
RADIATOR
The radiators are cross-flow types (horizontal
tubes) with design features that provide greater
strength along with sufficient heat transfer capabili-
Fig. 1 Cooling System Operation ± 2.5L VM Diesel
Fig. 2 Coolant Pressure Bottle ± 2.5L VM Diesel
Fig. 3 Low Coolant Warning Sensor Connector ±
2.5L VM Diesel
7 - 2 COOLING SYSTEMNS/GS
GENERAL INFORMATION (Continued)

THERMOSTAT OPERATION
2.5 VM DIESEL
The engine cooling thermostats are wax pellet
driven, reverse poppet choke type. They are designed
to provide the fastest warm up possible by prevent-
ing leakage through them and to guarantee a mini-
mum engine operating temperature (Fig. 10). The
thermostat has a hole to bleed off air in the cooling
system during engine warm up. The thermostat
begins to open at 80É C62É (176É F64É).
PRESSURE/VENT CAP
WARNING: Engine coolant can reach temperatures
of 200É fahrenheit or greater. If the cooling system
is opened with coolant at a high temperature, hot
coolant can be forced out of the system under high
pressures, causing personal injury. Allow system to
cool down prior to removing the pressure cap.
The pressure/vent cap is secured to the coolant
tank neck by a means of a cam lock system. This cap
releases excess pressure at some point within a
range of 90-117 kPa (13- 17 psi) for gasoline engines,
and 110±124 kPa (16±18 psi) for diesel engines. The
actual pressure relief point (in pounds) is labeled on
top of the cap (Fig. 11).
The cooling system will operate at pressures
slightly above atmospheric pressure. This results in a
higher coolant boiling point allowing increased radi-
ator cooling capacity. The cap (Fig. 11) contains a
spring-loaded pressure relief valve. This valve opens
when system pressure reaches approximately 103
kPa (15 psi).
When the engine is cooling down, vacuum is
formed within the cooling system. To prevent collapse
of the radiator and coolant hoses from this vacuum, a
vacuum valve is used within the cap. This valve pre-
vents excessive pressure differences from occurring
between the closed cooling system and the atmo-
sphere. If the vacuum valve is stuck shut, the radia-
tor and/or cooling system hoses will collapse on cool-
down.
Fig. 7 Water PumpÐ2.0L Gasoline Engine
Fig. 8 Water PumpÐ2.0L Gasoline Engine
Fig. 9 Water PumpÐ2.5L VM Diesel
Fig. 10 Thermostat and Housing Ð 2.5L VM Diesel
7 - 4 COOLING SYSTEMNS/GS
DESCRIPTION AND OPERATION (Continued)

Initial belt adjustment is done with a adjustable
tensioner pulley. After the initial adjustment is per-
formed, an automatic belt tensioner is used to main-
tain correct belt tension at all times. Do not attempt
to check belt tension with a belt tension gauge on
vehicles equipped with an automatic belt tensioner.
Refer to Automatic Belt Tensioner in this group.
AUTOMATIC BELT TENSIONER
Drive belt tension is controlled by a spring loaded
automatic belt tensioner located below and to the
front of the engine oil filter (Fig. 12). This tensioner
is connected to a pivot bracket and a pulley (Fig. 12).
The pivot bracket rotates on a pivot pin attached to
the engine. Special machined washers with rubber
o-rings (Fig. 12) are used at each side of the pivot
bracket to help keep dirt and water away from the
pivot pin.
If a defective belt tensioner is suspected, a check of
this pivot bracket and pivot pin should be made. Cor-
rosion may have formed at the pin and may cause
the pivot bracket to stick. Belt slippage will result.
WARNING: BECAUSE OF HIGH SPRING PRES-
SURE, DO NOT ATTEMPT TO DISASSEMBLE THE
AUTOMATIC BELT TENSIONER. UNIT IS SERVICED
AS AN ASSEMBLY.
THERMOSTAT
DIAGNOSIS
Diesel engines, due to their inherent efficiency are
slower to warm up than gasoline powered engines,
and will operate at lower temperatures when the
vehicle is unloaded. Because of this, lower tempera-
ture gauge readings for diesel versus gasoline
engines may, at times be normal.
Typically, complaints of low engine coolant temper-
ature are observed as low heater output when com-
bined with cool or cold outside temperatures.
To help promote faster engine warm-up, an electric
engine block heater must be used with cool or cold
outside temperatures. This will help keep the engine
coolant warm when the vehicle is parked. Use the
block heater if the outside temperature is below 4ÉC
(40ÉF).Do not use the block heater if the out-
side temperature is above 4ÉC (40ÉF).
