CTS 2003-2005

Removal & Installation

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CAUTION
Never open the radiator cap or the cooling system when the engine is hot. The system is under pressure and will release scalding hot coolant and steam which can cause severe burns and other bodily harm. After the engine has cooled, drain the coolant into a suitable container. Coolant should be reused unless it is contaminated or several years old.

2.8L & 3.6L Engines



  1. Drain the cooling system.
  2.  
  3. Disconnect the heater hoses from the heater core.
  4.  
  5. Remove the thermostat housing bolts.
  6.  
  7. Remove the thermostat housing with the heater pipes, hoses and bolts.
  8.  
  9. Carefully clean the sealing surfaces with a plastic gasket scraper.
  10.  
  11. Remove the thermostat.
  12.  

To install:

  1. Assemble the heater pipes and hoses to the thermostat housing.
  2.  
  3. Install a new gasket to the thermostat housing.
  4.  
  5. Install the thermostat.
  6.  
  7. Install the thermostat housing bolts to the thermostat housing. Partially install the thermostat housing bolts in order to retain the gasket.
  8.  
  9. Install the thermostat housing with the heater pipes, heater hoses, gasket and bolts.
  10.  
  11. Install the thermostat housing bolts and tighten to 15 ft. lbs. (20 Nm).
  12.  
  13. Connect the heater hoses to the heater core.
  14.  
  15. Fill the cooling system.
  16.  

3.1L, 3.4L (VIN X) & 3.8L Engines





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



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



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Fig. Remove the thermostat from the housing . . .



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



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Fig. Remove the radiator cap . . .



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



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



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Fig. Thermostat location arrangement-1997 3.4L (VIN X) engine



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Fig. Exploded view of the thermostat arrangement-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.
  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.
  10.  

3.2L Engines



  1. Drain the cooling system.
  2.  
  3. Remove the radiator inlet hose from the coolant outlet pipe.
  4.  
  5. Remove the bolt securing the oil level indicator tube, coolant outlet pipe and engine front lifting bracket from the cylinder head.
  6.  
  7. Remove the coolant outlet pipe from the thermostat housing.
  8.  
  9. Remove the O-ring seals from the coolant outlet pipe. Discard the O-rings.
  10.  
  11. Remove the intake manifold.
  12.  
  13. Remove the thermostat housing bolts.
  14.  
  15. Remove the thermostat housing with thermostat, from the engine.
  16.  
  17. Remove and discard the seal ring.
  18.  
  19. Remove the thermostat from the thermostat housing.
  20.  

To install:

  1. Install the thermostat into the thermostat housing.
  2.  
  3. Install a new seal ring.
  4.  
  5. Position the thermostat housing with thermostat, to the engine.
  6.  
  7. Install the thermostat housing bolts and tighten to 15 ft. lbs. (20 Nm).
  8.  
  9. Install the intake manifold.
  10.  
  11. Lubricate 2 new O-ring seals with coolant.
  12.  
  13. Install the new O-ring seals around the coolant outlet pipe grooves.
  14.  
  15. Insert the coolant outlet pipe (3) into the thermostat housing.
  16.  
  17. Install the bolt securing the oil level indicator tube, coolant outlet pipe and engine front lifting bracket to the cylinder head and tighten to 15 ft. lbs. (20 Nm).
  18.  
  19. Connect the radiator inlet hose to the coolant outlet pipe.
  20.  
  21. Fill the cooling system.
  22.  

3.4L (VIN E) Engine





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Fig. Thermostat arrangement-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.
    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 Engine





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

5.7L Engines




NOTE
The water pump inlet (thermostat housing) and thermostat MUST be replaced as an assembly. The thermostat is not serviceable separately

  1. Drain the cooling system.
  2.  
  3. Remove the cooling fan assembly.
  4.  
  5. Reposition the outlet hose clamp at the water pump inlet.
  6.  
  7. Remove the outlet hose from the water pump inlet.
  8.  
  9. Remove the thermostat housing bolts.
  10.  
  11. Remove the thermostat housing.
  12.  

To install:

  1. Install a new thermostat housing.
  2.  
  3. Ensure that the new thermostat housing has an O-ring seal and is in the groove correctly.
  4.  
  5. Install the thermostat housing bolts and tighten to 11 ft. lbs. (15 Nm).
  6.  
  7. Install the outlet hose to the thermostat housing.
  8.  
  9. Position the outlet hose clamp at the thermostat housing.
  10.  
  11. Install the cooling fan assembly.
  12.  
  13. Fill the cooling system.
  14.  

 
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