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How do I change the thermostat in an 03 Chev Impala 3.8 engine (where is it? potential problems?


3.1L & 3.8L

3.1L & 3.8L Engines




  1. Disconnect the negative battery cable.
  2.  
  3. Partially drain the cooling system into a suitable container, to a level below the thermostat.

  4.  
  5. It is usually possible to leave the radiator hose attached and simply remove the thermostat housing (also called a water outlet) and flex the radiator hose enough to service the thermostat. It is good practice, however, to remove the radiator hose so the thermostat housing can be given a thorough cleaning. Debris on the thermostat housing sealing surface can cause leaks.
  6.  
  7. Some applications may have electrical connections to sensors which mount in the thermostat housing. Use care when detaching these connectors.
  8.  
  9. Unfasten the thermostat housing bolts and remove the housing.

  10.  
  11. Remove the thermostat by simply pulling out. Discard the gasket.



    Click image to see an enlarged view

    Fig. Unfasten the water outlet attaching bolts, then remove the outlet-3.1L engine shown




    Click image to see an enlarged view

    Fig. View of the thermostat in its seat in the intake manifold-3.1L engine shown




    Click image to see an enlarged view

    Fig. Remove the thermostat from the housing . . .




    Click image to see an enlarged view

    Fig. . . . then remove and discard the gasket from the thermostat




    Click image to see an enlarged view

    Fig. The thermostat on this 3.1L is mounted horizontally and uses an offset housing/water outlet




    Click image to see an enlarged view

    Fig. Exploded view of the thermostat arrangement-3.8L engines

  12.  


To install:

  1. Clean all parts well. Make sure the sealing surfaces on both the thermostat housing gasket flange and the intake manifold are clean and free of corrosion damage. It is good practice to run a thread cutting tap or a clean bolt into the threaded holes in the manifold to clean out old sealer and dirt. The threads should be clean so the thermostat cover clamps the gasket evenly at assembly.
  2.  
  3. Position the thermostat in the intake manifold. Make sure it is seated.
  4.  
  5. Position a new gasket over the thermostat. If no gasket is used, apply a 0.125 in. (3mm) bead of RTV sealer to the thermostat housing and install the housing. Lightly lubricate the bolts with clean engine oil. Torque to 18-20 ft. lbs. (23-27 Nm).
  6.  
  7. If removed, attach the radiator hose to the thermostat housing.
  8.  
  9. Refill the engine with the proper mix of DEX-COOL®and water. Connect the negative battery cable, start the engine and check for leaks.



    Click image to see an enlarged view

    Fig. Remove the radiator cap . . .




    Click image to see an enlarged view

    Fig. . . . then fill the cooling system with the proper type and amount of coolant

  10.  


3.4L (VIN E) Engine




  1. Partially drain the cooling system.
  2.  
  3. Using hose clamp pliers, reposition the hose clamp at the thermostat housing. Disconnect the radiator hose from the thermostat housing.
  4.  
  5. Remove the exhaust crossover pipe using the following procedure:

    1. Carefully remove the throttle body air duct.
    2.  
    3. Reposition the AIR pipe for access.

    4.  
    5. Remove the exhaust crossover heat shield bolts and remove the heat shield.
    6.  
    7. Remove the crossover bolts and lift the crossover from the engine.
    8.  
    9. Remove the thermostat housing bolts and remove the thermostat from the engine. Discard the gasket.




      Click image to see an enlarged view

      Fig. Thermostat arrangement-3.4L (VIN E) engine

    10.  


  6.  


To install:

  1. Clean all parts well. Make sure the sealing surfaces on both the thermostat housing gasket flange and the intake manifold are clean and free of corrosion damage. It is good practice to run a thread cutting tap or a clean bolt into the threaded holes in the manifold to clean out old sealer and dirt. The threads should be clean so the thermostat cover clamps the gasket evenly at assembly.
  2.  
  3. Position the thermostat in the intake manifold. Make sure it is seated.

