Engine Cooling System & Automatic Transmission Cooling System: Overview Dodge Dakota III

Scheme 1

The cooling system regulates engine operating temperature. It allows the engine to reach normal operating temperature as quickly as possible. It also maintains normal operating temperature and prevents overheating.

The cooling system provides a means of heating the passenger compartment and cooling the automatic 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.

1. Radiator
2. Cooling fan (mechanical/Electrical)
3. Thermal viscous fan drive
4. Fan shroud
5. Radiator pressure cap
6. Thermostat
7. Coolant reserve/overflow system
8. Transmission oil cooler (if equipped with an automatic transmission)
9. Coolant
10. Water pump
11. Hoses and hose clamps

OPERATION

The cooling system regulates engine operating temperature. It allows the engine to reach normal operating temperature as quickly as possible. It also maintains normal operating temperature and prevents overheating.

The cooling system also provides a source of hot water (coolant) for heating the passenger compartment. The cooling system is pressurized and uses a centrifugal water pump to circulate coolant throughout the system.

1. When engine is cold the thermostat is closed. The cooling system has no flow through the radiator. The coolant flows through the engine, water pump, and heater.
2. When engine is warm the thermostat is full open. The coolant flows through the radiator, heater, and water pump.

All engines utilize an ambient overflow bottle for coolant recovery/reserve.

An optional factory installed maximum duty cooling package is available on most models. This package will provide additional cooling capacity for vehicles used under extreme conditions such as trailer towing in high ambient temperatures.

The automatic belt tensioner maintains belt tension by using internal spring pressure, a pivoting arm and pulley to press against the drive belt.

Scheme 2

On 4.7L engines, the tensioner (3) is equipped with an indexing tang on back of tensioner and an indexing stop on tensioner housing. If a new belt is being installed, tang must be within approximately 24 mm (.94 inches) of indexing stop. Belt is considered new if it has been used 15 minutes or less.

If the above specification cannot be met, check for

1. The wrong belt being installed (incorrect length/width)
2. Worn bearings on an engine accessory (A/C compressor, power steering pump, water pump, idler pulley or generator)
3. A pulley on an engine accessory being loose
4. Misalignment of an engine accessory
5. Belt incorrectly routed.

Note. A used belt should be replaced if tensioner indexing arrow has moved to the minimum tension indicator. Tensioner travel stops at this point.

1. Remove accessory drive belt «(Refer to COOLING/ACCESSORY DRIVE/DRIVE BELTS - REMOVAL)»(ref-247624-S17004004882007020100000) .
2. Remove tensioner assembly from mounting bracket (1). WARNING: BECAUSE OF HIGH SPRING PRESSURE, DO NOT ATTEMPT TO DISASSEMBLE AUTOMATIC TENSIONER. UNIT IS SERVICED AS AN ASSEMBLY EXCEPT FOR PULLEY ON TENSIONER.
3. Remove pulley bolt. Remove pulley from tensioner.

DESCRIPTION

The coolant recovery containers integral to the upper fan shroud assembly and is made of high temperature plastic.

The coolant recovery container works in conjunction 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 coolant to 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. Coolant will then be drawn from the coolant tank and returned to a proper level in the radiator.

Scheme 3

1. Remove RH radiator seal.
2. Remove coolant recovery container hose (2).
3. Disconnect washer pump electrical connector (3).
4. Remove coolant recovery container mounting bolts (4) and clip.
5. Remove coolant recovery container (1) from vehicle

The heater warms the engine coolant providing easier engine starting and faster warm-up in low temperatures. Connecting the power cord to a grounded 110-120 volt AC electrical outlet with a grounded three wire extension cord provides the electricity needed to heat the element.

The Engine Coolant Temperature (ECT) sensor is used to sense engine coolant temperature. The sensor protrudes into an engine water jacket.

The ECT sensor is a two-wire Negative Thermal Coefficient (NTC) sensor. Meaning, as engine coolant temperature increases, resistance (voltage) in the sensor decreases. As temperature decreases, resistance (voltage) in the sensor increases.

At key-on, the Powertrain Control Module (PCM) sends out a regulated 5 volt signal to the ECT sensor. The PCM then monitors the signal as it passes through the ECT sensor to the sensor ground (sensor return).

When the engine is cold, the PCM will operate in Open Loop cycle. It will demand slightly richer air-fuel mixtures and higher idle speeds. This is done until normal operating temperatures are reached.

The PCM uses inputs from the ECT sensor for the following calculations

1. for engine coolant temperature gauge operation through CCD or PCI (J1850) communications
2. Injector pulse-width
3. Spark-advance curves
4. ASD relay shut-down times
5. Idle Air Control (IAC) motor key-on steps
6. Pulse-width prime-shot during cranking
7. O2 sensor closed loop times
8. Purge solenoid on/off times
9. EGR solenoid on/off times (if equipped)
10. Leak Detection Pump operation (if equipped)
11. Radiator fan relay on/off times (if equipped)
12. Target idle speed

Scheme 4

The Engine Coolant Temperature (ECT) sensor (3) on the 3.7L engine is installed into a water jacket at front of intake manifold near rear of generator.

1. Partially drain the cooling system. «(Refer to COOLING - STANDARD PROCEDURE)»(ref-247624-S05505992522007020100000) .
2. Disconnect the electrical connector from the sensor (3).
3. Remove the sensor from the intake manifold.

Scheme 5

The Engine Coolant Temperature (ECT) sensor (1) on the 4.7L V-8 engine is located near the front of the intake manifold.

1. Partially drain the cooling system «(Refer to COOLING - STANDARD PROCEDURE)»(ref-247624-S05505992522007020100000) .
2. Disconnect the electrical connector from the ECT sensor (1).
3. Remove the sensor (1) from the intake manifold.

Scheme 6

1. Apply thread sealant to sensor threads.
2. Install engine coolant sensor into intake manifold. (3). Tighten sensor to 11 N.m (97.3 in. lbs.) torque.
3. Connect the electrical connector.
4. Fill the cooling system «(Refer to COOLING - STANDARD PROCEDURE)»(ref-247624-S05505992522007020100000) .

Scheme 7

1. Apply thread sealant to sensor threads.
2. Install ECT sensor (1) to engine.
3. Tighten sensor to 11 N.m (97.3 in. lbs.) torque.
4. Connect electrical connector to sensor (1).
5. Fill cooling system «(Refer to COOLING - STANDARD PROCEDURE)»(ref-247624-S05505992522007020100000) .

Scheme 8

Scheme 9

The thermostat on the 5.7L gas powered engine is located beneath the thermostat housing (1) at the front of the intake manifold.

The thermostat is a wax pellet driven, reverse poppet choke type.

Coolant leakage into the pellet container will cause the thermostat to fail in the open position. Thermostats very rarely stick. Do not attempt to free a thermostat with a prying device.

The same thermostat is used for winter and summer seasons. An engine should not be operated without a thermostat, except for servicing or testing. Operating without a thermostat causes longer engine warm-up time, unreliable warm-up performance, increased exhaust emissions and crankcase condensation that can result in sludge formation.

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.

The radiator supplies sufficient heat transfer using the cooling fins interlaced between the horizontal tubes in the radiator core to cool the engine.

A vent valve in the center of the cap will remain shut as long as the cooling system is pressurized. As the coolant cools, it contracts and creates a vacuum in cooling system. This causes the vacuum valve to open and coolant in reserve/overflow tank to be drawn through connecting hose into radiator. If the vacuum valve is stuck shut, or overflow hose is kinked, radiator hoses will collapse on cool-down.