engine oil DODGE RAM 1500 1998 2.G Owner's Guide

exhaust pipe may indicate a faulty cylinder head gas-
ket, cracked engine cylinder block or cylinder head.
A convenient check for exhaust gas leakage into
cooling system is provided by a commercially avail-
able Block Leak Check tool. Follow manufacturers
instructions when using this product.
COMBUSTION LEAKAGE TEST - WITHOUT
PRESSURE TESTER
DO NOT WASTE reusable coolant. If the solution
is clean, drain the coolant into a clean container for
reuse.
WARNING: DO NOT REMOVE CYLINDER BLOCK
DRAIN PLUGS OR LOOSEN RADIATOR DRAIN-
COCK WITH SYSTEM HOT AND UNDER PRESSURE.
SERIOUS BURNS FROM COOLANT CAN OCCUR.
Drain sufficient coolant to allow thermostat
removal. (Refer to 7 - COOLING/ENGINE/ENGINECOOLANT THERMOSTAT - REMOVAL). Remove
accessory drive belt (Refer to 7 - COOLING/ACCES-
SORY DRIVE/DRIVE BELTS - REMOVAL).
Add coolant to radiator to bring level to within 6.3
mm (1/4 in) of the top of the thermostat housing.
CAUTION: Avoid overheating. Do not operate
engine for an excessive period of time. Open drain-
cock immediately after test to eliminate boil over.
Start engine and accelerate rapidly three times, to
approximately 3000 rpm while observing coolant. If
internal engine combustion gases are leaking into
cooling system, bubbles will appear in coolant. If bub-
bles do not appear, internal combustion gas leakage
is not present.
DIAGNOSIS AND TESTING - COOLING SYSTEM DIESEL ENGINE
COOLING SYSTEM DIAGNOSIS - DIESEL ENGINE
CONDITION POSSIBLE CAUSES CORRECTION
TEMPERATURE GAUGE READS
LOW1. Vehicle is equipped with a heavy
duty cooling system.1. None. System operating normally.
NOTE: Information on dash cluster
is displayed based on broadcast
datd from ECM. DTC will be set for
engine sensore circuit concern.2. Thermostat stuck open 2. Inspect and test thermostat.
3. Coolant level low. 3. Fill cooling system. (Refer to 7 -
COOLING - STANDARD
PROCEDURE)
4. Temperature gauge not
functioning correctly.4. Check cluster (Refer to 8 -
ELECTRICAL/INSTRUMENT
CLUSTER - DIAGNOSIS AND
TESTING)
5. Engine sensor stuck in range 5. Monitor sensor with DRB III to
verify sensor reading changes with
increasing temperature.
6. Engine sensor failed out of
range.A DTC will be set.
7. Electronically Controlled Vicsous
Fan Drive not operating properly.7. Check Electronically Controlled
Viscous Fan Drive (Refer to 7 -
COOLING/ENGINE/FAN DRIVE
VISCOUS CLUTCH - DIAGNOSIS
AND TESTING)
DRCOOLING 7 - 7
COOLING (Continued)

CONDITION POSSIBLE CAUSES CORRECTION
3. Is the temperature warning
illuminating unnecessarily?3. (Refer to 8 - ELECTRICAL/
INSTRUMENT CLUSTER -
SCHEMATIC - ELECTRICAL).
4. Coolant low in coolant reserve/
overflow tank and radiator?4. Check for coolant leaks and
repair as necessary. (Refer to 7 -
COOLING - DIAGNOSIS AND
TESTING).
5. Pressure cap not installed tightly.
If cap is loose, boiling point of
coolant will be lowered. Also refer
to the following Step 6.5. Tighten cap
6. Poor seals at the radiator cap. 6. (a) Check condition of cap and
cap seals. Refer to Radiator Cap.
Replace cap if necessary.
(b) Check condition of radiator filler
neck. If neck is bent or damaged,
replace radiator (5.9L) or degas
bottle (3.7L, 4.7L).
7. Coolant level low in radiator but
not in coolant reserve/overflow
tank. This means the radiator is not
drawing coolant from the coolant
reserve/overflow tank as the engine
cools (5.9L).7. (a) Check condition of radiator
cap and cap seals. Refer to
Radiator Cap in this Group. Replace
cap if necessary.
