COOLING SYSTEM DIAGNOSIS-DIESEL ENGINE
CONDITION POSSIBLE CAUSES CORRECTION
TEMPERATURE GAUGE
READS LOW1. Diesel engines, due to their
inherent effiency are slower to warm
up than gasoline powered engines,
and will operate at lower
temperatures when the vehicle is
unloaded.1. The low gauge reading may
be normal. Refer to thermostats
in the manual text for
information. See Thermostat
Diagnosis-Diesel Engine.
2. Is the temperature gauge
connected to the temperature gauge
coolant sensor on the engine?2. Check, the engine
temperature sensor connector
in the engine compartment.
3. Is the temperature gauge
operating OK?3. Check gauge operation.
Repair as necessary.
4. Coolant level low in cold ambient
temperatures accompanied with poor
heater performance.4. Check coolant level in the
coolant tank. Inspect system for
leaks. Repair leaks as
necessary. Refer to the Coolant
section for WARNINGS and
precautions before removing
the pressure cap.
5. Improper operation of internal
heater doors or heater controls.5. Inspect heater and repair as
necessary. Refer to Heating
and Air Conditioning for
procedures.
TEMPERATURE GAUGE
READS HIGH. COOLANT
MAY OR MAY NOT BE
LOST OR LEAKING FROM
COOLING SYSTEM1. Trailer is being towed, a steep hill
is being climbed, vehicle is operated
in slow moving traffic, or engine is
being idled with very high ambient
(outside) temperature and the air
conditioning is on. Higher altitudes
could aggravate these conditions.1. This may be a temporary
condition and repair is not
necessary. Turn off the air
conditioning and attempt to
drive the vehicle without any of
the previous conditions.
Observe the temperature
gauge. The gauge should return
to the normal range. If the
gauge does not return to
normal range, determine the
cause for the overheating and
repair.
2. Temperature gauge reading
incorrectly.2. Check gauge. Refer to I/P
group.
3. Coolant low in coolant tank and
radiator.3. Check for coolant leaks and
repair as necessary.
4. Pressure cap not installed tightly.
If cap is loose, boiling point of
coolant will be lowered.4. Tighten cap.
5. Poor seals at pressure/vent cap. 5. (a) Check condition of cap
and cap seals. (b) Check
condition of coolant tank filler
neck. Make sure it does not
leak pressure.
7a - 2 COOLING 2.5L TURBO DIESELRG
COOLING 2.5L TURBO DIESEL (Continued)
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CONDITION POSSIBLE CAUSES CORRECTION
4. Has undercoating been applied to
any unnecessary components?4. Clean undercoating as
necessary.
STEAM IS COMING FROM
FRONT OF VEHICLE
NEAR GRILL AREA WHEN
WEATHER IS WET,
ENGINE IS WARMED UP
AND RUNNING, AND
VEHICLE IS STATIONARY.
TEMPERATURE GAUGE
IS IN NORMAL RANGE1. During wet weather, moisture
(snow, ice, or rain condensation) on
the radiator will evaporate when the
thermostat opens. This opening
allows heated water into the radiator.
When the moisture contacts the hot
radiator, steam may be emitted. This
usually occurs in cold weather with
no fan or airflow to blow it away.1. Occasional steam emitting
from this area is normal. No
repair is necessary.
COOLANT ODOR 1. Coolant color is not necessarily an
indication of adequate corrosion or
temperature protection. Do not rely
on coolant color for determining
condition of coolant.1. Refer to Coolant in this group
for antifreeze tests. Adjust
antifreeze-to-water ratio as
necessary.
COOLANT LEVEL
CHANGES IN COOLANT
TANK. TEMPERATURE
GAUGE IS IN NORMAL
RANGE1. Level changes are to be expected
as coolant volume fluctuates with
engine temperature. If the level in
the tank was between the HOT and
COLD marks at normal engine
operating temperature, the level
should return to within that range
after operation at elevated
temperatures.1. This a normal condition. No
repair necessary.
DIAGNOSIS AND TESTING - COOLING SYSTEM
LEAK TEST
WARNING: THE WARNING WORDS ªDO NOT OPEN
HOTº ON THE RADIATOR PRESSURE CAP IS A
SAFETY PRECAUTION. WHEN HOT, PRESSURE
BUILDS UP IN COOLING SYSTEM. TO PREVENT
SCALDING OR INJURY, THE RADIATOR CAP
SHOULD NOT BE REMOVED WHILE THE SYSTEM
IS HOT OR UNDER PRESSURE.
