1998 DODGE RAM 1500 light

The cylinder reservoir can be replaced when neces-
sary. However, the aluminum body section of the
master cylinder is not a repairable component.
NOTE: If diagnosis indicates that an internal mal-
function has occurred, the aluminum body section
must be replaced as an assembly.
OPERATION
The master cylinder bore contains a primary and
secondary piston. The primary piston supplies
hydraulic pressure to the front brakes. The secondary
piston supplies hydraulic pressure to the rear brakes.
DIAGNOSIS AND TESTING - MASTER
CYLINDER/POWER BOOSTER
(1) Start engine and check booster vacuum hose
connections. A hissing noise indicates vacuum leak.
Correct any vacuum leak before proceeding.
(2) Stop engine and shift transmission into Neu-
tral.
(3) Pump brake pedal until all vacuum reserve in
booster is depleted.
(4) Press and hold brake pedal under light foot
pressure. The pedal should hold firm, if the pedal
falls away master cylinder is faulty (internal leak-
age).
(5) Start engine and note pedal action. It should
fall away slightly under light foot pressure then hold
firm. If no pedal action is discernible, power booster,
vacuum supply, or vacuum check valve is faulty. Pro-
ceed to the POWER BOOSTER VACUUM TEST.
(6) If the POWER BOOSTER VACUUM TEST
passes, rebuild booster vacuum reserve as follows:
Release brake pedal. Increase engine speed to 1500
rpm, close the throttle and immediately turn off igni-
tion to stop engine.
(7) Wait a minimum of 90 seconds and try brake
action again. Booster should provide two or more vac-
uum assisted pedal applications. If vacuum assist is
not provided, booster is faulty.
POWER BOOSTER VACUUM TEST
(1) Connect vacuum gauge to booster check valve
with short length of hose and T-fitting (Fig. 44).
(2) Start and run engine at curb idle speed for one
minute.
(3) Observe the vacuum supply. If vacuum supply
is not adequate, repair vacuum supply.
(4) Clamp hose shut between vacuum source and
check valve.
(5) Stop engine and observe vacuum gauge.
(6) If vacuum drops more than one inch HG (33
millibars) within 15 seconds, booster diaphragm or
check valve is faulty.
POWER BOOSTER CHECK VALVE TEST
(1) Disconnect vacuum hose from check valve.
(2) Remove check valve and valve seal from
booster.
(3) Use a hand operated vacuum pump for test.
(4) Apply 15-20 inches vacuum at large end of
check valve (Fig. 45).
(5) Vacuum should hold steady. If gauge on pump
indicates vacuum loss, check valve is faulty and
should be replaced.
Fig. 44 Typical Booster Vacuum Test Connections
1 - TEE FITTING
2 - SHORT CONNECTING HOSE
3 - CHECK VALVE
4 - CHECK VALVE HOSE
5 - CLAMP TOOL
6 - INTAKE MANIFOLD
7 - VACUUM GAUGE
Fig. 45 Vacuum Check Valve And Seal
1 - BOOSTER CHECK VALVE
2 - APPLY TEST VACUUM HERE
3 - VALVE SEAL
DRBRAKES - BASE 5 - 25
MASTER CYLINDER (Continued)

PEDAL
DESCRIPTION
NOTE: The brake pedal is serviced as a complete
assembly including accelerator pedal and the
bracket.
A suspended-type brake pedal is used. The pedal is
attached to the pedal support bracket with a pivot
shaft pin and bushings. If the bushings become dry a
spray lubricant can be used to eliminate noises. The
booster push rod is attached to the pedal with a clip.
The pedal, bushings, pivot pin and support bracket
are not serviceable components (Fig. 50).
OPERATION
The brake pedal is attached to the booster push
rod. When the pedal is depressed, the primary
booster push rod is depressed which moves the
booster secondary rod. The booster secondary rod
depress the master cylinder piston.
REMOVAL
NOTE: The brake pedal is serviced as a complete
assembly including accelerator pedal and the
bracket.
(1) Disconnect the negative battery cable.
(2) Remove the steering column opening cover(Re-
fer to 23 - BODY/INSTRUMENT PANEL/STEERING
COLUMN OPENING COVER - REMOVAL).(3) Remove the brake lamp switch and discard(Re-
fer to 8 - ELECTRICAL/LAMPS/LIGHTING - EXTE-
RIOR/BRAKE LAMP SWITCH - REMOVAL).
