1998 DODGE RAM 1500 system

TONE WHEEL
DIAGNOSIS AND TESTING - REAR WHEEL
SPEED SENSOR
Diagnosis of base brake conditions which are
mechanical in nature should be performed first. This
includes brake noise, lack of power assist, parking
brake, or vehicle vibration during normal braking.
The Antilock brake system performs several self-
tests every time the ignition switch is turned on and
the vehicle is driven. The CAB monitors the system
inputs and outputs circuits to verify the system is
operating properly. If the CAB senses a malfunction
in the system it will set a DTC into memory and trig-
ger the warning lamp.
NOTE: The MDS or DRB III scan tool is used to
diagnose the Antilock Brake system. For test proce-
dures refer to the Chassis Diagnostic Manual.
HYDRAULIC/MECHANICAL
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 sys-
tem to control the slip of the rear wheels in partial
braking range. The braking force of the rear wheels
is controlled electronically by using the inlet and out-
let valves located in the integrated control unit
(ICU).
OPERATION - ELECTRONIC VARIABLE BRAKE
PROPORTIONING
EVBP is able to decrease, hold and increase rear
brake pressure without activating full ABS control.
Upon entry into EVBP the inlet valve for the rear
brake circuit is switched on so that the fluid supply
from the master cylinder is shut off. In order to
decrease the rear brake pressure, the outlet valve for
the rear brake circuit is pulsed. This allows fluid to
enter the low pressure accumulator (LPA) in the
hydraulic control unit (HCU) resulting in a drop in
fluid pressure to the rear brakes. In order to increase
the rear brake pressure, the outlet valve is switched
off and the inlet valve is pulsed. This increases the
pressure to the rear brakes.
The EVBP will remain functional during many
ABS fault modes. If both the red BRAKE and amber
ABS warning indicators are illuminated, the EVBP
may not be functioning.
HCU (HYDRAULIC CONTROL
UNIT)
DESCRIPTION
The HCU consists of a valve body, pump motor, low
pressure accumulators, inlet valves, outlet valves and
noise attenuators.
OPERATION
Accumulators in the valve body store extra fluid
released to the system for ABS mode operation. The
pump provides the fluid volume needed and is oper-
ated by a DC type motor. The motor is controlled by
the CAB.
The valves modulate brake pressure during
antilock braking and are controlled by the CAB.
The HCU provides three channel pressure control
to the front and rear brakes. One channel controls
the rear wheel brakes in tandem. The two remaining
channels control the front wheel brakes individually.
During antilock braking, the solenoid valves are
opened and closed as needed.
During normal braking, the HCU solenoid valves
and pump are not activated. The master cylinder and
power booster operate the same as a vehicle without
an ABS brake system.
NOTE: The three modes mentioned below do occur
but not necessarily in the order listed everytime.
During antilock braking, solenoid valve pressure
modulation occurs in three stages, pressure increase,
pressure hold, and pressure decrease. The valves are
all contained in the valve body portion of the HCU.
PRESSURE DECREASE
The outlet valve is opened and the inlet valve is
closed during the pressure decrease cycle.
A pressure decrease cycle is initiated when speed
sensor signals indicate high wheel slip at one or
more wheels. At this point, the CAB closes the inlet
then opens the outlet valve, which also opens the
return circuit to the accumulators. Fluid pressure is
allowed to bleed off (decrease) as needed to prevent
wheel lock.
Once the period of high wheel slip has ended, the
CAB closes the outlet valve and begins a pressure
increase or hold cycle as needed.
PRESSURE HOLD
Both solenoid valves are closed in the pressure
hold cycle but only the inlet valve is energized. Fluid
apply pressure in the control channel is maintained
at a constant rate. The CAB maintains the hold cycle
until sensor inputs indicate a pressure change is nec-
essary.
DRBRAKES - ABS 5 - 49

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)

