Dodge Durango (DN). Manual — part 253

COOLING SYSTEM DIAGNOSIS CHART

CONDITION

POSSIBLE CAUSES

CORRECTION

TEMPERATURE GAUGE
READS LOW

1. Has a Diagnostic Trouble Code
(DTC) been set indicating a stuck open
thermostat?

1. Refer to Group 25, Emission Systems
for On-Board Diagnostics and DTC
information. Replace thermostat if
necessary.

2. Is the temperature sending unit
connected?

2. Check the temperature sensor
connector. Refer to Group 8E. Repair
connector if necessary.

3. Is the temperature gauge operating
OK?

3. Check gauge operation. Refer to
Group 8E. Repair as necessary.

4. Coolant level low in cold ambient
temperatures accompanied with poor
heater performance.

4. Check coolant level in the coolant
reserve/overflow tank and the radiator.
Inspect system for leaks. Repair leaks
as necessary. Refer to the Coolant
section of the manual text for
WARNINGS and CAUTIONS associated
with removing the radiator cap.

5. Improper operation of internal heater
doors or heater controls.

5. Inspect heater and repair as
necessary. Refer to Group 24, Heating
and Air Conditioning for procedures.

TEMPERATURE GAUGE
READS HIGH OR THE
COOLANT WARNING
LAMP ILLUMINATES.
COOLANT MAY OR MAY
NOT BE LOST OR
LEAKING FROM THE
COOLING SYSTEM

1. Trailer is being towed, a steep hill is
being climbed, vehicle is operated in
slow moving traffic, or engine is being
idled with very high ambient (outside)
temperatures and the air conditioning is
on. Higher altitudes could aggravate
these conditions.

1. This may be a temporary condition
and repair is not necessary. Turn off the
air conditioning and attempt to drive the
vehicle without any of the previous
conditions. Observe the temperature
gauge. The gauge should return to the
normal range. If the gauge does not
return to the normal range, determine
the cause for overheating and repair.
Refer to Possible Causes (2-20).

2. Is the temperature gauge reading
correctly?

2. Check gauge. Refer to Group 8E.
Repair as necessary.

3. Is the temperature warning
illuminating unnecessarily?

3. Check warning lamp operation. Refer
to Group 8E. Repair as necessary.

4. Coolant low in coolant reserve/
overflow tank and radiator?

4. Check for coolant leaks and repair as
necessary. Refer to Testing Cooling
System for Leaks in this Group.

5. Pressure cap not installed tightly. If
cap is loose, boiling point of coolant will
be lowered. Also refer to the following
Step 6.

5. Tighten cap

6. Poor seals at the radiator cap.

6. (a) Check condition of cap and cap
seals. Refer to Radiator Cap. Replace
cap if necessary.

(b) Check condition of radiator filler
neck. If neck is bent or damaged,
replace radiator.

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COOLING SYSTEM

7 - 11

DIAGNOSIS AND TESTING (Continued)

CONDITION

POSSIBLE CAUSES

CORRECTION

7. Coolant level low in radiator but not
in coolant reserve/overflow tank. This
means the radiator is not drawing
coolant from the coolant reserve/
overflow tank as the engine cools

7. (a) Check condition of radiator cap
and cap seals. Refer to Radiator Cap in
this Group. Replace cap if necessary.

(b) Check condition of radiator filler
neck. If neck is bent or damaged,
replace radiator.

(c) Check condition of the hose from the
radiator to the coolant tank. It should fit
tight at both ends without any kinks or
tears. Replace hose if necessary.

(d) Check coolant reserve/overflow tank
and tanks hoses for blockage. Repair as
necessary.

8. Incorrect coolant concentration

8. Check coolant. Refer to Coolant
section in this Group for correct
coolant/water mixture ratio.

9. Coolant not flowing through system

9. Check for coolant flow at radiator filler
neck with some coolant removed,
engine warm and thermostat open.
Coolant should be observed flowing
through radiator. If flow is not observed,
determine area of obstruction and repair
as necessary.

10. Radiator or A/C condenser fins are
dirty or clogged.

10. Remove insects and debris. Refer to
Radiator Cleaning in this Group.

11. Radiator core is corroded or
plugged.

11. Have radiator re-cored or replaced.

12. Aftermarket A/C installed without
proper radiator.

12. Install proper radiator.

13. Fuel or ignition system problems.

13. Refer to Fuel and Ignition System
Groups for diagnosis.

14. Dragging brakes.

14. Check and correct as necessary.
Refer to Group 5, Brakes for correct
procedures.

15. Bug screen or cardboard is being
used, reducing airflow.

15. Remove bug screen or cardboard.

16. Thermostat partially or completely
shut.

16. Check thermostat operation and
replace as necessary. Refer to
Thermostats in this Group.

17. Viscous fan drive not operating
properly.

17. Check fan drive operation and
replace as necessary. Refer to Viscous
Fan Drive in this Group.

18. Cylinder head gasket leaking.

18. Check for cylinder head gasket
leaks. Refer to Cooling System-Testing
For Leaks in this Group. For repair, refer
to Group 9, Engines.

