trailer DODGE RAM 1500 1998 2.G Workshop Manual

DESCRIPTION SPECIFICATION
REAR AXLE   .03 L (1 oz)
9 1/4 2.32 L (4.9 pts.)***
10 1/2 AA 2.25 L (4.75 pts.)
11 1/2 AA 3.62 L (7.65 pts)
*** With Trac-Lok add 118 ml (4 oz.) of Limited Slip
Additive.
** Includes 0.9L (1.0 qts.) for coolant reservoir.
*Nominal refill capacities are shown. A variation may
be observed from vehicle to vehicle due to
manufacturing tolerance and refill procedure.
MAINTENANCE SCHEDULES
DESCRIPTION
DESCRIPTION
Maintenance Schedule Information not included in
this section, is located in the appropriate Owner's
Manual.
There are two maintenance schedules that show
therequiredservice for your vehicle.
First is ScheduleªBº. It is for vehicles that are
operated under the conditions that are listed below
and at the beginning of the schedule.
²Day or night temperatures are below 0É C (32É
F).
²Stop and go driving.
²Extensive engine idling.
²Driving in dusty conditions.
²Short trips of less than 16 km (10 miles).
²More than 50% of your driving is at sustained
high speeds during hot weather, above 32É C (90É F).
²Trailer towing.
²Taxi, police, or delivery service (commercial ser-
vice).
²Off-road or desert operation.
²If equipped for and operating with E-85
(ethanol) fuel.
NOTE: If ANY of these apply to the vehicle then
change the engine oil every 3,000 miles (5 000 km)
or 3 months, whichever comes first and follow
schedule ªBº of the(Maintenance Schedules(sec-
tion of this manual.
NOTE: Most vehicles are operated under the condi-
tions listed for Schedule(B(.
Second is ScheduleªAº. It is for vehicles that are
not operated under any of the conditions listed under
Schedule9B9.Use the schedule that best describes the driving
conditions. Where time and mileage are listed, follow
the interval that occurs first.
CAUTION: Failure to perform the required mainte-
nance items may result in damage to the vehicle.
At Each Stop for Fuel
²Check the engine oil level about 5 minutes after
a fully warmed engine is shut off. Checking the oil
level while the vehicle is on level ground will
improve the accuracy of the oil level reading. Add oil
only when the level is at or below the ADD or MIN
mark.
²Check the windshield washer solvent and add if
required.
Once a Month
²Check tire pressure and look for unusual wear
or damage.
²Inspect the battery and clean and tighten the
terminals as required.
²Check the fluid levels of coolant reservoir, brake
master cylinder, power steering and transmission
and add as needed.
²Check all lights and all other electrical items for
correct operation.
At Each Oil Change
²Change the engine oil filter.
²Inspect the exhaust system.
²Inspect the brake hoses.
²Inspect the CV joints (if equipped) and front sus-
pension components.
²Check the automatic transmission fluid level.
²Check the manual transmission fluid level.
²Check the coolant level, hoses, and clamps.
²Rotate the tires at each oil change interval
shown on Schedule ªAº 10 000 km (6,000 miles) or
every other interval shown on Schedule ªBº 10 000
km (6,000 miles).
Tire Rotation
²Rotate the tires at 6,000 miles (10 000 km).
Schedule ªBº
Follow schedule ªBº if you usually operate your
vehicle under one or more of the following conditions.
²Day or night temperatures are below 0É C (32É
F).
²Stop and go driving.
²Extensive engine idling.
²Driving in dusty conditions.
²Short trips of less than 16 km (10 miles).
²More than 50% of your driving is at sustained
high speeds during hot weather, above 32É C (90É F).
0 - 6 LUBRICATION & MAINTENANCEDR
FLUID CAPACITIES (Continued)

²Trailer towing.
²Snowplowing.
²Heavy Loading.
²Taxi, police, or delivery service (commercial ser-
vice).
²Off-road or desert operation.