(b) Check condition of radiator filler
neck. If neck is bent or damaged,
replace radiator.
(c) Check condition of the hose from
the radiator to the coolant tank. It
should fit tight at both ends without
any kinks or tears. Replace hose if
necessary.
(d) Check coolant reserve/overflow
tank and tanks hoses for blockage.
Repair as necessary.
8. Incorrect coolant concentration 8. Check coolant. (Refer to
LUBRICATION & MAINTENANCE/
FLUID TYPES - DESCRIPTION).
9. Coolant not flowing through
system9. Check for coolant flow at radiator
filler neck with some coolant
removed, engine warm and
thermostat open. Coolant should be
observed flowing through radiator. If
flow is not observed, determine area
of obstruction and repair as
necessary.
10. Radiator or A/C condenser fins
are dirty or clogged.10. Remove insects and debris.
(Refer to 7 - COOLING -
STANDARD PROCEDURE).
7 - 12 COOLINGDR
COOLING (Continued)

CONDITION POSSIBLE CAUSES CORRECTION
Temperature gauge reading is
inconsistent (fluctuates, cycles or is
erratic)1. During cold weather operation,
with the heater blower in the high
position, the gauge reading may
drop slightly.1. A normal condition. No correction
necessary.
2. Temperature gauge or engine
mounted gauge sensor defective or
shorted. Also, corroded or loose
wiring in this circuit.2. Check operation of gauge and
repair if necessary. (Refer to 8 -
ELECTRICAL/INSTRUMENT
CLUSTER - DIAGNOSIS AND
TESTING).
3. Gauge reading rises when
vehicle is brought to a stop after
heavy use (engine still running)3. A normal condition. No correction
is necessary. Gauge should return
to normal range after vehicle is
driven.
4. Gauge reading high after
re-starting a warmed up (hot)
engine.4. A normal condition. No correction
is necessary. The gauge should
return to normal range after a few
minutes of engine operation.
5. Coolant level low in radiator (air
will build up in the cooling system
causing the thermostat to open
late).5. Check and correct coolant leaks.
(Refer to 7 - COOLING -
DIAGNOSIS AND TESTING).
6. Cylinder head gasket leaking
allowing exhaust gas to enter
cooling system causing a
thermostat to open late.6. (a) Check for cylinder head
gasket leaks. (Refer to 7 -
COOLING - DIAGNOSIS AND
TESTING).
(b) Check for coolant in the engine
oil. Inspect for white steam emitting
from the exhaust system. Repair as
necessary.
7. Water pump impeller loose on
shaft.7. Check water pump and replace
as necessary. (Refer to 7 -
COOLING/ENGINE/WATER PUMP -
REMOVAL).
8. Loose accessory drive belt.
(water pump slipping)8. (Refer to 7 - COOLING/
ACCESSORY DRIVE/DRIVE BELTS
- DIAGNOSIS AND TESTING).
Check and correct as necessary.
9. Air leak on the suction side of
the water pump allows air to build
up in cooling system causing
thermostat to open late.9. Locate leak and repair as
necessary.
PRESSURE CAP IS BLOWING
OFF STEAM AND/OR COOLANT
TO COOLANT TANK.
TEMPERATURE GAUGE READING
MAY BE ABOVE NORMAL BUT
NOT HIGH. COOLANT LEVEL MAY
BE HIGH IN COOLANT RESERVE/
OVERFLOW TANK1. Pressure relief valve in radiator
cap is defective.1. Check condition of radiator cap
and cap seals. (Refer to 7 -
COOLING/ENGINE/RADIATOR
PRESSURE CAP - DIAGNOSIS
AND TESTING). Replace cap as
necessary.
7 - 14 COOLINGDR
COOLING (Continued)

STANDARD PROCEDURE - REFILLING
COOLING SYSTEM 5.9L DIESEL ENGINE
Clean cooling system prior to refilling (Refer to 7 -
COOLING - STANDARD PROCEDURE).
(1) Close radiator drain plug.
CAUTION: Due to the use of the one-way check
valve, the engine must not be operating when refill-
ing the cooling system.
