GM Lumina/Grand Prix/Cutlass Supreme/Regal 1988-1996

Thermostat

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The thermostat is used to control the flow of engine coolant. When the engine is cold, the thermostat is closed to prevent coolant from circulating through the engine. As the engine begins to warm up, the thermostat opens to allow the coolant to flow through the radiator and cool the engine to its normal operating temperature. Fuel economy and engine durability is increased when operated at normal operating temperature.

REMOVAL & INSTALLATION




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. When draining the coolant, keep in mind that cats and dogs are attracted by ethylene glycol antifreeze, and are quite likely to drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantity. Always drain the coolant into a sealable container. Coolant should be reused unless it is contaminated or several years old.

2.2L Engine

See Figure 1



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Fig. Fig. 1: Thermostat and housing mounting-2.2L engine

  1. Disconnect the negative battery cable.
  2.  
  3. Partially drain the coolant, into a suitable container, to a level below the thermostat housing.
  4.  
  5. If replacing the coolant outlet, disconnect the upper coolant hose from the outlet.
  6.  
  7. Unfasten the three retaining nuts, then remove the outlet and thermostat.
  8.  
  9. If damaged remove and discard the studs from the housing.
  10.  
  11. Thoroughly clean the gasket mating surfaces.
  12.  

To install:
  1. If removed, install new studs and tighten to 89 inch lbs. (10 Nm).
  2.  
  3. Apply a suitable sealer, then install the thermostat and the thermostat housing and secure with the three nuts. Tighten the nuts to 89 inch lbs. (10 Nm).
  4.  
  5. If removed, connect the upper coolant hose to the outlet.
  6.  
  7. Refill the cooling system to the proper level with the correct type of coolant.
  8.  
  9. Connect the negative battery cable.
  10.  

2.3L Engine

See Figure 2



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Fig. Fig. 2: Thermostat, housing and outlet assemblies-2.3L engine

  1. Remove the air cleaner assembly.
  2.  
  3. Disconnect the negative battery cable.
  4.  
  5. Partially drain the engine coolant, into a suitable drainPan, to a level below the thermostat.
  6.  
  7. Disconnect the radiator and heater hoses from the coolant outlet.
  8.  
  9. Detach the electrical connectors from the coolant outlet.
  10.  
  11. Remove the pipe and retaining bolts from the coolant outlet.
  12.  
  13. Remove the outlet and thermostat.
  14.  

To install:
  1. Thoroughly clean the gasket mating surfaces.
  2.  
  3. Using a new gasket and RTV sealant, install the thermostat and outlet. Tighten the retaining bolts to 19 ft. lbs. (26 Nm).
  4.  
  5. Connect the pipe to the coolant outlet.
  6.  
  7. Attach the electrical connectors and the hoses to the coolant outlet.
  8.  
  9. Refill the radiator with the specified amount of engine coolant
  10.  
  11. Connect the negative battery cable, then install the air cleaner.
  12.  
  13. Start the engine and check for leaks.
  14.  

2.5L Engine

See Figure 3



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Fig. Fig. 3: On the 2.5L engine, remove the thermostat cap and use the handle to lift the thermostat from the housing

  1. Disconnect the negative battery cable.
  2.  
  3. Partially drain the engine coolant from the radiator to a level below the thermostat.
  4.  
  5. Remove the thermostat housing cap.
  6.  
  7. Remove the thermostat by using the wire handle to lift it out of the housing.
  8.  

To install:
  1. Insert the thermostat and seal into the housing.
  2.  
  3. Install the thermostat housing cap
  4.  
  5. Refill the engine with the proper amount of engine coolant.
  6.  
  7. Connect the negative battery cable. Start the engine and check for leaks.
  8.  

2.8L, 3.1L and 1991 3.4L Engines

See Figures 4, 5, 6, 7, 8, 9, 10 and 11



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Fig. Fig. 4: View of the thermostat location-1992 3.1L engine



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Fig. Fig. 5: Unfasten the water outlet attaching bolts, then remove the outlet



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Fig. Fig. 6: Remove the thermostat from the housing...



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Fig. Fig. 7: ... then remove and discard the gasket from the thermostat



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Fig. Fig. 8: Remove the radiator cap...