With engine not running, remove pressure/vent cap
from the coolant recovery pressure container and
wipe the filler neck sealing seat clean. The coolant
recovery pressure container should be full.
Attach the Cooling System Tester 7700 or equiva-
lent to the radiator, as shown in (Fig. 1) and apply
104 kPa (15 psi) pressure. If the pressure drops more
than 13.8 kPa (2 psi) in 2 minutes, inspect all points
for external leaks.
All radiator and heater hoses should be shaken
while at 104 kPa (15 psi), since some leaks occur only
while driving due to engine movement.
If there are no external leaks, after the gauge dial
shows a drop in pressure, detach the tester. Startengine and run until the thermostat opens, allowing
the coolant to expand. Reattach the cooling system
tester. If the needle on the dial fluctuates it indicates
a combustion leak, usually a head gasket leak.
WARNING: WITH TOOL IN PLACE, PRESSURE WILL
BUILD UP FAST. EXCESSIVE PRESSURE BUILT UP,
BY CONTINUOUS ENGINE OPERATION, MUST BE
RELEASED TO A SAFE PRESSURE POINT. NEVER
PERMIT PRESSURE TO EXCEED 138 kPa (20 psi).
If the needle on the dial does not fluctuate, raise
the engine rpm a few times. If an abnormal amount
of coolant or steam emits from the tailpipe, it may
indicate a coolant leak caused by a faulty head gas-
ket, cracked engine block, or cracked cylinder head.
There may be internal leaks that can be deter-
mined by removing the oil dipstick. If water globules
appear intermixed with the oil it will indicate an
internal leak in the engine. If there is an internal
leak, the engine must be disassembled for repair.
7a - 6 COOLING 2.5L TURBO DIESELRG
COOLING 2.5L TURBO DIESEL (Continued)
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DIAGNOSIS AND TESTING - COOLING SYSTEM
FLOW CHECK
To determine whether coolant is flowing through
the cooling system, use the following procedures:
(1) If engine is cold, idle engine until normal oper-
ating temperature is reached. Then feel the upper
radiator hose. If it is hot, coolant is circulating.
WARNING: DO NOT REMOVE THE COOLING SYS-
TEM PRESSURE CAP WITH THE SYSTEM HOT AND
UNDER PRESSURE BECAUSE SERIOUS BURNS
FROM COOLANT CAN OCCUR.(2) Remove pressure/vent cap when engine is cold,
idle engine until thermostat opens, you should
observe coolant flow while looking down in the cool-
ant recovery pressure container. Once flow is
detected install the pressure/vent cap.
DIAGNOSIS AND TESTING - COOLING SYSTEM
AERATION
Low coolant level in a cross flow radiator will
equalize in both tanks with engine off. With engine
at running and at operating temperature, the high
pressure inlet tank runs full and the low pressure
outlet tank drops, resulting in cooling system aera-
tion. Aeration will draw air into the water pump
resulting in the following:
²High reading shown on the temperature gauge.
²Loss of coolant flow through the heater core.
²Corrosion in the cooling system.
²Water pump seal may run dry, increasing the
risk of premature seal failure.
²Combustion gas leaks into the coolant can also
cause the above problems.
CLEANING
Drain cooling system and refill with clean water.
Refer to procedures in this section. Run engine with
pressure/vent cap installed until upper radiator hose
is hot. Stop engine and drain water from system. If
water is dirty; fill, run, and drain system again, until
water runs clear.
INSPECTION
After performing a cleaning/flush procedure,
inspect all hoses, clamps and connections for deterio-
ration and leaks. Inspect radiator and heater core for
leaks.
Fig. 1 PRESSURE TESTING COOLING SYSTEM
1 - COOLING SYSTEM PRESSURE TESTER
2 - COOLANT RECOVERY PRESSURE CONTAINER
RGCOOLING 2.5L TURBO DIESEL7a-7
COOLING 2.5L TURBO DIESEL (Continued)
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ACCESSORY DRIVE
TABLE OF CONTENTS
page page
ACCESSORY DRIVE
SPECIFICATIONS.........................9
BELT TENSIONER
REMOVAL...............................9
INSTALLATION............................9
IDLER PULLEY
REMOVAL..............................10
INSTALLATION...........................10DRIVE BELTS
DESCRIPTION...........................10
OPERATION.............................10
DIAGNOSIS AND TESTING.................11
ACCESSORY DRIVE BELT................11
REMOVAL..............................11
INSTALLATION...........................11
ACCESSORY DRIVE
SPECIFICATIONS
SPECIFICATIONS - ACCESSORY BELT TENSION
ACCESSORY DRIVE
BELTGAUGE
2.5L DIESEL ENGINE
A/C Compressor/
GeneratorDynamic Tensioner
Power Steering Belt 300 N (67 lbs.)