NOTE: The diesel engine is equipped with two one-
way check valves (jiggle pins). The check valves
are used as a servicing feature and will vent air
when the system is being filled. Water pressure (or
flow) will hold the valves closed.
(2) Fill the cooling system with a 50/50 mixture of
water and antifreeze.
(3) Fill coolant reserve/overflow tank to the FULL
mark.
(4) Start and operate engine until thermostat
opens. Upper radiator hose should be warm to touch.
(5) If necessary, add 50/50 water and antifreeze
mixture to the coolant reserve/overflow tank to main-
tain coolant level. This level should be between the
ADD and FULL marks. The level in the reserve/over-
flow tank may drop below the ADD mark after three
or four warm-up and cool-down cycles.
STANDARD PROCEDURE - ADDING
ADDITIONAL COOLANT
The use of aluminum cylinder blocks, cylinder
heads and water pumps requires special corrosion
protection. Only MopartAntifreeze/Coolant, 5
Year/100,000 Mile Formula (glycol base coolant with
corrosion inhibitors called HOAT, for Hybrid Organic
Additive Technology) is recommended. This coolant
offers the best engine cooling without corrosion when
mixed with 50% distilled water to obtain a freeze
point of -37ÉC (-35ÉF). If it loses color or becomes con-
taminated, drain, flush, and replace with fresh prop-
erly mixed coolant solution.
CAUTION: Do not use coolant additives that are
claimed to improve engine cooling.
Do not remove the radiator cap to add coolant to
the system. When adding coolant to maintain the cor-
rect level, do so only at the reserve/overflow bottle.
Remove the radiator cap only for testing or when
refilling the system after service. Removing the cap
unnecessarily can cause loss of coolant and allow air
to enter the system, which produces corrosion.
WARNING: DO NOT REMOVE OR LOOSEN THE
RADIATOR CAP WITH THE COOLING SYSTEM HOTAND UNDER PRESSURE. SERIOUS BURNS FROM
THE COOLANT OR HIGH PRESSURE STEAM CAN
OCCUR.
SPECIFICATIONS
TORQUE
DESCRIPTION N´m Ft.
Lbs.In.
Lbs.
Bolt - Automatic Belt
Tensioner to Block41 30 -
Bolt - Automatic Belt
Tensioner Pulley61 45 -
Bolt - Automatic Belt
Tensioner Pulley - Diesel43 32 -
Bolt - Block Heater 2 - 17
Bolts - Generator/
Compressor Mounting
Bracket
# 1 and 2 54 40 -
# 3 40 30 -
Bolts - Generator/
Compressor Mounting
Bracket - Diesel24 18 -
Bolts - Fan Shroud to
Radiator Mounting - All
Except 5.9L Diesel6-55
5.9L Diesel 11.8 - 105
Bolts - Radiator to Support 8.5 - 75
Bolts - Fan Blade to
Viscous Fan Drive24 18 -
Fan Drive - All Except
8.0L/5.9L Diesel50 37 -
8.0L/5.9L Diesel 115 85 -
Bolt - Idler Pulley 54 40 -
Bolt - Idler Pulley - Diesel 43 32 -
Bolts - Thermostat Housing
- All Except 5.9L13 - 112
Bolts - Thermostat Housing
5.9L23 16 -
Bolts - Thermostat Housing
- Diesel10 - 89
Bolts - Power Steering Oil
Cooler8.4 - 75
Bolts - Transmission
Auxiliary Oil Cooler6-55
DRCOOLING 7 - 19
COOLING (Continued)

DESCRIPTION N´m Ft.
Lbs.In.
Lbs.
Nuts - Transmission Oil
Cooler Tube31.5 24 -
Bolts - Coolant Bottle 8.5 - 75
Tube Nuts - Transmission
Oil Cooler to Transmission
5.9L/46RE 31.5 24 -
3.7L/4.7L/5.7L/45RFE 20 18 -
Bolts - Water Pump -
Diesel24 18 -
Bolts - Water Pump - 4.7L 58 43 -
Block Heater - Diesel 55 41 -
Transmission Oil Cooler -
Diesel
M8 24 18 -
M12 77 57 -
SPECIFICATIONS -
SPECIFICATIONS
DESCRIPTION SPECIFICATION
Metric Standard
3.7/4.7L/5.7L
Engine15.4L 16.2 qts.- to the
middle of the
cold fill range
5.9L Diesel
Engine28L 29.5 qts.
