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