BELT TENSIONER
REMOVAL
WARNING: BECAUSE OF HIGH SPRING TENSION,
DO NOT ATTEMPT TO DISASSEMBLE THE AUTO-
MATIC BELT TENSIONER. THE TENSIONER IS SER-
VICED AS AN ASSEMBLY.
(1) Remove the power steering belt (Refer to 7 -
COOLING/ACCESSORY DRIVE/DRIVE BELTS -
REMOVAL).
(2) Remove the accessory drive belt (Refer to 7 -
COOLING/ACCESSORY DRIVE/DRIVE BELTS -
INSTALLATION).
(3) Remove the belt tensioner retaining bolt and
remove tensioner (Fig. 1).
INSTALLATION
(1) Install belt tensioner and retaining bolt (Fig.
1). Torque bolt to 47 N´m (35ft. lbs.).(2) Install the accessory drive belt (Refer to 7 -
COOLING/ACCESSORY DRIVE/DRIVE BELTS -
INSTALLATION).
(3) Install the power steering belt (Refer to 7 -
COOLING/ACCESSORY DRIVE/DRIVE BELTS -
INSTALLATION).
Fig. 1 BELT TENSIONER AND IDLER PULLEY
1 - BELT TENSIONER RETAINING BOLT
2 - BELT TENSIONER
3 - IDLER PULLEY
4 - VIBRATION DAMPER/CRANKSHAFT PULLEY
5 - VIBRATION DAMPER/CRANKSHAFT PULLEY RETAINING
BOLTS
RGACCESSORY DRIVE7a-9
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STANDARD PROCEDURE - COOLANT LEVEL
CHECK
NOTE: Do not remove pressure/vent cap for routine
coolant level inspections.
The coolant reserve system provides a quick visual
method for determining the coolant level without
removing the pressure/vent cap.With the engine
cold and not running,simply observe the level of
the coolant in the coolant recovery pressure container
(Fig. 2). The coolant level should be between the MIN
and MAX marks.
STANDARD PROCEDURE - REFILLING
COOLING SYSTEM
Remove pressure/vent cap (Fig. 1) and fill system,
using a 50/50 mix of MopartAntifreeze/Coolant, 5
Year/100,000 Mile Formula and distilled water.
Continue filling system until full.Be careful not
to spill coolant on drive belts or the generator.
Fill coolant recovery pressure container (Fig. 1) to
at least the MAX mark with 50/50 solution. It may
be necessary to add coolant to the coolant recovery
pressure container after three or four warm up/cool
down cycles to maintain coolant level between the
MAX and MIN mark. This will allow trapped air to
be removed from the system.
STANDARD PROCEDURE - DRAINING COOLING
SYSTEM
WARNING: DO NOT REMOVE OR LOOSEN THE
COOLANT PRESSURE/VENT CAP, CYLINDER
BLOCK DRAIN PLUGS, OR THE DRAINCOCK WHEN
THE SYSTEM IS HOT AND UNDER PRESSURE
BECAUSE SERIOUS BURNS FROM THE COOLANT
CAN OCCUR.
(1)Without removing pressure/vent cap and
with system not under pressure, open the drain-
cock. The draincock is located on the lower right side
of radiator (Fig. 3).
(2) After the coolant recovery pressure container is
empty, then remove coolant pressure/vent cap.
Fig. 1 UNDERHOOD FLUID FILL LOCATIONS
1 - COOLANT PRESSURE/VENT CAP
2 - BRAKE MASTER CYLINDER
3 - INTELLIGENT POWER MODULE
4 - BATTERY
5 - COOLANT RECOVERY PRESSURE CONTAINER6 - OIL DIPSTICK
7 - WINDSHIELD SOLVENT RESEVOIR
8 - AIR FILTER HOUSING
9 - ENGINE OIL FILL CAP
7a - 16 ENGINERG
COOLANT (Continued)
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ENGINE COOLANT TEMP
SENSOR
DESCRIPTION
The engine coolant temperature sensor threads
into a coolant passage in the cylinder head (Fig. 7).
New sensors have sealant applied to the threads.
OPERATION
The coolant temperature (ECT) sensor is a nega-
tive temperature coefficient (NTC) thermistor (resis-
tance varies inversley with temperature). This means
at cold tempertures its resistance is high so the volt-
age signal will be high. As coolant temperture
increases, resistance decreases and the signal voltage
will be low. This allows the sensor to provide an ana-
log voltage signal to the ECM.