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Fig. Fig. 9: ... then fill the cooling system with the proper type and amount of coolant



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Fig. Fig. 10: Thermostat mounting-3.1L engines through 1993



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Fig. Fig. 11: Thermostat mounting - 1994-96 3.1L engines

  1. Disconnect the negative battery cable.
  2.  
  3. Partially drain the engine cooling system, into a suitable container, to a level below the thermostat.
  4.  
  5. If replacing the water outlet, detach the radiator hose from the outlet.
  6.  
  7. Unfasten the water outlet attaching bolts and remove the water outlet.
  8.  
  9. Remove the thermostat. Remove and discard the gasket.
  10.  
  11. Thoroughly clean the manifold water inlet and water outlet mating surfaces.
  12.  

To install:
  1. Position the thermostat into the inlet manifold.
  2.  
  3. Apply a 0.125 in. (3mm) bead of RTV sealer to the thermostat housing.
  4.  
  5. Install the water outlet to the inlet manifold, then tighten the attaching bolts to 18 ft. lbs. (23 Nm).
  6.  
  7. Attach the radiator hose to the water outlet housing.
  8.  
  9. Refill the engine with the specified type and amount of engine coolant. Connect the negative battery cable, start the engine and check for coolant leaks.
  10.  

1992-96 3.4L Engines

See Figure 12



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Fig. Fig. 12: Unbolt the housing, then remove the thermostat-1995 3.4L engine shown

  1. Disconnect the negative battery cable.
  2.  
  3. Remove the air cleaner and duct assembly.
  4.  
  5. Partially drain the engine cooling system, into a suitable container, to a level below the thermostat.
  6.  
  7. Remove the engine torque strut bolt from the engine.
  8.  
  9. Disconnect the upper radiator hose from the housing.
  10.  
  11. Properly relieve the fuel system pressure. For details, please refer to Fuel System of this repair guide.
  12.  
  13. Disconnect the fuel lines from the fuel rail.
  14.  
  15. Remove the heater hose bracket at the thermostat housing stud.
  16.  
  17. Disconnect the heater hose from the throttle body.
  18.  
  19. Unfasten the thermostat housing retaining bolts, then remove the housing.
  20.  
  21. Remove the thermostat. Remove and discard the gasket.
  22.  

To install:
  1. Thoroughly clean the gasket mating surfaces.
  2.  
  3. Position the thermostat, then install a new gasket.
  4.  
  5. Attach the thermostat housing to the inlet manifold. Coat the retaining bolts with RTV sealer before installing them. Tighten the bolts to 18 ft. lbs. (25 Nm).
  6.  
  7. Connect the heater hose to the throttle body.
  8.  
  9. Install the heater hose bracket at the thermostat housing stud.
  10.  
  11. Connect the fuel lines to the fuel rails.
  12.  
  13. Attach the upper radiator hose to the thermostat housing.
  14.  
  15. Install the engine torque strut-to-engine bolt.
  16.  
  17. Install the air cleaner assembly, then connect the negative battery cable.
  18.  
  19. Refill the engine with the specified type and amount of engine coolant. Start the engine and check for coolant leaks.
  20.  

3.8L Engine

See Figure 13



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Fig. Fig. 13: Thermostat and housing mounting-3.8L engine

  1. Disconnect the negative battery cable.
  2.  
  3. Remove the air cleaner and duct assembly.
  4.  
  5. Partially drain the engine cooling system, into a suitable container, to a level below the thermostat.
  6.  
  7. Disconnect the radiator hose from the water outlet.
  8.  
  9. If necessary, detach the electrical connections from the throttle body assembly.
  10.  
  11. Unfasten the water outlet attaching bolts, then remove the water outlet.
  12.  
  13. Remove the thermostat. Remove and discard the gasket.
  14.  
  15. Thoroughly clean the manifold water inlet and water outlet mating surfaces.
  16.  

To install:
  1. Position the thermostat into the intake manifold with a new gasket.
  2.  
  3. Install the water outlet to the intake manifold with RTV sealer. Tighten the attaching bolts to 20 ft. lbs. (27 Nm).
  4.  
  5. Connect the radiator hose to the water outlet housing.
  6.  
  7. If necessary, attach the electrical connections to the throttle body assembly.
  8.  
  9. Install the air cleaner assembly, then connect the negative battery cable.
  10.  
  11. Refill the engine with the specified type and amount of engine coolant. Start the engine and check for coolant leaks.
  12.  

 
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