Repair Pontiac Mid-size 1974-1983 Repair Guide

Heater Core

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REMOVAL & INSTALLATION





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Fig. Fig. 1 Exploded view of the heater assembly components-1980-81 LeMans shown



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Fig. Fig. 2 Heater cable routing-Phoenix and Ventura



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Fig. Fig. 3 Heater control cable and panel mounting-LeMans and Grand Prix



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Fig. Fig. 4 To remove the heater core, unfasten the lower windshield trim panel screws ...



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Fig. Fig. 5 ... then remove the lower windshield trim panel



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Fig. Fig. 6 Remove the rubber seal from around the cowl screen



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Fig. Fig. 7 If necessary, disconnect the windshield washer hose



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Fig. Fig. 8 Unfasten the windshield cowl screen retainers ...



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Fig. Fig. 9 ... then remove the cowl screen



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Fig. Fig. 10 Unfasten the heater case cover retaining bolts ...



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Fig. Fig. 11 ... then remove the heater case cover assembly



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Fig. Fig. 12 Unscrew the heater hose clamps ...



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Fig. Fig. 13 ... then disconnect the heater hoses from the core



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Fig. Fig. 14 Remove the heater core bracket retaining bolt ...



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Fig. Fig. 15 ... then remove the heater core from the case

1974-77 GTO, LeMans and Grand Am
WITHOUT AIR CONDITIONING
  1. Drain the radiator.
  2.  
  3. Disconnect the heater hoses at the air inlet assembly.
  4.  
  5. Remove nuts from core studs on firewall (under hood). Remove the glove box.
  6.  

On 1977 LeMans, remove glove box and door, then remove heater outlet from case. Remove defroster duct screw on all models.

  1. From inside the car, pull the heater assembly from the firewall.
  2.  
  3. Disconnect control cables and wires, then remove heater assembly.
  4.  
  5. To remove core, unhook retaining springs or strips.
  6.  
  7. To install, reverse removal procedure, making sure core is properly sealed during installation.
  8.  

WITH AIR CONDITIONING
  1. Drain the coolant.
  2.  
  3. Disconnect the water hoses at the heater core tubes to prevent spilling coolant during removal.
  4.  
  5. Remove the glove compartment.
  6.  
  7. Remove the cold air duct and heater outlet.
  8.  
  9. Remove the defroster duct attaching screw.
  10.  
  11. Remove the screws and nuts which retain the case to the dash. Remove the blower motor resistor to gain access to the upper retaining nut inside the evaporator case.
  12.  
  13. Move the core and case assembly rearward to free the attaching studs from the cowl and remove the core and case assembly.
  14.  
  15. Disconnect the temperature cable and vacuum hoses from the core and case assembly.
  16.  
  17. Remove the core and case assembly from the car.
  18.  
  19. Remove the heater core retaining screws and core.
  20.  
  21. Reverse the above steps for installation.
  22.  

1978-81 LeMans and Grand Am
WITHOUT AIR CONDITIONING
  1. On some vehicles, it may be necessary to remove the lower windshield trim, rubber seals and/or screens for access to the heater core.
  2.  
  3. Disconnect the hoses from the core tubes. Plug them to avoid coolant loss.
  4.  
  5. On the engine side of the firewall, remove the heater core cover from the case.
  6.  
  7. Remove the core bracket and ground screw.
  8.  
  9. Lift out the core.
  10.  
  11. Reverse the procedure for installation.
  12.  

WITH AIR CONDITIONING
  1. Operate the wipers to the up position.
  2.  
  3. Disconnect the hoses at the core tubes.
  4.  
  5. Remove the sealing material and screens from the cooling module.
  6.  
  7. Disconnect all wires from the case.
  8.  
  9. Move the lower windshield reverse molding out of the way.
  10.  
  11. Tape a strip of wood to the lower edge of the glass for protection.
  12.  
  13. Remove the module core cover screws.
  14.  
  15. Cut the cover seal with a knife.
  16.  
  17. Pry the cover off from the side, not from the top.
  18.  
  19. Lift out the core.
  20.  
  21. Installation is the reverse of removal. Use all new sealer when installing.
  22.  