REMOVAL
WARNING: DO NOT REMOVE OR LOOSEN THE
COOLANT PRESSURE/VENT CAP, CYLINDER
BLOCK DRAIN PLUGS, OR THE DRAINCOCK WHEN
THE SYSTEM IS HOT AND UNDER PRESSURE
BECAUSE SERIOUS BURNS FROM THE COOLANT
CAN OCCUR.
(1) Drain the cooling system. (Refer to 7 - COOL-
ING/ENGINE/COOLANT - STANDARD PROCE-
DURE).
(2) Disconnect coolant temperature sensor electri-
cal connector (Fig. 8).
(3) Remove coolant temperature sensor from cylin-
der head (Fig. 8).
INSTALLATION
(1) Install coolant temperature sensor in cylinder
head (Fig. 8).
(2) Connect coolant temperature sensor electrical
connector (Fig. 8).
(3) Refill the cooling system. (Refer to 7 - COOL-
ING/ENGINE/COOLANT - STANDARD PROCE-
DURE).
(4) Connect the negative battery cable.
ENGINE COOLANT
THERMOSTAT
DESCRIPTION
A pellet-type thermostat controls the operating
temperature of the engine by controlling the amount
of coolant flow to the radiator (Fig. 9).
OPERATION
The thermostat starts to open at 80ÉC (176ÉF).
Above this temperature, coolant is allowed to flow to
the radiator. This provides quicker engine warmup
and overall temperature control.
The same thermostat is used for winter and sum-
mer seasons. An engine should not be operated with-
out a thermostat, except for servicing or testing.
Operating without a thermostat causes other prob-
lems. These are: longer engine warmup time, unreli-
able warmup performance, increased exhaust
emissions and crankcase condensation. This conden-
sation can result in sludge formation.
REMOVAL
NOTE: The thermostat is not serviced separately.
The thermostat and housing must be replaced as
an assembly.
(1) Disconnect negative battery cable.
(2) Drain cooling system (Refer to 7 - COOLING/
ENGINE/COOLANT - STANDARD PROCEDURE).
(3) Remove front wiper unit to gain access to ther-
mostat housing(Refer to 8 - ELECTRICAL/WIPERS/
WASHERS/WIPER MODULE - REMOVAL).
Fig. 8 COOLANT TEMPERATURE SENSOR
LOCATION
1 - EGR SOLENOID
2 - UPPER RADIATOR HOSE
3 - COOLANT TEMPERATURE SENSOR
4 - INTAKE MANIFOLD INLET
5 - INTAKE MANIFOLD/CYLINDER HEAD COVER
RGENGINE7a-19
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(4) Disconnect upper radiator hose adapter tube,
water pump hose, and EGR hose at thermostat hous-
ing.
(5) Remove both thermostat housing attaching
bolts and housing (Fig. 10).
INSTALLATION
(1) Install thermostat housing, gasket, and retain-
ing bolts (Fig. 10). Torque bolts to 27.5N´m.
(2) Connect upper radiator hose adapter tube,
water pump hose, and EGR cooler hose to thermostat
housing.
(3) Install front wiper unit (Refer to 8 - ELECTRI-
CAL/WIPERS/WASHERS/WIPER MODULE -
INSTALLATION).
(4) Refill cooling system (Refer to 7 - COOLING/
ENGINE/COOLANT - STANDARD PROCEDURE).
(5) Connect negative battery cable.
RADIATOR
DESCRIPTION
The radiator is a cross-flow type (horizontal tubes)
with design features that provide greater strength
along with sufficient heat transfer capabilities tokeep the engine satisfactorily cooled. The radiator
has plastic side tanks and aluminum cooling tubes.
OPERATION
The radiator functions as a heat exchanger, using
air flow across the exterior of the radiator tubes. This
heat is then transferred from the coolant and into
the passing air.
REMOVAL
(1) Disconnect negative cable from battery.
(2) Remove radiator upper crossmember support.
(Refer to 23 - BODY/EXTERIOR/GRILLE OPENING
REINFORCEMENT - REMOVAL).
WARNING: DO NOT REMOVE THE CYLINDER
BLOCK PLUG OR THE RADIATOR DRAINCOCK
WITH THE SYSTEM HOT AND UNDER PRESSURE
BECAUSE SERIOUS BURNS FROM COOLANT CAN
OCCUR.
