Engine Cooling System: Diagnosis Dodge Nitro I

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. Also inspect transmission dipstick for water globules and transmission fluid cooler for leakage.

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. See REMOVAL . Remove accessory drive belt . See REMOVAL .

Add coolant to radiator to bring level to within 6.3 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.

COOLING SYSTEM RELATED DIAGNOSTICS

The Powertrain Control Module (PCM) has been programmed to monitor certain cooling system components

1. If the engine has remained cool for too long a period, such as with a stuck open thermostat, a Diagnostic Trouble Code (DTC) can be set.
2. 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 indicate an actual problem, a DTC is stored. The DTC will be stored in the PCM memory for eventual display to the service technician. Refer to OPERATION .

ACCESSING DIAGNOSTIC TROUBLE CODES

To read DTC's and to obtain cooling system data. Refer to OPERATION .

ERASING TROUBLE CODES

After the problem has been repaired, use the diagnostic scan tool to erase a DTC. Refer to the appropriate Powertrain Diagnostic Procedures service information for operation of the diagnostic scan tool.

Establish what driving conditions caused the complaint. Abnormal loads on the cooling system such as the following may be the cause

1. Prolonged idle
2. Very high ambient temperature
3. Slight tail wind at idle
4. Slow traffic
5. Traffic jams
6. High speed or steep grades
7. Any accessory that fully or partially blocks grill opening

COOLING-INSPECTION

After performing a cleaning/flush procedure, inspect all hoses, clamps and connections for deterioration and leaks. Inspect radiator and heater core for leaks.

COOLANT-CONCERTRATION 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 use of a hydrometer or Tool 8266, 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 8286 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.

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 are not recommended.

INSPECTION

1. Remove fan blade assembly from viscous fan drive unit (four bolts).
2. Lay fan on a flat surface with leading edge facing down. With tip of blade touching flat surface, replace fan if clearance between opposite blade and surface is greater than 2.0 mm (.090 inch). Rocking motion of opposite blades should not exceed 2.0 mm (.090 inch). Test all blades in this manner.
3. Inspect fan assembly for cracks, bends, loose rivets or broken welds. Replace fan if any damage is found.

ON-BOARD DIAGNOSTICS

All models are equipped with On-Board Diagnostics for certain cooling system components. If the Powertrain Control Module (PCM) detects low engine coolant temperature, it will record a Diagnostic Trouble Code (DTC). For other DTC numbers, refer to OPERATION .

Scheme 19

1. Disconnect negative battery cable.
2. Remove engine cover. Refer to «REMOVAL»(ref-306142-S07058402912008120900000) . Refer to «REMOVAL»(ref-306143-S20513227792008120900000) .
3. Partially drain cooling system. See «STANDARD PROCEDURE»(ref-306154-S25259837052008120900000) .
4. Disconnect upper radiator hose and bypass hoses at thermostat housing (2).
5. Remove thermostat housing retaining bolts, support bracket and housing from cylinder head, discard gasket.

Scheme 20

Do not waste reusable coolant. If solution is clean, drain coolant into a clean container for reuse.

If thermostat (3) 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. See «STANDARD PROCEDURE»(ref-306154-S25259837052008120900000) .
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.

Scheme 21

1. Disconnect and isolate negative battery cable
2. Drain cooling system. See «STANDARD PROCEDURE»(ref-306154-S25259837052008120900000) .
3. Remove air housing. Refer to «REMOVAL»(ref-306143-S23132016952008120900000) .
4. Remove upper intake manifold. Refer to «REMOVAL»(ref-306142-S16054353982008120900000) . Refer to «REMOVAL»(ref-306143-S33795118172008120900000) .
5. Remove radiator tube mounting nuts.
6. Remove radiator hose at thermostat housing.
7. Remove thermostat housing bolts, thermostat housing and thermostat.
8. Clean thermostat housing mating surface on lower intake manifold.

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.

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.

Scheme 22

The water pump on the 2.8L diesel has a die cast aluminum housing. It bolts directly to the engine block.

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 23

The water pump (1) on 3.7L engines is bolted directly to the engine timing chain case cover (2).

1. Clean gasket mating surfaces.
2. Using a new gasket, position water pump and install mounting bolts as shown. (Scheme 23) Tighten water pump mounting bolts to 54 N.m (40 ft. lbs.) torque.
3. Spin water pump to be sure that pump impeller does not rub against timing chain case/cover.
4. Connect radiator lower hose to water pump. 1 - GENERATOR PULLEY 2 - ACCESSORY DRIVE BELT 3 - POWER STEERING PUMP PULLEY 4 - CRANKSHAFT PULLEY 5 - IDLER PULLEY 6 - TENSIONER 7 - A/C COMPRESSOR PULLEY 8 - WATER PUMP PULLEY
5. Install accessory drive belt (2). See «INSTALLATION»(ref-306154-S38527570572008120900000).
6. Position upper fan shroud and fan blade/viscous fan drive assembly.
7. Be sure the upper and lower portions of the fan shroud are firmly connected. All air must flow through the radiator.
8. Install two fan shroud-to-radiator screws.
9. Be sure of at least 25 mm (1.0 inches) between tips of fan blades and fan shroud.
10. Fill cooling system. See «STANDARD PROCEDURE»(ref-306154-S25259837052008120900000).
11. Connect negative battery cable.
12. Start and warm the engine. Check for leaks.