²If equipped for and operating with E-85
(ethanol) fuel.NOTE: If ANY of these apply to the vehicle then
change the engine oil every 3,000 miles (5 000 km)
or 3 months, whichever comes first and follow
schedule ªBº of the(Maintenance Schedules(sec-
tion of this manual.
If none of these apply to the vehicle, then change
the engine oil at every interval shown on schedule
(A(of the(Maintenance Schedules(section of this
manual.
Miles 3,000 6,000 9,000 12,000 15,000
(Kilometers) (5 000) (10 000) (14 000) (19 000) (24 000)
Change engine oil and engine oil filter.XXXX X
Lubricate outer tie rod ends 2500/3500
(4X4) models only.XX
Change rear axle fluid.X
Change front axle fluid (4X4).X
Inspect brake linings.X
Inspect engine air cleaner filter, replace
if necessary.X
Miles 18,000 21,000 24,000 27,000 30,000
(Kilometers) (29 000) (34 000) (38 000) (43 000) (48 000)
Change engine oil and engine oil filter.XXXX X
Lubricate outer tie rod ends 2500/3500
(4X4) models only.XX X
Change rear axle fluid.X
Change front axle fluid (4X4).X
Check transfer case fluid level (4X4). X
Inspect brake linings. X
Inspect engine air cleaner filter, replace
if necessary.X
Replace spark plugs.X
Inspect PCV valve, replace as necessary.X*
Drain and refill automatic tranmission fluid
and change main sump filter (45RFE/
545RFE only).X
DRLUBRICATION & MAINTENANCE 0 - 7
MAINTENANCE SCHEDULES (Continued)

Miles 102,000 108,000 114,000 120,000
(Kilometers) (163 000) (173 000) (182 000) (192 000)
[Months] [102] [108] [114] [120]
Change engine oil and engine oil filter. X X X X
Drain and refill transfer case fluid (4X4). X
Flush and replace engine coolant, if not done at 60 mos. X
Lubricate outer tie rod ends 2500/3500 (4X4) models
only.XXX X
Inspect brake linings. X
Inspect auto tension drive belt and replace if required
(3.7L/4.7L/5.7L).X³X³
Replace ignition cables.X
Replace engine air cleaner filter.X
Replace spark plugs.X
Inspect PCV Valve, replace as necessary X*
* This maintenance is recommended by the manu-
facture to the owner but is not required to maintain
the emissions warranty.
³ This maintenance is not required if previously
replaced.
Inspection and service should also be performed
anytime a malfunction is observed or suspected.
WARNING: You can be badly injured working on or
around a motor vehicle. Do only that service work
for which you have the knowledge and the right
equipment. If you have any doubt about your ability
to perform a service job, take your vehicle to a
competent mechanic.
MAINTENANCE SCHEDULES Ð 24±VALVE
CUMMINS TURBO DIESEL
There are two maintenance schedules that show
therequiredservice for your vehicle.
First is ScheduleªBº. It is for vehicles that are
operated under the conditions that are listed below
and at the beginning of the schedule.
²Day or night temperatures are below 0É C (32É
F).
²Stop and go driving.
²Extensive engine idling.
²Driving in dusty conditions.
²Short trips of less than 16 km (10 miles).
²More than 50% of your driving is at sustained
high speeds during hot weather, above 32É C (90É F).²Trailer towing.
²Taxi, police, or delivery service (commercial ser-
vice).
²Off-road or desert operation.
NOTE: Most vehicles are operated under the condi-
tions listed for Schedule(B(.
Second is ScheduleªAº. It is for vehicles that are
not operated under any of the conditions listed under
Schedule9B9.
Use the schedule that best describes your driving
conditions. Where time and mileage are listed, follow
the interval that occurs first.
CAUTION: Failure to perform the required mainte-
nance items may result in damage to the vehicle.At Each Stop for Fuel
²Check the engine oil level about 15 minutes
after a fully warmed engine is shut off. Checking the
oil level while the vehicle is on level ground will
improve the accuracy of the oil level reading. Add oil
only when the level is at or below the ADD or MIN
mark.
²Check the windshield washer solvent and add if
required.
²Drain water from the fuel filter.
