuits and has a switch for indicat-
ing low fluid levels. The reservoir is the only service-
able component.
The fluid compartments of the nylon reservoir are
interconnected to permit fluid level equalization.
However, the equalization feature does not affect cir-
cuit separation in the event of a front or rear brake
malfunction. The reservoir compartments will retain
enough fluid to operate the functioning hydraulic cir-
cuit.
Care must be exercised when removing/installing
the master cylinder connecting lines. The threads in
the cylinder fluid ports can be damaged if care is not
exercised. Start all brake line fittings by hand to
avoid cross threading.
Fig. 42 FLUID RESERVOIR
1 - MASTER CYLINDER CAP
2 - FLUID RESERVOIR
3 - FLUID LEVEL SWITCH
4 - MASTER CYLINDER
5 - MOUNTING BOLT
6 - GROMMETS
Fig. 43 JUNCTION BLOCK
1 - BRAKE LINES
2 - JUNCTION BLOCK
5 - 24 BRAKES - BASEDR
FLUID RESERVOIR (Continued)

STANDARD PROCEDURE - MASTER CYLINDER
BLEEDING
A new master cylinder should be bled before instal-
lation on the vehicle. Required bleeding tools include
bleed tubes and a wood dowel to stroke the pistons.
Bleed tubes can be fabricated from brake line.
(1) Mount master cylinder in vise.
(2) Attach bleed tubes to cylinder outlet ports.
Then position each tube end into reservoir (Fig. 46).
(3) Fill reservoir with fresh brake fluid.
(4) Press cylinder pistons inward with wood dowel.
Then release pistons and allow them to return under
spring pressure. Continue bleeding operations until
air bubbles are no longer visible in fluid.
REMOVAL
REMOVAL - ALL EXCEPT HYDROBOOST
(1) Depress the brake pedal five times to deplete
any vacuum that may remain in the booster unit.
(2) Siphon and drain the fluid from the reservoir.
(3) Disconnect the electrical connector for the low
fluid level.
(4) Place a towel or rag under the master cylinder
outlet port area to protect the vehicle from brake
fluid damage.
(5) Remove the brake lines from the master cylin-
der (Fig. 47).
(6) Remove the mounting nuts from the master
cylinder (Fig. 47).
(7) Remove the master cylinder.NOTE: Gently ease the master cylinder & reservoir
assembly away from the booster, During removal
the master cylinder should be kept as perpendicular
to the front of the booster as possible to avoid
excess interference with the booster output rod
(Fig. 49) and in order not to dislodge the output rod
from its seat inside the booster.
REMOVAL - HYDROBOOST
(1) Remove the brake lines from the master cylin-
der (Fig. 48).
(2) Disconnect the electrical connector for the low
fluid level.
(3) Remove the mounting nuts from the master
cylinder (Fig. 48).
(4) Remove the master cylinder.
NOTE: Using care remove the master cylinder
directly forward in order not to dislodge the output
rod from its seat inside the booster.Fig. 46 Master Cylinder Bleeding±Typical
1 - BLEEDING TUBES
2 - RESERVOIR
Fig. 47 MASTER CYLINDER
1 - MASTER CYLINDER RESERVOIR
2 - POWER BRAKE BOOSTER
3 - BRAKE LINES
4 - MASTER CYLINDER
5 - 26 BRAKES - BASEDR
MASTER CYLINDER (Continued)

INSTALLATION
INSTALLATION - ALL EXCEPT HYDROBOOST
NOTE: If master cylinder is replaced bleed cylinder
before installation.
NOTE: Make sure the output rod of the brake
booster is in position and retained by a output rod
retaining ring, by looking into the boosters master
cylinder mounting hole. This position will enable
the output rod to enter inside of the master cylinder
plunger sleeve during installation. Proper position
is obtained when the output rod is centered perpen-
dicular to the master cylinder mounting hole (Fig.
49).
NOTE: Prior to installing the master cylinder assem-
bly check that there is a vacuum seal present at the
shoulder of the master cylinder flange and it's neck.
A square seal must be present to ensure vacuum
integrity with the booster.
(1) Gently install the master cylinder on the
booster mounting studs.
NOTE: Take precautions to locate the master cylin-
der plunger over the booster output rod, before
installing the master cylinder. If correctly fitted the
master cylinder should slide easily onto the booster
output rod before the mounting studs are engaged
in the flange holes of the master cylinder.(2) Install new mounting nuts and tighten to 25
N´m (221 in. lbs.)