  4.  
  5. Install the thermostat housing and bolts. Torque the bolts to 18 ft. lbs. (25 Nm).
  6.  
  7. Connect the hoses and reposition the clamps.
  8.  
  9. Install the exhaust crossover pipe. Torque the bolts to 18 ft. lbs. (25 Nm).
  10.  
  11. Install the exhaust crossover pipe heat shield and tighten the bolts to 89 inch lbs. (10 Nm).
  12.  
  13. Install the AIR pipe.
  14.  
  15. Install the throttle body air duct.
  16.  
  17. Refill the engine with the proper mix of DEX-COOL®and water. Check for leaks.

  18.  


  1. Partially drain the cooling system.
  2.  
  3. Using hose clamp pliers, reposition the hose clamp at the thermostat housing. Disconnect the radiator hose from the thermostat housing.
  4.  
  5. Remove the exhaust crossover pipe using the following procedure:

    1. Carefully remove the throttle body air duct.
    2.  
    3. Reposition the AIR pipe for access.
    4.  
    5. Remove the exhaust crossover heat shield bolts and remove the heat shield.

    6.  
    7. Remove the crossover bolts and lift the crossover from the engine.
    8.  
    9. Remove the thermostat housing bolts and remove the thermostat from the engine. Discard the gasket.



      Click image to see an enlarged view

      Fig. Thermostat arrangement-3.4L (VIN E) engine

    10.  


  6.  


To install:

  1. Clean all parts well. Make sure the sealing surfaces on both the thermostat housing gasket flange and the intake manifold are clean and free of corrosion damage. It is good practice to run a thread cutting tap or a clean bolt into the threaded holes in the manifold to clean out old sealer and dirt. The threads should be clean so the thermostat cover clamps the gasket evenly at assembly.
  2.  
  3. Position the thermostat in the intake manifold. Make sure it is seated.
  4.  
  5. Install the thermostat housing and bolts. Torque the bolts to 18 ft. lbs. (25 Nm).
  6.  
  7. Connect the hoses and reposition the clamps.
  8.  
  9. Install the exhaust crossover pipe. Torque the bolts to 18 ft. lbs. (25 Nm).
  10.  
  11. Install the exhaust crossover pipe heat shield and tighten the bolts to 89 inch lbs. (10 Nm).
  12.  
  13. Install the AIR pipe.

  14.  
  15. Install the throttle body air duct.
  16.  
  17. Refill the engine with the proper mix of DEX-COOL®and water. Check for leaks.
  18.  


3.5L & 3.9L Engines





NOTE
This engine uses a combination water inlet housing and thermostat assembly. If replacement is required, the entire assembly must be replaced.



  1. Partially drain the cooling system into a suitable container.
  2.  
  3. Using hose clamp pliers, remove the hose clamps from the water inlet housing.
  4.  
  5. Disconnect the radiator hose and the heater hose from the water inlet housing.
  6.  
  7. Remove the surge tank inlet hose clamp and disconnect the surge tank inlet hose from the water inlet housing.
  8.  
  9. Remove the water inlet housing bolts and remove the water inlet/thermostat assembly



    Click image to see an enlarged view

    Fig. The thermostat and water inlet assembly are combined in one assembly and must be serviced together-3.5L (VIN H) engine

  10.  


To install:

  1. Clean all parts well. Make sure there are no traces of dirt or debris on the sealing surfaces.
  2.  
  3. Install the inlet/thermostat assembly to the engine. Install the housing bolts using RTV Sealer GM no. 1052366, or equivalent. Torque the housing bolts to 80 inch lbs. (9 Nm). Do not over-torque.
  4.  
  5. Connect the surge tank hose, heater hose and radiator hose to the inlet housing.
  6.  
  7. Refill the cooling system with the correct mix of DEX-COOL®and water.
  8.  
  9. Inspect for leaks.
  10.  