(4)On vehicles equipped with adjustable ped-
als.Disconnect the adjuster cable to the pedal (Fig.
51).
(5) Remove the steering column (Refer to 19 -
STEERING/COLUMN - REMOVAL).
(6) Remove the brake booster (Fig. 52)(Refer to 5 -
BRAKES/HYDRAULIC/MECHANICAL/POWER
BRAKE BOOSTER - REMOVAL).
(7) Disconnect the electrical connectors.
(8) Remove the module mounting bolts.
(9) Disconnect the accelerator pedal cable.
(10) Remove the pedal assembly mounting nuts/
fasteners (Fig. 52).
INSTALLATION
(1) Install the pedal assembly to the vehicle (Fig.
52).
(2) Install the mounting bolts (Fig. 52) and tighten
to 28 N´m (21 ft. lbs.).
(3) Reconnect the accelerator cable to the pedal.
(4) Install the module mounting bolts and tighten
to 38 N´m (28 ft. lbs.).
(5) Reconnect the electrical connectors.
(6) Install the brake booster (Refer to 5 - BRAKES/
HYDRAULIC/MECHANICAL/POWER BRAKE
BOOSTER - INSTALLATION).
(7) Install the steering column (Refer to 19 -
STEERING/COLUMN - INSTALLATION).
(8) Install a new brake lamp switch. (Refer to 8 -
ELECTRICAL/LAMPS/LIGHTING - EXTERIOR/
BRAKE LAMP SWITCH - REMOVAL).
Fig. 50 BRAKE PEDAL
1 - CLIP
2 - BUSHINGS
3 - PIVOT SHAFT PIN
4 - PEDAL ASSEMBLY
ADJUSTABLE PEDAL SHOWN
NON ADJUSTABLE PEDAL IS SIMILIAR
5-PAD
Fig. 51 PEDAL/CABLE
1 - CABLE
2 - BRAKE PEDAL ASSEMBLY
5 - 28 BRAKES - BASEDR

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)

INSTALLATION
(1) Install support plate on axle flange (Fig. 66).
Tighten attaching bolts to 115 N´m (85 ft. lbs.).
(2) Install parking brake cable in the brake lever.
(3) Install the park brake shoes (Refer to 5 -
BRAKES/PARKING BRAKE/SHOES - INSTALLA-
TION). (Fig. 66).
(4) Install axle shaft, (Refer to 3 - DIFFEREN-
TIAL & DRIVELINE/REAR AXLE - 9 1/4/AXLE
SHAFTS - INSTALLATION).
(5) Adjust brake shoes to drum with brake gauge
(Refer to 5 - BRAKES/PARKING BRAKE/SHOES -
ADJUSTMENTS).
(6) Install the rotor (Refer to 5 - BRAKES/HY-
DRAULIC/MECHANICAL/ROTORS - INSTALLA-
TION).
(7) Install the caliper adapter (Refer to 5 -
BRAKES/HYDRAULIC/MECHANICAL/DISC
BRAKE CALIPER ADAPTER - INSTALLATION).
(8) Install the caliper (Refer to 5 - BRAKES/HY-
DRAULIC/MECHANICAL/DISC BRAKE CALIPERS
- INSTALLATION).
(9) Install the wheel and tire assembly (Refer to 22
- TIRES/WHEELS/WHEELS - STANDARD PROCE-
DURE).
PARKING BRAKE
DESCRIPTION
The parking brakes are operated by a system of
cables and levers attached to a primary and second-
ary shoe positioned within the drum section of the
rotor.
The drum-in-hat design utilizes an independent set
of shoes to park the vehicle (Fig. 67).
OPERATION
To apply the parking brake the pedal is depressed.
This creates tension in the cable which pulls forward
on the park brake lever. The lever pushes the park
brake shoes outward and into contact with the drum
section of the rotor. The contact of shoe to rotor parks
the vehicle.
A torsion locking mechanism is used to hold the
pedal in an applied position. Parking brake release is
accomplished by the hand release.
A parking brake switch is mounted on the parking
brake lever and is actuated by movement of the
lever. The switch, which is in circuit with the red
warning light in the dash, will illuminate the warn-
ing light whenever the parking brake is applied.
