GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2003 🢒 Blazer - 4WD - RHD 🢒 Engine 🢒 Engine Cooling 🢒 Engine Coolant Thermostat Replacement

Removal Procedure
  1. Remove the necessary coolant from the radiator. Refer to Cooling System Draining and Filling .

    2. Object Number: 444792 Size: SH
  2. Disconnect the breather tube at the air cleaner outlet duct.

    3. Object Number: 312278 Size: SH
  3. Remove the air cleaner outlet duct retaining wingnut.

    4. Object Number: 10940 Size: SH
  4. Disconnect the IAT sensor harness connector.

    5. Object Number: 424556 Size: SH
  5. Remove the air cleaner outlet duct from the throttle body.
  6. Remove the throttle body bracket. Refer to Throttle Body Assembly Replacement in Engine Controls - 4.3L.

    7. Object Number: 42901 Size: SH
  7. Remove the thermostat housing mounting bolts.

    8. Object Number: 42895 Size: SH
  8. Remove the thermostat housing from the lower intake manifold and set aside.

    9. Object Number: 42903 Size: SH
  9. Remove the coolant thermostat.
  10. Clean all the sealing surfaces of the coolant outlet.
  11. Clean the sealing surface on the lower intake manifold.

Installation Procedure

    Object Number: 42903 Size: SH

    Important: In order to prevent leakage, thoroughly clean all parts and sealing surfaces.

  1. Install the coolant thermostat with a new gasket or O-ring. Ensure the gasket or O-ring is in the correct position.

    2. Object Number: 42895 Size: SH
  2. Place the thermostat housing on the lower intake manifold.

    3. 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.

  3. Install the thermostat housing mounting bolts.

    4. Tighten
    Tighten thermostat housing mounting bolts to 19 N·m (14 lb ft).

  4. Install the throttle body bracket. Refer to Throttle Body Assembly Replacement in Engine Controls - 4.3L.

    5. Notice: 

       • Handle the MAF sensor carefully.
       • Do not drop the MAF sensor in order to prevent damage to the MAF sensor.
       • Do not damage the screen located on the air inlet end of the MAF.
       • Do not touch the sensing elements.
       • Do not allow solvents and lubricants to come in contact with the sensing elements.
       • Use a small amount of a soap based solution in order to aid in the installation.


    Object Number: 424556 Size: SH
  5. Install air cleaner outlet duct to throttle body.
  6. Install air cleaner outlet duct to MAF sensor.

    7. Tighten
    Tighten the hose clamp to 4 N·m (32 lb in).


    Object Number: 10940 Size: SH
  7. Connect the IAT sensor harness connector.

    8. Object Number: 312278 Size: SH
  8. Install the air cleaner outlet duct retaining wingnut.

    9. Tighten
    Tighten the wingnut to 2 N·m (18 lb in).


    Object Number: 444792 Size: SH
  9. Connect the breather tube to the air cleaner outlet duct.
  10. Fill the cooling system with specified coolant and concentration. Refer to Cooling System Draining and Filling .
  11. Inspect all sealing surfaces for leaks after starting the engine.