GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 1998 🢒 GMC Suburban - 4WD 🢒 HVAC 🢒 Heating, Ventilation and Air Conditioning 🢒 Heater Core Replacement

Removal Procedure
  1. Drain the coolant. Refer to Cooling System Draining and Filling
  2. Remove the instrument panel storage compartment. Refer to Instrument Panel Carrier Replacement in Instrument Panel, Gauges and Console.
  3. Disconnect the electrical connectors, as necessary.
  4. Remove the center floor air distribution duct.
  5. Remove the hinge pillar trim panels. Refer to Instrument Panel Carrier Replacement in Instrument Panel, Gauges and Console.
  6. Remove the blower motor cover.
  7. Remove the blower motor. Refer to Blower Motor and Fan Replacement .
  8. Remove the steering column. Refer to the applicable procedure:
    9. •  Steering Column Replacement in Steering Wheel and Column -- Standard
    •  Steering Column Replacement in Steering Wheel and Column -- Tilt:
  9. Roll back the instrument panel. Refer to Instrument Panel Carrier Replacement in Instrument Panel, Gauges and Console.
  10. Remove the coolant recovery reservoir. Refer to Coolant Recovery Reservoir Replacement in Engine Cooling.
  11. Remove the heater hoses. Refer to Heater Hoses Replacement .

    12. Object Number: 257083 Size: SH
  12. While holding the heater case to the cowl, remove the screw on the interior side of the cowl, near the evaporator pipe, if equipped.

    13. Object Number: 257087 Size: SH
  13. On the engine side of the cowl, remove the 4 screws that hold the heater case to the cowl.
  14. On the engine side of the cowl, remove the 2 nuts that hold the heater case to the cowl.
  15. Remove the heater case.

    16. Ask an assistant for help, if necessary.

  16. Remove the 7 screws that hold the heater cover to the heater case.
  17. Remove the heater cover.
  18. Remove the heater core from the retainer.

Installation Procedure
  1. Install the heater core into the retainer.
  2. Install the 7 screws that hold the heater cover to the heater case. Replace the seals.
  3. Install the heater cover.

    4. Verify that the heater cover is properly sealed.

  4. Install the heater case.

    5. If necessary, ask an assistant for help.


    Object Number: 257087 Size: SH
  5. On the engine side of the cowl, install the nuts that hold the heater case to the cowl.
  6. On the engine side of the cowl, install the 4 screws that hold the heater case to the cowl.

    7. Object Number: 257083 Size: SH
  7. On the interior side of the cowl, install the screw.

    8. 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.

  8. Tighten the following fasteners:

    9. Tighten

        • Tighten the screws on the engine side of the cowl to 1.9 N·m (17 lb in).
        • Tighten the two nuts to 2.8 N·m (25 lb in).
        • Tighten the screw on the interior side of the cowl to 11 N·m (97 lb in).
  9. Install the heater hoses. Refer to Heater Hoses Replacement .
  10. Install the coolant recovery reservoir. Refer to Coolant Recovery Reservoir Replacement in Engine Cooling.
  11. Roll forward the instrument panel. Refer to Instrument Panel Carrier Replacement in Instrument Panel, Gauges and Console.
  12. Install the steering column. Refer to the applicable procedure:
    13. •  Steering Column Replacement in Steering Wheel and Column -- Standard:
    •  Steering Column Replacement in Steering Wheel and Column -- Tilt:
  13. Install the blower motor. Refer to Blower Motor and Fan Replacement .
  14. Install the blower motor cover.
  15. Install the hinge pillar trim panels. Refer to Instrument Panel Carrier Replacement in Instrument Panel, Gauges and Console.
  16. Install the center floor air distribution duct.
  17. Connect the electrical connectors, as necessary.
  18. Install the instrument panel storage compartment. Refer to Instrument Panel Carrier Replacement in Instrument Panel, Gauges and Console.
  19. Add the engine coolant. Refer to Cooling System Draining and Filling in Engine Cooling.
  20. Inspect the system for leaks.