0 - 12 LUBRICATION & MAINTENANCEDR
MAINTENANCE SCHEDULES (Continued)

Once a Month
²Check tire pressure and look for unusual wear
or damage.
²Inspect the batteries and clean and tighten the
terminals as required.
²Check the fluid levels of coolant reservoir, brake
master cylinder, power steering and transmission
and transfer case (if equipped), add as needed.
²Check Filter MinderŸ. Replace air cleaner
filter element if necessary.
²Check all lights and all other electrical items for
correct operation.
At Each Oil Change
²Change the engine oil filter.
²Inspect the exhaust system.
²Inspect the brake hoses.
²Inspect the CV joints (if equipped) and front sus-
pension components.
²Check the automatic transmission fluid level.
²Check the manual transmission fluid level.
²Check the coolant level, hoses, and clamps.
Tire Rotation
²Rotate the tires every 7,500 miles (12 000 km).
Engine Oil Change Chart Notes
²LTier 1 EPA (250 hp or 305 hp) Engines Only
(see engine data label for your engine type)
²² California LEV (235 hp) Engines Only (see
engine data label for your engine type)
Schedule ªBº
Follow schedule ªBº if you usually operate your
vehicle under one or more of the following conditions.
²Day or night temperatures are below 0É C (32É
F).
²Stop and go driving.
²Extensive engine idling.
²Driving in dusty conditions.
²Short trips of less than 16 km (10 miles).
²More than 50% of your driving is at sustained
high speeds during hot weather, above 32É C (90É F).
²Trailer towing.
²Taxi, police, or delivery service (commercial ser-
vice).
²Off-road or desert operation.
Miles 3,750 7,500 11,250 15,000 18,750
(Kilometers) (6 000) (12 000) (18 000) (24 000) (30 000)
Change engine oil and engine oil filter. X² XL²X²XL²X²
Lubricate outer tie rod ends 2500/3500
(4X4) models only.XX
Inspect water pump weep hole for
blockage.X
Replace fuel filter element. Clean the water
in fuel sensor.X
Change rear axle fluid. X
Change front axle fluid (4X4). X
Inspect brake linings.X
Inspect and adjust parking brake if
necessary.X
DRLUBRICATION & MAINTENANCE 0 - 13
MAINTENANCE SCHEDULES (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

OPERATION
OPERATION - COOLING SYSTEM
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 also provides a means of heat-
ing 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 throughout the system.
All engines utilize an ambient overflow bottle for
coolant recovery/reserve.
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.
OPERATION - HOSE CLAMPS
The spring type hose clamp applies constant ten-
sion on a hose connection. To remove a spring type
hose clamp, only use constant tension clamp pliers
designed to compress the hose clamp.
DIAGNOSIS AND TESTING
DIAGNOSIS AND TESTINGÐON-BOARD
DIAGNOSTICS (OBD)
COOLING SYSTEM RELATED DIAGNOSTICS
The Engine Control Module (ECM) has been pro-
grammed to monitor certain cooling system compo-
nents:
²If the engine has remained cool for too long a
period, such as with a stuck open thermostat, a Diag-
nostic Trouble Code (DTC) can be set.
²If an open or shorted condition has developed in
the electronically controlled viscous fan clutch circuit,
a Diagnostic Trouble Code (DTC) can be set.
²If fan speed is not detected a DTC will be set.
²Coolant temperature sensor circuit problems can
set a DTC.
If the problem is sensed in a monitored circuit
often enough to indicated an actual problem, a DTC
is stored. The DTC will be stored in the ECM mem-
ory for eventual display to the service technician.
(Refer to 25 - EMISSIONS CONTROL - DESCRIP-
TION).
ACCESSING DIAGNOSTIC TROUBLE CODES
To read DTC's and to obtain cooling system data,
(Refer to 25 - EMISSIONS CONTROL - DESCRIP-
TION).
ERASING TROUBLE CODES
After the problem has been repaired, use the
DRBIIItscan tool to erase a DTC. Refer to the
appropriate Powertrain Diagnostic Procedures ser-
vice information for operation of the DRBIIItscan
tool.