Parking brake adjustment is controlled by a cable
tensioner mechanism. The cable tensioner, once
adjusted at the factory, should not need further
adjustment under normal circumstances. Adjustment
may be required if a new tensioner, or cables are
installed, or disconnected.
CABLES
REMOVAL
REMOVAL - FRONT PARKING BRAKE CABLE
(1) Raise and support vehicle.
(2) Lockout the parking brake cable (Fig. 69).
(3) Loosen adjusting nut to create slack in front
cable.
(4) Remove the front cable from the cable connec-
tor.
Fig. 66 SUPPORT PLATE WITH BRAKES MOUNTED
1 - SUPPORT PLATE
2 - MOUNTING NUTS
Fig. 67 SUPPORT PLATE WITH BRAKES MOUNTED
1 - SUPPORT PLATE
2 - MOUNTING NUTS
5 - 36 BRAKES - BASEDR
SUPPORT PLATE (Continued)

INSTALLATION - LEFT REAR CABLE
(1) Install the brake cable to the brake lever (Fig.
72).
(2) Install the brake cable to the frame bracket.
(3) Install the left brake cable to the equalizer.
(4) Adjust the brake cable at the equalizer and
adjuster nut.
SHOES
REMOVAL
(1) Raise and support the vehicle.
(2) Remove the tire and wheel assembly.
(3) Remove the disc brake caliper,(Refer to 5 -
BRAKES/HYDRAULIC/MECHANICAL/DISC
BRAKE CALIPERS - REMOVAL).
(4) Remove the disc brake rotor, (Refer to 5 -
BRAKES/HYDRAULIC/MECHANICAL/ROTORS -
REMOVAL).
(5) Lockout the parking brake cable (Fig. 74).
(6) Disengage the park brake cable from behind
the rotor assembly to allow easier disassembly of the
park brake shoes (Fig. 75).
(7) Remove the axleshaft (Fig. 76) (Refer to 3 -
DIFFERENTIAL & DRIVELINE/REAR AXLE - 9 1/4/
AXLE SHAFTS - REMOVAL).
(8) Disassemble the rear park brake shoes (Fig.
67).
CLEANING - REAR DRUM IN HAT BRAKE
Clean the individual brake components, including
the support plate exterior, with a water dampened
cloth or with brake cleaner. Do not use any other
cleaning agents. Remove light rust and scale fromthe brake shoe contact pads on the support plate
with fine sandpaper.
INSPECTION - REAR DRUM IN HAT BRAKE
As a general rule, riveted brake shoes should be
replaced when worn to within 0.78 mm (1/32 in.) of
the rivet heads. Bonded lining should be replaced
when worn to a thickness of 1.6 mm (1/16 in.).
Examine the lining contact pattern to determine if
the shoes are bent or the drum is tapered. The lining
should exhibit contact across its entire width. Shoes
exhibiting contact only on one side should be
replaced and the drum checked for runout or taper
(Fig. 77).
Fig. 73 PARKING BRAKE CABLE
1 - SUPPORT PLAT
2 - CABLE
3 - LEVER
Fig. 74 LOCK OUT PARKING CABLE
1 - LOCKING PLIERS
2 - PARKING BRAKE CABLE
Fig. 75 DISENGAGEMENT OF CABLE
1 - LEVER
2 - CABLE END
DRBRAKES - BASE 5 - 39
CABLES (Continued)

Inspect the adjuster screw assembly. Replace the
assembly if the star wheel or threads are damaged,
or the components are severely rusted or corroded
(Fig. 77).
Discard the brake springs and retainer components
if worn, distorted or collapsed. Also replace the
springs if a brake drag condition had occurred. Over-
heating will distort and weaken the springs.
Inspect the brake shoe contact pads on the support
plate, replace the support plate if any of the pads are
worn or rusted through. Also replace the plate if it is
bent or distorted (Fig. 77).
INSTALLATION
NOTE: On a new vehicle or after parking brake lin-
ing replacement, it is recommended that the park-
ing brake system be conditioned prior to use. This
is done by making one stop from 25 mph on dry
pavement or concrete using light to moderate force
on the parking brake foot pedal.
(1) Reassemble the rear park brake shoes (Fig. 67)
or (Fig. 78).
