Dodge Dakota (R1). Manual - part 257

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

All gasoline powered models are 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).

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 RADIATOR DRAIN-
COCK WITH SYSTEM HOT AND PRESSURIZED.
SERIOUS BURNS FROM COOLANT CAN OCCUR.

Do not waste reusable coolant. If solution is clean,

drain coolant into a clean container for reuse.

If thermostat is being replaced, be sure that

replacement is specified thermostat for vehicle model
and engine type.

Factory installed thermostat housings on 3.9L and

5.9L engines are installed on a gasket with an anti-
stick coating. This will aid in gasket removal and
clean-up.

(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) Air

Conditioned

vehicles:

Remove

support

bracket (generator mounting bracket-to-intake mani-
fold) located near rear of generator (Fig. 15).

NOTE: On air conditioning equipped vehicles, the
generator must be partially removed.

(4) Remove accessory drive belt (Refer to 7 -

COOLING/ACCESSORY

DRIVE/DRIVE

BELTS

REMOVAL) (Fig. 16).

(5) Remove two generator mounting bolts. Do not

remove any wiring at generator. If equipped with
4WD, unplug 4WD indicator lamp wiring harness
(located near rear of generator).

(6) Remove generator. Position generator to gain

access for thermostat gasket removal.

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). SNAP-ON CLAMP TOOL (NUMBER HPC-20)
MAY BE USED FOR LARGER CLAMPS. ALWAYS
WEAR SAFETY GLASSES WHEN SERVICING CON-
STANT TENSION CLAMPS.

CAUTION: A number or letter is stamped into the
tongue of constant tension clamps (Fig. 17). If
replacement is necessary, use only an original
equipment clamp with matching number or letter.

(7) Remove radiator upper hose clamp and upper

hose at thermostat housing.

(8) Position wiring harness (behind thermostat

housing) to gain access to thermostat housing.

(9) Remove thermostat housing mounting bolts,

thermostat housing, gasket and thermostat (Fig. 18).
Discard old gasket.

INSTALLATION

(1) Clean mating areas of intake manifold and

thermostat housing.

Fig. 15 Generator Support Bracket—3.9L and 5.9L

Engine

1 - IDLER PULLEY BUSHING
2 - A/C AND/OR GENERATOR MOUNTING BRACKET
3 - IDLER PULLEY
4 - SCREW AND WASHER

7 - 40

ENGINE

ENGINE COOLANT THERMOSTAT - 3.9L/5.9L (Continued)

(2) Install thermostat (spring side down) into

recessed machined groove on intake manifold (Fig.
18).

(3) Install gasket on intake manifold and over

thermostat (Fig. 18).

(4) Position thermostat housing to intake manifold.

Note the word FRONT stamped on housing (Fig. 19).
For adequate clearance, this must be placed towards
front of vehicle. The housing is slightly angled for-
ward after installation to intake manifold.

(5) Install two housing-to-intake manifold bolts.

Tighten bolts to 23 N·m (200 in. lbs.) torque.

(6) Install radiator upper hose to thermostat hous-

ing.

CAUTION: When installing the serpentine accessory
drive belt, the belt must be routed correctly. If not,
engine may overheat due to water pump rotating in
wrong direction. Refer to (Fig. 20) for correct 3.9L
and 5.9L engine belt routing. The correct belt with
correct length must be used.

(7) Air Conditioned vehicles; Install generator.

Tighten bolts to 41 N·m (30 ft. lbs.).

(8) Install support bracket (generator mounting

bracket-to-intake manifold) (Fig. 15). Tighten bolts to
54 N·m (40 ft. lbs.) torque.

(9) Install accessory drive belt (Fig. 16)(Refer to 7 -

COOLING/ACCESSORY

DRIVE/DRIVE

BELTS

INSTALLATION).

(10) Fill cooling system (Refer to 7 - COOLING -

STANDARD PROCEDURE).

(11) Connect battery negative cable.

