GM Chevy Mid-Size Cars 1964-1988 Repair Guide

Heater Core

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REMOVAL & INSTALLATION



See Figures 1 and 2

1964-67 Except Air Conditioned Cars
  1. Disconnect the negative battery cable, then drain the radiator.
  2.  


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

  1. Remove the heater hoses from the core. The top hose connects to the water pump and the lower hose goes to the thermostat housing.
  2.  
  3. Remove the cables and all electrical connections from the heater and defroster assembly.
  4.  
  5. Remove the nuts from the core case studs located on the firewall.
  6.  
  7. From inside the car, remove the case-to-firewall mounting screws and also the heater and defroster assembly.
  8.  
  9. Remove the retaining springs and core.
  10.  

To install:
  1. Install the core and retaining spring, making sure the core-to-case sealer is in good shape.
  2.  
  3. Install the heater and defroster assembly, then install and tighten the case-to-firewall mounting screws.
  4.  
  5. Install the nuts to the core case studs on the firewall.
  6.  
  7. Install the cables and engage all electrical connectors to the heater and defroster assembly.
  8.  
  9. Engage the heater hoses to the core.
  10.  
  11. Connect the negative battery cable, then refill the engine cooling system and check for leaks.
  12.  



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Fig. Fig. 1: Example of a heater control cable assembly-1978 shown



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Fig. Fig. 2: Heater hose mounting-V8 engines (V6 similar)

1968-77 Except Air Conditioned Cars
  1. Disconnect the negative battery cable.
  2.  
  3. Drain the radiator.
  4.  


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

  1. Disconnect the heater hoses. Plug the core inlet and outlet.
  2.  
  3. Remove the nuts from the air distributor duct studs on the firewall.
  4.  
  5. On post-1969 models remove the glove box and radio, then the defroster duct-to-distributor duct screw.
  6.  
  7. Pull the defroster duct out of the way, and then pull the distributor duct from the firewall mounting. Remove the resistor wires. Lay the duct on the floor.
  8.  
  9. Remove the core assembly from the distributor duct.
  10.  

To install:
  1. Install the core assembly to the distributor duct, the reposition and secure the duct to the firewall mounting. If necessary, use new sealer on the duct flange.
  2.  
  3. On post-1969 models, install the defroster duct-to-distributor duct screw, then install the glove box and radio.
  4.  
  5. Install the nuts to the air distributor duct studs on the firewall.
  6.  
  7. Remove the plugs, then connect the heater hoses to the core tubes.
  8.  
  9. Connect the negative battery cable, then properly refill the engine cooling system and check for leaks.
  10.  

1978 and Later Without A/C
  1. Disconnect the negative battery cable and drain the cooling system.
  2.  


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

  1. Disconnect and plug the heater hoses from the core tubes.
  2.  
  3. Disengage the electrical connectors from the module case.
  4.  
  5. Unbolt and remove the module's front cover and lift out the core.
  6.  

To install:
  1. Install the core and apply sealant to the module cover, then install the cover and secure.
  2.  
  3. Engage the electrical connectors to the module case.
  4.  
  5. Remove the plugs, then connect the heater hoses to the core tubes.
  6.  
  7. Connect the negative battery cable, then refill the engine cooling system and check for leaks.
  8.  

1967 and Later With A/C

See Figures 3 through 18

  1. Disconnect the negative battery cable, then drain the engine cooling system to a level below heater core.
  2.  


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

  1. Disconnect and plug the heater hoses at the core tubes. Plugging the hoses will help prevent excessive coolant leakage.
  2.  
  3. Remove the module's rubber seal and screen. If necessary, disconnect the washer nozzle from the cowl.
  4.  
  5. If necessary, remove the right windshield wiper arm.
  6.  
  7. As applicable, remove or disengage, the diagnostic connector, high blower relay, thermostatic switch, ground strap and/or electrical connectors from the heater core module cover.
  8.  
  9. Loosen the retainers and remove the module's top cover. The cover is sealed to the module and this seal must be broken before the cover can be removed. Be absolutely sure that all cover fasteners are removed before attempting to break the seal or cover damage will result. Take your time and be careful not to force and crack or otherwise damage the cover.
  10.  

On many late model vehicles, cover interference with the vehicle's bulkhead will may removal difficult. On these vehicles it will be necessary to loosen the windshield's chromed lower trim plate for the necessary clearance.

  1. With the top cover removed, loosen or unclip the core retainer, then carefully lift the core from the vehicle.
  2.  

To install:
  1. Thoroughly clean the mating surfaces of the cover and the module of all old sealer.
  2.  
  3. Install the heater core to the module and secure the retaining bracket.
  4.  
  5. Apply a coating of sealant to the cover, then install the cover and tighten the fasteners. If the windshield trim plate was loosened for clearance, reposition and secure it.
  6.  
  7. