AutoZone 2005 Toyota Prius 1.5L Gas/Elec DOHC 4cyl | Repair Guides | Engine Cooling | Thermostat | Removal & Installation 1 | AutoZone.com

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    Avalanche, Sierra, Silverado, C&K Series, 1999-2005

    Removal & Installation 1

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    CAUTION
    Never open, service or drain the radiator or cooling system when hot; serious burns can occur from the steam and hot coolant. Also, when draining engine coolant, keep in mind that cats and dogs are attracted to ethylene glycol antifreeze and could drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantities. Always drain coolant into a sealable container. Coolant should be reused unless it is contaminated or is several years old.


    CAUTION
    Never open, service or drain the radiator or cooling system when hot; serious burns can occur from the steam and hot coolant. Also, when draining engine coolant, keep in mind that cats and dogs are attracted to ethylene glycol antifreeze and could drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantities. Always drain coolant into a sealable container. Coolant should be reused unless it is contaminated or is several years old.

    4.3L Engine



    1. Drain the radiator until the coolant is below the thermostat level (below the level of the intake manifold).
    2.  
    3. Remove the water outlet elbow assembly from the engine. Remove the thermostat from the engine.
    4.  

    To install:

    1. Clean the gasket surfaces on the water outlet elbow and the intake manifold. Use a new gasket when installing the elbow to the manifold.
    2.  
    3. Install the new thermostat making sure the spring side is inserted into the engine. Tighten the thermostat housing bolts to 21 ft. lbs. (28 Nm).
    4.  
    5. Refill the cooling system. Start the engine and check for leaks.

      Click image to see an enlarged view

      Fig. Remove the thermostat housing bolts-4.3L engines



      Click image to see an enlarged view

      Fig. Remove the thermostat housing from the engine-4.3L engines



      Click image to see an enlarged view

      Fig. Remove the thermostat from the housing-4.3L engines



      Click image to see an enlarged view

      Fig. Thermostat housing-4.3L engines

    6.  

    1. Drain the radiator until the coolant is below the thermostat level (below the level of the intake manifold).
    2.  
    3. Remove the water outlet elbow assembly from the engine. Remove the thermostat from the engine.
    4.  

    To install:

    1. Clean the gasket surfaces on the water outlet elbow and the intake manifold. Use a new gasket when installing the elbow to the manifold.
    2.  
    3. Install the new thermostat making sure the spring side is inserted into the engine. Tighten the thermostat housing bolts to 21 ft. lbs. (28 Nm).
    4.  
    5. Refill the cooling system. Start the engine and check for leaks.

      Click image to see an enlarged view

      Fig. Remove the thermostat housing bolts-4.3L engines



      Click image to see an enlarged view

      Fig. Remove the thermostat housing from the engine-4.3L engines



      Click image to see an enlarged view

      Fig. Remove the thermostat from the housing-4.3L engines



      Click image to see an enlarged view

      Fig. Thermostat housing-4.3L engines

    6.  

    4.3L, 5.0L, 5.7L And 7.4L Engines




    CAUTION
    Never open, service or drain the radiator or cooling system when hot; serious burns can occur from the steam and hot coolant. Also, when draining engine coolant, keep in mind that cats and dogs are attracted to ethylene glycol antifreeze and could drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantities. Always drain coolant into a sealable container. Coolant should be reused unless it is contaminated or is several years old.

    1. Drain the radiator until the coolant is below the thermostat level (below the level of the intake manifold).
    2.  
    3. Remove the water outlet elbow assembly from the engine. Remove the thermostat from the engine, or, on the 4.8L, from inside the adapter elbow.
    4.  

    To install:

    1. Clean the gasket surfaces on the water outlet elbow and the intake manifold. Use a new gasket when installing the elbow to the manifold.
    2.  
    3. Install the new thermostat making sure the spring side is inserted into the engine. Tighten the thermostat housing bolts to:

      4.3L, 5.0L, 5.7L tighten the studs to 21 ft. lbs. (28 Nm)
       
      7.4L tighten the bolts to 27 ft. lbs. (37 Nm).
       

    4.  
    5. Refill the cooling system. Start the engine and check for leaks.

      Click image to see an enlarged view

      Fig. Remove the thermostat housing bolts



      Click image to see an enlarged view

      Fig. Remove the thermostat housing from the engine



      Click image to see an enlarged view

      Fig. Remove the thermostat from the housing



      Click image to see an enlarged view

      Fig. Thermostat housing-4.3L engines



      Click image to see an enlarged view

      Fig. Thermostat housing-5.0L and 5.7L engines



      Click image to see an enlarged view

      Fig. Thermostat housing-7.4L engines C/K series

    6.  

    4.8L, 5.3L & 6.0L Engines



    1. Remove the air inlet duct.
    2.  
    3. Drain the cooling system.
    4.  
    5. Remove the radiator outlet hose.
    6.  
    7. Remove the thermostat housing bolts.
    8.  
    9. Remove the thermostat from the water pump housing.
      NOTE
      The O-ring seal is integral to the thermostat housing



      Click image to see an enlarged view

      Fig. Thermostat housing-4.8L, 5.3L and 6.0L engines

    10.  

