2012 Jeep Wrangler JK Factory Service Manual 07 - Cooling

THERMOSTAT

DIESEL ENGINE

DIESEL ENGINE

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

DESCRIPTION

DESCRIPTION

CAUTION:

Do not operate an engine without a thermostat, except for servicing or testing.

A pellet-type thermostat 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.

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.

The thermostat is part of the housing.

OPERATION

OPERATION

The wax pellet is located in a sealed container at the spring end of the thermostat. When heated, the pellet expands, overcoming closing spring tension and water pump pressure to force the valve to open.

DIAGNOSIS AND TESTING - ENGINE COOLANT THERMOSTAT

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.

3.6L

3.6L

WARNING:

Do not loosen radiator draincock with system hot and pressurized. Serious burns from coolant can occur.

CAUTION:

The Thermostat and housing is serviced as an assembly. Do not remove the thermostat from the housing, damage to the thermostat may occur.

Do not waste reusable coolant. If solution is clean, drain coolant into a clean container for reuse.

If thermostat is being replaced, be sure that replacement is specified thermostat for vehicle model and engine type.

  1. Disconnect negative battery cable at battery.

    2.  
  2. Remove the air intake assembly (Refer to 09 - Engine/Air Intake System/BODY, Air Cleaner - Removal) .

    3.  
  3. Drain cooling system (Refer to 07 - Cooling - Standard Procedure) .

    4.  
  4. Remove upper radiator hose clamp and upper radiator hose at thermostat housing (1).

    5.  
  5. Remove thermostat housing mounting bolts, thermostat housing (1) and thermostat (3).

    6.  

3.6L COOLANT CROSSOVER

3.6L COOLANT CROSSOVER

  1. Remove the thermostat housing assembly (1) (Refer to 07 - Cooling/Engine/THERMOSTAT - Removal) .

    2.  
  2. Remove the accessory drive belt (7) (Refer to 07 - Cooling/Accessory Drive/BELT, Serpentine - Removal) .

    3.  
  3. Remove the Heater supply hose from the coolant crossover (1).

    4.  
  4. Remove the coolant crossover mounting bolts. Take notice to the four bolts (2) that bolt directly to the timing cover.

    5.  
  5. Remove the coolant crossover and discard Gaskets.

    6.  

2.8L

2.8L



NOTE:

The Thermostat Housing is located below the EGR Cooler. IF the Thermostat needs replacing. You must replace the housing assembly.


  1. Disconnect the negative battery cable.

    2.  
  2. Raise and support the vehicle (Refer to 04 - Vehicle Quick Reference/Hoisting/Standard Procedure) .

    3.  
  3. If equipped, remove the skid plate.

    4.  
  4. Drain the cooling system (Refer to 07 - Cooling - Standard Procedure) .

    5.  
  5. Close the radiator petcock.

    6.  
  6. If equipped, install the skid plate.

    7.  
  7. Remove the drivers side front wheel.

    8.  
  8. Remove the inner wheel well splash shield (3) (Refer to 23 - Body/Exterior/SHIELD, Splash - Removal) .

    9.  
  9. Disconnect the upper radiator hose at the thermostat housing (4) and position aside.

    10.  
  10. Remove the lower radiator hose at the water intake elbow (9) and position aside

    11.  
  11. Remove the coolant reservoir return hose at the water intake elbow (7).

    12.  
  12. Remove the lower heater return hose from the water intake elbow (8).

    13.  
  13. Remove the lower EGR cooler supply hose at the cooler (5).

    14.  
  14. Remove the heater hose supply hose at the thermostat housing (6).

    15.  
  15. Remove the lower bypass hose at the water intake elbow.

    16.  
  16. Remove the EGR cooler return hose at the cooler (1).

    17.  
  17. Disconnect the temperature sensor wire harness connector (2).

    18.  
  18. Remove nuts (3) and the thermostat housing (4) from intake manifold, discard gasket.

    NOTE:

    When removing the hoses from the thermostat. Make a reference mark by using a paint pen or marker for easy installation.


    19.  
  19. Remove the lower bypass hose (3).

    20.  
  20. Remove the temperature sensor (4).

    21.  
  21. Remove the EGR Cooler supply hose (5).

    22.  

3.6L

3.6L

CAUTION:

The Thermostat and housing is serviced as an assembly. Do not remove the thermostat from the housing, damage to the thermostat may occur.

  1. Clean mating areas of timing chain cover and thermostat housing (1).

    2.  
  2. Install a new gasket on to the thermostat housing.

    3.  
  3. Position thermostat housing (1) on the water crossover.

    4.  
  4. Install two thermostat housing bolts. Tighten bolts to 28 N·m (248 in. lbs.).

    5.  
  5. Install upper radiator hose on thermostat housing (1).

    6.  
  6. Fill cooling system (Refer to 07 - Cooling - Standard Procedure) .

    7.  
  7. Install the air intake system (Refer to 09 - Engine/Air Intake System/BODY, Air Cleaner - Installation) .

    8.  
  8. Connect negative battery cable to battery.

    9.  
  9. Start and warm the engine. Check for leaks.

    10.  

3.6L COOLANT CROSSOVER

3.6L COOLANT CROSSOVER


  1. Clean gasket sealing surfaces.

    2.  
  2. Install new gasket onto the coolant crossover.

    NOTE:

    The shorter M6 mounting bolts (2), bolt directly to the engine timing cover.


    3.  
  3. Hand tighten the M6 mounting bolts . Tighten the bolts in a criss-cross pattern to 12 N·m (106 in. lbs.).

    4.  
  4. Install the heater supply hose to the coolant crossover (1).

    5.  
  5. Install the accessory drive belt (Refer to 07 - Cooling/Accessory Drive/BELT, Serpentine - Installation) .

    6.  
  6. Install the thermostat housing (Refer to 07 - Cooling/Engine/THERMOSTAT - Installation) .

    7.  

2.8L

2.8L

  1. Install the temperature sensor (4). Tighten sensor (4) to 11 N·m (97 in. lbs.).

    2.  
  2. Align and Install the lower bypass hose (3) and EGR cooler supply hose (5).

    3.  
  3. Install a new gasket onto housing.


    4.  
  4. Install the thermostat housing (4). Tighten nuts (3) to 12 N·m (106 in. lbs.).

    5.  
  5. Install the EGR cooler return hose (1).

    6.  
  6. Install the lower bypass hose to the water intake elbow.

    7.  
  7. Connect the temperature sensor wire harness connector (2).

    8.  
  8. Install the heater supply hose (6).

    9.  
  9. Install the EGR supply hose (5).

    10.  
  10. Install the heater return hose (8).

    11.  
  11. Install the coolant reservoir return hose on the water intake elbow (7).

    12.  
  12. Install the lower radiator hose on the water intake elbow (9).

    13.  
  13. Install the upper radiator hose on the thermostat housing (4).

    14.  
  14. Install the inner wheel well splash shield (3) (Refer to 23 - Body/Exterior/SHIELD, Splash - Installation) .

    15.  
  15. Install the drivers side front wheel.

    16.  
  16. Lower the vehicle.

    17.  
  17. Fill the cooling system (Refer to 07 - Cooling - Standard Procedure) .

    18.  
  18. Connect the negative battery cable.

    19.