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 electrical harness connector
(Fig. 6).
(5) Remove the brake lines from the rwal valve
(Fig. 6).
(6) Remove rwal valve mounting nuts and remove
the rwal valve (Fig. 6).
INSTALLATION
(1) Install rwal valve and Tighten the nuts to 15
N´m (11 ft. lbs.) (Fig. 6).
(2) Install the brake lines to the rwal valve and
tighten to 19 N´m (170 in. lbs.) (Fig. 6).
(3) Install the electrical harness connector to the
rwal valve and secure the connector.
(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).
Fig. 6 RWAL VALVE
1 - RWAL VALVE
2 - MOUNTING NUTS
DRBRAKES - ABS 5 - 51
RWAL VALVE (Continued)

(2) Apply a light coating of grease to the inside
diameter of the master cylinder push rod eye.
(3) Install clutch master cylinder on dash panel
and tighten clutch master cylinder nuts to 28 N´m
(21 ft. lbs.).
(4) Install clutch master cylinder push rod pin.
(5) Connect clutch pedal position interlock switch
wires.
(6) Install plastic clip securing hydraulic line to
the dash panel into the lower dash panel flange.
(7) Install plastic clip securing hydraulic line to
the dash panel onto the upper dash panel stud.
(8) Raise vehicle.
(9) Install slave cylinder and verify cylinder rod is
properly seated in release lever.
(10) Install and tighten slave cylinder nuts to 23
N´m (17 ft. lbs.).
(11) Ifnewclutch linkage is being installed, con-
nect the clutch hydraulic line to the clutch slave cyl-
inder.
CAUTION: Once the clutch hydraulic line is con-
nected to the slave cylinder, it should never be dis-
connected.
(12) Lower vehicle.
(13) Operate linkage several times to verify proper
operation.
CLUTCH PEDAL POSITION
SWITCH
DESCRIPTION
A clutch pedal position switch (CPPS) is mounted
on the clutch master cylinder push rod (Fig. 20). The
wiring harness connector is inside of the vehicle
under the left side of the instrument panel.
NOTE: Switch is serviced with clutch master cylin-
der.
OPERATION
The clutch pedal position switch is used to prevent
starter motor engagement unless the clutch pedal is
depressed. An input from this switch is also used to
either shut down/prevent operation of the speed con-
trol system when pedal is depressed. The position
switch is an integral part of the clutch master cylin-
der push rod.
DIAGNOSIS AND TESTING
(1) Disconnect switch 2-wire connector attached to
pedal support bracket, under instrument panel to left
of clutch pedal (Fig. 21).(2) Check switch continuity with an ohmmeter
while operating clutch pedal.
²Pedal Depressed - Continuity
²Pedal Released - No Continuity
(3) If continuity is not present or always present,
replace clutch master cylinder. Switch is not serviced
separately.
Fig. 20 LOCATION, CLUTCH PEDAL
POSITION SWITCH
1 - CLUTCH MASTER CYLINDER
2 - CLUTCH PEDAL POSITION SWITCH
Fig. 21 CLUTCH SWITCH TEST POINT
1 - PEDAL SUPPORT BRACKET
2 - ELECTRICAL CONNECTOR
DRCLUTCH 6 - 13
LINKAGE (Continued)