(3) Drain the cooling system (Refer to 7 - COOL-
ING/ENGINE/COOLANT - STANDARD PROCE-
DURE).
Fig. 9 THERMOSTAT HOUSING LOCATION
1 - CYLINDER HEAD COVER
2 - THERMOSTAT HOUSING
3 - AIR BLEED
4 - WATER PUMP
5 - WATER PUMP HOUSING TO THERMOSTAT HOUSING
BYPASS HOSE
6 - E G R VA LV E
Fig. 10 THERMOSTAT HOUSING ASSEMBLY
1 - THERMOSTAT HOUSING GASKET
2 - THERMOSTAT HOUSING
3 - RETAINING BOLTS
4 - CYLINDER HEAD
5 - CYLINDER HEAD COVER/INTAKE MANIFOLD
7a - 20 ENGINERG
ENGINE COOLANT THERMOSTAT (Continued)
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DIAGNOSIS AND TESTING - COOLING SYSTEM
PRESSURE CAP
Dip the pressure cap in water. Clean any deposits
off the vent valve or its seat and apply cap to end of
the Pressure Cap Test Adaptor that is included with
the Cooling System Tester 7700. Working the
plunger, bring the pressure to 104 kPa (15 psi) on the
gauge. If the pressure cap fails to hold pressure of at
least 97 kPa (14 psi), replace the pressure cap.
CAUTION: The Cooling System Tester Tool is very
sensitive to small air leaks that will not cause cool-
ing system problems. A pressure cap that does not
have a history of coolant loss should not be
replaced just because it leaks slowly when tested
with this tool. Add water to the tool. Turn tool
upside down and recheck pressure cap to confirm
that cap is bad.
If the pressure cap tests properly while positioned
on Cooling System Tester (Fig. 20), but will not hold
pressure or vacuum when positioned on the filler
neck. Inspect the filler neck and cap top gasket for
irregularities that may prevent the cap from sealing
properly.
DIAGNOSIS AND TESTING - PRESSURE
RELIEF TEST
The pressure cap upper gasket (seal) pressure
relief can be checked by removing the overflow hose
at the radiator filler neck nipple (Fig. 21). Attach the
Radiator Pressure Tool to the filler neck nipple and
pump air into the radiator. Pressure cap upper gas-
ket should relieve at 69-124 kPa (10-18 psi) and hold
pressure at 55 kPa (8 psi) minimum.WARNING: THE WARNING WORDS ªDO NOT OPEN
HOTº ON THE RADIATOR PRESSURE CAP IS A
SAFETY PRECAUTION. WHEN HOT, PRESSURE
BUILDS UP IN COOLING SYSTEM. TO PREVENT
SCALDING OR INJURY, THE RADIATOR CAP
SHOULD NOT BE REMOVED WHILE THE SYSTEM
IS HOT OR UNDER PRESSURE.
There is no need to remove the radiator cap at any
timeexceptfor the following purposes:
(1) Check and adjust coolant freeze point.
(2) Refill system with new coolant.
(3) Conducting service procedures.
(4) Checking for vacuum leaks.
WARNING: IF VEHICLE HAS BEEN RUN RECENTLY,
WAIT 15 MINUTES BEFORE REMOVING CAP. THEN
PLACE A SHOP TOWEL OVER THE CAP AND WITH-
OUT PUSHING DOWN ROTATE COUNTERCLOCK-
WISE TO THE FIRST STOP. ALLOW FLUIDS TO
ESCAPE THROUGH THE OVERFLOW TUBE AND
WHEN THE SYSTEM STOPS PUSHING COOLANT
AND STEAM INTO THE CRS TANK AND PRESSURE
DROPS PUSH DOWN AND REMOVE THE CAP COM-
PLETELY. SQUEEZING THE RADIATOR INLET HOSE
WITH A SHOP TOWEL (TO CHECK PRESSURE)
BEFORE AND AFTER TURNING TO THE FIRST
STOP IS RECOMMENDED.
CLEANING
Use only a mild soap to clean the pressure cap.
Fig. 20 Testing Cooling System Pressure Cap
1 - PRESSURE CAP
2 - PRESSURE TESTER
Fig. 21 Radiator Pressure Cap Filler Neck
1 - OVERFLOW NIPPLE
2 - MAIN SPRING
3 - GASKET RETAINER
4 - STAINLESS-STEEL SWIVEL TOP
5 - RUBBER SEALS
6 - VENT VALVE
7 - PRESSURE BOTTLE
8 - FILLER NECK
RGENGINE7a-25
RADIATOR PRESSURE CAP (Continued)
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