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