Engine Cooling System: Diagnosis Dodge Durango III

INTERNAL LEAKAGE INSPECTION

Remove engine oil pan drain plug and drain a small amount of engine oil. If coolant is present in the pan, it will drain first because it is heavier than oil. An alternative method is to operate engine for a short period to churn the oil. After this is done, remove engine dipstick and inspect for water globules.

Operate engine without pressure cap on radiator until thermostat opens. Attach a Pressure Tester to filler neck. If pressure builds up quickly it indicates a combustion leak exists. This is usually the result of a cylinder head gasket leak or crack in engine. Repair as necessary.

If there is not an immediate pressure increase, pump the Pressure Tester. Do this until indicated pressure is within system range of 110 kPa (16 psi). Fluctuation of gauge pointer indicates compression or combustion leakage into cooling system.

Because the vehicle is equipped with a catalytic converter, do not remove spark plug cables or short out cylinders to isolate compression leak.

If the needle on dial of pressure tester does not fluctuate, race engine a few times to check for an abnormal amount of coolant or steam. This would be emitting from exhaust pipe. Coolant or steam from exhaust pipe may indicate a faulty cylinder head gasket, cracked engine cylinder block or cylinder head.

A convenient check for exhaust gas leakage into cooling system is provided by a commercially available Block Leak Check tool. Follow manufacturers instructions when using this product.

COMBUSTION LEAKAGE TEST - WITHOUT PRESSURE TESTER

DO NOT WASTE reusable coolant. If solution is clean, drain coolant into a clean container for reuse.

Drain sufficient coolant to allow thermostat removal. Refer to THERMOSTAT, REMOVAL . Remove accessory drive belt. Refer to BELT, SERPENTINE, REMOVAL .

Add coolant to radiator to bring level to within 6 mm (1/4 in) of top of thermostat housing.

Start engine and accelerate rapidly three times, to approximately 3000 RPM while observing coolant. If internal engine combustion gases are leaking into cooling system, bubbles will appear in coolant. If bubbles do not appear, internal combustion gas leakage is not present.

INSPECTION

Visually inspect the pressure valve gasket on the cap. Replace cap if the gasket is swollen, torn or worn. Inspect the area around radiator filler neck for white deposits that indicate a leaking cap.

COOLANT CONCENTRATION TESTING

Coolant concentration should be checked when any additional coolant was added to system or after a coolant drain, flush and refill. The coolant mixture offers optimum engine cooling and protection against corrosion when mixed to a freeze point of -37°C (-34°F) to -46°C (-50°F). The a hydrometer or a refractometer can be used to test coolant concentration.

A hydrometer will test the amount of glycol in a mixture by measuring the specific gravity of the mixture. The higher the concentration of ethylene-glycol, the larger the number of balls that will float, and higher the freeze protection (up to a maximum of 60% by volume glycol).

A refractometer, Tool (special tool #8286, Refractometer) will test the amount of glycol in a coolant mixture by measuring the amount a beam of light bends as it passes through the fluid. Refer to SPECIAL TOOLS .

Some coolant manufactures use other types of glycols into their coolant formulations. Propylene-glycol is the most common new coolant. However, propylene-glycol based coolants do not provide the same freezing protection and corrosion protection and is not recommended.

Scheme 2

The 350W radiator cooling fan used on the 3.6L/5.7L engines is an electrical fan and is integral to the fan shroud (1). The motor is control by two relays that control the high and the low speeds.

Scheme 3

The 850W cooling fan is integrated into the fan shroud and is located between the radiator (1) and the engine.

The fan is controlled by a duty cycle signal from the PCM.

The signal is sent the cooling fan control module located on the cooling fan motor assembly. The module deciphers the signal and controls the fan motor to set the speed required for sufficient cooling.

ACTIVATING THE FAN WITH THE SCAN TOOL

Under the Engine Systems test heading, there is a subheading. "Fan solenoid test", that has the selections, on/off. Activating the fan with the scan tool will run the fan at a limited 72% duty cycle, which will help troubleshoot any system problems, and also help with the deaeration procedure.

Note. Engine doesn't need to be running to activate the fan with the scan tool.

INSPECTING FOR INLET RESTRICTIONS

Inadequate heater performance may be caused by a metal casting restriction in the heater hose inlet.

DO NOT WASTE reusable coolant. If solution is clean, drain the coolant into a clean container for reuse.

1. Drain sufficient coolant from the radiator to decrease the level below the heater hose inlet.
2. Remove the heater hose.
3. Inspect the inlet for metal casting flash or other restrictions.

Scheme 4

Note. The water pump on 3.6L engines is bolted directly to the engine timing chain case cover.

