Thermostat DODGE RAM 1500 1998 2.G Owner's Manual

indicated by the instrument panel gauge or by poor
heater performance unless a DTC is present. Refer to
the Diagnosis section of this group for other probable
causes.
The DTC can also be accessed through the
DRBIIItscan tool. Refer to the appropriate Power-
train Diagnostic Procedures information for diagnos-
tic information and operation of the DRBIIItscan
tool.
REMOVAL
WARNING: DO NOT LOOSEN THE RADIATOR
DRAINCOCK WITH THE COOLING SYSTEM HOT
AND PRESSURIZED. SERIOUS BURNS FROM THE
COOLANT CAN OCCUR.Do not waste reusable coolant. If the solution is
clean, drain the coolant into a clean container for
reuse.
If the thermostat is being replaced, be sure that
the replacement is the specified thermostat for the
vehicle model and engine type.
(1) Disconnect the negative battery cable.
(2) Drain the cooling system (Refer to 7 - COOL-
ING - STANDARD PROCEDURE).
(3) Raise and support the vehicle.
(4) Remove the splash shield.
(5) Remove the lower radiator hose clamp and the
lower radiator hose at the thermostat housing.
(6) Remove the thermostat housing mounting
bolts, thermostat housing and thermostat (Fig. 24).
INSTALLATION
(1) Clean the mating areas of the timing chain
cover and the thermostat housing.
(2) Install the thermostat (spring side down) into
the recessed machined groove on the timing chain
cover (Fig. 24).
(3) Position the thermostat housing on the timing
chain cover.
(4) Install the housing-to-timing chain cover bolts.
Tighten the bolts to 13 N´m (112 in. lbs.).
CAUTION: The housing must be tightened evenly
and the thermostat must be centered into the
recessed groove in the timimg chain cover. If not, it
may result in a cracked housing, damaged timing
chain cover threads or coolant leaks.
(5) Install the lower radiator hose on the thermo-
stat housing.
(6) Install the splash shield.
(7) Lower the vehicle.
(8) Fill the cooling system (Refer to 7 - COOLING
- STANDARD PROCEDURE).
(9) Connect negative battery cable.
(10) Start and warm the engine. Check for leaks.
Fig. 23 Thermostat Cross Section View 3.7L/4.7L
1 - FROM HEATER AND DEGAS CONTAINER
2 - FROM RADIATOR
3 - TO WATER PUMP
4- THERMOSTAT
DRENGINE 7 - 45
ENGINE COOLANT THERMOSTAT - 3.7L/4.7L (Continued)

ENGINE COOLANT
THERMOSTAT - 5.9L DIESEL
DESCRIPTION
CAUTION: Do not operate an engine without a ther-
mostat, except for servicing or testing. An engine
with the thermostat removed will operate in the
radiator bypass mode, causing an overheat condi-
tion.
The thermostat of the 5.9L diesel engine is located
in the front of the cylinder head, underneath the
thermostat housing (Fig. 25).
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 will cause overheat-
ing.
OPERATION
The wax pellet is located in a sealed container at
the spring end of the thermostat. When heated, the
pellet expands, overcoming closing spring tension
and water pump pressure to force the valve to open.
Fig. 24 Thermostat and Thermostat Housing 3.7L/4.7L
1 - THERMOSTAT HOUSING
2 - THERMOSTAT LOCATION3 - THERMOSTAT AND GASKET
4 - TIMING CHAIN COVER
Fig. 25 Thermostat±5.9L Diesel-Typical
1 - THERMOSTAT HOUSING
2 - CYLINDER HEAD
3 - THERMOSTAT
7 - 46 ENGINEDR
ENGINE COOLANT THERMOSTAT - 3.7L/4.7L (Continued)

DIAGNOSIS AND TESTING - THERMOSTAT
The cooling system used with the diesel engine
provides the extra coolant capacity and extra cooling
protection needed for higher GVWR (Gross Vehicle
Weight Rating) and GCWR (Gross Combined Weight
Rating) vehicles.
This system capacity will not effect warm up or
cold weather operating characteristics if the thermo-
stat is operating properly. This is because coolant
will be held in the engine until it reaches the ther-
mostat ªsetº temperature.
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, the elec-
tric 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.
