Dodge Ram Truck 1500-2500-3500. Manual — part 225

The diesel engine cooling system consists of :

•

Cross-flow radiator

•

Belt driven water pump

•

Cooling fan (attached to the electronic viscous fan drive)

•

Belt driven Electronic viscous fan drive

•

Engine mounted fan shroud

•

Radiator pressure cap

•

Vertically mounted thermostat

•

Coolant reserve/recovery system

•

Engine mounted Transmission oil cooler (Automatic Only)

•

Coolant

Coolant flow circuits for the 5.9L diesel engine are shown in.

HOSE CLAMPS

The cooling system utilizes spring type hose clamps. If
a spring type clamp replacement is necessary, replace
with the original Mopar

T

equipment spring type clamp.

CAUTION: A number or letter is stamped into the
tongue of constant tension clamps. If replacement
is necessary, use only a original equipment clamp
with matching number or letter and ensure the
clamp has the same size width.

OPERATION

COOLING SYSTEM

The cooling system regulates engine operating temperature. It allows the engine to reach normal operating temper-
ature 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 and cool-
ing the automatic transmission fluid (if equipped). The cooling system is pressurized and uses a centrifugal water
pump to circulate coolant throughout the system.

•

When engine is cold the thermostat is closed. The cooling system has no flow through the radiator. The cool-
ant flows through the engine, water pump, and heater.

•

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 tem-
peratures.

HOSE CLAMPS

The spring type hose clamp applies constant tension on a hose connection. To remove a spring type hose clamp,
only use constant tension clamp pliers designed to compress the hose clamp.

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COOLING

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DIAGNOSIS AND TESTING

ON-BOARD DIAGNOSTICS (OBD)

COOLING SYSTEM RELATED DIAGNOSTICS

The Engine Control Module (ECM) has been programmed to monitor certain cooling system components:

•

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.

•

If an open or shorted condition has developed in the electronically controlled viscous fan clutch circuit, a Diag-
nostic Trouble Code (DTC) can be set.

•

If fan speed is not detected a DTC will be set.

•

Coolant temperature sensor circuit problems can set a DTC.

If the problem is sensed in a monitored circuit often enough to indicated an actual problem, a DTC is stored. The
DTC will be stored in the ECM memory for eventual display to the service technician. (Refer to 25 - EMISSIONS
CONTROL - DESCRIPTION).

ACCESSING DIAGNOSTIC TROUBLE CODES

To read DTC’s and to obtain cooling system data, (Refer to 25 - EMISSIONS CONTROL - DESCRIPTION).

ERASING TROUBLE CODES

After the problem has been repaired, use the DRBIII

T

scan tool to erase a DTC. Refer to the appropriate Powertrain

Diagnostic Procedures service information for operation of the DRBIII

T

scan tool.

COOLING SYSTEM - TESTING FOR LEAKS

ULTRAVIOLET LIGHT METHOD

A leak detection additive is available through the parts department that can be added to cooling system. The addi-
tive is highly visible under ultraviolet light (black light). Pour one ounce of additive into cooling system. Place heater
control unit in HEAT position. Start and operate the engine until the radiator upper hose is warm to the touch. Aim
the commercially available black light tool at the components to be checked. If leaks are present, the black light will
cause the additive to glow a bright green color.

The black light can be used in conjunction with a pressure tester to determine if any external leaks exist.

DR/DH

COOLING

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PRESSURE TESTER METHOD

The engine should be at normal operating tempera-
ture. Recheck the system cold if the cause of coolant
loss is not located during the warm engine examina-
tion.

WARNING: HOT, PRESSURIZED COOLANT CAN
CAUSE INJURY BY SCALDING.

Carefully remove the radiator pressure cap from the
filler neck and check the coolant level. Push down on
the cap to disengage it from the stop tabs. Wipe the
inside of the filler neck and examine the lower inside
sealing seat for nicks, cracks, paint, dirt and solder
residue. Inspect the radiator-to- reserve/overflow tank
hose for internal obstructions. Insert a wire through
the hose to be sure it is not obstructed.

Inspect the cams on the outside of the filler neck. If
the cams are damaged, seating of the pressure cap
valve and tester seal will be affected.

Attach pressure tester (7700 or an equivalent) to radi-
ator filler neck.