TESTING
NOTE: The DRB scan tool shoud be used to moni-
tor engine coolant temperature on the diesel
engine. Refer to the 1998 GS Powertrain Diagnostic
Manual for thermostat diagnosis procedure.
Fig. 12 Automatic Belt Tensioner Assembly
7 - 6 COOLING SYSTEMNS/GS
DESCRIPTION AND OPERATION (Continued)

BATTERY
CONTENTS
page page
GENERAL INFORMATION
INTRODUCTION......................... 1
SAFETY PRECAUTIONS AND WARNINGS..... 1
DESCRIPTION AND OPERATION
BATTERY IGNITION OFF DRAW (IOD)........ 1
CHARGING TIME REQUIRED............... 2
DIAGNOSIS AND TESTING
BATTERY BUILT-IN TEST INDICATOR........ 2
BATTERY IGNITION OFF DRAW (IOD)........ 3
BATTERY LOAD TEST..................... 4
BATTERY OPEN CIRCUIT VOLTAGE TEST..... 6SERVICE PROCEDURES
BATTERY CHARGING..................... 6
CHARGING COMPLETELY DISCHARGED
BATTERY............................. 7
VISUAL INSPECTION..................... 7
REMOVAL AND INSTALLATION
BATTERY TRAY.......................... 9
BATTERY............................... 8
SPECIFICATIONS
BATTERY SPECIFICATIONS............... 10
TORQUE.............................. 10
GENERAL INFORMATION
INTRODUCTION
The battery stores, stabilizes, and delivers electri-
cal current to operate various electrical systems in
the vehicle. The determination of whether a battery
is good or bad is made by its ability to accept a
charge. It also must supply high-amperage current
for a long enough period to be able to start the vehi-
cle. The capability of the battery to store electrical
current comes from a chemical reaction. This reac-
tion takes place between the sulfuric acid solution
(electrolyte) and the lead +/- plates in each cell of the
battery. As the battery discharges, the plates react
with the acid from the electrolyte. When the charging
system charges the battery, the water is converted to
sulfuric acid in the battery. The concentration of acid
in the electrolyte is measured as specific gravity
using a hydrometer. The original equipment (OE)
battery is equipped with a hydrometer (test indica-
tor) built into the battery cover. The specific gravity
indicates the battery's state-of-charge. The OE bat-
tery is sealed and water cannot be added.
The battery is vented to release gases that are cre-
ated when the battery is being charged and dis-
charged. The battery top, posts, and terminals should
be cleaned when other under hood maintenance is
performed.
When the electrolyte level is below the top of the
plates, Clear in the test Indicator, the battery must
be replaced. The battery must be completely charged,
and the battery top, posts, and cable clamps must be
cleaned before diagnostic procedures are performed.
SAFETY PRECAUTIONS AND WARNINGS
WARNING: DO NOT ALLOW JUMPER CABLE
CLAMPS TO TOUCH EACH OTHER WHEN CON-
NECTED TO A BOOSTER SOURCE. DO NOT USE
OPEN FLAME NEAR BATTERY. REMOVE METALLIC
JEWELRY WORN ON HANDS OR WRISTS TO AVOID
INJURY BY ACCIDENTAL ARCING OF BATTERY
CURRENT.
WHEN USING A HIGH OUTPUT BOOSTING DEVICE,
DO NOT ALLOW THE DISABLED VEHICLE'S BAT-
TERY TO EXCEED 16 VOLTS. PERSONAL INJURY
OR DAMAGE TO ELECTRICAL SYSTEM CAN
RESULT.
TO PROTECT THE HANDS FROM BATTERY ACID, A
SUITABLE PAIR OF HEAVY DUTY RUBBER
GLOVES, NOT THE HOUSEHOLD TYPE, SHOULD
BE WORN WHEN REMOVING OR SERVICING A
BATTERY. SAFETY GLASSES ALSO SHOULD BE
WORN.
DESCRIPTION AND OPERATION
BATTERY IGNITION OFF DRAW (IOD)
A completely normal vehicle will have a small
amount of current drain on the battery with the key
out of the ignition. It can range from 5 to 25 milli-
amperes after all the modules time out. If a vehicle
will not be operated for approximately a 20 days, the
IOD fuse should be pulled to eliminate the vehicle
electrical drain on the battery. The IOD fuse is
NSBATTERY 8A - 1

located in the Power Distribution Center (PDC).
Refer to the PDC cover for proper fuse.
CHARGING TIME REQUIRED
WARNING: NEVER EXCEED 20 AMPS WHEN
CHARGING A COLD -1ÉC (30ÉF) BATTERY. PER-
SONAL INJURY MAY RESULT.