SPECIAL TOOLS
COOLING
Pliers Constant Pressure Hose Clamp - 6094
3/8º Quick Connect Release Tool - 6935
SPANNER WRENCHÐ6958
Cooling System Pressure Tester - 7700A
Adapter Pins 8346
7 - 20 COOLINGDR
COOLING (Continued)

INSTALLATION
(1) Install tensioner on to the mounting bracket.
Tighten bolt to 41 N´m (30 ft. lbs.).
(2) Install tensioner and bracket assembly
(3) Install accessory drive belt (Refer to 7 - COOL-
ING/ACCESSORY DRIVE/DRIVE BELTS - INSTAL-
LATION).
BELT TENSIONER - 5.9L
DIESEL
DESCRIPTION
Drive belts on all engines are equipped with a
spring loaded automatic belt tensioner (Fig. 4). This
tensioner maintains constant belt tension at all times
and requires no maintenance or adjustment.
CAUTION: Do not attempt to check belt tension with
a belt tension gauge on vehicles equipped with an
automatic belt tensioner.
OPERATION
WARNING: THE AUTOMATIC BELT TENSIONER
ASSEMBLY IS SPRING LOADED. DO NOT ATTEMPT
TO DISASSEMBLE THE TENSIONER ASSEMBLY.
The automatic belt tensioner maintains correct belt
tension using a coiled spring within the tensioner
housing. The spring applies pressure to the tensioner
arm pressing the arm into the belt, tensioning the
belt.
REMOVAL
WARNING: BECAUSE OF HIGH SPRING PRES-
SURE, DO NOT ATTEMPT TO DISASSEMBLE AUTO-
MATIC TENSIONER. UNIT IS SERVICED AS AN
ASSEMBLY.
(1) Remove accessory drive belt (Refer to 7 -
COOLING/ACCESSORY DRIVE/DRIVE BELTS -
REMOVAL).
(2) Remove tensioner mounting bolt (Fig. 5) and
remove tensioner.
Fig. 4 Accessory Drive Belt - 5.9L Diesel
1 - GENERATOR
2 - WATER PUMP
3 - IDLER
4 - POWER STEERING PUMP
5 - RADIATOR FAN PULLEY
6 - CRANKSHAFT
7 - AUTOMATIC TENSIONER
8 - A/C COMPRESSOR
Fig. 5 AUTOMATIC BELT TENSIONER 5.9L DIESEL
ENGINE
1 - GENERATOR
2 - WATER PUMP
3 - IDLER
4 - POWER STEERING PUMP
5 - RADIATOR FAN PULLEY
6 - CRANKSHAFT
7 - AUTOMATIC TENSIONER
8 - A/C COMPRESSOR
DRACCESSORY DRIVE 7 - 23
BELT TENSIONER-5.7L (Continued)

DIAGNOSIS AND TESTING - RADIATOR
CAP................................58
CLEANING............................59
INSPECTION..........................59
WATER PUMP - 3.7L/4.7L
DESCRIPTION
DESCRIPTION - WATER PUMP...........59
DESCRIPTION - WATER PUMP BYPASS....59
OPERATION
OPERATIONÐWATER PUMP............60
OPERATION - WATER PUMP BYPASS.....60
REMOVAL.............................60
CLEANING............................61
INSPECTION..........................61
INSTALLATION.........................61
WATER PUMP - 5.9L DIESEL
DESCRIPTION.........................62OPERATION...........................62
DIAGNOSIS AND TESTINGÐWATER PUMP . . . 62
REMOVAL.............................62
CLEANING............................62
INSPECTION..........................62
INSTALLATION.........................62
WATER PUMP - 5.7L
REMOVAL.............................63
INSTALLATION.........................63
WATER PUMP - 8.0L
DIAGNOSIS AND TESTING - WATER PUMP . . . 63
REMOVAL.............................64
CLEANING............................66
INSPECTION..........................66
INSTALLATION.........................66
COOLANT
DESCRIPTION
DESCRIPTION - ENGINE COOLANT
ETHYLENE-GLYCOL MIXTURES
CAUTION: Richer antifreeze mixtures cannot be
measured with normal field equipment and can
cause problems associated with 100 percent ethyl-
ene-glycol.