Operate the tester pump to apply 103.4 kPa (15 psi)
pressure to the system. If the hoses enlarge excessively or bulges while testing, replace as necessary. Observe the
gauge pointer and determine the condition of the cooling system according to following criteria:

Holds Steady: If the pointer remains steady for two minutes, serious coolant leaks are not present in system. How-
ever, there could be an internal leak that does not appear with normal system test pressure. If it is certain that
coolant is being lost and leaks cannot be detected, inspect for interior leakage or perform Internal Leakage Test.
Refer to INTERNAL LEAKAGE INSPECTION .

Drops Slowly: Indicates a small leak or seepage is occurring. Examine all of the connections for seepage or slight
leakage with a flashlight. Inspect the radiator, hoses, gasket edges and heater. Seal the small leak holes with a
Sealer Lubricant (or equivalent). Repair the leak holes and inspect the system again with pressure applied.

Drops Quickly: Indicates that serious leakage is occurring. Examine the system for external leakage. If leaks are
not visible, inspect for internal leakage. Large radiator leak holes should be repaired by a reputable radiator repair
shop.

INTERNAL LEAKAGE INSPECTION

Remove the 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 the engine dipstick and inspect for water globules. Also inspect the transmission dip-
stick for water globules and transmission fluid cooler for leakage.

WARNING: WITH RADIATOR PRESSURE TESTER TOOL INSTALLED ON RADIATOR, DO NOT ALLOW PRES-
SURE TO EXCEED 145 kPa (21 PSI). PRESSURE WILL BUILD UP QUICKLY IF A COMBUSTION LEAK IS
PRESENT. TO RELEASE PRESSURE, ROCK TESTER FROM SIDE TO SIDE. WHEN REMOVING TESTER, DO
NOT TURN TESTER MORE THAN 1/2 TURN IF SYSTEM IS UNDER PRESSURE.

Operate the engine without the pressure cap on the radiator until the thermostat opens. Attach a Pressure Tester to
the 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 the gauge pointer indicates compression or combustion leakage
into cooling system.

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

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COOLING

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If the needle on dial of the 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 the solution is clean, drain the coolant into a clean container for reuse.

WARNING: DO NOT REMOVE CYLINDER BLOCK DRAIN PLUGS OR LOOSEN RADIATOR DRAINCOCK WITH
SYSTEM HOT AND UNDER PRESSURE. SERIOUS BURNS FROM COOLANT CAN OCCUR.

Drain sufficient coolant to allow thermostat removal. (Refer to 7 - COOLING/ENGINE/ENGINE COOLANT THER-
MOSTAT - REMOVAL). Remove accessory drive belt (Refer to 7 - COOLING/ACCESSORY DRIVE/DRIVE BELTS -
REMOVAL).

Add coolant to radiator to bring level to within 6.3 mm (1/4 in) of the top of the thermostat housing.

CAUTION: Avoid overheating. Do not operate engine for an excessive period of time. Open draincock imme-
diately after test to eliminate boil over.

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 DIESEL ENGINE

COOLING SYSTEM DIAGNOSIS - DIESEL ENGINE

CONDITION

POSSIBLE CAUSES

CORRECTION

TEMPERATURE GAUGE READS
LOW

1. Vehicle is equipped with a heavy
duty cooling system.

1. None. System operating normally.

NOTE: Information on dash cluster
is displayed based on broadcast
data from ECM. DTC will be set for
engine sensor circuit concern.

2. Thermostat stuck open

2. Inspect and test thermostat.

3. Coolant level low.

3. Fill cooling system. (Refer to 7 -
COOLING - STANDARD
PROCEDURE)

4. Temperature gauge not
functioning correctly.

4. Check cluster (Refer to 8 -
ELECTRICAL/INSTRUMENT
CLUSTER - DIAGNOSIS AND
TESTING)

5. Engine sensor stuck in range

5. Monitor sensor with DRB III to
verify sensor reading changes with
increasing temperature.

6. Engine sensor failed out of
range.

6. A DTC will be set.

7. Electronically Controlled Viscous
Fan Drive not operating properly.

7. Check Electronically Controlled
Viscous Fan Drive (Refer to 7 -
COOLING/ENGINE/FAN DRIVE
VISCOUS CLUTCH - DIAGNOSIS
AND TESTING)

TEMPERATURE GAUGE READS
HIGH. COOLANT MAY OR MAY
NOT BE LEAKING FROM SYSTEM

1. Vehicle overloaded, high ambient
(outside) temperatures with A/C
turned on, stop and go driving or
prolonged operation at idle speeds.

1. Temporary condition, repair not
required. Notify customer of vehicle
operation instructions located in
Owners Manual.

DR/DH

COOLING

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