Dodge Durango (DN). Manual — part 252
WATER PUMP BYPASS HOSE—5.2L/5.9L
ENGINES
DESCRIPTION
A rubber water pump bypass hose (Fig. 10) is used
between the intake manifold and water pump on all
5.2L/5.9L engines.
OPERATION
When the thermostat is in the closed position the
bypass hose allows the water pump to circulate the
engine coolant through the cylinder block while at
the same time preventing the coolant from flowing
through the radiator, this allows the coolant to heat
up quicker thus bring the engine to operating tem-
perature faster.
AUTOMATIC TRANSMISSION OIL COOLERS
DESCRIPTION
CAUTION: On in-radiator type oil coolers, if trans-
mission oil cooler is leaking, engine coolant may
enter cooler, or transmission oil may enter engine
cooling system. Both engine cooling system and
transmission oil circuit should be drained, flushed,
and inspected.
There are two types of transmission oil coolers
used. One type of cooler is the in-radiator type or oil
to coolant type. This type oil cooler is not serviceable.
The second type used is a remote type auxiliary oil
cooler or oil to air cooler. The oil to air type cooler is
located in front of the radiator, and is serviceable.
AUTOMATIC BELT TENSIONER
DESCRIPTION
Correct drive belt tension is required to ensure
optimum performance of the belt driven engine acces-
sories. If specified tension is not maintained, belt
slippage may cause; engine overheating, lack of
power steering assist, loss of air conditioning capac-
ity, reduced generator output rate, and greatly
reduced belt life.
It is not necessary to adjust belt tension on the
4.7L, 5.2L or 5.9L engines. These engines are
equipped with an automatic belt tensioner (Fig. 13)
(Fig. 14). The tensioner maintains correct belt ten-
sion at all times. Due to use of this belt tensioner, do
Fig. 10 Water Pump Bypass Hose—5.2L/5.9L
Engines
1 – WATER PUMP BYPASS HOSE
2 – FAN BLADE ASSEMBLY
3 – VISCOUS FAN DRIVE
4 – WATER PUMP AND PULLEY
Fig. 11 Oil Flow to Cooler—Top View (Typical)
1 – TRANSMISSION OIL COOLER
2 – AUTOMATIC TRANSMISSION
3 – RETURN LINE
4 – PRESSURE LINE
Fig. 12 Auxiliary Transmission Oil Cooler—Typical
1 – RADIATOR
2 – A/C CONDENSER (IF EQUIPPED)
3 – TRANSMISSION AUXILIARY OIL COOLER
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COOLING SYSTEM
7 - 7
DESCRIPTION AND OPERATION (Continued)
not attempt to use a belt tension gauge on 4.7L, 5.2L
or 5.9L engines.
OPERATION
The automatic belt tensioner maintains belt ten-
sion by using internal spring pressure, a pivoting
arm and pulley to press against the drive belt.
BLOCK HEATER
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 for all
models. The heater is equipped with a power cord.
The cord is attached to an engine compartment com-
ponent with tie-straps. The heater is mounted in a
core hole of the engine cylinder block in place of a
freeze plug with the heating element immersed in
engine coolant.
OPERATION
The heater warms the engine providing easier
engine starting and faster warm-up in low tempera-
tures. The power cord must be connected to a
grounded 110-120 volt AC electrical outlet with a
grounded, three wire extension cord, this provides
the electricity to warm the heating element.
HOSE CLAMPS
DESCRIPTION
The cooling system utilizes both worm drive and
spring type hose clamps. If a spring type clamp
replacement is necessary, replace with the original
Mopar
t equipment spring type clamp.
CAUTION: A number or letter is stamped into the
tongue of constant tension clamps. If replacement
is necessary, use only a original equipment clamp
with matching number or letter (Fig. 16).
OPERATION
The worm type hose clamp uses a specified torque
value to maintain proper tension on a hose connec-
tion.
