Dodge Nitro. Manual - part 525

A pellet-type thermostat (5) controls the operating temperature of the engine by controlling the amount of 
coolant flow to the radiator. On all engines the thermostat is closed below 195°F (90°C). Above this 
temperature, coolant is allowed to flow to the radiator. This provides quick engine warm up and overall 
temperature control. On the 3.7L engine the thermostat is designed to block the flow of the coolant bypass 
journal by 50% instead of completely blocking the flow. This design controls coolant temperature more 
accurately. 

The same thermostat is used for winter and summer seasons. An engine should not be operated without a 
thermostat, except for servicing or testing. Operating without a thermostat causes other problems. These are: 
longer engine warm-up time, unreliable warm-up performance, increased exhaust emissions and crankcase 
condensation. This condensation can result in sludge formation. 

DESCRIPTION-THERMOSTAT-2.8L DIESEL 

1 - FROM HEATER
2 - FROM RADIATOR
3 - TO WATER PUMP
4 - ENGINE BYPASS
5 - THERMOSTAT

CAUTION: Do not operate an engine without a thermostat, except for servicing or 

testing.

 

2007 Dodge Nitro R/T 

2007 ENGINE Cooling - Nitro

  

Fig. 64: Thermostat Housing, Gasket, Bolts & Bracket 
Courtesy of CHRYSLER LLC 

A pellet-type thermostat controls the operating temperature of the engine by controlling the amount of coolant 
flow to the radiator. 

OPERATION 

OPERATION 

1 - GASKET
2 - THERMOSTAT HOUSING
3 - BOLT(S)
4 - BRACKET

 

2007 Dodge Nitro R/T 

2007 ENGINE Cooling - Nitro

  

The thermostat starts to open at 80°C (176°F). Above this temperature, coolant is allowed to flow to the 
radiator. This provides quicker engine warm-up and overall temperature control. 

The same thermostat is used for winter and summer seasons. An engine should not be operated without a 
thermostat, except for servicing or testing. Operating without a thermostat causes other problems. These are: 
longer engine warm-up time, unreliable warm-up performance, increased exhaust emissions and crankcase 
condensation. This condensation can result in sludge formation. 

DIAGNOSIS AND TESTING 

ENGINE COOLANT THERMOSTAT 

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 .  

REMOVAL 

REMOVAL-4.0L 

Fig. 65: Thermostat Assembly - 4.0L 
Courtesy of CHRYSLER LLC 

1 - UPPER RADIATOR HOSE
2 - HOSE CLAMP
3 - THERMOSTAT HOUSING MOUNTING BOLT
4 - THERMOSTAT HOUSING
5 - UPPER RADIATOR HOSE TUBE
6 - UPPER RADIATOR HOSE TUBE MOUNTING NUTS

 

2007 Dodge Nitro R/T 

2007 ENGINE Cooling - Nitro

  

1. Disconnect and isolate negative battery cable  

2. Drain cooling system. See STANDARD PROCEDURE.  

3. Remove air housing. Refer to REMOVAL .  

4. Remove upper intake manifold. Refer to REMOVAL .  

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.  

REMOVAL-2.8L DIESEL 

Fig. 66: Identifying Thermostat 
Courtesy of CHRYSLER LLC 

1. Disconnect negative battery cable.  

2. Remove engine cover. Refer to REMOVAL .  

3. Partially drain cooling system. See STANDARD PROCEDURE.  

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.  

REMOVAL- 3.7L 

 

2007 Dodge Nitro R/T 

2007 ENGINE Cooling - Nitro