A ªCold Weather Coverº is available from the parts
department through the Mopar Accessories product
line. This accessory cover is designed to block airflow
entering the radiator and engine compartment to
promote faster engine warm-up. It attaches to the
front of the vehicle at the grill opening.The cover is
to be used with cool or cold temperatures only.
If used with high outside temperatures, serious
engine damage could result.Refer to the litera-
ture supplied with the cover for additional informa-
tion.
(1) To determine if the thermostat is defective, it
must be removed from the vehicle (Refer to 7 -
COOLING/ENGINE/ENGINE COOLANT THERMO-
STAT - REMOVAL).
(2) After the thermostat has been removed, exam-
ine the thermostat and inside of thermostat housing
for contaminants. If contaminants are found, the
thermostat may already be in a ªstuck openº position.
Flush the cooling system before replacing thermostat
(Refer to 7 - COOLING - STANDARD PROCE-
DURE).
(3) Place the thermostat into a container filled
with water.
(4) Place the container on a hot plate or other suit-
able heating device.
(5) Place a commercially available radiator ther-
mometer into the water.
(6) Apply heat to the water while observing the
thermostat and thermometer.
(7) The thermostat will begin to open at 85.5 -
89.4ÉC. (186 - 193ÉF ). If the valve starts to movebefore this temperature is reached, it is opening too
early. Replace thermostat. The thermostat should be
fully open (valve will stop moving) at 97ÉC (207ÉF). If
the valve is still moving when the water temperature
reaches 97ÉC (207ÉF), it is opening too late. Replace
thermostat. If the valve refuses to move at any time,
replace thermostat.
REMOVAL
WARNING: DO NOT LOOSEN THE RADIATOR
DRAINCOCK WITH THE SYSTEM HOT AND PRES-
SURIZED. SERIOUS BURNS FROM THE COOLANT
CAN OCCUR.
Do not waste reusable coolant. If the solution is
clean, drain the coolant into a clean container for
reuse.
(1) Disconnect the battery negative cables.
(2) Drain cooling system until coolant level is
below thermostat (Refer to 7 - COOLING - STAN-
DARD PROCEDURE).
WARNING: CONSTANT TENSION HOSE CLAMPS
ARE USED ON MOST COOLING SYSTEM HOSES.
WHEN REMOVING OR INSTALLING, USE ONLY
TOOLS DESIGNED FOR SERVICING THIS TYPE OF
CLAMP, SUCH AS SPECIAL CLAMP TOOL (NUMBER
6094).
CAUTION: A number or letter is stamped into the
tongue of constant tension clamps. If replacement
is necessary, use only an original equipment clamp
with a matching number or letter.
(3) Remove radiator hose clamp and hose from
thermostat housing.
(4) Remove the three (3) water outlet-to-cylinder
head bolts and remove the water outlet connector
(Fig. 26).
(5) Clean the mating surfaces of the water outlet
connector and clean the thermostat seat groove at
the top of the thermostat housing (Fig. 26).
INSTALLATION
(1) Inspect thermostat seal for cuts or nicks.
Replace if damaged.
(2) Install the thermostat into the groove in the
top of the cylinder head (Fig. 26).
(3) Install the thermostat housing and bolts.
Tighten the bolts to 10 N´m (89 in. lbs.) torque.
(4) Install the radiator upper hose and clamp.
(5) Fill the cooling system with coolant (Refer to 7
- COOLING - STANDARD PROCEDURE).
(6) Connect the battery negative cables.
DRENGINE 7 - 47
ENGINE COOLANT THERMOSTAT - 5.9L DIESEL (Continued)

(7) Start the engine and check for coolant leaks.
Run engine to check for proper thermostat operation.
ENGINE COOLANT
THERMOSTAT - 8.0L
DESCRIPTION
CAUTION: Do not operate an engine without a ther-
mostat, except for servicing or testing.
The thermostat on all gas powered engines is
located beneath the thermostat housing at the front
of the intake manifold (Fig. 27).
The thermostat is a moveable sleeve type.
Coolant leakage into the pellet container will cause
the thermostat to fail in the open position. Thermo-
stats very rarely stick. Do not attempt to free a ther-
mostat with a prying device.
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 longer engine
warmup time, unreliable warmup performance,
increased exhaust emissions and crankcase condensa-
tion that can result in sludge formation.
OPERATION
The wax pellet is located in a sealed container at
the spring end of the thermostat. When heated, the
pellet expands, overcoming closing spring tension
and water pump pressure to force the valve to open.