DIAGNOSIS AND TESTING - COOLING SYSTEM
- TESTING FOR LEAKS
ULTRAVIOLET LIGHT METHOD
A leak detection additive is available through the
parts department that can be added to cooling sys-
tem. The additive is highly visible under ultraviolet
light (black light). Pour one ounce of additive into
cooling system. Place heater control unit in HEAT
position. Start and operate the engine until the radi-
ator upper hose is warm to the touch. Aim the com-
mercially available black light tool at the components
to be checked. If leaks are present, the black light
will cause the additive to glow a bright green color.
The black light can be used in conjunction with a
pressure tester to determine if any external leaks
exist (Fig. 5).
Fig. 4 Spring Clamp Size Location
1 - SPRING CLAMP SIZE LOCATION
DRCOOLING 7 - 5
COOLING (Continued)

CONDITION POSSIBLE CAUSES CORRECTION
INADEQUATE AIR CONDITIONER
PERFORMANCE (COOLING
SYSTEM SUSPECTED)1. Radiator and/or A/C condenser
air flow obstructed.1. Remove obstruction and/or clean.
2. Electronically controlled viscous
fan drive not working.2. Check viscous fan drive (Refer to
7 - COOLING/ENGINE/FAN DRIVE
VISCOUS CLUTCH - DIAGNOSIS
AND TESTING)
3. Air seals around radiator
damaged or missing.3. Inspect air seals, repair or
replace as necessary.
INADEQUATE HEATER
PERFORMANCE. GAUGE MAY OR
MAY NOT READ LOW.1. Heavy duty cooling system, and
cooler ambient temperatures.1. None. Normal condition.
2. Obstruction in heater hoses. 2. Remove hoses, remove
obstruction.
3. Electronically controlled viscous
fan stuck on.Check viscous fan drive. (Refer to 7
- COOLING/ENGINE/FAN DRIVE
VISCOUS CLUTCH - DIAGNOSIS
AND TESTING)
4. Water pump damaged. 4. Replace water pump.
HEAT ODOR 1. Damaged or missing drive line
heat shields.1. Repair or replace damaged or
missing heat shields.
2. Electronically controlled viscous
fan drive damaged.2. Check viscous fan drive. (Refer
to 7 - COOLING/ENGINE/FAN
DRIVE VISCOUS CLUTCH -
DIAGNOSIS AND TESTING)
DIAGNOSIS AND TESTING - PRELIMINARY
CHECKS
ENGINE COOLING SYSTEM OVERHEATING
Establish what driving conditions caused the com-
plaint. Abnormal loads on the cooling system such as
the following may be the cause:
²PROLONGED IDLE
²VERY HIGH AMBIENT TEMPERATURE
²SLIGHT TAIL WIND AT IDLE
²SLOW TRAFFIC
²TRAFFIC JAMS
²HIGH SPEED OR STEEP GRADES
Driving techniques that avoid overheating are:
²Idle with A/C off when temperature gauge is at
end of normal range.
²Increasing engine speed for more air flow is rec-
ommended.
TRAILER TOWING:
Consult Trailer Towing section of owners manual.
Do not exceed limits.RECENT SERVICE OR ACCIDENT REPAIR:
Determine if any recent service has been per-
formed on vehicle that may effect the cooling system.
This may be:
²Engine adjustments (incorrect timing)
²Slipping engine accessory drive belt(s)
²Brakes (possibly dragging)
²Changed parts. Incorrect water pump or pump
rotating in wrong direction due to belt not correctly
routed
²Reconditioned radiator or cooling system refill-
ing (possibly under filled or air trapped in system).
²Service to electrically controlled viscous fan
clutch
NOTE: If investigation reveals none of the previous
items as a cause for an engine overheating com-
plaint, refer to COOLING SYSTEM DIAGNOSIS
CHART BELOW.