19. Heater core leaking.

19. Check heater core for leaks. Refer
to Group 24, Heating and Air
Conditioning. Repair as necessary.

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COOLING SYSTEM

DN

DIAGNOSIS AND TESTING (Continued)

CONDITION

POSSIBLE CAUSES

CORRECTION

TEMPERATURE GAUGE
READING IS
INCONSISTENT
(FLUCTUATES, CYCLES
OR IS ERRATIC)

1. During cold weather operation, with
the heater blower in the high position,
the gauge reading may drop slightly.

1. A normal condition. No correction is
necessary.

2. Temperature gauge or engine
mounted gauge sensor defective or
shorted. Also, corroded or loose wiring
in this circuit.

2. Check operation of gauge and repair
if necessary. Refer to Group 8E,
Instrument Panel and Gauges.

3. Gauge reading rises when vehicle is
brought to a stop after heavy use
(engine still running)

3. A normal condition. No correction is
necessary. Gauge should return to
normal range after vehicle is driven.

4. Gauge reading high after re-starting a
warmed up (hot) engine.

4. A normal condition. No correction is
necessary. The gauge should return to
normal range after a few minutes of
engine operation.

5. Coolant level low in radiator (air will
build up in the cooling system causing
the thermostat to open late).

5. Check and correct coolant leaks.
Refer to Cooling System-Testing for
leaks in this group.

6. Cylinder head gasket leaking allowing
exhaust gas to enter cooling system
causing a thermostat to open late.

6. (a) Check for cylinder head gasket
leaks. Refer to Cooling System-Testing
for Leaks in this group.

(b) Check for coolant in the engine oil.
Inspect for white steam emitting from the
exhaust system. Repair as necessary.

7. Water pump impeller loose on shaft.

7. Check water pump and replace as
necessary. Refer to water Pumps in this
group.

8. Loose accessory drive belt. (water
pump slipping)

8. Refer to Accessory Drive Belts in this
group. Check and correct as necessary.

9. Air leak on the suction side of the
water pump allows air to build up in
cooling system causing thermostat to
open late.

9. Locate leak and repair as necessary.

PRESSURE CAP IS
BLOWING OFF STEAM
AND/OR COOLANT TO
COOLANT TANK.
TEMPERATURE GAUGE
READING MAY BE ABOVE
NORMAL BUT NOT HIGH.
COOLANT LEVEL MAY BE
HIGH IN COOLANT
RESERVE/OVERFLOW
TANK

1. Pressure relief valve in radiator cap
is defective.

1. Check condition of radiator cap and
cap seals. Refer to Radiator Caps in this
group. Replace cap as necessary.

COOLANT LOSS TO THE
GROUND WITHOUT
PRESSURE CAP
BLOWOFF. GAUGE
READING HIGH OR HOT

1. Coolant leaks in radiator, cooling
system hoses, water pump or engine.

1. Pressure test and repair as
necessary. Refer to Cooling System-
Testing For Leaks in this group.

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COOLING SYSTEM

7 - 13

DIAGNOSIS AND TESTING (Continued)

CONDITION

POSSIBLE CAUSES

CORRECTION

DETONATION OR
PRE-IGNITION (NOT
CAUSED BY IGNITION
SYSTEM). GAUGE MAY
OR MAY NOT BE
READING HIGH

1. Engine overheating.

1. Check reason for overheating and
repair as necessary.

2. Freeze point of coolant not correct.
Mixture is too rich or too lean.

2. Check coolant concentration. Refer to
the Coolant section of this group and
adjust ratio as required.

HOSE OR HOSES
COLLAPSE WHILE
ENGINE IS RUNNING

1. Vacuum created in cooling system on
engine cool-down is not being relieved
through coolant reserve/overflow
system.

1. (a) Radiator cap relief valve stuck.
Refer to Radiator Cap in this group.
Replace if necessary

(b) Hose between coolant reserve/
overflow tank and radiator is kinked.
Repair as necessary.

(c) Vent at coolant reserve/overflow tank
is plugged. Clean vent and repair as
necessary.

(d) Reserve/overflow tank is internally
blocked or plugged. Check for blockage
and repair as necessary.

NOISY VISCOUS
FAN/DRIVE

1. Fan blades loose.

1. Replace fan blade assembly. Refer to
Cooling System Fans in this Group

2. Fan blades striking a surrounding
object.

2. Locate point of fan blade contact and
repair as necessary.

3. Air obstructions at radiator or air
conditioning condenser.

3. Remove obstructions and/or clean
debris or insects from radiator or A/C
condenser.

4. Thermal viscous fan drive has
defective bearing.

4. Replace fan drive. Bearing is not
serviceable. Refer to Viscous Fan Drive
in this group.

5. A certain amount of fan noise may be
evident on models equipped with a
thermal viscous fan drive. Some of this
noise is normal.

5. Refer to Viscous Fan Drive in this
group for an explanation of normal fan
noise.

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COOLING SYSTEM

DN

DIAGNOSIS AND TESTING (Continued)