DIAGNOSIS AND TESTING - THERMOSTAT
ON-BOARD DIAGNOSTICS
Allgasoline powered modelsare equipped with
On-Board Diagnostics for certain cooling system com-
ponents. Refer to On-Board Diagnostics (OBD) in the
Diagnosis section of this group for additional infor-
mation. If the powertrain control module (PCM)
detects low engine coolant temperature, it will record
a Diagnostic Trouble Code (DTC) in the PCM mem-
ory. Do not change a thermostat for lack of heat as
indicated by the instrument panel gauge or by poor
heater performance unless a DTC is present. Refer to
the Diagnosis section of this group for other probable
causes. For other DTC numbers, (Refer to 25 - EMIS-
SIONS CONTROL - DESCRIPTION).
Fig. 26 Thermostat Removal/Installation
1 - THERMOSTAT HOUSING
2 - CYLINDER HEAD
3 - THERMOSTAT
Fig. 27 Thermostat - 8.0L V-10 Engine
1 - COOLANT TEMP. SENSOR (FOR PCM)
2 - HEATER SUPPLY FITTING
3 - BOLTS (6)
4 - HOUSING WITH INTEGRAL SEAL
5 - THERMOSTAT
6 - RUBBER LIP SEAL
7 - TEMP. GAUGE SENDING UNIT
7 - 48 ENGINEDR
ENGINE COOLANT THERMOSTAT - 5.9L DIESEL (Continued)

The DTC can also be accessed through the DRB
scan tool. Refer to the appropriate Powertrain Diag-
nostic Procedures information for diagnostic informa-
tion and operation of the DRB scan tool.
REMOVAL
WARNING: DO NOT LOOSEN THE RADIATOR
DRAINCOCK WITH THE SYSTEM HOT AND PRES-
SURIZED. SERIOUS BURNS FROM THE COOLANT
CAN OCCUR.
Do not waste reusable coolant. If the solution is
clean, drain the coolant into a clean container for
reuse.
If the thermostat is being replaced, be sure that
the replacement is the specified thermostat for the
vehicle model and engine type.
A rubber lip-type seal with a metal shoulder is
pressed into the intake manifold beneath the thermo-
stat (Fig. 28).
(1) Disconnect negative battery cable at battery.
(2) Drain cooling system until coolant level is
below thermostat (Refer to 7 - COOLING - STAN-
DARD PROCEDURE).
(3) Remove the two support rod mounting bolts
and remove support rod (intake manifold-to-genera-
tor mount) (Fig. 29).
WARNING: CONSTANT TENSION HOSE CLAMPS
ARE USED ON MOST COOLING SYSTEM HOSES.
WHEN REMOVING OR INSTALLING, USE ONLY
TOOLS DESIGNED FOR SERVICING THIS TYPE OF
CLAMP, SUCH AS SPECIAL CLAMP TOOL (NUMBER
6094).CAUTION: A number or letter is stamped into the
tongue of constant tension clamps. If replacement
is necessary, use only an original equipment clamp
with a matching number or letter.
(4) Remove upper radiator hose clamp. Remove
upper radiator hose at thermostat housing.
(5) Disconnect the wiring connectors at both of the
sensors located on thermostat housing.
(6) Remove six thermostat housing mounting bolts,
thermostat housing and thermostat.
INSTALLATION
(1) Clean mating areas of intake manifold and
thermostat housing.
(2) Check the condition (for tears or cracks) of the
rubber thermostat seal located in the intake manifold
(Fig. 28). The thermostat should fit snugly into the
rubber seal.
(3) If seal replacement is necessary, coat the outer
(metal) portion of the seal with MopartGasket
Maker. Install the seal into the manifold using Spe-
cial Seal Tool number C-3995-A with handle tool
number C-4171.
(4) Install thermostat into recessed machined
groove on intake manifold (Fig. 28).
(5) Install thermostat housing (Fig. 30).
(6) Install housing-to-intake manifold bolts.
Tighten bolts to 25 N´m (220 in. lbs.) torque.
CAUTION: Housing bolts should be tightened
evenly to prevent damage to housing and to pre-
vent leaks.
(7) Connect the wiring to both sensors.
(8) Install the upper radiator hose and hose clamp
to thermostat housing.