(2) Install the axleshaft (Fig. 76) (Refer to 3 - DIF-
FERENTIAL & DRIVELINE/REAR AXLE - 9 1/4/
AXLE SHAFTS - INSTALLATION) or (Refer to 3 -
DIFFERENTIAL & DRIVELINE/REAR AXLE - 11
1/2 AA/10 1/2 AA/AXLE SHAFTS - INSTALLATION).
(3) Install the park brake cable to the lever behind
the support plate.
(4) Unlock the park brake cable.
(5) Install the disc brake rotor (Refer to 5 -
BRAKES/HYDRAULIC/MECHANICAL/ROTORS -
INSTALLATION).(6) Install the disc brake caliper (Refer to 5 -
BRAKES/HYDRAULIC/MECHANICAL/DISC
BRAKE CALIPERS - INSTALLATION).
(7) Adjust the rear brake shoes (Refer to 5 -
BRAKES/PARKING BRAKE/SHOES - ADJUST-
MENTS).
Fig. 76 AXLE SHAFT
1 - AXLE SHAFT
2 - SUPPORT PLATE
3 - CALIPER
4 - PARK BRAKE SHOE ASSEMBLY
Fig. 77 PARK BRAKE SHOES
1 - SUPPORT PLATE
2 - SHOES
3 - RETURN SPRINGS
4 - RETAINER CLIPS
5 - ADJUSTER
Fig. 78 SHOE ASSEMBLY
1 - Park Brake Shoes
2 - Hold Downs
3 - Return Springs
5 - 40 BRAKES - BASEDR
SHOES (Continued)

(12) Rotate rotor to verify that the park brake
shoes are not dragging on the brake drum. If park
brake shoes are dragging, remove rotor and back off
star wheel adjuster one notch and recheck for brake
shoe drag against drum. Continue with the previous
step until brake shoes are not dragging on brake
drum.
(13) Install disc brake caliper on caliper adapter
(Refer to 5 - BRAKES/HYDRAULIC/MECHANICAL/
DISC BRAKE CALIPERS - INSTALLATION).
(14) Install wheel and tire.
(15) Tighten the wheel mounting nuts in the
proper sequence until all nuts are torqued to half the
specified torque. Then repeat the tightening sequence
to the full specified torque of 180 N´m (135 ft. lbs.)
1500 & 2500 Series or 195 N´m (145 ft. lbs.) 3500
Series.
(16) Lower vehicle.
(17) Apply and release the park brake pedal one
time. This will seat and correctly adjust the park
brake cables.
CAUTION: Before moving vehicle, pump brake
pedal several times to ensure the vehicle has a firm
enough pedal to stop the vehicle.
NOTE: On a new vehicle or after parking brake lin-
ing replacement, it is recommended that the park-
ing brake system be conditioned prior to use. This
is done by making one stop from 25 mph on dry
pavement or concrete using light to moderate force
on the parking brake foot pedal.
(18) Road test the vehicle to ensure proper func-
tion of the vehicle's brake system.
ADJUSTMENT - WITH ADJUSTING TOOL
Adjustment can be made with a standard brake
gauge or with adjusting tool. Adjustment is per-
formed with the complete brake assembly installed
on the backing plate.
(1) Be sure parking brake lever is fully released.
(2) Raise vehicle so rear wheels can be rotated
freely.
(3) Remove plug from each access hole in brake
support plates.
(4) Loosen parking brake cable adjustment nut
until there is slack in front cable.
(5) Insert adjusting tool through support plate
access hole and engage tool in teeth of adjusting
screw star wheel (Fig. 82).
(6) Rotate adjuster screw star wheel (move tool
handle upward) until slight drag can be felt when
wheel is rotated.
(7) Back off adjuster screw star wheel until brake
drag is eliminated.(8) Repeat adjustment at opposite wheel. Be sure
adjustment is equal at both wheels.
(9) Install support plate access hole plugs.
(10) Adjust parking brake cable and lower vehicle.
(11) Depress park brake pedal and make sure park
brakes hold the vehicle staionary.
(12) Release park brake pedal.
PEDAL
REMOVAL
(1) Release the parking brake.
(2) Raise the vehicle.
(3) Loosen the cable tensioner nut at the equalizer
to create slack in the front cable.
(4) Lower the vehicle.
(5) Remove the knee bolster, (Refer to 23 - BODY/
INSTRUMENT PANEL/STEERING COLUMN
OPENING COVER - REMOVAL).