3.5L Engine





NOTE
This engine uses a combination water inlet housing and thermostat assembly. If replacement is required, the entire assembly must be replaced.



  1. Partially drain the cooling system into a suitable container.
  2.  
  3. Using hose clamp pliers, remove the hose clamps from the water inlet housing.
  4.  
  5. Disconnect the radiator hose and the heater hose from the water inlet housing.

  6.  
  7. Remove the surge tank inlet hose clamp and disconnect the surge tank inlet hose from the water inlet housing.
  8.  
  9. Remove the water inlet housing bolts and remove the water inlet/thermostat assembly



    Click image to see an enlarged view

    Fig. The thermostat and water inlet assembly are combined in one assembly and must be serviced together-3.5L (VIN H) engine

  10.  


To install:

  1. Clean all parts well. Make sure there are no traces of dirt or debris on the sealing surfaces.
  2.  
  3. Install the inlet/thermostat assembly to the engine. Install the housing bolts using RTV Sealer GM #1052366, or equivalent. Torque the housing bolts to 80 inch lbs. (9 Nm). Do not over-torque.
  4.  
  5. Connect the surge tank hose, heater hose and radiator hose to the inlet housing.
  6.  
  7. Refill the cooling system with the correct mix of DEX-COOL®and water.

  8.  
  9. Inspect for leaks.
  10.  


3.8L Engine




  1. Disconnect the negative battery cable.
  2.  
  3. Partially drain the cooling system into a suitable container, to a level below the thermostat.
  4.  
  5. It is usually possible to leave the radiator hose attached and simply remove the thermostat housing (also called a water outlet) and flex the radiator hose enough to service the thermostat. It is good practice, however, to remove the radiator hose so the thermostat housing can be given a thorough cleaning. Debris on the thermostat housing sealing surface can cause leaks.
  6.  
  7. Some applications may have electrical connections to sensors which mount in the thermostat housing. Use care when detaching these connectors.
  8.  
  9. Unfasten the thermostat housing bolts and remove the housing.

  10.  
  11. Remove the thermostat by simply pulling out. Discard the gasket.



    Click image to see an enlarged view

    Fig. Unfasten the water outlet attaching bolts, then remove the outlet




    Click image to see an enlarged view

    Fig. View of the thermostat in its seat in the intake manifold




    Click image to see an enlarged view

    Fig. Remove the thermostat from the housing . . .




    Click image to see an enlarged view

    Fig. . . . then remove and discard the gasket from the thermostat




    Click image to see an enlarged view

    Fig. The thermostat on this engine is mounted horizontally and uses an offset housing/water outlet




    Click image to see an enlarged view

    Fig. Exploded view of the thermostat arrangement-3.8L engines

  12.  


To install:

  1. Clean all parts well. Make sure the sealing surfaces on both the thermostat housing gasket flange and the intake manifold are clean and free of corrosion damage. It is good practice to run a thread cutting tap or a clean bolt into the threaded holes in the manifold to clean out old sealer and dirt. The threads should be clean so the thermostat cover clamps the gasket evenly at assembly.
  2.  
  3. Position the thermostat in the intake manifold. Make sure it is seated.
  4.  
  5. Position a new gasket over the thermostat. If no gasket is used, apply a 0.125 in. (3mm) bead of RTV sealer to the thermostat housing and install the housing. Lightly lubricate the bolts with clean engine oil. Torque to 18-20 ft. lbs. (23-27 Nm).
  6.  
  7. If removed, attach the radiator hose to the thermostat housing.
  8.  
  9. Refill the engine with the proper mix of DEX-COOL®and water. Connect the negative battery cable, start the engine and check for leaks.



    Click image to see an enlarged view

    Fig. Remove the radiator cap . . .




    Click image to see an enlarged view

    Fig. . . . then fill the cooling system with the proper type and amount of coolant


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