The time required to charge a battery will vary
depending upon the following factors.
SIZE OF BATTERY
A completely discharged large heavy-duty battery
may require more recharging time than a completely
discharged small capacity battery, refer to the Bat-
tery Charging Timetable for charging times.
TEMPERATURE
A longer time will be needed to charge a battery at
-18ÉC (0ÉF) than at 27ÉC (80ÉF). When a fast charger
is connected to a cold battery, current accepted by
battery will be very low at first. In time, the battery
will accept a higher rate as battery temperature
warms.
CHARGER CAPACITY
A charger which can supply only five amperes will
require a much longer period of charging than a
charger that can supply 20 amperes or more.
STATE OF CHARGE
A completely discharged battery requires more
charging time than a partially charged battery. Elec-
trolyte is nearly pure water in a completely dis-
charged battery. At first, the charging current
amperage will be low. As water is converted back to
sulfuric acid inside the battery, the current amp rate
will rise. Also, the specific gravity of the electrolyte
will rise, bringing the green ball (Fig. 1) into view at
approximately 75 percent state-of-charge.
DIAGNOSIS AND TESTING
BATTERY BUILT-IN TEST INDICATOR
USING TEST INDICATOR
The Test Indicator (Fig. 1), (Fig. 2) and (Fig. 3)
measures the specific gravity of the electrolyte. Spe-
cific Gravity (SG) of the electrolyte will show state-
of-charge (voltage). The test indicator WILL NOT
show cranking capacity of the battery. Refer to Bat-
tery Load Test for more information. Look into the
sight glass (Fig. 1), (Fig. 3) and note the color of the
indicator. Refer to the following description of colors:
NOTE: GREEN = 75 to 100% state-of-charge
The battery is adequately charged for further test-
ing and may be returned to use. If the vehicle will
not crank for a maximum 15 seconds, refer to BAT-
TERY LOAD TEST in this Group for more informa-
tion.
NOTE: BLACK OR DARK=0to75%state-of-charge
The battery is INADEQUATELY charged and must
be charged until green dot is visible, (12.4 volts or
greater) before the battery is tested or returned to
BATTERY CHARGING TIMETABLE
Charging
Amperage5
Amperes10
Amperes20
Amperes
Open Circuit
VoltageHours Charging at 21ÉC (70ÉF)
12.25 to 12.39 6 hours 3 hours 1.5 hours
12.00 to 12.24 8 hours 4 hours 2 hours
11.95 to 11.99 12 hours 6 hours 3 hours
10.00 to 11.94 14 hours 7 hours 3.5 hours
less than 10.00 See Charging Completely
Discharged Battery
Fig. 1 Reading Test Indicator
Fig. 2 Battery Construction and Test Indicator
8A - 2 BATTERYNS
DESCRIPTION AND OPERATION (Continued)

use. Refer to Causes of Battery Discharging in this
Group for more information.
NOTE: CLEAR COLOR = Replace Battery
WARNING: DO NOT CHARGE, ASSIST BOOST,
LOAD TEST, OR ADD WATER TO THE BATTERY
WHEN CLEAR COLOR DOT IS VISIBLE. PERSONAL
INJURY MAY OCCUR.
A clear color dot shows electrolyte level in battery
is below the test indicator (Fig. 1). Water cannot be
added to a maintenance free battery. The battery
must be replaced. A low electrolyte level may be
caused by an over charging condition. Refer to Gen-
erator Test Procedures on Vehicle.
CAUSES OF BATTERY DISCHARGING
It is normal to have a small 5 to 25 milliamperes
continuous electrical draw from the battery. This
draw will take place with the ignition in the OFF
position, and the courtesy, dome, storage compart-
ments, and engine compartment lights OFF. The con-
tinuous draw is due to various electronic features or
accessories that require electrical current with the
ignition OFF to function properly. When a vehicle is
not used over an extended period of approximately 20
days the IOD fuse should be pulled. The fuse is
located in the power distribution center. Disconnec-
tion of this fuse will reduce the level of battery dis-
charge. Refer to Battery Diagnosis and Testing table
and to the proper procedures.
ABNORMAL BATTERY DISCHARGING
²Corroded battery posts, cables or terminals.
²Loose or worn generator drive belt.
²Electrical loads that exceed the output of the
charging system due to equipment or accessories
installed after delivery.
²Slow driving speeds in heavy traffic conditions
or prolonged idling with high-amperage electrical
systems in use.²Defective electrical circuit or component causing
excess Ignition Off Draw (IOD). Refer to Battery
Ignition Off Draw (IOD).
