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For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2006 🢒 GMC Sierra Denali 🢒 Engine 🢒 Engine Cooling 🢒 Engine Coolant Thermostat Replacement

Engine Coolant Thermostat Replacement 8.1L Engine

Removal Procedure

    Object Number: 751425 Size: SH
  1. Drain the cooling system. Refer to Cooling System Draining and Filling .
  2. Reposition the inlet hose clamp at the water outlet.
  3. Remove the inlet hose from the water outlet.

    4. Object Number: 635643 Size: SH
  4. Remove the water outlet bolts (2).
  5. Remove the water outlet (1).
  6. Remove the thermostat (3).

Installation Procedure

    Object Number: 635643 Size: SH
  1. Install the thermostat (3).
  2. Install the water outlet (1).

    3. Notice: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.

  3. Install the water outlet bolts (2).

    4. Tighten
    Tighten the bolts to 30 N·m (22 lb ft).


    Object Number: 751425 Size: SH
  4. Install the inlet hose to the water outlet.
  5. Position the inlet hose clamp at the water outlet.
  6. Fill the cooling system. Refer to Cooling System Draining and Filling .

Engine Coolant Thermostat Replacement 6.6L (LLY) Engine

Removal Procedure


    Object Number: 1367688 Size: SH
  1. Remove the water outlet. Refer to Water Outlet Tube Replacement .
  2. Remove the bolt for the fuel line bracket.
  3. Remove the fuel line bracket.
  4. Remove the thermostat housing cover bolts.
  5. Remove the thermostat housing cover.
  6. Remove the thermostats and seals.

Inspection Procedure
  1. Inspect the thermostats for sticking, cracks, and/or leakage of wax.
  2. Replace the thermostats if damage is found.
  3. Clean the thermostat housing and thermostat housing cover sealing surfaces.

Installation Procedure

    Object Number: 654534 Size: SH
  1. Install the thermostats and seals to the thermostat housing.

    2. The rear thermostat (4) has 2 vent valves. Install with the vent valves towards the rear of engine.

    Notice: Refer to Fastener Notice in the Preface section.


    Object Number: 1367688 Size: SH
  2. Install the thermostat housing cover.
  3. Install the thermostat housing cover bolts.

    4. Tighten
    Tighten the bolts to 21 N·m (15 lb ft).

  4. Install the fuel line bracket.
  5. Install the fuel line bracket bolt.

    6. Tighten
    Tighten the bolt to 21 N·m (15 lb ft).

  6. Install the water outlet tube. Refer to Water Outlet Tube Replacement .

Engine Coolant Thermostat Replacement 4.3L Engine

Removal Procedure

    Object Number: 360851 Size: SH
  1. Drain the cooling system. Refer to Cooling System Draining and Filling .
  2. Loosen the air cleaner outlet duct clamp at the mass airflow/intake air temperature (MAF/IAT) sensor.

    3. Object Number: 701705 Size: SH
  3. Remove the positive crankcase ventilation (PCV) hose.

    4. Object Number: 489179 Size: SH
  4. Remove the air cleaner adapter nut.

    5. Object Number: 489176 Size: SH
  5. In order to remove the air cleaner outlet duct, pivot the duct upward until the hinge clip releases from the lip on the throttle body.

    6. Object Number: 367002 Size: SH
  6. Reposition the inlet hose clamp at the water outlet.
  7. Remove the inlet hose from the water outlet.

    8. Object Number: 42901 Size: SH
  8. Remove the water outlet studs.

    9. Object Number: 42895 Size: SH
  9. Remove the water outlet.

    10. Object Number: 42903 Size: SH
  10. Remove the thermostat.
  11. Clean the sealing surface of the water outlet.
  12. Clean the sealing surface of the intake manifold.
  13. Remove and discard the O-ring seal.

Installation Procedure

    Object Number: 42903 Size: SH
  1. Install a NEW O-ring seal to the thermostat.
  2. Install the thermostat.

    3. Object Number: 42895 Size: SH
  3. Install the water outlet.

    4. Object Number: 42901 Size: SH

    Notice: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.

  4. Install the water outlet studs.

    5. Tighten
    Tighten the studs to 25 N·m (18 lb ft).


    Object Number: 367002 Size: SH
  5. Install the inlet hose to the water outlet.
  6. Position the inlet hose clamp at the water outlet.

    7. Object Number: 489176 Size: SH
  7. Align the hinge clip with the lip on the throttle body.

    8. In order to install the air cleaner outlet duct, pivot the air cleaner outlet duct downward until the mounting stud is through the hole.


    Object Number: 489179 Size: SH
  8. Install the air cleaner adapter nut.

    9. Object Number: 701705 Size: SH
  9. Install the PCV hose.

    10. Object Number: 360851 Size: SH
  10. Tighten the air cleaner outlet duct clamp at the MAF/IAT sensor.

    11. Tighten
    Tighten the clamps to 4 N·m (35 lb in).

  11. Fill the cooling system. Refer to Cooling System Draining and Filling .
  12. Inspect the cooling system for leaks.