Fig. 16 Automatic Belt Tensioner—3.9L and 5.9L

Engines

1 - IDLER PULLEY
2 - TENSIONER
3 - FAN BLADE

Fig. 17 SPRING CLAMP SIZE LOCATION

1 - SPRING CLAMP SIZE LOCATION

Fig. 18 Thermostat—3.9L and 5.9L Engines

1 - THERMOSTAT HOUSING
2 - GASKET
3 - INTAKE MANIFOLD
4 - THERMOSTAT
5 - MACHINED GROOVE

ENGINE

7 - 41

ENGINE COOLANT THERMOSTAT - 3.9L/5.9L (Continued)

(12) Start and warm the engine. Check for leaks.

ENGINE COOLANT
THERMOSTAT - 4.7L

DESCRIPTION

CAUTION: Do not operate an engine without a ther-
mostat, except for servicing or testing.

A pellet-type thermostat controls the operating

temperature of the engine by controlling the amount
of coolant flow to the radiator. On all engines the
thermostat is closed below 195°F (90°C). Above this
temperature, coolant is allowed to flow to the radia-
tor. This provides quick engine warm up and overall
temperature control. On the 4.7L engine the thermo-
stat is designed to block the flow of the coolant
bypass journal by 50% instead of completely blocking
the flow. This design controls coolant temperature
more accurately (Fig. 21) .

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 other prob-
lems. These are: longer engine warmup time, unreli-
able

warmup

performance,

increased

exhaust

emissions and crankcase condensation. This conden-
sation 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

All gasoline powered models are equipped with

Fig. 19 Thermostat Position—5.2L and 5.9L Engines

Fig. 20 Belt Routing—5.2L and 5.9L Engines

1 - IDLER PULLEY
2 - GENERATOR PULLEY
3 - A/C COMPRESSOR PULLEY
4 - IF W/OUT A/C
5 - POWER STEERING PUMP PULLEY
6 - WATER PUMP PULLEY
7 - CRANKSHAFT PULLEY
8 - AUTOMATIC TENSIONER

7 - 42

ENGINE

ENGINE COOLANT THERMOSTAT - 3.9L/5.9L (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 RADIATOR DRAIN-
COCK WITH SYSTEM HOT AND PRESSURIZED.
SERIOUS BURNS FROM COOLANT CAN OCCUR.

Do not waste reusable coolant. If solution is clean,

drain coolant into a clean container for reuse.

If thermostat is being replaced, be sure that

replacement is specified thermostat for vehicle model
and engine type.

(1) Disconnect negative battery cable at battery.
(2) Drain cooling system (Refer to 7 - COOLING -

STANDARD PROCEDURE).

(3) Raise vehicle on hoist.
(4) Remove splash shield.
(5) Remove lower radiator hose clamp and lower

radiator hose at thermostat housing.

(6) Remove thermostat housing mounting bolts,

thermostat housing and thermostat (Fig. 22).

INSTALLATION

(1) Clean mating areas of timing chain cover and

thermostat housing.

(2) Install thermostat (spring side down) into

recessed machined groove on timing chain cover (Fig.
22).

(3) Position thermostat housing on timing chain

cover.

(4) Install two housing-to-timing chain cover bolts.

Tighten bolts to 13 N·m (112 in. lbs.) torque.

CAUTION: Housing must be tightened evenly and
thermostat must be centered into recessed groove
in timimg chain cover. If not, it may result in a
cracked housing, damaged timing chain cover
threads or coolant leaks.

(5) Install lower radiator hose on thermostat hous-

ing.

(6) Install splash shield.
(7) Lower vehicle.
(8) Fill cooling system (Refer to 7 - COOLING -

STANDARD PROCEDURE).

(9) Connect negative battery cable to battery.
(10) Start and warm the engine. Check for leaks.

Fig. 21 Thermostat Cross Section View 4.7L

1 - FROM HEATER
2 - FROM RADIATOR
3 - TO WATER PUMP
4 - ENGINE BYPASS
5 - THERMOSTAT

ENGINE

7 - 43

ENGINE COOLANT THERMOSTAT - 4.7L (Continued)

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