1975-79 Ventura, Phoenix
  1. Disconnect battery.
  2.  
  3. Drain radiator, disconnect heater hoses at core and plug core tubes.
  4.  
  5. Remove nuts from core case studs on firewall.
  6.  
  7. Remove glove box and glove box door.
  8.  
  9. From inside car, drill out lower right-hand heater case stud with 1 / 4 in. drill.
  10.  
  11. Pull entire heater case, with core, from firewall.
  12.  
  13. Disconnect cables and blower resistor connector, then remove case from car.
  14.  
  15. Remove core from case.
  16.  
  17. To install, reverse removal procedure. Use sealer around core and replace drilled stud with new screw and stamped nut.
  18.  

Grand Prix Through 1976
WITHOUT AIR CONDITIONING
  1. Drain the radiator.
  2.  
  3. Disconnect the heater hoses at the air inlet assembly.
  4.  

The water pump hose goes to the right-hand heater core pipe, the other hose (from rear of right cylinder head) goes to the left-hand heater core pipe.

  1. Remove the nuts from the core studs on the firewall (under hood). Remove the glove compartment.
  2.  
  3. From inside the car, remove the defroster nozzle retaining screw from the heater case and pull the heater assembly from the firewall.
  4.  
  5. Disconnect the control cables, vacuum hoses and wires, then remove the heater assembly.
  6.  
  7. Remove the core.
  8.  
  9. To install, reverse the removal procedure, making sure the core is properly sealed during installation.
  10.  

WITH AIR CONDITIONING
  1. Drain the radiator.
  2.  
  3. Disconnect the heater hoses.
  4.  
  5. Remove the retaining nuts from the core case studs on the engine side of the firewall.
  6.  
  7. Remove the glove box.
  8.  
  9. Remove the defroster duct retaining screw from the heater case and pull the heater assembly from the firewall.
  10.  
  11. Disconnect the heater control cables and wires.
  12.  
  13. Remove the core tube seal and core assembly retaining strips and remove the core.
  14.  
  15. Reverse the steps to install.
  16.  

1977 Grand Prix
WITHOUT AIR CONDITIONING
  1. Disconnect the negative battery terminal.
  2.  
  3. Drain the cooling system, disconnect the heater hoses, and plug the core tubes.
  4.  
  5. Remove the screws and nuts from the heater module on the engine side.
  6.  
  7. Remove the glove box to gain access to, and remove, the defroster duct screw, and the control cables.
  8.  
  9. Loosen the sealer and remove the case assembly and core from inside the vehicle.
  10.  
  11. Installation is the reverse of removal. Use a strip caulk type sealer when installing the case assembly to the firewall.
  12.  

WITH AIR CONDITIONING
  1. Drain the cooling system.
  2.  
  3. Remove the heater hoses and plug the core tubes.
  4.  
  5. Remove the core stud nuts retaining the case to the firewall.
  6.  
  7. Remove the blower motor resistor to gain access to the upper retaining nut inside the evaporator case.
  8.  
  9. Remove the glove box, the cold air duct, and the heater distributor tube.
  10.  
  11. Remove the lower defroster duct tube screw.
  12.  
  13. Remove the core to case retaining screw and pull the assembly from the cowl.
  14.  
  15. Remove the temperature cable and the vacuum hoses from the assembly.
  16.  
  17. Remove the case assembly and remove the core from the case.
  18.  
  19. Installation is in the reverse of removal.
  20.  

1978-83 Grand Prix
WITHOUT AIR CONDITIONING
  1. Disconnect the hoses at the core tubes and position them vertically to prevent coolant loss.
  2.  
  3. Remove the core cover from the module.
  4.  
  5. Remove the core bracket and ground screw.
  6.  
  7. Lift out the core.
  8.  
  9. Installation is the reverse of removal. Replace any damaged sealer.
  10.  

WITH AIR CONDITIONING
  1. Position the wipers in the UP position.
  2.  
  3. Disconnect and unplug the heater hoses.
  4.  
  5. Remove the module top cover seals.
  6.  
  7. Remove the module top screens.
  8.  
  9. Disconnect all electrical connectors.
  10.  
  11. Move the lower windshield reverse molding out of the way.
  12.  
  13. Remove the cowl brackets.
  14.  
  15. Tape a strip of wood to the lower edge of the windshield glass, to protect the glass.
  16.  
  17. Remove the top cover screws.
  18.  
  19. Cut the sealing material along the cowl with a knife.
  20.  
  21. Pry the cover off from the side, not from the top.
  22.  
  23. Remove the core and seal.
  24.  

Installation is the reverse of removal. Use all new sealing material.

 
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