GM Service Manual Online
For 1990-2009 cars only

Auxiliary Heater Core Replacement LHD Only

Removal Procedure

    Caution: Refer to Battery Disconnect Caution in the Preface section.


    Object Number: 859627  Size: SH
  1. Disconnect the negative battery cable.
  2. Drain the cooling system.
  3. Caution: Refer to Vehicle Lifting Caution in the Preface section.

  4. Raise the vehicle. Refer to Lifting and Jacking the Vehicle in General Information.
  5. Move the clamps up the heater core hoses.
  6. Notice: Blow remainder of coolant out of heater core with an air hose to prevent spilling coolant on vehicle interior when removing heater core.


    Object Number: 859635  Size: SH
  7. Remove the hoses from the heater core.

  8. Object Number: 866368  Size: SH
  9. Remove the left and right lower trim panel extensions by pulling outward at the dual lock locations. Then rotate the panels outward to disengage the hinges from the console.

  10. Object Number: 860403  Size: SH
  11. Remove the I/P lower closeout panel by pulling out at the top edge and then rotating the top downward.

  12. Object Number: 859644  Size: SH
  13. Remove the screws and the clips on the lower heater duct.
  14. Notice: Take care not to damage heater duct-to-rear floor heater duct seal.

  15. Drop the heater duct straight down and carefully slide out sideways.

  16. Object Number: 859422  Size: SH
  17. Release the temperature cable hold down clip from the lower heater core cover by carefully lifting up on the plastic tab while pushing down on the top of the cable.
  18. Slide the cable off of the temperature door hook.
  19. Remove the temperature cable. Service linkage shown in illustration.

  20. Object Number: 860364  Size: SH
  21. Remove the screw and the heater core side cover.

  22. Object Number: 861046  Size: SH
  23. Remove the screws and the lower heater core cover.

  24. Object Number: 859428  Size: SH
  25. Remove the screw and the lower heater core retainer.
  26. Notice: Place absorbent towels under heater core pipe to heater core joints to prevent spilling any residual coolant on carpeting.

  27. Remove the heater core.

Installation Procedure

    Notice: Be careful not to damage heater core pipe seal when installing pipes through cowl. Lubricate pipes with petroleum jelly.


    Object Number: 859428  Size: SH
  1. Install the heater core.
  2. Install the lower heater core retainer and screw.
  3. Notice: Refer to Fastener Notice in the Preface section.


    Object Number: 861046  Size: SH
  4. Install the lower heater core cover and screws.
  5. Tighten
    Tighten the lower heater core cover screws to 1.7 N·m (15 lb in).


    Object Number: 860364  Size: SH
  6. Install the heater core side cover and screw.
  7. Tighten
    Tighten the side heater core cover screws to 1.7 N·m (15 lb in).


    Object Number: 859652  Size: SH
  8. Push the temperature cable over the pin and snap the temperature cable hold down clip over the temperature cable holder.
  9. Notice: Take care not to damage heater duct-to-rear floor heater duct seal.


    Object Number: 859644  Size: SH
  10. Install the heater duct by carefully sliding in sideways and up into position.
  11. Install the screws and clips on the lower heater duct.
  12. Tighten
    Tighten the lower heater duct to 1.7 N·m (15 lb in).


    Object Number: 860872  Size: SH
  13. Install the left and the right lower trim panel extensions by inserting the hinges into the console openings. Then rotate the closed and push in at the dual lock locations.

  14. Object Number: 860403  Size: SH
  15. Install the I/P lower closeout panel by inserting the bottom clip into the module heater duct and rotating upward to snap in the top clip.
  16. Caution: Refer to Vehicle Lifting Caution in the Preface section.


    Object Number: 861027  Size: SH
  17. Raise the vehicle. Refer to Lifting and Jacking the Vehicle in General Information.
  18. Important: Be careful not to push the hoses onto the heater core so far that the foam seal is unseated.

  19. Install the hose and the clamp on the heater core outlet. Position the clamp at a 7-8 o'clock position.

  20. Object Number: 861024  Size: SH
  21. Install the hose and clamp on the heater core inlet. Position the clamp at a 6 o'clock position.
  22. Fill and pressure test the cooling system.
  23. Connect the negative battery cable.

Auxiliary Heater Core Replacement RHD Domestic Only

Removal Procedure

    Caution: Refer to Battery Disconnect Caution in the Preface section.


    Object Number: 859418  Size: SH
  1. Disconnect the negative battery cable.
  2. Remove the air cleaner housing cover and the air induction hose at the intake manifold.
  3. Drain the cooling system.
  4. Remove the heater inlet hose from the engine outlet and blow the remainder of the coolant out of the heater core with a low pressure air hose to prevent spilling coolant on the vehicle interior when removing the core.
  5. Install the heater inlet hose on the engine outlet and position the clamp at the 4 o'clock position as viewed from the left side of the vehicle.

  6. Object Number: 866368  Size: SH
  7. Remove the right lower trim panel extension by pulling outward at the dual lock locations. Then rotate the panel outward to disengage the hinges from the console.

  8. Object Number: 860696  Size: SH
  9. Remove the shift lock cable from the clamp at the front edge of the heater pipe cover.
  10. Remove the pipe cover screws and remove the pipe cover.
  11. Notice: Place absorbent towels under heater core pipe to heater core joints to prevent spilling any residual coolant on carpeting.


    Object Number: 860841  Size: SH
  12. Remove the heater core pipe to core screws.

  13. Object Number: 860843  Size: SH
  14. Remove the O-ring and the plastic seal from each joint and discard.

  15. Object Number: 860844  Size: SH
  16. Rotate the upper pipe upward, and the lower pipe downward, and pull the heater core out of the HVAC module.

Installation Procedure

    Notice: Install plastic seal with barbs toward heater core. Improper installation will damage seal and prevent joint sealing.


    Object Number: 860843  Size: SH

    Important: Service heater core assemblies include the pipes attached to the core. Remove the pipes from the heater core and save the O-rings and the seals. Return the unused pipes with the used heater core.

    Important: Do not install the heater core upside down. The core openings should be offset towards the top of the core.

  1. Install the heater core into the HVAC module and press firmly to seat.

  2. Object Number: 860845  Size: SH

    Important: To ease assembly of the pipe to the heater core, dip the O-ring in coolant to make tacky.

  3. Install the upper pipe plastic seal, the O-ring, and the pipe to the heater core.
  4. Important: Start all the screws before tightening.

  5. Install the upper pipe to the heater core screws and tighten.

  6. Object Number: 860847  Size: SH
  7. Install the lower pipe plastic seal, the O-ring, and the pipe to the heater core.
  8. Important: Start all the screws before tightening.

  9. Install the lower pipe to the heater core screws and tighten.

  10. Object Number: 860696  Size: SH
  11. Install the heater core pipe cover and screws.
  12. Install the park lock cable into the clamp at the front edge of the heater pipe cover.

  13. Object Number: 860872  Size: SH
  14. Install the right lower trim panel extensions by inserting the hinges into the console openings. Then rotate closed and push in at the dual lock location.
  15. Fill and pressure test the cooling system.
  16. Connect the negative battery cable.