Scheme 5

1. Disconnect negative battery cable from battery.
2. Disconnect the intake air temperature sensor (2).
3. Loosen the clamps (1, 4). Remove the air intake hose and resignator (3) assembly.
4. Drain the cooling system. Refer to «STANDARD PROCEDURE»(ref-465940-S34230748332012042300000) .
5. Remove the accessory drive belt. Refer to «BELT, SERPENTINE, REMOVAL»(ref-465940-S20367993122012042300000) . 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. Always wear safety glasses when servicing constant tension clamps. CAUTION: A number or letter is stamped into the tongue of constant tension clamps (4). If replacement is necessary, use only an original equipment clamp with matching number or letter.
6. Remove the lower heater hose (1) at the water pump and position aside.
7. Remove the lower radiator hose (3) from the water pump and position aside.
8. Remove idler pulley (4). Refer to «PULLEY, IDLER, REMOVAL»(ref-465940-S42156660462012042300000) .
9. Remove the eleven water pump mounting bolts. Take notice to the four water pump bolts (2) that bolt directly to the timing cover. CAUTION: Do not pry on the water pump at the timing chain case/cover. The machined surfaces may be damaged resulting in leaks.
10. Remove water pump (1) and seal.

Scheme 6

1. Disconnect negative battery cable.
2. Remove the air intake assembly. Refer to «BODY, AIR CLEANER, REMOVAL»(ref-465933-S00984640022012042300000) or «BODY, AIR CLEANER, REMOVAL, 5.7L»(ref-465934-S30952154692012042300000) .
3. Remove the resonator mounting bracket.
4. Remove cooling fan assembly. Refer to «FAN, COOLING, REMOVAL»(ref-465940-S32398312912012042300000) .
5. Drain coolant into a clean container. Refer to «STANDARD PROCEDURE»(ref-465940-S34230748332012042300000) .
6. Remove the upper radiator hose from the thermostat housing (1) and position aside.
7. Remove serpentine belt. Refer to «BELT, SERPENTINE, REMOVAL»(ref-465940-S20367993122012042300000) .
8. Remove idler pulley (5).
9. Remove belt tensioner assembly (4). Refer to «TENSIONER, BELT, REMOVAL»(ref-465940-S07481246852012042300000) .
10. Remove lower radiator hose from the water pump and position aside.
11. Remove the upper metal heater tube from the cylinder head.
12. Remove water pump mounting bolts (6) and remove pump (3).

Inspect the water pump assembly for cracks in the housing, Water leaks from shaft seal, Loose or rough turning bearing or Impeller rubbing either the pump body or timing chain case/cover.

Scheme 7

Scheme 8

1. Clean mating surfaces. NOTE: Take notice the lengths of the mounting bolts. Some M6 bolts mount directly to the timing cover (2).
2. Using a new gasket, position water pump (1) and hand tighten the M6 mounting bolts.
3. Hand tighten the idler pulley (4) bolt.
4. Hand tighten the upper M8 and M10 water pump to engine block mounting bolts. NOTE: Tightening the water pump fasteners in sequential order, will insure proper sealing surface.
5. Tighten the bolts 1 - 12 in the sequence shown in illustration. Tighten the bolts to their respective torque: Tighten M6 mounting bolts to 12 N.m (9 ft. lbs.). Tighten M8 bolts to 25 N.m (18 ft. lbs.). Tighten M10 bolt to 55 N.m (41 ft. lbs.). Repeat the tightening sequence until the proper torque has been met.
6. Spin water pump to be sure that pump impeller does not rub against timing chain case/cover. CAUTION: A number or letter is stamped into the tongue of constant tension clamps (4). If replacement is necessary, use only an original equipment clamp with matching number or letter.
7. Install the lower radiator hose (2).
8. Install the lower return heater hose (1). CAUTION: When installing the serpentine accessory drive belt, belt must be routed correctly. If not, engine may overheat due to water pump rotating in wrong direction.
9. Install accessory drive belt (4). Refer to «BELT, SERPENTINE, INSTALLATION»(ref-465940-S28892887022012042300000) .
10. Evacuate air and refill cooling system. Refer to «STANDARD PROCEDURE»(ref-465940-S34230748332012042300000) .
11. Install the air intake hose and resignator (3) assembly at the air filter housing (4).
12. Connect the intake air temperature sensor (2).
13. Connect negative battery cable.
14. Check the cooling system for leaks. Refer to «DIAGNOSIS AND TESTING»(ref-465940-S27246341182012042300000) .

The radiator cooling fins should be checked for damage or deterioration. Inspect cooling fins to make sure they are not bent or crushed, these areas result in reduced heat exchange causing the cooling system to operate at higher temperatures. Inspect the plastic end tanks for cracks, damage or leaks.

Inspect the radiator neck for damage or distortion.

DIAGNOSIS AND TESTING - ENGINE COOLANT THERMOSTAT

The thermostat is operated by a wax filled chamber (pellet) which is sealed. When heated coolant reaches a predetermined temperature the wax pellet expands enough to overcome the closing spring and water pump pressure, which forces the valve to open. Coolant leakage into the pellet will cause a thermostat to fail open. Do not attempt to free up a thermostat with a screwdriver.

Thermostat diagnostics is included in powertrain control module's (PCM) programing for on-board diagnosis. The malfunction indicator light (MIL) will illuminate and a diagnostic trouble code (DTC) will be set when an "open too soon" condition occurs. Do not change a thermostat for lack of heater performance or temperature gauge position, unless a DTC is present. For other probable causes. Refer to DIAGNOSIS AND TESTING . Thermostat failing shut is the normal long term mode of failure, and normally, only on high mileage vehicles. The temperature gauge will indicate this .