Fig. 28 Thermostat Seal - 8.0L V-10 Engine
1 - METAL SEAL SHOULDER
2 - RUBBER LIP SEAL
3 - THERMOSTAT OPENING
Fig. 29 Support Rod - 8.0L V-10 Engine
1 - BOLTS
2 - SUPPORT ROD
DRENGINE 7 - 49
ENGINE COOLANT THERMOSTAT - 8.0L (Continued)

(9) Install support rod.
(10) Fill cooling system (Refer to 7 - COOLING -
STANDARD PROCEDURE).
(11) Connect negative battery cable to battery.
(12) Start and warm engine. Check for leaks.
FAN DRIVE VISCOUS CLUTCH-
GAS ENGINES
DESCRIPTION
The thermal viscous fan drive (Fig. 31) is a sili-
cone-fluid- filled coupling used to connect the fan
blades to the water pump shaft. The coupling allows
the fan to be driven in a normal manner. This is
done at low engine speeds while limiting the top
speed of the fan to a predetermined maximum level
at higher engine speeds.
OPERATION
A thermostatic bimetallic spring coil is located on
the front face of the viscous fan drive unit (a typical
viscous unit is shown in (Fig. 32). This spring coilreacts to the temperature of the radiator discharge
air. It engages the viscous fan drive for higher fan
speed if the air temperature from the radiator rises
above a certain point. Until additional engine cooling
is necessary, the fan will remain at a reduced rpm
regardless of engine speed.
Only when sufficient heat is present, will the vis-
cous fan drive engage. This is when the air flowing
through the radiator core causes a reaction to the
bimetallic coil. It then increases fan speed to provide
the necessary additional engine cooling.
Once the engine has cooled, the radiator discharge
temperature will drop. The bimetallic coil again
reacts and the fan speed is reduced to the previous
disengaged speed.
DIAGNOSIS AND TESTING - VISCOUS FAN
DRIVE
NOISE
NOTE: It is normal for fan noise to be louder (roar-
ing) when:
²The underhood temperature is above the engage-
ment point for the viscous drive coupling. This may
occur when ambient (outside air temperature) is very
high.
Fig. 30 Thermostat - 8.0L V-10 Engine
1 - COOLANT TEMP. SENSOR (FOR PCM)
2 - HEATER SUPPLY FITTING
3 - BOLTS (6)
4 - HOUSING WITH INTEGRAL SEAL
5 - THERMOSTAT
6 - RUBBER LIP SEAL
7 - TEMP. GAUGE SENDING UNIT
Fig. 31 Viscous Fan
1 - WATER PUMP BYPASS HOSE
2 - FAN BLADE ASSEMBLY
3 - VISCOUS FAN DRIVE
4 - WATER PUMP AND PULLEY
5 - Bolts (4)
7 - 50 ENGINEDR
ENGINE COOLANT THERMOSTAT - 8.0L (Continued)

²Engine loads and temperatures are high such as
when towing a trailer.
²Cool silicone fluid within the fan drive unit is
being redistributed back to its normal disengaged
(warm) position. This can occur during the first 15
seconds to one minute after engine start-up on a cold
engine.
LEAKS
Viscous fan drive operation is not affected by small
oil stains near the drive bearing. If leakage appears
excessive, replace the fan drive unit.
VISCOUS DRIVE
If the fan assembly free-wheels without drag (the
fan blades will revolve more than five turns when
spun by hand), replace the fan drive. This spin test
must be performed when the engine is cool.
For the following test, the cooling system must be
in good condition. It also will ensure against exces-
sively high coolant temperature.
WARNING: BE SURE THAT THERE IS ADEQUATE
FAN BLADE CLEARANCE BEFORE DRILLING.
(1) Drill a 3.18-mm (1/8-in) diameter hole in the
top center of the fan shroud.
(2) Obtain a dial thermometer with an 8 inch stem
(or equivalent). It should have a range of -18É-to-
105ÉC (0É-to-220É F). Insert thermometer through the
hole in the shroud. Be sure that there is adequate
clearance from the fan blades.
(3) Connect a tachometer and an engine ignition
timing light. The timing light is to be used as a
strobe light. This step cannot be used on the diesel
engine.(4) Block the air flow through the radiator. Secure
a sheet of plastic in front of the radiator. Use tape at
the top to secure the plastic and be sure that the air
flow is blocked.