(3) Install the brake lines and tighten to 19 N´m
(170 in. lbs.)
(4) Reconnect the electrical connector for the low
fluid level switch.
(5) Fill and bleed the base brake system. (Refer to
5 - BRAKES - STANDARD PROCEDURE).
INSTALLATION - HYDROBOOST
NOTE: If master cylinder is replaced bleed cylinder
before installation.
(1) Install the master cylinder on the booster
mounting studs (Fig. 48).
(2) Install new mounting nuts and tighten to 25
N´m (221 in. lbs.)
(3) Install the brake lines and tighten to 19 N´m
(170 in. lbs.)
(4) Reconnect the elctrical connector for the low
fluid level switch.
(5) Fill and bleed the base brake system. (Refer to
5 - BRAKES - STANDARD PROCEDURE).
Fig. 48 HYDROBOOST MASTER CYLINDER
1 - HYDROBOOST UNIT
2 - MASTER CYLINDER RESERVOIR
3 - MASTER CYLINDER
4 - MOUNTING NUTS
Fig. 49 OUTPUT ROD ORIENTATION
1 - MASTER CYLINDER RESERVOIR
2 - CHECK VALVE
3 - VACUUM BOOST UNIT
4 - BOOSTER MOUNTING STUDS
5 - INPUT ROD
6 - OUTPUT ROD
7 - MASTER CYLINDER MOUNTING STUDS
8 - MASTER CYLINDER PLUNGER SLEEVE
9- MASTER CYLINDER
10 - ELECTRICAL CONNECTOR
DRBRAKES - BASE 5 - 27
MASTER CYLINDER (Continued)

HYDRO-BOOST BRAKE
BOOSTER
DIAGNOSIS AND TESTING - HYDRAULIC
BOOSTER
The hydraulic booster uses hydraulic pressure from
the power steering pump. Before diagnosing a
booster problem, first verify the power steering pump
is operating properly. Perform the following checks.
²Check the power steering fluid level.
²Check the brake fluid level.
²Check all power steering hoses and lines for
leaks and restrictions.
²Check power steering pump pressure.
NOISES
The hydraulic booster unit will produce certain
characteristic booster noises. The noises may occur
when the brake pedal is used in a manner not asso-
ciated with normal braking or driving habits.
HISSING
A hissing noise may be noticed when above normal
brake pedal pressure is applied, 40 lbs. or above. The
noise will be more noticeable if the vehicle is not
moving. The noise will increase with the brake pedal
pressure and an increase of system operating temper-
ature.
CLUNK-CHATTER-CLICKING
A clunk-chatter-clicking may be noticed when the
brake pedal is released quickly, after above normal
brake pedal pressure is applied 50-100 lbs..
BOOSTER FUNCTION TEST
With the engine off depress the brake pedal several
times to discharge the accumulator. Then depress the
brake pedal using 40 lbs. of force and start the
engine. The brake pedal should fall and then push
back against your foot. This indicates the booster is
operating properly.
ACCUMULATOR LEAKDOWN
(1) Start the engine, apply the brakes and turn the
steering wheel from lock to lock. This will ensure the
accumulator is charged. Turn off the engine and let
the vehicle sit for one hour. After one hour thereshould be at least two power assisted brake applica-
tion with the engine off. If the system does not retain
a charge the booster must be replaced.
(2) With the engine off depress the brake pedal
several times to discharge the accumulator. Grasp
the accumulator and see if it wobbles or turns. If it
does the accumulator has lost a gas charge and the
booster must be replaced.
SEAL LEAKAGE
If the booster leaks from any of the seals the
booster assembly must be replaced (Fig. 54).
²INPUT ROD SEAL:Fluid leakage from rear
end of the booster.
²PISTON SEAL:Fluid leakage from vent at
front of booster.
²HOUSING SEAL:Fluid leakage between hous-
ing and housing cover.
²SPOOL VALVE SEAL:Fluid leakage near
spool plug.
²RETURN PORT FITTING SEAL:Fluid leak-
age from port fitting.