The use of aluminum cylinder blocks, cylinder
heads and water pumps requires special corrosion
protection. Only MopartAntifreeze/Coolant, 5
year/100,000 Mile Formula (ethylene-glycol base cool-
ant with corrosion inhibitors called HOAT, for Hybrid
Additive Technology) is recommended. This coolant
offers the best engine cooling without corrosion when
mixed with 50% distilled water to obtain a freeze
point of -37ÉC (-35ÉF).
The required ethylene-glycol (antifreeze) and water
mixture depends upon the climate and vehicle oper-
ating conditions. The antifreeze concentrationmust
alwaysbe a minimum of 44 percent, year-round in
all climates.If percentage is lower than 44 per-
cent, engine parts may be eroded by cavitation,
and cooling system components may be
severely damaged by corrosion.Maximum protec-
tion against freezing is provided with a 68% anti-
freeze concentration, which prevents freezing down to
-67.7É C (-90É F). A higher percentage will freeze at a
warmer temperature. Also, a higher percentage of
antifreeze can cause the engine to overheat becausethe specific heat of antifreeze is lower than that of
water.
Use of 100 percent ethylene-glycol will cause for-
mation of additive deposits in the system, as the cor-
rosion inhibitive additives in ethylene-glycol require
the presence of water to dissolve. The deposits act as
insulation, causing temperatures to rise to as high as
149É C (300É F). This temperature is hot enough to
melt plastic and soften solder. The increased temper-
ature can result in engine detonation. In addition,
100 percent ethylene-glycol freezes at 22É C (-8É F ).
PROPYLENE-GLYCOL MIXTURES
It's overall effective temperature range is smaller
than that of ethylene-glycol. The freeze point of 50/50
propylene-glycol and water is -32É C (-26É F). 5É C
higher than ethylene-glycol's freeze point. The boiling
point (protection against summer boil-over) of propy-
lene-glycol is 125É C (257ÉF)at96.5 kPa (14 psi),
compared to 128É C (263É F) for ethylene-glycol. Use
of propylene-glycol can result in boil-over or freeze-up
on a cooling system designed for ethylene-glycol. Pro-
pylene glycol also has poorer heat transfer character-
istics than ethylene glycol. This can increase cylinder
head temperatures under certain conditions.
Propylene-glycol/ethylene-glycol Mixtures can
cause the destabilization of various corrosion inhibi-
tors, causing damage to the various cooling system
components. Also, once ethylene-glycol and propy-
lene-glycol based coolants are mixed in the vehicle,
conventional methods of determining freeze point will
not be accurate. Both the refractive index and spe-
cific gravity differ between ethylene glycol and propy-
lene glycol.
DRENGINE 7 - 31

OPERATION
Coolant flows through the engine block absorbing
the heat from the engine, then flows to the radiator
where the cooling fins in the radiator transfers the
heat from the coolant to the atmosphere. During cold
weather the ethylene-glycol or propylene-glycol cool-
ant prevents water present in the cooling system
from freezing within temperatures indicated by mix-
ture ratio of coolant to water.
COOLANT RECOVERY
CONTAINER- GAS ENGINES
DESCRIPTION
The coolant reserve/overflow tank is mounted on
top of the fan shroud, and is made of high tempera-
ture plastic (Fig. 1).
OPERATION
The coolant reserve/overflow system works in con-
junction with the radiator pressure cap. It utilizes
thermal expansion and contraction of coolant to keep
coolant free of trapped air. It provides a volume for
expansion and contraction of coolant. It also provides
a convenient and safe method for checking coolant
level and adjusting level at atmospheric pressure.
This is done without removing the radiator pressure
cap. The system also provides some reserve coolantto the radiator to cover minor leaks and evaporation
or boiling losses.
As the engine cools, a vacuum is formed in the
cooling system of both the radiator and engine. Cool-
ant will then be drawn from the coolant tank and
returned to a proper level in the radiator.