(5) Be sure that the air conditioner (if equipped)
and blowe fan is turned off.
WARNING: USE EXTREME CAUTION WHEN THE
ENGINE IS OPERATING. DO NOT STAND IN A
DIRECT LINE WITH THE FAN. DO NOT PUT YOUR
HANDS NEAR THE PULLEYS, BELTS OR FAN. DO
NOT WEAR LOOSE CLOTHING.
(6) Start the engine and operate at 2400 rpm.
Within ten minutes the air temperature (indicated on
the dial thermometer) should be up to 88É C (190É F).
Fan driveengagementshould start to occur at/be-
tween:
²3.7L Automatic - 93É C - 99ÉC (200É F - 210É F)
²3.7L Manual/4.7L Automatic/5.9L - 85É - 91É C
(185É - 195É F)
²4.7L Manual - 74É - 79É C (165É - 175É F)
²5.7L
²5.9L
²Engagement is distinguishable by a definite
increasein fan flow noise (roaring). The timing light
also will indicate an increase in the speed of the fan.
(7) When viscous drive engagement is verified,
remove the plastic sheet. Fan drivedisengagement
should start to occur at or between:
²3.7L Automatic - 76ÉC - 81ÉC (168É F - 178É F)
²3.7L Manual/4.7L Auto/ 5.9L - 67ÉC - 73ÉC (153É
F - 163É F)
²4.7L Manual - 56ÉC - 62ÉC (133É F - 143É F)
²5.7L
²5.9L
²8.0L engine - 93É to 101É C (190É - 205É F) Min-
imum 73ÉC (163ÉF). A definitedecreaseof fan flow
noise (roaring) should be noticed. If not, replace the
defective viscous fan drive unit.
CAUTION: Some engines equipped with serpentine
drive belts have reverse rotating fans and viscous
fan drives. They are marked with the word
REVERSE to designate their usage. Installation of
the wrong fan or viscous fan drive can result in
engine overheating.
Fig. 32 Viscous Fan Drive - Typical
1 - VISCOUS FAN DRIVE
2 - THERMOSTATIC SPRING
3 - MOUNTING NUT TO WATER PUMP HUB
DRENGINE 7 - 51
FAN DRIVE VISCOUS CLUTCH-GAS ENGINES (Continued)

RADIATOR-3.7L/4.7L/5.7L
DESCRIPTION
The radiator is a aluminum cross-flow design with
horizontal tubes through the radiator core and verti-
cal plastic side tanks (Fig. 38).
This radiator does not contain an internal trans-
mission oil cooler.
OPERATION
The radiator supplies sufficient heat transfer using
the cooling fins interlaced between the horizontal
tubes in the radiator core to cool the engine.
DIAGNOSIS AND TESTING - RADIATOR
COOLANT FLOW
Use the following procedure to determine if coolant
is flowing through the cooling system.
(1) Idle engine until operating temperature is
reached. If the upper radiator hose is warm to the
touch, the thermostat is opening and coolant is flow-
ing to the radiator.
WARNING: HOT, PRESSURIZED COOLANT CAN
CAUSE INJURY BY SCALDING. USING A RAG TO
COVER THE RADIATOR PRESSURE CAP, OPEN
RADIATOR CAP SLOWLY TO THE FIRST STOP. THIS
WILL ALLOW ANY BUILT-UP PRESSURE TO VENT
TO THE RESERVE/OVERFLOW TANK. AFTER PRES-
SURE BUILD-UP HAS BEEN RELEASED, REMOVE
CAP FROM FILLER NECK.
(2) Drain a small amount of coolant from the radi-
ator until the ends of the radiator tubes are visible
through the filler neck. Idle the engine at normal
operating temperature. If coolant is flowing past the
exposed tubes, the coolant is circulating.
REMOVAL
(1) Disconnect battery negative cables.
WARNING: DO NOT REMOVE THE CYLINDER
BLOCK DRAIN PLUGS OR LOOSEN THE RADIATOR
DRAINCOCK WITH THE SYSTEM HOT AND UNDER
PRESSURE. SERIOUS BURNS FROM THE COOL-
ANT CAN OCCUR.
(2) Drain the cooling system (Refer to 7 - COOL-
ING - STANDARD PROCEDURE).