(6) Disconnect the brake lamp wire from the
switch on the pedal assembly.
(7) Roll the carpet back, loosen the front cable
grommet from the floorpan and the cable retainer.
(8) Disengage the release rod (Fig. 83) from the
arm on the pedal assembly.
(9) Remove the bolts/nuts from the pedal assembly
and remove the assembly.
INSTALLATION
(1) Position the replacement pedal assembly on the
dash and cowl.
Fig. 82 Brake Adjustment
1 - STAR WHEEL
2 - LEVER
3 - BRAKE SHOE WEB
4 - SCREWDRIVER
5 - ADJUSTING TOOL
6 - ADJUSTER SPRING
5 - 42 BRAKES - BASEDR
SHOES (Continued)

BRAKES - ABS
TABLE OF CONTENTS
page page
BRAKES - ABS
DESCRIPTION.........................45
OPERATION...........................45
STANDARD PROCEDURE - ABS BRAKE
BLEEDING...........................46
SPECIFICATIONS
TORQUE CHART......................46
FRONT WHEEL SPEED SENSOR
DESCRIPTION.........................47
OPERATION...........................47
REMOVAL.............................48
INSTALLATION.........................48
REAR WHEEL SPEED SENSOR
DIAGNOSIS AND TESTING - REAR WHEEL
ANTILOCK...........................48
REMOVAL.............................48
INSTALLATION.........................48TONE WHEEL
DIAGNOSIS AND TESTING - REAR WHEEL
SPEED SENSOR......................49
HYDRAULIC/MECHANICAL
DESCRIPTION - ELECTRONIC VARIABLE
BRAKE PROPORTIONING...............49
OPERATION - ELECTRONIC VARIABLE
BRAKE PROPORTIONING...............49
HCU (HYDRAULIC CONTROL UNIT)
DESCRIPTION.........................49
OPERATION...........................49
REMOVAL.............................50
INSTALLATION.........................50
R WA L VA LV E
DESCRIPTION.........................50
OPERATION...........................50
REMOVAL.............................51
INSTALLATION.........................51
BRAKES - ABS
DESCRIPTION
The antilock brake system (ABS) is an electroni-
cally operated, three channel brake control system.
The vehicle has Electronic Variable Brake Propor-
tioning (EVBP) designed into the system which elim-
inates the combination/proportioning valve.
The system is designed to prevent wheel lockup
and maintain steering control during braking. Pre-
venting lockup is accomplished by modulating fluid
pressure to the wheel brake units.
The hydraulic system is a three channel design.
The front wheel brakes are controlled individually
and the rear wheel brakes in tandem. The ABS elec-
trical system is separate from other electrical circuits
in the vehicle. A specially programmed controller
antilock brake unit operates the system components.
ABS system major components include:
²Controller Antilock Brakes (CAB)
²Hydraulic Control Unit (HCU)
²Wheel Speed Sensors (WSS)
²ABS Warning Light
OPERATION
Battery voltage is supplied to the CAB. The CAB
performs a system initialization procedure at start
up. A check of the ABS motor is performed at 15miles per hour. Initialization consists of a static and
dynamic self check of system electrical components.
The static and dynamic checks occurs at ignition
start up. During the dynamic check, the CAB briefly
cycles solenoids to verify operation. An audible noise
may be heard during this self check. This noise
should be considered normal. The ABS motor and
pump are then checked at a speed of 15 mile per
hour.
If an ABS component exhibits a fault during ini-
tialization, the CAB illuminates the amber warning
light and registers a fault code in the microprocessor
memory.
The CAB monitors wheel speed sensor inputs con-
tinuously while the vehicle is in motion. However,
the CAB will not activate any ABS components as
long as sensor inputs indicate normal braking.
During normal braking, the master cylinder, power
booster and wheel brake units all function as they
would in a vehicle without ABS. The HCU compo-
nents are not activated.
The purpose of the antilock system is to prevent
wheel lockup. Preventing lockup helps maintain vehi-
cle braking action and steering control.
The antilock CAB activates the system whenever
sensor signals indicate periods of wheel slip.
The antilock system prevents lockup during a
wheel slip condition by modulating fluid apply pres-
sure to the wheel brake units.
DRBRAKES - ABS 5 - 45