REMOVAL
(1) Remove recovery hose from radiator.
(2) Remove the coolant container to fan shroud
mounting bolt.
(3) Tilt the container backward towards the engine
to disengage the mounting pin locking features and
lift the container away from the fan shroud (Fig. 1).
INSTALLATION
(1) Align the coolant container mounting pins into
the slots on the fan shroud and push the container
onto the fan shroud.
(2) Secure the container to the fan shroud with the
bolt. Tighten to 8.5N´m (75 in-lbs).
NOTE: Ensure that the locking feature on the
mounting pins has engaged.
(3) Connect the recovery hose to the radiator (Fig.
1).
RADIATOR FAN - GAS
ENGINES
REMOVAL
CAUTION: If the viscous fan drive is replaced
because of mechanical damage, the cooling fan
blades should also be inspected. Inspect for fatigue
cracks, loose blades, or loose rivets that could
have resulted from excessive vibration. Replace fan
blade assembly if any of these conditions are
found. Also inspect water pump bearing and shaft
assembly for any related damage due to a viscous
fan drive malfunction.
(1) Disconnect negative battery cable from battery.
(2) Remove coolant reserve/overflow container from
fan shroud and lay aside.Do Notdisconnect the
hoses or drain coolant from the container.
(3) The thermal viscous fan drive/fan blade assem-
bly is attached (threaded) to the water pump hub
shaft (Fig. 3). Remove the fan blade/viscous fan drive
assembly from the water pump by turning the
mounting nut counterclockwise as viewed from the
front. Threads on the viscous fan drive areRIGHT-
HAND.A 36 MM Fan Wrench should be used to pre-
vent pulley from rotating (Fig. 2).
Fig. 1 Coolant Recovery Bottle - Gas Engine
1 - SCREW
2 - COOLANT RECOVERY CONTAINER
3 - RADIATOR/RADIATOR CAP
4 - FAN SHROUD
DRENGINE 7 - 33
COOLANT (Continued)

REMOVAL
(1) Disconnect the battery negative cable.
(2) Drain the coolant (Refer to 7 - COOLING -
STANDARD PROCEDURE).
(3) Remove the power cord from the heater by
unplugging (Fig. 7).
(4) Loosen (but do not completely remove) the
screw at center of block heater (Fig. 7).
(5) Remove the block heater by carefully prying
from side-to-side. Note the direction of the heating
element coil (up or down). The element coil must be
installed correctly to prevent damage.
INSTALLATION
(1) Clean and inspect the block heater hole.
(2) Install the new O-ring seal(s) to heater.
(3) Insert the block heater into cylinder block and
position the element properly.
(4) With the heater fully seated, tighten center
screw to 2 N´m (17 in. lbs.).
(5) Fill the cooling system with the recommended
coolant. (Refer to 7 - COOLING - STANDARD PRO-
CEDURE).
(6) Start and warm the engine.
(7) Check the block heater for leaks.
ENGINE BLOCK HEATER - 5.9L
DIESEL
DESCRIPTION
WARNING: DO NOT OPERATE ENGINE UNLESS
BLOCK HEATER CORD HAS BEEN DISCONNECTED
FROM POWER SOURCE AND SECURED IN PLACE.
THE POWER CORD MUST BE SECURED IN ITS
RETAINING CLIPS AND ROUTED AWAY FROM
EXHAUST MANIFOLDS AND MOVING PARTS.
An optional engine block heater is available on all
models. The heater is equipped with a power cord.
The heater is mounted in a threaded hole of the
engine cylinder block with the heating element
immersed in engine coolant. The cord is attached to
an engine compartment component with tie-straps.
The 5.9L diesel engine has the block heater located
on the right side of the engine below the exhaust
manifold next to the oil cooler (Fig. 8).
Fig. 6 Engine Block Heater - 3.7L/4.7L
1 - ENGINE BLOCK HEATER
Fig. 7 Engine Block Heater
1 - FREEZE PLUG HOLE
2 - BLOCK HEATER
3 - SCREW
4 - POWER CORD (120V AC)
5 - HEATING COIL
6 - OIL FILTER
DRENGINE 7 - 37
ENGINE BLOCK HEATER (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)