WARNING: CONSTANT TENSION HOSE CLAMPS
ARE USED ON MOST COOLING SYSTEM HOSES.
WHEN REMOVING OR INSTALLING, USE ONLY
TOOLS DESIGNED FOR SERVICING THIS TYPE OF
CLAMP. ALWAYS WEAR SAFETY GLASSES WHEN
SERVICING CONSTANT TENSION CLAMPS.CAUTION: A number or letter is stamped into the
tongue of constant tension clamps. If replacement
is necessary, use only an original equipment clamp
with a matching number or letter and the correct
width.
(3) Remove the hose clamps and hoses from radia-
tor.
(4) Remove the coolant reserve/overflow tank hose
from the radiator filler neck.
(5) Remove the coolant reserve/overflow tank from
the fan shroud (pull straight up). The tank slips into
slots on the fan shroud.
(6) Unclip the power steering hoses from the fan
shroud.
(7) Disconnect the electrical connectors at the
windshield washer reservoir tank and remove the
tank.
(8) Remove the fan shroud mounting bolts and pull
up and out of the radiator tank clips (Fig. 36). Posi-
tion shroud rearward over the fan blades towards
engine.
(9) Disconnect the transmission cooler lines from
the transmission cooler, then plug the transmission
lines and cooler to prevent leakage.
(10) Disconnect the power steering lines from the
power steering cooler, then plug the power steering
lines and cooler to prevent leakage.
Fig. 36 Fan Shroud - Gas Engine
1 - RADIATOR
2 - SCREWS
3 - FAN SHROUD
4 - SLIDE MOUNT
7 - 54 ENGINEDR

RADIATOR - 5.9L DIESEL
DESCRIPTION
The radiator is a aluminum cross-flow design with
horizontal tubes through the radiator core and verti-
cal plastic side tanks (Fig. 38).
This radiator does not contain an internal trans-
mission oil cooler.
OPERATION
The radiator supplies sufficient heat transfer using
the cooling fins interlaced between the horizontal
tubes in the radiator core to cool the engine.
DIAGNOSIS AND TESTING - RADIATOR
COOLANT FLOW
Use the following procedure to determine if coolant
is flowing through the cooling system.
(1) Idle engine until operating temperature is
reached. If the upper radiator hose is warm to the
touch, the thermostat is opening and coolant is flow-
ing to the radiator.
WARNING: HOT, PRESSURIZED COOLANT CAN
CAUSE INJURY BY SCALDING. USING A RAG TO
COVER THE RADIATOR PRESSURE CAP, OPEN
RADIATOR CAP SLOWLY TO THE FIRST STOP. THIS
WILL ALLOW ANY BUILT-UP PRESSURE TO VENT
TO THE RESERVE/OVERFLOW TANK. AFTER PRES-
SURE BUILD-UP HAS BEEN RELEASED, REMOVE
CAP FROM FILLER NECK.
(2) Drain a small amount of coolant from the radi-
ator until the ends of the radiator tubes are visible
through the filler neck. Idle the engine at normal
operating temperature. If coolant is flowing past the
exposed tubes, the coolant is circulating.
REMOVAL
(1) Disconnect both battery negative cables.
WARNING: DO NOT REMOVE THE CYLINDER
BLOCK DRAIN PLUGS OR LOOSEN THE RADIATOR
DRAINCOCK WITH THE SYSTEM HOT AND UNDER
PRESSURE. SERIOUS BURNS FROM COOLANT
CAN OCCUR.
(2) Drain the cooling system (Refer to 7 - COOL-
ING - STANDARD PROCEDURE).
WARNING: CONSTANT TENSION HOSE CLAMPS
ARE USED ON MOST COOLING SYSTEM HOSES.
WHEN REMOVING OR INSTALLING, USE ONLY
TOOLS DESIGNED FOR SERVICING THIS TYPE OF
CLAMP, SUCH AS SPECIAL CLAMP TOOL (NUMBER6094). ALWAYS WEAR SAFETY GLASSES WHEN
SERVICING CONSTANT TENSION CLAMPS.
CAUTION: A number or letter is stamped into the
tongue of constant tension clamps. If replacement
is necessary, use only an original equipment clamp
with a matching number or letter.
(3) Remove air box and turbocharger inlet tube.
(4) Remove coolant tank hose, washer bottle hose
and the positive battery cable from the fastening
clips located on top of the radiator.
