GM Full Size Vans 1987-1997 Repair Guide

Heater Core

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REMOVAL & INSTALLATION



Without Air Conditioning
ALL MODELS

See Figure 1

  1. Disconnect the negative battery cable.
  2.  
  3. Remove the coolant recovery bottle.
  4.  
  5. Place a pan under the van and disconnect the heater intake and outlet hoses. Quickly remove and plug the hoses and support them in an upright position. Drain the coolant from the heater core into the pan.
  6.  


CAUTION
When draining engine coolant, keep in mind that cats and dogs are attracted to ethylene glycol antifreeze and could drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantity. Always drain coolant into a sealable container. Coolant should be reused unless it is contaminated or is several years old.

  1. Remove the heater distributor duct-to-case attaching screws and the duct-to-engine cover screw. Remove the duct.
  2.  
  3. Remove the engine cover.
  4.  
  5. Remove all the instrument panel attaching screws.
  6.  
  7. Carefully lower the steering column. Raise and support the right side of the instrument panel. Refer to Suspension & Steering for further details.
  8.  
  9. Remove the defroster duct-to-case attaching screws and the two screws attaching the distributor to the heater case.
  10.  
  11. Disconnect the temperature door cable. Carefully fold the cable back and out of the way.
  12.  
  13. Remove the three nuts from the engine compartment side of the distributor case and the screw from the passenger compartment side.
  14.  
  15. Remove the heater case and core assembly.
  16.  
  17. Remove the core retaining straps and remove the core.
  18.  

To install:
  1. Install the core.
  2.  
  3. Install the core retaining straps.
  4.  
  5. Install the heater case and core assembly.
  6.  
  7. Fasten the three nuts on the engine compartment side of the distributor case and the screw on the passenger compartment side.
  8.  
  9. Connect the temperature door cable.
  10.  
  11. Install the defroster duct-to-case attaching screws and the two screws attaching the distributor to the heater case.
  12.  
  13. Install the steering column.
  14.  
  15. Fasten all the instrument panel attaching screws.
  16.  
  17. Install the engine cover.
  18.  
  19. Install the duct. Install the heater distributor duct-to-case attaching screws and the duct-to-engine cover screw.
  20.  
  21. Connect the heater intake and outlet hoses.
  22.  
  23. Fill the cooling system.
  24.  
  25. Install the coolant recovery bottle.
  26.  
  27. Connect the negative battery cable.
  28.  

With Air Conditioning
1987-89 MODELS
  1. Disconnect the battery ground cable.
  2.  
  3. Remove the engine cover.
  4.  
  5. Remove the steering column to instrument panel bolts. Lower the column carefully.
  6.  
  7. Remove the upper and lower instrument panel attaching screws. Remove the radio support bracket screw.
  8.  
  9. Raise and support the right side of the instrument panel.
  10.  
  11. Remove the lower right instrument panel bracket.
  12.  
  13. Remove the vacuum actuator from the kick panel.
  14.  
  15. Disconnect the temperature cable and vacuum hoses at the case. Remove the heater distributor duct from over the engine hump.
  16.  
  17. Remove the two defroster duct-to-firewall attaching screws below the windshield.
  18.  
  19. Under the hood, disconnect and plug the heater hoses at the firewall.
  20.  
  21. Remove the three nuts and one screw (inside) holding the heater case to the firewall.
  22.  
  23. Remove the case from the van. Remove the gasket for access to the screws holding the case together. Remove the temperature cable support bracket. Remove the screws and separate the case. Remove the heater core.
  24.  

To install:
  1. Install the heater core.
  2.  
  3. Assemble the case and fasten the screws.
  4.  
  5. Install the temperature cable support bracket.
  6.  
  7. Position the gasket, then install the case in the van.
  8.  
  9. Fasten the three nuts and one screw (inside) holding the heater case to the firewall.
  10.  
  11. Connect and plug the heater hoses at the firewall.
  12.  
  13. Install the two defroster duct-to-firewall attaching screws below the windshield.
  14.  
  15. Install the heater distributor duct.
  16.  
  17. Connect the temperature cable and vacuum hoses at the case.
  18.  
  19. Install the vacuum actuator at the kick panel.
  20.  
  21. Install the lower right instrument panel bracket.
  22.  
  23. Fasten the radio support bracket screw.
  24.  
  25. Fasten the upper and lower instrument panel attaching screws.
  26.  
  27. Install the steering column to instrument panel bolts.
  28.  
  29. Install the engine cover.
  30.  
  31. Connect the battery ground cable.
  32.  
  33. Refill the cooling system as necessary.
  34.  

1990-95 MODELS
  1. Disconnect the battery ground cable.
  2.  
  3. Remove the engine cover.
  4.  
  5. Remove the steering column-to-instrument panel bolts. Lower the column carefully.
  6.  
  7. Remove the upper and lower instrument panel attaching screws. Remove the radio support bracket screw.
  8.  
  9. Raise and support the right side of the instrument panel.
  10.  
  11. Remove the lower right instrument panel bracket.
  12.  
  13. Remove the vacuum actuator from the kick panel.
  14.  
  15. Disconnect the temperature cable and vacuum hoses at the case. Remove the heater distributor duct from over the engine hump.
  16.  
  17. Remove the two defroster duct-to-firewall attaching screws below the windshield.
  18.  
  19. Under the hood, disconnect and plug the heater hoses at the firewall.
  20.  
  21. Remove the three nuts and one screw (inside) holding the heater case to the firewall.
  22.  
  23. Remove the case from the van. Remove the gasket for access to the screws holding the case together. Remove the temperature cable support bracket. Remove the screws and separate the case. Remove the heater core.
  24.  