Fig. 54 Hydraulic Booster Seals
1 - PUMP
2 - GEAR
3 - INPUT SEAL
4 - HOUSING SEAL
5 - ACCUMULATOR SEAL
6 - PISTON SEAL
7 - SPOOL PLUG SEAL
8 - RETURN
5 - 30 BRAKES - BASEDR

HYDRAULIC BOOSTER DIAGNOSIS CHART
CONDITION POSSIBLE CAUSES CORRECTION
Slow Brake Pedal Return 1. Excessive seal friction in booster. 1. Replace booster.
2. Faulty spool valve action. 2. Replace booster.
3. Restriction in booster return hose. 3. Replace hose.
4. Damaged input rod. 4. Replace booster.
Excessive Brake Pedal
Effort.1. Internal or external seal leakage. 1. Replace booster.
2. Faulty steering pump. 2. Replace pump.
Brakes Self Apply 1. Dump valve faulty. 1. Replace booster.
2. Contamination in hydraulic
system.2. Flush hydraulic system and replace
booster.
3. Restriction in booster return hose. 3. Replace hose.
Booster Chatter, Pedal
Vibration1. Slipping pump belt. 1. Replace power steering belt.
2. Low pump fluid level. 2. Fill pump and check for leaks.
Grabbing Brakes 1. Low pump flow. 1. Test and repair/replace pump.
2. Faulty spool valve action. 2. Replace booster.
STANDARD PROCEDURE - BLEEDING
The hydraulic booster is generally self-bleeding,
this procedure will normally bleed the air from the
booster. Normal driving and operation of the unit will
remove any remaining trapped air.
(1) Fill power steering pump reservoir.
(2) Disconnect fuel shutdown relay and crank the
engine for several seconds, Refer to Fuel System for
relay location and WARNING.
(3) Check fluid level and add if necessary.
(4) Connect fuel shutdown relay and start the
engine.
(5) Turn the steering wheel slowly from lock to
lock twice.
(6) Stop the engine and discharge the accumulator
by depressing the brake pedal 5 times.
(7) Start the engine and turn the steering wheel
slowly from lock to lock twice.
(8) Turn off the engine and check fluid level and
add if necessary.
NOTE: If fluid foaming occurs, wait for foam to dis-
sipate and repeat steps 7 and 8.
REMOVAL
NOTE: If the booster is being replaced because the
power steering fluid is contaminated, flush the
power steering system before replacing the booster.
(1) With engine off depress the brake pedal 5
times to discharge the accumulator.
(2) Remove brake lines from master cylinder.
(3) Remove mounting nuts from the master cylin-
der.
(4) Remove the bracket from the hydraulic booster
lines and master cylinder mounting studs.
(5) Remove the master cylinder.
(6) Remove the return hose and the two pressure
lines from the hydraulic booster (Fig. 55).
(7) Remove the booster push rod clip, washer and
rod remove from the brake pedal.
(8) Remove the mounting nuts from the hydraulic
booster and remove the booster.
DRBRAKES - BASE 5 - 31
HYDRO-BOOST BRAKE BOOSTER (Continued)

INSTALLATION
(1) Install the hydraulic booster and tighten the
mounting nuts to 28 N´m (21 ft. lbs.).
(2) Install the booster push rod, washer and clip
onto the brake pedal.
(3) Install the master cylinder on the mounting
studs. and tighten the mounting nuts to 23 N´m (17
ft. lbs.).
(4) Install the brake lines to the master cylinder
and tighten to 19-200 N´m (170-200 in. lbs.).
(5) Install the hydraulic booster line bracket onto
the master cylinder mounting studs.
(6) Install the master cylinder mounting nuts and
tighten to 23 N´m (17 ft. lbs.).
(7) Install the hydraulic booster pressure lines to
the bracket and booster.
(8) Tighten the pressure lines to 41 N´m (30 ft.
lbs.).
NOTE: Inspect o-rings on the pressure line fittings
to insure they are in good condition before installa-
tion. Replace o-rings if necessary.
(9) Install the return hose to the booster.
(10) Bleed base brake system, (Refer to 5 -
BRAKES/HYDRAULIC/MECHANICAL - STAN-
DARD PROCEDURE).
(11) Fill the power steering pump with fluid,
(Refer to 19 - STEERING/PUMP - STANDARD PRO-
CEDURE).
CAUTION: MOPAR (MS-9602) ATF+4 is to be used in
the power steering system. No other power steering
or automatic transmission fluid is to be used in thesystem. Damage may result to the power steering
pump and system if any other fluid is used, and do
not overfill.
