Dodge Durango (DN). Manual — part 256

higher percentage will freeze at a warmer tempera-
ture. Also, a higher percentage of antifreeze can
cause the engine to overheat because the 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
149 deg. C (300) deg. F). This temperature is hot
enough to melt plastic and soften solder. The
increased temperature can result in engine detona-
tion. In addition, 100 percent ethylene-glycol freezes
at 22 deg. C (-8 deg. 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 -32 deg. C (-26 deg. F).
5 deg. C higher than ethylene-glycol’s freeze point.
The boiling point (protection against summer boil-
over) of propylene-glycol is 125 deg. C (257 deg. F )
at 96.5 kPa (14 psi), compared to 128 deg. C (263
deg. F) for ethylene-glycol. Use of propylene-glycol
can result in boil-over or freeze-up on a cooling sys-
tem designed for ethylene-glycol. Propylene glycol
also has poorer heat transfer characteristics than
ethylene glycol. This can increase cylinder head tem-
peratures 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.

OPERATION

ETHYLENE-GLYCOL MIXTURES

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 coolant prevents water
present in the cooling system from freezing within
temperatures indicated by mixture ratio of coolant to
water.

COOLANT SELECTION AND ADDITIVES

The presence of aluminum components in the cool-

ing system requires strict corrosion protection. Main-
tain coolant at specified level with a mixture of
ethylene-glycol based antifreeze and water. Daimler-

Chrysler Corporation recommends Mopar Antifreeze
or equivalent. If coolant becomes contaminated or
looses color, drain and flush cooling system and fill
with correctly mixed solution.

CAUTION: Do not use coolant additives that are
claimed to improve engine cooling.

COOLANT—ADDING ADDITIONAL

Do not remove radiator cap to add coolant to

system. When adding coolant to maintain correct
level, do so at coolant reserve/overflow tank. Use a
50/50 mixture of ethylene glycol antifreeze containing
Alugard 340-2

y and low mineral content water.

Remove radiator cap only for testing or when refill-
ing system after service. Removing cap unnecessarily
can cause loss of coolant and allow air to enter sys-
tem, which produces corrosion.

COOLANT LEVEL CHECK

The cooling system is closed and designed to main-

tain coolant level to top of radiator.

WARNING: DO NOT OPEN RADIATOR DRAINCOCK
WITH ENGINE RUNNING OR WHILE ENGINE IS HOT
AND COOLING SYSTEM IS UNDER PRESSURE.

Remove radiator cap. The coolant level should be

to top of radiator. If not, and if coolant level in cool-
ant recovery bottle is at ADD mark, check for:

• An air leak in coolant reserve/overflow tank or

its hose

• An air leak in radiator filler neck

• Leak in pressure cap seal to radiator filler neck

COOLING SYSTEM—DRAINING AND FILLING

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.

DO NOT WASTE reusable coolant. If solution is

clean, drain coolant into a clean container for reuse.

DRAINING

NOTE: On the 4.7L engine the thermostat is an inlet
side thermostat. This means that the engine coolant
will not drain when the radiator drain petcock is
opened. It will be necessary to remove the thermo-
stat housing and thermostat to allow the coolant
traped in the engine block to drain.

(1) Remove radiator pressure cap.
(2) Loosen radiator petcock.

DN

COOLING SYSTEM

7 - 23

SERVICE PROCEDURES (Continued)

(3) Place a drain pan under the thermostat hous-

ing, then remove the thermostat housing and ther-
mostat (4.7L only).

(4) Remove cylinder block drain plugs. Refer to

(Fig. 26) (Fig. 27).

REFILLING

Clean cooling system prior to refilling. Refer to

Cooling System Cleaning section of this group.

(1) Install cylinder block drain plug(s) s. Coat the

threads with Mopar

t Thread Sealant with Teflon.

(2) Close radiator petcock.
(3) Fill cooling system with a 50/50 mixture of

water and Mopar

t Antifreeze/Coolant.

(4) Fill coolant reserve/overflow tank to FULL

mark on indicator stick.

(5) Start and operate engine until thermostat

opens (upper radiator hose warm to touch).