²Defective charging system.
²Defective battery.
BATTERY IGNITION OFF DRAW (IOD)
High current draw on the battery with the ignition
OFF will discharge a battery. After a dead battery is
serviced the vehicle Ignition Off Draw (IOD) should
be checked. Determine if a high current draw condi-
tion exists first check the vehicle with a test lamp.
(1) Verify that all electrical accessories are OFF.
²Remove key from ignition switch
²Turn off all lights
²Liftgate and glove box door is closed
²Sun visor vanity lights are OFF
²All doors are closed
²Allow the Illuminated Entry System to time out
in approximately 30 seconds, if equipped.
²During Transmission Control Module (TCM)
power down there will be 500 milliamperes present
for 20 minutes. Afterwards less than 1.0 milliampere.
(2) Disconnect battery negative cable (Fig. 4).
CAUTION: Always disconnect the meter before
opening a door.
(3) Using an multimeter, that has least a milliam-
pere range of 200 mA. Set meter to the highest mA
range. Install meter between the battery negative
cable and battery negative post (Fig. 5). Carefully
remove the test lamp without disconnecting the
meter. After all modules time-out the total vehicle
IOD should be less than 25 milliamperes. If ignition
off draw is more than 25 milliamperes go to Step 4.
(4) Each time the test lamp or milliampere meter
is disconnected and connected, all electronic timer
functions will be activated for approximately one
minute. The Body Control Module (BCM) ignition off
draw can reach 90 milliamperes.
(5) Remove the PDC fuses:
²Interior lamps
²Brake lamp
²IOD
(6) If there is any reading, with fuses removed
there is a short circuit in the wiring. Refer to Group
8W, wiring diagrams. If reading is less than 25 mA
go to Step 8.
(7) Install all fuses. After installing fuse, the cur-
rent can reach 90 mA. After time-out the reading
should not exceed 25 mA. If OK go to. If not, discon-
nect:
²Radio
²Body Control Module
²Remote Keyless Entry Module
Fig. 3 Test Indicator
NSBATTERY 8A - 3
DIAGNOSIS AND TESTING (Continued)

(8) Disconnect one component at time, to see if any
component is at fault. If the high reading is not elim-
inated there is a short circuit in the wiring. Refer to
Group 8W, wiring diagrams.
(9) Remove interior and brake lamp fuses. Install
the fuses. The milliampere reading should be 2-4 mA.
If reading is higher than 4 mA:
(a) Disconnect PCM.
(b) If reading is OK, replace PCM.(c) If reading does not change, disconnect the
TCM.
(d) If reading is OK, replace TCM.
(e) If reading stays, there is a short circuit to
one of the modules. Refer to Group 8W, Wiring
Diagrams.
BATTERY LOAD TEST
A fully charged battery must have cranking capac-
ity, to provide the starter motor and ignition system
enough power to start the engine over a broad range
of ambient temperatures. A battery load test will ver-
ify the actual cranking capability of the battery.
WARNING: IF BATTERY SHOWS SIGNS OF FREEZ-
ING, LEAKING, LOOSE POSTS, OR EXCESSIVELY
LOW ELECTROLYTE LEVEL, DO NOT TEST. ACID
BURNS OR AN EXPLOSIVE CONDITION MAY
RESULT.
(1) Remove both battery cables, negative cable
first. The battery top, cables and posts should be
BATTERY DIAGNOSIS AND TESTING
STEPS POSSIBLE CAUSE CORRECTION
VISUAL INSPECTION
Check for possible damage to
battery and clean battery.(1) Loose battery post, Cracked
battery cover or case, Leaks or Any
other physical
(2) Battery OK.(1) Replace Battery
(2) Check state of charge. Refer to
Test Indicator.
TEST INDICATOR
Check Charge Eye Color(1) GREEN
(2) BLACK
(3) CLEAR(1) Battery is charged. Perform
Battery 0pen Circuit Voltage Test
(2) Perform Battery Charging
procedure.
(3) Replace Battery.
BATTERY OPEN CIRCUIT
VOLTAGE TEST(1) Battery is above 12.40 Volts
(2) Battery is below 12.40 Volts.(1) Perform the Battery Load Test.
(2) Perform Battery Charging
procedure.
BATTERY CHARGING (1) Battery accepted Charge.
(2) Battery will not accept charge(1) Ensure that the indicator eye is
GREEN and perform Battery 0pen
Circuit Voltage Test
(2) Perform Charging a Completely
Discharged Battery.
BATTERY LOAD TEST (1) Acceptable minimum voltage.