    To install:

    1. Install the thermostat to the water pump housing making sure the spring side is inserted into the engine.
    2.  
    3. Install the bolts.
      1. Tighten the bolts to 11 ft. lbs. (15 Nm).
      2.  

    4.  
    5. Install the radiator outlet hose.
    6.  
    7. Fill the cooling system.
    8.  
    9. Install the air inlet duct.
    10.  
    11. Test the system for leaks.
    12.  


    NOTE
    Important: The thermostat is not serviceable separately. The water pump inlet and thermostat must be replaced as an assembly.

    1. Drain the cooling system.
    2.  
    3. Loosen the air cleaner outlet duct clamps at the following locations:

      Throttle body
       
      Mass airflow/intake air temperature (MAF/IAT) sensor
       

    4.  
    5. Remove the radiator inlet hose clip from the outlet duct.
    6.  
    7. Remove the air cleaner outlet duct.
    8.  
    9. Reposition the outlet hose clamp at the water pump.
    10.  
    11. Remove the outlet hose from the water pump.
    12.  
    13. Remove the water pump inlet bolts.
    14.  
    15. Remove the water pump inlet and thermostat from the water pump.

      Click image to see an enlarged view

      Fig. Water pump inlet/thermostat assembly location

    16.  

    To install:

    1. Install the thermostat and water pump inlet to the water pump.
    2.  
    3. Install the water pump inlet bolts.
    4.  
    5. Tighten the water pump inlet bolts to 11 ft. lbs. (15 Nm).
    6.  
    7. Install the outlet hose to the water pump.
    8.  
    9. Position the outlet hose clamp at the water pump.
      NOTE
      Important: Align the arrow at the throttle body end of the duct with the throttle body attaching stud.

    10.  
    11. Install the air cleaner outlet duct.
    12.  
    13. Install the radiator inlet hose clip to the outlet duct.
    14.  
    15. Tighten the air cleaner outlet duct clamps at the following locations:

      Throttle body
       
      Mass airflow/intake air temperature (MAF/IAT) sensor
       

    16.  
    17. Tighten the air cleaner outlet duct clamp screws to 62 inch lbs. (7 Nm).
    18.  
    19. Fill the cooling system and check for leaks.
    20.  

    1. Remove the air inlet duct.
    2.  
    3. Drain the cooling system.
    4.  
    5. Remove the radiator outlet hose.
    6.  
    7. Remove the thermostat housing bolts.
    8.  
    9. Remove the thermostat from the water pump housing.
      NOTE
      The O-ring seal is integral to the thermostat housing



      Click image to see an enlarged view

      Fig. Thermostat housing-4.8L, 5.3L and 6.0L engines

    10.  

    To install:

    1. Install the thermostat to the water pump housing making sure the spring side is inserted into the engine.
    2.  
    3. Install the bolts.
      1. Tighten the bolts to 11 ft. lbs. (15 Nm).
      2.  

    4.  
    5. Install the radiator outlet hose.
    6.  
    7. Fill the cooling system.
    8.  
    9. Install the air inlet duct.
    10.  
    11. Test the system for leaks.
    12.  

    4.8L, 5.3L, 6.0L & 6.2L Engines



    1. Remove the air inlet duct.
    2.  
    3. Drain the cooling system.
    4.  
    5. Remove the radiator outlet hose.
    6.  
    7. Remove the thermostat housing bolts.
    8.  
    9. Remove the thermostat from the water pump housing.
      NOTE
      The O-ring seal is integral to the thermostat housing



      Click image to see an enlarged view

      Fig. Thermostat housing-4.8L, 5.3L, 6.0L and 6.2L engines

    10.  

    To install:

    1. Install the thermostat to the water pump housing making sure the spring side is inserted into the engine.
    2.  
    3. Install the bolts.
      1. Tighten the bolts to 11 ft. lbs. (15 Nm).
      2.  

    4.  
    5. Install the radiator outlet hose.
    6.  
    7. Fill the cooling system.
    8.  
    9. Install the air inlet duct.
    10.  
    11. Test the system for leaks.
    12.  

    5.7L & 7.4L Engines



    1. Drain the coolant until the radiator coolant level is below the thermostat.
    2.  
    3. Remove the following items:

      The bolts or studs
       
      The coolant outlet
       
      The thermostat from the housing
       
      The gasket, if needed
       

    4.  
    5. Clean the thermostat housing and the cooling outlet sealing surfaces.

      Click image to see an enlarged view

      Fig. Thermostat mounting-typical

    6.  

    To install:

    1. Install the following items:

      The thermostat into the housing
       
      The gasket, if needed
       
      The coolant outlet
       

    2.  
    3. Install the bolts or the studs
    4.  
    5. Tighten the bolts or the studs as follows:

      On 5.7L and 7.4L engines: 21 ft. lbs. (28 Nm).
       