(6) If necessary, add a 50/50 water and Mopar

t

Antifreeze/Coolant mixture to the coolant reserve/
overflow tank. This is done to maintain coolant level
between the FULL and ADD marks. The level in the
reserve/overflow tank may drop below the ADD mark
after three or four warm-up and cool-down cycles.

COOLING SYSTEM—CLEANING/REVERSE
FLUSHING

CLEANING

Drain cooling system and refill with water. Run

engine with radiator cap installed until upper radia-
tor hose is hot. Stop engine and drain water from
system. If water is dirty, fill system with water, run
engine and drain system. Repeat until water drains
clean.

REVERSE FLUSHING

Reverse flushing of cooling system is the forcing of

water through the cooling system. This is done using
air pressure in the opposite direction of normal cool-
ant flow. It is usually only necessary with very dirty
systems with evidence of partial plugging.

REVERSE FLUSHING RADIATOR

Disconnect radiator hoses from radiator inlet and

outlet. Attach a section of radiator hose to radiator
bottom outlet fitting and insert flushing gun. Con-
nect a water supply hose and air supply hose to
flushing gun.

CAUTION: Internal

radiator

pressure

must

not

exceed 138 kPa (20 psi) as damage to radiator may
result.

Allow radiator to fill with water. When radiator is

filled, apply air in short blasts. Allow radiator to
refill between blasts. Continue this reverse flushing
until clean water flows out through rear of radiator
cooling tube passages. Have radiator cleaned more
extensively by a radiator repair shop.

REVERSE FLUSHING ENGINE

Drain cooling system. Remove thermostat housing

and thermostat. Install thermostat housing. Discon-
nect radiator upper hose from radiator and attach
flushing gun to hose. Disconnect radiator lower hose

Fig. 26 Cylinder Block Drain Plug—5.2L/5.9L

Engines—Typical

1 – BLOCK DRAIN PLUG

Fig. 27 Cylinder Block Drain Plug—4.7L Engine—

Typical

1 – CYLINDER BLOCK DRAIN PLUG
2 – EXHAUST MANIFOLD AND HEAT SHIELD

7 - 24

COOLING SYSTEM

DN

SERVICE PROCEDURES (Continued)

from water pump and attach a lead-away hose to
water pump inlet fitting.

CAUTION: On vehicles equipped with a heater
water control valve, be sure heater control valve is
closed (heat off). This will prevent coolant flow with
scale and other deposits from entering heater core.

Connect water supply hose and air supply hose to

flushing gun. Allow engine to fill with water. When
engine is filled, apply air in short blasts, allowing
system to fill between air blasts. Continue until clean
water flows through the lead away hose.

Remove lead away hose, flushing gun, water sup-

ply hose and air supply hose. Remove thermostat
housing and install thermostat. Install thermostat
housing with a replacement gasket. Refer to Thermo-
stat Replacement. Connect radiator hoses. Refill cool-
ing system with correct antifreeze/water mixture.
Refer to Refilling the Cooling System.

CHEMICAL CLEANING

In some instances, use a radiator cleaner (Mopar

Radiator Kleen or equivalent) before flushing. This
will soften scale and other deposits and aid flushing
operation.

CAUTION: Follow manufacturers instructions when
using these products.

REMOVAL AND INSTALLATION

COOLANT RESERVE/OVERFLOW TANK

NOTE: The coolant reservoir/overflow tank is inte-
geral to the upper fan shroud. Refer to Fan Shroud
in this section for proper removal/installation proce-
dures.

WATER PUMP—5.2L/5.9L ENGINES

REMOVAL

The water pump can be removed and installed

without discharging the air conditioning system (if
equipped).

(1) Disconnect battery negative cable.
(2) Drain cooling system. Refer to Cooling Sys-

tem—Draining and Filling in this group.

(3) Do not waste reusable coolant. If solution is

clean, drain coolant into a clean container for reuse.

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) (Fig. 38). SNAP-ON CLAMP TOOL (NUMBER
HPC-20) MAY BE USED FOR LARGER CLAMPS.
ALWAYS WEAR SAFETY GLASSES WHEN SERVIC-
ING CONSTANT TENSION CLAMPS.

CAUTION: A number or letter is stamped into the
tongue of constant tension clamps (Fig. 39). If
replacement is necessary, use only an original
equipment clamp with matching number or letter.