To install:
  1. Install the heater core.
  2.  
  3. Assemble the case and fasten the screws.
  4.  
  5. Install the temperature cable support bracket.
  6.  
  7. Position the gasket, then install the case in the van.
  8.  
  9. Fasten the three nuts and one screw (inside) holding the heater case to the firewall.
  10.  
  11. Connect and plug the heater hoses at the firewall.
  12.  
  13. Fasten the two defroster duct-to-firewall attaching screws below the windshield.
  14.  
  15. Install the heater distributor duct.
  16.  
  17. Connect the temperature cable and vacuum hoses at the case.
  18.  
  19. Install the vacuum actuator at the kick panel.
  20.  
  21. Install the lower right instrument panel bracket.
  22.  
  23. Fasten the radio support bracket screw.
  24.  
  25. Fasten the upper and lower instrument panel attaching screws.
  26.  
  27. Fasten the steering column-to-instrument panel bolts.
  28.  
  29. Install the engine cover.
  30.  
  31. Connect the battery ground cable.
  32.  
  33. Refill the cooling system as necessary.
  34.  

1996-97 MODELS

See Figure 1

  1. Drain the coolant.
  2.  


CAUTION
Please refer to General Information & Maintenance before discharging the compressor or disconnecting air conditioning lines. Damage to the air conditioning system or personal injury could result. Consult your local laws concerning refrigerant discharge and recycling. In many areas it may be illegal for anyone but a certified technician to service the A/C system. Always use an approved recovery station when discharging the air conditioning.

  1. Have the system discharged by a qualified technician using an approved recovery/recycling station.
  2.  
  3. Remove the coolant recovery tank and the battery from the van.
  4.  
  5. Remove the A/C accumulator.
  6.  
  7. Disconnect the heater hoses from the core.
  8.  
  9. Remove the right kick panel and knee bolster.
  10.  
  11. Disconnect the outer floor air outlet duct.
  12.  
  13. Loosen the screws front the heater case.
  14.  
  15. Carefully open the heater core access door and loosen the retainers from the core.
  16.  
  17. Remove the heater core.
  18.  



Click image to see an enlarged view

Fig. Fig. 1: View of the heater core mounting - 1996-97 models

To install:
  1. Install the heater core and fasten the retainers.
  2.  
  3. Carefully close the core access door, then tighten the heater case screws.
  4.  
  5. Connect the outer floor air inlet duct.
  6.  
  7. Unstall the right knee bolster and kick panel.
  8.  
  9. Connect the heater hoses to the core.
  10.  
  11. Install the A/C accumulator.
  12.  
  13. Install the battery and coolant recovery tank.
    1. Have the system recharged by a qualified technician using an approved recycling/recovery station.
    2.  
    3. Refill the engine coolant system.
    4.  

  14.  

Auxiliary Heater and Air Conditioner
1987-95 MODELS

See Figure 2


CAUTION
When draining engine coolant, keep in mind that cats and dogs are attracted to ethylene glycol antifreeze and could drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantity. Always drain coolant into a sealable container. Coolant should be reused unless it is contaminated or is several years old.

  1. Drain the cooling system.
  2.  
  3. Disconnect the battery ground cable.
  4.  
  5. Disconnect the heater hoses at the core tubes.
  6.  
  7. Remove the heater case-to-floor studs.
  8.  
  9. Remove the case cover.
  10.  
  11. Disconnect the wiring at the case.
  12.  
  13. Lift the case from the van.
  14.  
  15. Remove the core cover and lift the core and seal from the case.
  16.  



Click image to see an enlarged view

Fig. Fig. 2: Sectional views of the auxiliary heater plumbing components - 1987-95 models

To install:
  1. Lower the core and seal into the case.
  2.  
  3. Install the core cover.
  4.  
  5. Install the case in the van.
  6.  
  7. Connect the wiring at the case.
  8.  
  9. Install the case cover.
  10.  
  11. Install the heater case-to-floor studs.
  12.  
  13. Connect the heater hoses at the core tubes.
  14.  
  15. Connect the battery ground cable.
  16.  
  17. Fill the cooling system.
  18.  

1996-97 MODELS

See Figure 3

  1. Disconnect the negative battery cable.
  2.  
  3. Remove the left rear quarter trim panels.
  4.  
  5. Remove the auxiliary heater and A/C as follows:
    1. Drain the coolant.
    2.  

  6.  


CAUTION
Please refer to General Information & Maintenance before discharging the compressor or disconnecting air conditioning lines. Damage to the air conditioning system or personal injury could result. Consult your local laws concerning refrigerant discharge and recycling. In many areas it may be illegal for anyone but a certified technician to service the A/C system. Always use an approved recovery station when discharging the air conditioning.

  1. Loosen the retainers from the bottom of the case.
  2.  
  3. Remove the heater core from the case.
  4.  



Click image to see an enlarged view

Fig. Fig. 3: Heater core assembly - 1996-97 models

To install:
  1. Install the heater core in the case and tighten the retainers to the bottom of the case.
  2.  
  3. Install the auxiliary heater as follows:
    1. Install the heater in the van and tighten the retaining nuts to 89 inch lbs. (10 Nm).
    2.  
    3. Engage the heater and A/C lines to the underside of the heater. Tighten the nut to 18 ft. lbs. (25 Nm).
    4.  
    5. Install the A/C and heater line cover and fasten the retaining screw.
    6.  
    7. Engage the electrical connections.
    8.  
    9. Connect the heater-to-floor and heater-to-roof ducts.
    10.  
    11. Have the system recharged by a qualified technician using an approved recycling/recovery station.
    12.  
    13. Refill the engine coolant system.
    14.  

  4.  
  5. Install the trim panel and connect the negative battery cables.
  6.  

 
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