(2) Unacceptable minimum voltage(1) Battery is OK to put in use,
perform Battery Ignition Off Draw
Test.
(2) Replace Battery and perform
Battery Ignition Off Draw Test.
CHARGING A COMPLETELY
DISCHARGED BATTERY(1) Battery accepted charge.
(2) Battery will not accept charge.(1) Ensure that the indicator eye is
GREEN and perform Battery 0pen
Circuit Voltage Test.
(2) Replace Battery.
IGNITION OFF DRAW TEST (1) IOD is 5-25 Milliamperes.
(2) IOD Exceeds 25 Milliamperes.(1) Vehicle is normal.
(2) Eliminate excess IOD draw.
Fig. 4 Disconnect Battery Negative Cable
8A - 4 BATTERYNS
DIAGNOSIS AND TESTING (Continued)

BATTERY OPEN CIRCUIT VOLTAGE TEST
An open circuit voltage no load test shows the
state of charge of a battery and whether it is ready
for a load test at 50 percent of the battery's cold
crank rating. Refer to Battery Load Test. If a battery
has open circuit voltage reading of 12.4 volts or
greater, and will not pass the load test, replace the
battery because it is defective. To test open circuit
voltage, perform the following operation.
(1) Remove both battery cables, negative cable
first. Battery top, cables and posts should be clean. If
green dot is not visible in indicator, charge the bat-
tery. Refer to Battery Charging Procedures.
(2) Connect a Volt/Ammeter/Load tester to the bat-
tery posts (Fig. 6). Rotate the load control knob of the
Carbon pile rheostat to apply a 300 amp load. Apply
this load for 15 seconds to remove the surface charge
from the battery, and return the control knob to off
(Fig. 7).
(3) Allow the battery to stabilize for 2 minutes,
and then verify the open circuit voltage (Fig. 9).
(4) This voltage reading will approximate the state
of charge of the battery. It will not reveal battery
cranking capacity. Refer to Battery Open Circuit
Voltage table.
SERVICE PROCEDURES
BATTERY CHARGING
WARNING: DO NOT CHARGE A BATTERY THAT
HAS EXCESSIVELY LOW ELECTROLYTE LEVEL.
BATTERY MAY SPARK INTERNALLY AND
EXPLODE. EXPLOSIVE GASES FORM OVER THE
BATTERY. DO NOT SMOKE, USE FLAME, OR CRE-
ATE SPARKS NEAR BATTERY. DO NOT ASSIST
BOOST OR CHARGE A FROZEN BATTERY. BAT-
TERY CASING MAY FRACTURE. BATTERY ACID IS
POISON, AND MAY CAUSE SEVERE BURNS. BAT-
TERIES CONTAIN SULFURIC ACID. AVOID CON-
TACT WITH SKIN, EYES, OR CLOTHING. IN THE
EVENT OF CONTACT, FLUSH WITH WATER AND
CALL PHYSICIAN IMMEDIATELY. KEEP OUT OF
REACH OF CHILDREN.
CAUTION: Disconnect the battery NEGATIVE cable
first. (Fig. 4) before charging battery to avoid dam-
age to electrical systems. Do not exceed 16.0 volts
while charging battery. Refer to the instructions
supplied with charging equipment
NOTE: The battery cannot be refilled with water, it
must be replaced.
A battery is considered fully charged when it will
meet all the following requirements.
²It has an open circuit voltage charge of at least
12.4 volts.
²It passes the 15 second load test, refer to the
Load Test Temperature chart.
²The built in test indicator dot is GREEN (Fig.
1).
Battery electrolyte will bubble inside of battery
case while being charged properly. If the electrolyte
boils violently, or is discharged from the vent holes
while charging, immediately reduce charging rate or
turn off charger. Evaluate battery condition. Battery
damage may occur if charging is excessive.
Some battery chargers are equipped with polarity
sensing devices to protect the charger or battery from
being damaged if improperly connected. If the bat-
tery state of charge is too low for the polarity sensor
to detect, the sensor must be bypassed for charger to
operate. Refer to operating instructions provided
with battery charger being used.
CAUTION: Charge battery until test indicator
appears green. Do not overcharge.
It may be necessary to jiggle the battery or vehicle
to bring the green dot in the test indicator into view.
Fig. 9 Testing Open Circuit Voltage
BATTERY OPEN CIRCUIT VOLTAGE
Open Circuit VoltsCharge Per-
centage
11.7 volts or less 0%
12.0 volts 25%
12.2 volts 50%
12.4 volts 75%
12.6 volts or more 100%
8A - 6 BATTERYNS
DIAGNOSIS AND TESTING (Continued)