GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 1998 🢒 Grand Prix 🢒 HVAC 🢒 HVAC Systems - Automatic 🢒 Heater Core Replacement

Removal Procedure
  1. Remove the air cleaner and duct assembly (3.1L only). Refer to Air Cleaner Assembly Replacement in Engine Controls - 3.1L.
  2. Remove the fuel injector sight shield (3.8L only). Refer to Fuel Injector Sight Shield Replacement in Engine Mechanical - 3.8L or Fuel Injector Sight Shield Replacement in Engine Mechanical - 3.8L.
  3. Drain the coolant. Refer to Cooling System Draining and Filling in Engine Cooling.
  4. Disconnect both of the heater hoses at the heater core. Refer to Heater Hoses Replacement (3.8L) or Heater Hoses Replacement (3.1L) .
  5. Remove the lower the floor console if equipped. Refer to Front Floor Console Replacement in Instrument Panel, Gauges and Console.
  6. Remove the RH and LH instrument panel insulators. Refer to Instrument Panel Insulator Replacement in Instrument Panel, Gauges and Console.

    7. Object Number: 295347 Size: SH
  7. Remove the heater core outlet cover screws.
  8. Remove the heater core outlet cover.

    9. Object Number: 295349 Size: SH
  9. Remove the heater core cover screws.
  10. Remove the heater core cover.

    11. Object Number: 143978 Size: SH
  11. Remove and discard the seals (1,2,3) from the heater core cover.

    12. Object Number: 296242 Size: SH
  12. Remove and discard the heater core outer seal (5) from the heater core.

    13. Object Number: 295351 Size: SH
  13. Remove the heater core clamp screw (1).
  14. Remove the heater core retaining clamp.
  15. Remove the heater core pipe retainer clamp screw (2).

    16. Object Number: 295353 Size: SH
  16. Remove the heater core from the HVAC lower case.

    17. Object Number: 143987 Size: SH
  17. Remove and discard the heater core lower seal (4) from the HVAC case.

    18. Object Number: 143992 Size: SH
  18. Remove and discard the heater core center seal (3) from the HVAC case.

    19. Object Number: 143985 Size: SH
  19. Remove and discard the heater core upper seal (2) from the HVAC lower case.

    20. Object Number: 143990 Size: SH
  20. Remove and discard the heater core side seals (1) from the HVAC lower case.

Installation Procedure

    Object Number: 143990 Size: SH
  1. Install the heater core side seals (1) from the HVAC lower case.

    2. Object Number: 143985 Size: SH
  2. Install the heater core upper seal (2) from the HVAC lower case.

    3. Object Number: 143992 Size: SH
  3. Install the heater core center seal (3) from the HVAC case.

    4. Object Number: 143987 Size: SH
  4. Install the heater core lower seal (4) from the HVAC case.

    5. Object Number: 295353 Size: SH
  5. Install the heater core from the HVAC lower case.

    6. Object Number: 295351 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.

  6. Install the heater core line clamp screw (2).

    7. Tighten
    Tighten the heater core line clamp screw to 1.5 N·m (13 lb in).

  7. Install the heater core mounting clip with a screw (1).

    8. Tighten
    Tighten the heater core mounting clip screw to 1.5 N·m (13 lb in)


    Object Number: 296242 Size: SH
  8. Install heater core outer seal (5) to the heater core.

    9. Object Number: 143978 Size: SH
  9. Install new seals (1,2,3) to the heater core cover.

    10. Object Number: 295349 Size: SH
  10. Install the heater core cover.
  11. Install the heater core cover screws.

    12. Tighten
    Tighten the heater core cover screws to 1.5 N·m (13 lb in).


    Object Number: 295347 Size: SH
  12. Install the heater core outlet cover.
  13. Install the heater core outlet cover screws.

    14. Tighten
    Tighten the heater core outlet cover screws to 1.5 N·m (13 lb in).

  14. Install the lower the floor console if equipped . Refer to Front Floor Console Replacement in Instrument Panel, Gauges and Console.
  15. Install the RH and LH instrument panel insulators. Refer to Instrument Panel Insulator Replacement in Instrument Panel, Gauges and Console.
  16. Connect both of the heater hoses at the heater core. Refer to Heater Hoses Replacement (3.8L) or Heater Hoses Replacement (3.1L) .

  17. Refill the coolant. Refer to Cooling System Draining and Filling in Engine Cooling.
  18. Install the air cleaner and duct assembly (3.1L only). Refer to Air Cleaner Assembly Replacement in Engine Controls - 3.1L.
  19. Install the fuel injector sight shield (3.8L only). Refer to Fuel Injector Sight Shield Replacement in Engine Mechanical - 3.8L or Fuel Injector Sight Shield Replacement in Engine Mechanical - 3.8L.