GM Service Manual Online
For 1990-2009 cars only

Heater Water Bypass Valve Replacement W/O C36

Tools Required

J 38185 Hose Clamp Pliers

Removal Procedure

  1. Remove the air cleaner. Refer to Air Cleaner Assembly Replacement in Engine Controls 4.3L.
  2. Remove the upper fan shroud. Refer to Engine Coolant Fan Upper Shroud Replacement .

  3. Object Number: 280258  Size: SH
  4. Drain the engine coolant. Refer to Cooling System Draining and Filling in Engine Cooling.
  5. Disconnect the vacuum hose from the bypass valve.
  6. Remove the heater inlet pipe (5) and the outlet pipe (6) from the bypass valves (4).
  7. Remove the bolt (3) that retains the valve (4) to the heater assembly.
  8. Remove the bypass valve (4) from the heater assembly.

Installation Procedure


    Object Number: 280258  Size: SH
  1. Install the bypass valve (4) to the heater assembly.
  2. 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 bolt (3) that retains the valve (4) to the heater assembly.
  4. Tighten
    Tighten the bolt to 4 N·m (35 lb in).

  5. Connect the vacuum hose to the bypass valve.
  6. Install the heater inlet pipe (5) and the outlet pipe (6) to the bypass valves.
  7. Refill the cooling system. Refer to Cooling System Draining and Filling in Engine Cooling.
  8. Install the upper fan shroud. Refer to Engine Coolant Fan Upper Shroud Replacement .
  9. Install the air cleaner. Refer to Air Cleaner Assembly Replacement in Engine Controls 4.3L.

Heater Water Bypass Valve Replacement W/ C36

Tools Required

J 38185 Hose Clamp Pliers

Removal Procedure

  1. Remove the air cleaner. Refer to Air Cleaner Assembly Replacement in Engine Controls 4.3L.
  2. Remove the upper fan shroud. Refer to Engine Coolant Fan Upper Shroud Replacement .

  3. Object Number: 280257  Size: SH
  4. Drain the engine coolant. Refer to Cooling System Draining and Filling in Engine Cooling.
  5. Disconnect the electrical connector from the valve.
  6. Disconnect the vacuum hose from the bypass valve.
  7. Remove the hose clamps from the outlet pipe (8) and from the inlet pipe (4).
  8. Remove the bolt (3) that retains the valve to the heater assembly.
  9. Remove the bypass valve (5) from the heater assembly.
  10. Remove the heater hoses from the engine to the hot water bypass valve.

Installation Procedure

  1. Install the heater hoses to the engine to the hot water bypass valve.

  2. Object Number: 280257  Size: SH
  3. Install the bypass valve (5) to the heater assembly.
  4. 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.

  5. Install the bolt (3) that retains the valve (5) to the heater assembly.
  6. Tighten
    Tighten the bolt to 4 N·m (35 lb in).

  7. Install the heater inlet pipe (4) and the outlet pipe to the bypass valves.
  8. Connect the vacuum hose to the valve.
  9. Connect the electrical connector to the valve.
  10. Refill the cooling system. Refer to Cooling System Draining and Filling in Engine Cooling.
  11. Install the upper fan shroud. Refer to Engine Coolant Fan Upper Shroud Replacement .
  12. Install the air cleaner. Refer to Air Cleaner Assembly Replacement in Engine Controls 4.3L.