Dodge Nitro. Manual — part 504

Air can only be removed from the system by gathering under the pressure cap. On the next heat up it will be
pushed past the pressure cap into the coolant recovery bottle by thermal expansion of the coolant. It then
escapes to the atmosphere in the coolant recovery bottle and is replaced with coolant on cool down.

To effectively deaerate the system, multiple thermal cycles of the system may be required.

ON-BOARD DIAGNOSTICS (OBD)

COOLING SYSTEM RELATED DIAGNOSTICS

The Powertrain Control Module (PCM) 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 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.

FLOW CHECK-DIESEL

To determine whether coolant is flowing through the cooling system, use the following procedures:

1. If engine is cold, idle engine until normal operating temperature is reached. Then feel the upper radiator

hose. If it is hot, coolant is circulating.

2. Remove pressure/vent cap when engine is cold, idle engine until thermostat opens, you should observe

coolant flow while looking down in the coolant recovery pressure container. Once flow is detected install
the pressure/vent cap.

NOTE:

Deaeration does not occur at engine idle, higher engine speeds are required.
Normal driving will deaerate cooling system.

WARNING:

Do not remove the cooling system pressure cap with the system hot
and under pressure because serious burns from coolant can occur.

2007 Dodge Nitro R/T

2007 ENGINE Cooling - Nitro

PRELIMINARY CHECKS

ENGINE COOLING SYSTEM OVERHEATING

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

Prolonged idle

Very high ambient temperature

Slight tail wind at idle

Slow traffic

Traffic jams

High speed or steep grades

Any accessory that fully or partially blocks grill opening

RECENT SERVICE OR ACCIDENT REPAIR:

Engine adjustments (incorrect timing)

Slipping accessory drive belt

Brakes (possibly dragging)

Changed parts (incorrect water pump)

Reconditioned radiator or cooling system refilling (possibly under filled or air trapped in system).

TRAILER TOWING:

Consult Trailer Towing section of owners manual. Do not exceed limits.

These charts are to be used as a quick-reference only.

NOTE:

If investigation reveals none of the previous items as a cause for an
engine overheating complaint, refer to following Cooling System
Diagnosis charts.

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 OPERATION .
Replace thermostat if necessary.

2. Is the temperature sending unit
connected?

2. Check the temperature sensor
connector. See DESCRIPTION.
Repair connector if necessary.

3. Is the temperature gauge
operating OK?

3. Check gauge operation. Repair
as necessary.

4. Coolant level low in cold
ambient temperatures

4. Check coolant level in the
coolant pressure bottle and the

2007 Dodge Nitro R/T

2007 ENGINE Cooling - Nitro

accompanied with poor heater
performance.

radiator. Inspect system for leaks.
Repair leaks as necessary.

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

5. Inspect heater and repair as
necessary. Refer to DIAGNOSIS
AND TESTING .

6. Electric fan functioning when
not required.

6. Inspect electric fan for proper
operation. Refer to FAN-
RADIATOR-ELECTRIC in this
article. Refer to SYSTEM
WIRING DIAGRAMS for
electric cooling fan and relay
circuit schematic data.

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.

2. Is the temperature gauge
reading correctly?

2. Check gauge. (Refer to
ENGINE TEMPERATURE
GAUGE ). Repair as necessary.

3. Is the temperature warning
illuminating unnecessarily?

3. Check warning lamp operation.
(Refer to TRANS TEMP
INDICATOR ). Repair as
necessary.

4. Coolant low in coolant pressure
bottle and radiator?

4. Check for coolant leaks and
repair as necessary.

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

7. Coolant not flowing through
system.

7. (a) Check condition of pressure
bottle cap and cap seals. See
DIAGNOSIS AND TESTING.
(b) Check condition of the hose

2007 Dodge Nitro R/T

2007 ENGINE Cooling - Nitro

from the radiator to the coolant
tank. It should fit tight at both
ends without any kinks or tears.
Replace hose if necessary.
(c) Check pressure bottle/overflow
tank and tank's hoses for blockage.
Repair as necessary.

8. Incorrect coolant concentration 8. Check coolant. See

DESCRIPTION for correct
coolant/water mixture ratio.

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

9. Remove insects and debris.

10. Radiator core is corroded or
plugged.

10. Replace radiator.

11. Fuel or ignition system
problems.

11. Refer to Fuel System article or
appropriate Engine Electrical
Diagnostic article for diagnosis
and testing procedures

12. Dragging brakes.

12. Check and correct as
necessary. Refer to DIAGNOSIS
AND TESTING for correct
procedures.

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

13. Remove bug screen or
cardboard.

14. Thermostat partially or
completely shut.

14. Check thermostat operation
and replace as necessary. See
REMOVAL.

15. Viscous fan drive not
operating properly.

15. Check fan drive operation and
replace as necessary. See
DIAGNOSIS AND TESTING.

16. Cylinder head gasket leaking. 16. Check for cylinder head gasket

leaks. See DIAGNOSIS AND
TESTING. For repair, . Refer to
REMOVAL .

17. Heater core leaking.

17. Check heater core for leaks.
Refer to REMOVAL . Repair as
necessary.

18. Electric fan not functioning.

18. Inspect electric fan for proper
operation. See DIAGNOSIS AND
TESTING.

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

2. Check operation of gauge and
repair if necessary. Refer to

2007 Dodge Nitro R/T

2007 ENGINE Cooling - Nitro