(4) Remove upper radiator hose clamp and hose at

radiator.

(5) The thermal viscous fan drive is attached

(threaded) to the water pump hub shaft (Fig. 29).
Remove fan/viscous fan drive assembly from water
pump by turning mounting nut counterclockwise as
viewed from front. Threads on viscous fan drive are
RIGHT HAND. A Snap-On 36 MM Fan Wrench
(number SP346 from Snap-On Cummins Diesel Tool
Set number 2017DSP) and Special Tool 6958 Span-
ner Wrench with Adapter Pins 8346 can be used.
Place Special Tool 6958 Spanner Wrench onto the
water pump pulley with Adapter Pins 8346 inserted
into the holes on the pulley (Fig. 28) to prevent pul-
ley from rotating. Do not attempt to remove fan/vis-
cous fan drive assembly from vehicle at this time.

Fig. 28 Viscous Fan Drive Removal / Installation

1 – SPECIAL TOOL 6958 SPANNER WRENCH WITH ADAPTER

PINS 8346

2 – FAN

DN

COOLING SYSTEM

7 - 25

SERVICE PROCEDURES (Continued)

(6) If water pump is being replaced, do not unbolt

fan blade assembly (Fig. 29) from thermal viscous
fan drive.

(7) Remove fan shroud attaching hardware (two

bolts at bottom-two clips at top).

(8) Remove fan shroud and fan blade/viscous fan

drive assembly from vehicle as a complete unit.

(9) After removing fan blade/viscous fan drive

assembly, do not place thermal viscous fan drive in
horizontal position. If stored horizontally, silicone
fluid in viscous fan drive could drain into its bearing
assembly and contaminate lubricant.

(10) Remove accessory drive belt as follows: The

drive belt is equipped with a spring loaded automatic
tensioner (Fig. 30). Relax tension from belt by rotat-
ing tensioner clockwise (as viewed from front) (Fig.
30). When all belt tension has been relaxed, remove
accessory drive belt.

(11) Remove lower radiator hose clamp and remove

lower hose at water pump.

(12) Remove heater hose clamp and heater hose

from heater hose coolant return tube.

(13) Loosen

heater

hose

coolant

return

tube

mounting bolt (Fig. 31) and remove tube from water
pump. Discard the old tube O-ring.

(14) Remove seven water pump mounting bolts.
(15) Loosen clamp at water pump end of bypass

hose (Fig. 29). Slip bypass hose from water pump
while removing pump from vehicle. Discard old gas-
ket.

CAUTION: Do not pry water pump at timing chain
case/cover. The machined surfaces may be dam-
aged resulting in leaks.

INSTALLATION

(1) Clean gasket mating surfaces.
(2) Using a new gasket, install water pump to

engine as follows: Guide water pump nipple into
bypass hose as pump is being installed. Install water
pump bolts. Tighten water pump mounting bolts to
40 N·m (30 ft. lbs.) torque.

(3) Position bypass hose clamp to bypass hose.
(4) Spin water pump to be sure that pump impel-

ler does not rub against timing chain case/cover.

(5) Install a new O-ring to the heater hose coolant

return tube (Fig. 31). Coat the new O-ring with anti-
freeze before installation.

(6) Install coolant return tube and its mounting

bolt to engine (Fig. 31). Be sure the slot in tube
bracket is bottomed to mounting bolt. This will prop-
erly position return tube.

(7) Connect radiator lower hose to water pump.
(8) Connect heater hose and hose clamp to coolant

return tube.

(9) Relax tension from belt tensioner (Fig. 30).

Install accessory drive belt.

Fig. 29 Fan Blade and Viscous Fan Drive—5.2L/5.9L

Engines

1 – WATER PUMP BYPASS HOSE
2 – FAN BLADE ASSEMBLY
3 – VISCOUS FAN DRIVE
4 – WATER PUMP AND PULLEY

Fig. 30 Automatic Belt Tensioner Assembly—5.2L/

5.9L Engines

1 – IDLER PULLEY
2 – TENSIONER
3 – FAN BLADE

7 - 26

COOLING SYSTEM

DN

REMOVAL AND INSTALLATION (Continued)