      On 7.4L engines: 27 ft. lbs. (37 Nm).
       

    6.  
    7. Refill the coolant to the cooling system.
    8.  
    9. Start the engine. Run the engine, with the radiator cap removed, until the radiator upper hose becomes hot. This indicates that the thermostat is open.
    10.  
    11. With the engine idling, add coolant to the radiator until the coolant level reaches the bottom of the filler neck.
    12.  
    13. Install the radiator cap to the radiator. Ensure that that the cap arrows line up with the overflow tube.
    14.  
    15. Inspect the cooling system for leaks.
    16.  

    6.5L Diesel Engine



    1. Drain the coolant until the radiator coolant level is below the thermostat.
    2.  
    3. Disconnect the radiator inlet hose.
    4.  
    5. Remove the bolt, stud and coolant outlet (4).
    6.  
    7. Remove the gaskets (3).
    8.  
    9. Remove both thermostats (2) from the housing.
    10.  
    11. Clean the sealing surfaces of the thermostat housing and the coolant outlet.

      Click image to see an enlarged view

      Fig. Exploded view of thermostat housing assembly-6.5L Diesel

    12.  

    To install:

    1. Install the thermostats (2) into the housing. Replace both thermostats to ensure that the cooling system functions properly.
    2.  
    3. Install the gaskets (3) into position.
    4.  
    5. Install the coolant outlet.
    6.  
    7. Install the bolt and the stud.
      1. Tighten the bolt and the stud to 31 ft. lbs. (42 Nm).
      2.  

    8.  
    9. Connect the radiator inlet hose.
    10.  
    11. Refill the coolant into the cooling system.
    12.  
    13. Start the engine. Run the engine with the radiator cap removed, until the upper radiator hose becomes hot (This indicates that the thermostat is still open).
    14.  
    15. With the engine idling, add coolant to the radiator until the coolant level reaches the bottom of the filler neck.
    16.  
    17. Install the radiator cap to the radiator. Ensure that that the arrows line up with the overflow tube.
    18.  
    19. Inspect the coolant system for leaks.
    20.  

    6.5L Engine



    1. Drain the coolant until the radiator coolant level is below the thermostat.
    2.  
    3. Disconnect the radiator inlet hose.
    4.  
    5. Remove the following components:

      The bolt
       
      The stud
       
      The coolant outlet
       

    6.  
    7. Remove the gaskets (2).
    8.  
    9. Remove the thermostats (2) from the housing.
    10.  
    11. Clean the sealing surfaces of the thermostat housing and the coolant outlet.

      Click image to see an enlarged view

      Fig. Thermostats and housing-6.5L engine

    12.  

    To install:

    1. Install the thermostats (2) into the housing. Replace both thermostats to ensure that the cooling system functions properly.
    2.  
    3. Install the gaskets (2) into position.
    4.  
    5. Install the coolant outlet.
    6.  
    7. Install the bolt and the stud.
    8.  
    9. Tighten the bolt and the stud to 31 ft. lbs. (42 Nm).
    10.  
    11. Connect the radiator inlet hose.
    12.  
    13. Refill the coolant into the cooling system.
    14.  
    15. Start the engine. Run the engine with the radiator cap removed, until the upper radiator hose becomes hot. This indicates that the thermostat is open.
    16.  
    17. With the engine idling, add coolant to the radiator until the coolant level reaches the bottom of the filler neck.
    18.  
    19. Install the radiator cap to the radiator. Ensure that that the arrows line up with the overflow tube.
    20.  
    21. Inspect the cooling system for leaks.
    22.  

    6.6L Diesel Engine



    1. Drain the engine coolant.
    2.  
    3. Remove the water outlet tube.
    4.  
    5. Remove the bolt for the fuel line bracket.
    6.  
    7. Remove the 4 bolts retaining the thermostat housing cover.
    8.  
    9. Remove the 2 thermostats with the seals.

      Click image to see an enlarged view

      Fig. Exploded view thermostat housing assembly-6.6L Engine

    10.  

    To install:

    1. Install the 2 thermostats with the seals to the thermostat housing. The rear thermostat (4) has 2 vent valves. Install with the vent valves towards the rear of engine.

      Click image to see an enlarged view

      Fig. View of thermostats in thermostat housing-6.6L engine

    2.  
    3. Install the thermostat housing cover.
      1. Tighten the thermostat housing cover bolts to 15 ft. lbs. (21 Nm).
      2.  

    4.  
    5. Install the fuel line bracket bolt.
      1. Tighten the fuel line bracket and bolt to 15 ft. lbs. (21 Nm).
      2.  

    6.  
    7. Install the water outlet tube.
    8.  
    9. Fill the engine coolant.
    10.  
    11. With the engine idling, add coolant to the radiator until the coolant level reaches the bottom of the filler neck.
    12.  
    13. Install the radiator cap to the radiator.
    14.  
    15. Inspect the coolant system for leaks.
    16.  

     
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