COOLING
TABLE OF CONTENTS
page page
COOLING
DESCRIPTION
DESCRIPTION - COOLING SYSTEM FLOW
3.7L/4.7L/5.7L ENGINE..................1
DESCRIPTION - COOLING SYSTEM FLOW -
5.9L DIESEL..........................3
DESCRIPTION - HOSE CLAMPS...........3
OPERATION
OPERATION - COOLING SYSTEM.........5
OPERATION - HOSE CLAMPS............5
DIAGNOSIS AND TESTING
DIAGNOSIS AND TESTINGÐON-BOARD
DIAGNOSTICS (OBD)...................5
DIAGNOSIS AND TESTING - COOLING
SYSTEM - TESTING FOR LEAKS..........5
DIAGNOSIS AND TESTING - COOLING
SYSTEM DIESEL ENGINE................7
DIAGNOSIS AND TESTING - PRELIMINARY
CHECKS............................10
STANDARD PROCEDURE
STANDARD PROCEDURE - COOLANT
LEVEL CHECK........................17STANDARD PROCEDURE - COOLING
SYSTEM CLEANING/REVERSE FLUSHING . . 17
STANDARD PROCEDURE - DRAINING
COOLING SYSTEM - ALL GAS ENGINES . . . 17
STANDARD PROCEDURE - REFILLING
COOLING SYSTEM - ALL GAS ENGINES . . . 18
STANDARD PROCEDURE - DRAINING
COOLING SYSTEM 5.9L DIESEL ENGINE . . . 18
STANDARD PROCEDURE - REFILLING
COOLING SYSTEM 5.9L DIESEL ENGINE . . . 19
STANDARD PROCEDURE - ADDING
ADDITIONAL COOLANT.................19
SPECIFICATIONS
TORQUE............................19
SPECIFICATIONS -....................20
SPECIAL TOOLS
COOLING...........................20
ACCESSORY DRIVE......................21
ENGINE...............................30
TRANSMISSION.........................67
COOLING
DESCRIPTION
DESCRIPTION - COOLING SYSTEM FLOW
3.7L/4.7L/5.7L ENGINE
The cooling system regulates engine operating tem-
perature. It allows the engine to reach normal oper-
ating temperature as quickly as possible. It also
maintains normal operating temperature and pre-
vents overheating.The cooling system provides a means of heating
the passenger compartment and cooling the auto-
matic transmission fluid (if equipped). The cooling
system is pressurized and uses a centrifugal water
pump to circulate coolant through the system. The
coolant recovery/reserve system utilizes an ambient
overflow bottle (Fig. 2).
An optional factory installed maximum duty cool-
ing package is available on most models. This pack-
age will provide additional cooling capacity for
vehicles used under extreme conditions such as
trailer towing in high ambient temperatures (Fig. 1).
DRCOOLING 7 - 1

Fig. 1 Engine Cooling System Flow - 3.7L/4.7L
1 - LH CYL. HEAD
2 - BLEED
3 - THERMOSTAT LOCATION
4 - RH CYL. HEAD
5 - RH BANK CYL. BLOCK6 - LH BANK CYL. BLOCK
7 - COOLANT TEMP. SENSOR
8 - FROM HEATER CORE
9 - TO HEATER CORE
7 - 2 COOLINGDR
COOLING (Continued)

DESCRIPTION - COOLING SYSTEM FLOW -
5.9L DIESEL
The diesel engine cooling system consists of :
²Cross-flow radiator
²Belt driven water pump
²Cooling fan (attached to the electronic viscous
fan drive)
²Belt driven Electronic viscous fan drive
²Two piece fan shroud
²Radiator pressure cap
²Vertically mounted thermostat
²Coolant reserve/recovery system
²Transmission oil cooler
²Coolant
Coolant flow circuits for the 5.9L diesel engine are
shown in (Fig. 3).
DESCRIPTION - HOSE CLAMPS
The cooling system utilizes spring type hose
clamps. If a spring type clamp replacement is neces-
sary, replace with the original Mopartequipment
spring type clamp.
CAUTION: A number or letter is stamped into the
tongue of constant tension clamps. If replacement
is necessary, use only a original equipment clamp
with matching number or letter and ensure the
clamp has the same size width (Fig. 4).
Fig. 2 5.7L Engine Coolant System Flow
1 - LH CYLINDER HEAD
2 - TO RADIATOR3 - FROM RADIATOR
4 - TO RH CYLINDER HEAD
DRCOOLING 7 - 3
COOLING (Continued)

Fig. 3 Cooling System Circulation - 5.9L Diesel Engine
7 - 4 COOLINGDR
COOLING (Continued)