(5) Remove hose clamps and hoses from radiator.
(6) Remove the power steering cooler mounting
bolts and position the power steering cooler out of
the way.
(7) Disconnect the transmission cooler lines at the
transmission cooler. The transmission cooler will
remain on the radiator and can be removed as an
assembly.
(8) Disconnect the electronic viscous fan drive elec-
trical connector.
(9) Using a fastener removal tool, remove the two
push pins and the lower shroud assembly and elec-
tronic viscous fan drive wiring from the upper shroud
assembly. Position wiring out of the way. Do not
impact or damage the electronic viscous fan drive or
pull it's wiring.
(10) Using a fastener tool, remove the wiring har-
ness bracket from the upper fan shroud.
(11) Remove the two radiator upper mounting
bolts (Fig. 38).
(12) Lift radiator straight up and out of engine
compartment. The bottom of the radiator is equipped
with two alignment dowels that fit into holes in the
lower radiator support panel. Rubber biscuits (insu-
lators) are installed to these dowels. Take care not to
damage cooling fins or tubes on the radiator and air
conditioning condenser or the electronic viscous fan
connector when removing.
CLEANING
Clean radiator fins are necessary for good heat
transfer. The radiator and oil cooler fins should be
cleaned when an accumulation of debris has
occurred. With the engine cold, apply cold water and
compressed air to the back (engine side) of the radi-
ator to flush the radiator and/or oil coolers of debris.
INSPECTION
Inspect the radiator side tanks for cracks, and bro-
ken or missing fittings. Inspect the joint where the
tanks seam up to the radiator core for signs of leak-
age and/or deteriorating seals.
Inspect radiator core for corroded, bent or missing
cooling fins. Inspect the core for bent or damaged
cooling tubes.
7 - 56 ENGINEDR

engine warm-up preventing the coolant from flowing
through the radiator (Fig. 44).
OPERATION
OPERATIONÐWATER PUMP
A centrifugal water pump circulates coolant
through the water jackets, passages, intake manifold,
radiator core, cooling system hoses and heater core,
this coolant absorbs the heat generated when the
engine is running. The pump is driven by the engine
crankshaft via a drive belt.
OPERATION - WATER PUMP BYPASS
When the thermostat is in the closed position the
bypass gallery is not obstructed allowing 100% flow.
When the thermostat is in the open position the pill
partially covers the bypass hole, reducing the amount
of bypass flow. This design allows the coolant to
reach operating temperature quickly when cold,
while adding extra cooling during normal tempera-
ture operation.
REMOVAL
The water pump on 3.7L/4.7L engines is bolted
directly to the engine timing chain case cover.
(1) Disconnect the negative battery cable.(2) Drain cooling system (Refer to 7 - COOLING -
STANDARD PROCEDURE).
(3) Remove fan/viscous fan drive assembly from
water pump (Fig. 45) (Refer to 7 - COOLING/EN-
GINE/FAN DRIVE VISCOUS CLUTCH -
REMOVAL). Do not attempt to remove fan/viscous
fan drive assembly from vehicle at this time.
WARNING: CONSTANT TENSION HOSE CLAMPS
ARE USED ON MOST COOLING SYSTEM HOSES.
WHEN REMOVING OR INSTALLING, USE ONLY
TOOLS DESIGNED FOR SERVICING THIS TYPE OF
CLAMP. ALWAYS WEAR SAFETY GLASSES WHEN
SERVICING CONSTANT TENSION CLAMPS.
CAUTION: A number or letter is stamped into the
tongue of constant tension clamps. If replacement
is necessary, use only an original equipment clamp
with matching number or letter and width.
(4) If the water pump is being replaced, do not
unbolt the fan blade assembly from the thermal vis-
cous fan drive.
Fig. 43 Water Pump and Timing Chain Cover - 4.7L
1 - INTEGRAL WATER PUMP PULLEY
2 - TIMING CHAIN COVER
3 - THERMOSTAT HOUSING
4 - HEATER HOSE FITTINGS
5 - WATER PUMP
Fig. 44 Water/Coolant Bypass Flow and Thermostat
1 - FROM HEATER AND DEGAS CONTAINER
2 - FROM RADIATOR
3 - TO WATER PUMP
4- THERMOSTAT
7 - 60 ENGINEDR
WATER PUMP - 3.7L/4.7L (Continued)