GM S-Series Pick-ups and SUV's 1994-1999 Repair Guide

Thermostat

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REMOVAL & INSTALLATION



2.2L Engine

See Figures 1 through 6



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Fig. Fig. 1: View of the thermostat and related components-2.2L engine

The thermostat is located in a housing protruding from the front of the engine, just above the water pump assembly.


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 engine cooling system to a level just below the thermostat.
  2.  
  3. Loosen the clamp that attaches the upper radiator hose to the water outlet and disconnect the hose from the outlet.
  4.  
  5. Remove the water outlet retainers, then lift the outlet from the housing.
  6.  
  7. Remove the thermostat from the housing, noting the orientation for installation purposes.
  8.  



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Fig. Fig. 2: Use pliers to disconnect the clamp that attaches the upper radiator hose to the water outlet ...



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Fig. Fig. 3: ... then disconnect the hose from the outlet



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Fig. Fig. 4: Location of the water outlet retainers



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Fig. Fig. 5: Unfasten the retainers and remove the water outlet assembly



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Fig. Fig. 6: Note the orientation of the thermostat and remove it from the housing

To install:
  1. Carefully clean the all traces of the old gasket or sealer from the housing and outlet.
  2.  
  3. Install the thermostat to the housing, oriented as noted during removal, then position a new gasket (if used).
  4.  
  5. Place a 1 / 8 in. (3mm) bead of RTV sealant in the groove on the water outlet sealing surface, then install the outlet while the sealer is still wet.
  6.  
  7. Install the outlet retainers and tighten to 18 ft. lbs. (25 Nm) on 1994 models and 89 inch lbs. (10 Nm) on 1995-99 models.
  8.  
  9. Attach the upper radiator hose to the water outlet and securely fasten the clamp.
  10.  
  11. Properly fill the engine cooling system and check for leaks.
  12.  

4.3L Engine

See Figures 7, 8 and 9



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Fig. Fig. 7: Unfasten the thermostat outlet-to-engine bolts



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Fig. Fig. 8: Remove the outlet from the intake manifold



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Fig. Fig. 9: Remove the thermostat from the housing

The thermostat is located between the water outlet and a housing built into the intake manifold.


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. Disconnect the negative battery cable.
  2.  
  3. Remove the air inlet duct.
  4.  
  5. Drain the cooling system to a level below the thermostat.
  6.  
  7. Remove the thermostat outlet-to-engine retainers (usually either 2 bolts or 1 bolt and 1 stud), then remove outlet from the intake manifold.
  8.  
  9. Remove the thermostat from the housing, noting the orientation for installation purposes.
  10.  

To install:
  1. Carefully clean the all traces of the old gasket or sealer from the housing and outlet.
  2.  
  3. Install the thermostat to the housing, oriented as noted during removal, then position a new gasket (if used).
  4.  
  5. Place a 1 / 8 in. bead of RTV sealant in the groove on the water outlet sealing surface, then install the outlet while the sealer is still wet.
  6.  
  7. Install the outlet retainers and tighten to 21 ft. lbs. (28 Nm) for the 4.3L 19-96 models or to 14 ft. lbs. (19 Nm) for the 1997-99 models.
  8.  
  9. Properly fill the engine cooling system and check for leaks.
  10.  
  11. Install the air inlet duct.
  12.