(12) Bleed the hydraulic booster (Refer to 5 -
BRAKES/HYDRAULIC/MECHANICAL/POWER
BRAKE BOOSTER - STANDARD PROCEDURE).
ROTORS
DIAGNOSIS AND TESTING
DISC BRAKE ROTOR
The rotor braking surfaces should not be refinished
unless necessary.
Light surface rust and scale can be removed with a
lathe equipped with dual sanding discs. The rotor
surfaces can be restored by machining with a disc
brake lathe if surface scoring and wear are light.
Replace the rotor for the following conditions:
²Severely Scored
²Tapered
²Hard Spots
²Cracked
²Below Minimum Thickness
ROTOR MINIMUM THICKNESS
Measure rotor thickness at the center of the brake
shoe contact surface. Replace the rotor if below min-
imum thickness, or if machining would reduce thick-
ness below the allowable minimum.
Rotor minimum thickness is usually specified on
the rotor hub. The specification is either stamped or
cast into the hub surface.
ROTOR RUNOUT
Check rotor lateral runout with dial indicator
C-3339 (Fig. 56). Excessive lateral runout will cause
brake pedal pulsation and rapid, uneven wear of the
brake shoes. Position the dial indicator plunger
approximately 25.4 mm (1 in.) inward from the rotor
edge.
NOTE: Be sure wheel bearing has zero end play
before checking rotor runout.
Maximum allowable rotor runout is 0.127 mm
(0.005 in.).
ROTOR THICKNESS VARIATION
Variations in rotor thickness will cause pedal pul-
sation, noise and shudder.
Measure rotor thickness at 6 to 12 points around
the rotor face (Fig. 57).
Fig. 55 HYDRO-BOOST UNIT
1 - INLET HOSE
2 - HYDRO-BOOST UNIT
3 - MASTER CYLINDER UNIT
4 - RETURN HOSE
5 - OUTLET HOSE
5 - 32 BRAKES - BASEDR
HYDRO-BOOST BRAKE BOOSTER (Continued)

FRONT WHEEL SPEED
SENSOR
DESCRIPTION
The ABS brake system uses 3 wheel speed sensors.
A sensor is mounted to each front hub/bearings. The
third sensor is mounted on top of the rear axle dif-
ferential housing.
OPERATION
The Wheel Speed Sensor consists of a magnet sur-
rounded by windings from a single strand of wire.
The sensor sends a small AC signal to the CAB. This
signal is generated by magnetic induction. The mag-
netic induction is created when a toothed sensor ring
(exciter ring or tone wheel) passes the stationary
magnetic WSS.
When the ring gear is rotated, the exciter ring
passes the tip of the WSS. As the exciter ring tooth
approaches the tip of the WSS, the magnetic lines of
force expand, causing the magnetic field to cut across
the sensor's windings. This, in turn causes current to
flow through the WSS circuit (Fig. 1) in one direc-
tion. When the exciter ring tooth moves away from
the sensor tip, the magnetic lines of force collapse
cutting the winding in the opposite direction. This
causes the current to flow in the opposite direction.
Every time a tooth of the exciter ring passes the tip
of the WSS, an AC signal is generated. Each AC sig-
nal (positive to negative signal or sinewave) is inter-
preted by the CAB. It then compares the frequency of
the sinewave to a time value to calculate vehicle
speed. The CAB continues to monitor the frequency
to determine a deceleration rate that would indicate
a possible wheel-locking tendency.
The signal strength of any magnetic induction sen-
sor is directly affected by:
²Magnetic field strength; the stronger the mag-
netic field, the stronger the signal
²Number of windings in the sensor; more wind-
ings provide a stronger signal
²Exciter ring speed; the faster the exciter ring/
tone wheel rotates, the stronger the signal will be
²Distance between the exciter ring teeth and
WSS; the closer the WSS is to the exciter ring/tone
wheel, the stronger the signal will be
The rear WSS is not adjustable. A clearance speci-
fication has been established for manufacturing toler-
ances. If the clearance is not within these
specifications, then either the WSS or other compo-
nents may be damaged. The clearance between the
WSS and the exciter ring is 0.005 ± 0.050 in.