These charts are to be used as a quick-reference
only. Refer to COOLING SYSTEM DIAGNOSIS
CHART
7 - 10 COOLINGDR
COOLING (Continued)

COOLING SYSTEM DIAGNOSIS CHART
CONDITION POSSIBLE CAUSES CORRECTION
TEMPERATURE GAUGE READS
LOW1. Has a Diagnostic Trouble Code
(DTC) been set indicating a stuck
open thermostat?1. (Refer to 25 - EMISSIONS
CONTROL - DESCRIPTION) for
On-Board Diagnostics and DTC
information. Replace thermostat if
necessary.
2. Is the temperature sending unit
connected?2. Check the temperature sensor
connector. (Refer to 8 -
ELECTRICAL/INSTRUMENT
CLUSTER - SCHEMATIC -
ELECTRICAL) Repair connector if
necessary.
3. Is the temperature gauge
operating OK?3. Check gauge operation. (Refer to
8 - ELECTRICAL/INSTRUMENT
CLUSTER/ENGINE
TEMPERATURE GAUGE -
DESCRIPTION). Repair as
necessary.
4. Coolant level low in cold ambient
temperatures accompanied with
poor heater performance.4. Check coolant level in the coolant
reserve/overflow tank or degas
bottle and the radiator. Inspect
system for leaks. Repair leaks as
necessary. Refer to the Coolant
section of the manual text for
WARNINGS and CAUTIONS
associated with removing the
radiator cap.
5. Improper operation of internal
heater doors or heater controls.5. Inspect heater and repair as
necessary. (Refer to 24 - HEATING
& AIR CONDITIONING -
DIAGNOSIS AND TESTING) for
procedures.
TEMPERATURE GAUGE READS
HIGH OR THE COOLANT
WARNING LAMP ILLUMINATES.
COOLANT MAY OR MAY NOT BE
LOST OR LEAKING FROM THE
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) temperatures 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 the normal range,
determine the cause for overheating
and repair. Refer to Possible
Causes (2-18).
2. Is the temperature gauge reading
correctly?2. Check gauge. (Refer to 8 -
ELECTRICAL/INSTRUMENT
CLUSTER - SCHEMATIC -
ELECTRICAL). Repair as
necessary.
DRCOOLING 7 - 11
COOLING (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)

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.
FAN DRIVE VISCOUS CLUTCH
- 5.9L DIESEL
DESCRIPTION
The electronically controlled viscous fan drive (Fig.
34) and (Fig. 33)is attached to the fan drive pulley
mounted to the engine. The coupling allows the fan
to be driven in a normal manner. The fan speed is
controlled by the electronic control module.
OPERATION
The Engine Control Module (ECM) controls the
level of engagement of the electronically controlled
viscous fan clutch by monitoring coolant tempera-
ture, intake manifold temperature, and air condition-
ing status. Based on cooling requirements, the ECMsends a signal to the viscous fan clutch to increase or
decrease the fan speed.
Fan speed is monitored by the ECM. Fan speeds
above or below a calibrated threshold will set a DTC.
Circuit concerns will also set fan clutch DTC's.
DIAGNOSIS AND TESTING - ELECTRONICALLY
CONTROLLED VISCOUS FAN DRIVE
NOISE
NOTE: It is normal for fan noise to be louder (roar-
ing) when:
²Fan duty cycle high. This may occur when ambi-
ent (outside air temperature) is very high.
²Engine loads and temperatures are high such as
when towing a trailer.
²Aggressive engine braking down a steep grade
where transmission temperatures may be high
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.
Fig. 33 Electronically Controlled Viscous Drive
1 - ELECTRONICALLY CONTROLLED VISCOUS FAN DRIVE
2 - MOUNTING NUT
3 - WIRING SUPPORT BRACKET
4 - ELECTRICAL CONNECTOR
Fig. 34 Fan Blade/Viscous Fan Drive - 5.9L Diesel
Engine
1 - ELECTRICAL CONNECTOR
2 - VISCOUS FAN DRIVE
3 - FAN BLADE
4 - BOLT (6)
5 - RADIATOR FAN PULLEY
7 - 52 ENGINEDR
FAN DRIVE VISCOUS CLUTCH-GAS ENGINES (Continued)