Fig. 13 Automatic Belt Tensioner—5.2L/5.9L Engines
1 – AUTOMATIC TENSIONER
2 – COIL AND BRACKET
3 – SCREW AND WASHER
Fig. 14 Automatic Belt Tensioner—4.7L Engine
1 – AUTOMATIC TENSIONER ASSEMBLY
Fig. 15 Block Heater—4.7L
1 – ENGINE BLOCK HEATER
7 - 8
COOLING SYSTEM
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DESCRIPTION AND OPERATION (Continued)
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.
VISCOUS FAN DRIVE
DESCRIPTION
CAUTION: Engines equipped with accessory 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 overheat-
ing.
The thermal viscous fan drive is a silicone-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.
On all 4.7L an electrical cooling fan located in the
fan shroud aids in low speed cooling, It is designed to
augment the viscous fan, However, it does not
replace the viscous fan.
A thermostatic bimetallic spring coil is located on
the front face of the viscous fan drive unit. This
spring coil reacts 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.
OPERATION
When sufficient heat is present, the viscous fan
drive will 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.
Fig. 16 Spring Clamp Size Location
1 – SPRING CLAMP SIZE LOCATION
Fig. 17 Fan Blade/Viscous Fan Drive—4.7L/5.2L/5.9L
Engines
1 – VISCOUS FAN DRIVE
2 – FAN BLADE
3 – SCREW AND WASHER
Fig. 18 Viscous Fan Drive—4.7L/5.2L/5.9L Engines—
Typical
1 – VISCOUS FAN DRIVE
2 – THERMOSTATIC SPRING
3 – MOUNTING NUT TO WATER PUMP HUB
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COOLING SYSTEM
7 - 9
DESCRIPTION AND OPERATION (Continued)
DIAGNOSIS AND TESTING
ON-BOARD DIAGNOSTICS (OBD)
COOLING SYSTEM RELATED DIAGNOSTICS
The powertrain control module (PCM) has been
programmed to monitor certain cooling system com-
ponents:
• If 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.
• If an open or shorted condition has developed in
the relay circuit controlling the electric radiator fan,
a Diagnostic Trouble Code (DTC) can be set.
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 PCM mem-
ory for eventual display to the service technician.
Refer to Group 25, Emission Control Systems for the
correct procedures.
ACCESSING DIAGNOSTIC TROUBLE CODES
To read DTC’s and to obtain cooling system data,
refer to Group 25, Emission Control Systems for the
correct procedures.
ERASING TROUBLE CODES
After the problem has been repaired, use the DRB
scan tool to erase a DTC. Refer to the appropriate
Powertrain Diagnostic Procedures service manual for
operation of the DRB scan tool.
DRB SCAN TOOL
For operation of the DRB scan tool, refer to the
appropriate Powertrain Diagnostic Procedures ser-
vice manual.
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:
PROLONGED
IDLE,
VERY
HIGH
AMBIENT
TEMPERATURE, SLIGHT TAIL WIND AT IDLE,
SLOW TRAFFIC, TRAFFIC JAMS, HIGH SPEED,
OR STEEP GRADES.
Driving techniques that avoid overheating are:
• Idle with A/C off when temperature gauge is at
end of normal range.
• Increase engine speed for more air flow is recom-
mended.
(1) TRAILER TOWING:
Consult Trailer Towing section of owners manual.
Do not exceed limits.
(2) AIR CONDITIONING; ADD-ON OR AFTER
MARKET:
A maximum cooling package should have been
ordered with vehicle if add-on or after market A/C is
installed. If not, maximum cooling system compo-
nents should be installed for model involved per
manufacturer’s specifications.
(3) RECENT SERVICE OR ACCIDENT REPAIR:
Determine if any recent service has been per-
formed on vehicle that may effect cooling system.
This may be:
• Engine adjustments (incorrect timing)
• Slipping engine accessory drive belt(s)
• Brakes (possibly dragging)
• Changed parts. Incorrect water pump, or pump
rotating in wrong direction due to belt not correctly
routed
• Reconditioned radiator or cooling system refill-
ing (possibly under filled or air trapped in system).
NOTE: If investigation reveals none of the previous
items as a cause for an engine overheating com-
plaint, refer to following Cooling System Diagnosis
charts.
These charts are to be used as a quick-reference
only. Refer to the group text for information.
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COOLING SYSTEM
DN
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