The assembly plant performs a ªRolls Testº on
every vehicle that leaves the assembly plant. One of
the test performed is a test of the WSS. To properlytest the sensor, the assembly plant connects test
equipment to the Data Link Connector (DLC). This
connector is located to the right of the steering col-
umn and attached to the lower portion of the instru-
ment panel (Fig. 2). The rolls test terminal is spliced
to the WSS circuit. The vehicle is then driven on a
set of rollers and the WSS output is monitored for
proper operation.
Fig. 1 Operation of the Wheel Speed Sensor
1 - MAGNETIC CORE
2 - CAB
3 - AIR GAP
4 - EXCITER RING
5 - COIL
Fig. 2 Data Link Connector - Typical
1 - 16±WAY DATA LINK CONNECTOR
DRBRAKES - ABS 5 - 47

PRESSURE INCREASE
The inlet valve is open and the outlet valve is
closed during the pressure increase cycle. The pres-
sure increase cycle is used to reapply thew brakes.
This cycle controls re-application of fluid apply pres-
sure.
REMOVAL
(1) Install a prop rod on the brake pedal to keep
pressure on the brake system.
(2) Disconnect the battery cables from the battery.
(3) Remove the battery.
(4) Disconnect the two electrical harness connec-
tors (Fig. 5).
(5) Remove the five brake lines from the HCU
(Fig. 5).
(6) Remove HCU/CAB mounting bolts and remove
the HCU/CAB (Fig. 5).
INSTALLATION
NOTE: If the CAB is being replaced with a new CAB
is must be reprogrammed with the use of a DRB III.
(1) Install HCU/CAB on the mounts and Tighten
the bolts to 15N´m (11 ft. lbs.) (Fig. 5).
(2) Install the five brake lines to the HCU and
tighten to 19 N´m (170 in. lbs.) (Fig. 5).
(3) Install the two electrical harness connectors to
the HCU/CAB and push down on the release to
secure the connectors.
(4) Install the battery.
(5) Install the battery cables to the battery.
(6) Remove the prop rod on the brake pedal.
(7) Bleed ABS brake system (Refer to 5 - BRAKES
- STANDARD PROCEDURE).
RWAL VALVE
DESCRIPTION
Rear Wheel Antilock (RWAL) brake system is stan-
dard equipment on 1500 series vehicles. The RWAL
brake system is designed to prevent rear wheel
lock-up on virtually all types of road surfaces. RWAL
braking is desirable because a vehicle which is
stopped without locking the rear wheels will retain
directional stability. This allows the driver to retain
greater control of the vehicle during braking.
The valve is located on the drivers side inner
fender under the hood. The valve modulates hydrau-
lic pressure to the rear brakes.
The RWAL components include:
²RWAL Valve
²Controller Antilock brake (CAB)
²Rear Wheel Speed Sensor (WSS)
OPERATION
When the brakes are applied, hydraulic fluid is
routed from the master cylinder's secondary circuit to
the RWAL valve. From there hydraulic fluid is routed
to the rear brakes. The Controller Antilock Brake
(CAB) contains an Electronic Variable Brake Propor-
tioning (EVBP) control algorithm, which proportions
the applied braking force to the rear wheels during
braking. The EVBP function of the RWAL system
takes the place of a conventional hydraulic propor-
tioning valve. The CAB monitors the rear wheel
speed through the rear wheel speed sensor and cal-
culates an estimated vehicle deceleration. When an
established deceleration threshold is exceeded, an
isolation valve is closed to hold the applied brake
pressure to the rear brakes constant. Upon further
increases in the estimated vehicle deceleration, the
isolation valve is selectively opened to increase rear
brake pressure in proportion to the front brake pres-
sure. If impending rear wheel lock-up is sensed, the
CAB signals the RWAL valve to modulate hydraulic
brake pressure to the rear wheels to prevent lock-up.
NORMAL BRAKING Since the RWAL valve also
performs the EVBP or proportioning function, vehicle
deceleration under normal braking may be sufficient
to trigger the EVBP function of the RWAL system
without full RWAL activity as would normally occur
during an impending rear wheel lock-up. As previ-
ously mentioned, the isolation valve is selectively
closed and opened to increase rear brake pressure in
proportion to the front brake pressure under EVBP
control. Slight brake pedal pulsations may be noticed
as the isolation valve is opened.
Fig. 5 HYDRAULIC CONTROL UNIT
1 - HYDRAULIC CONTROL UNIT
2 - MOUNTING BOLTS
5 - 50 BRAKES - ABSDR
HCU (HYDRAULIC CONTROL UNIT) (Continued)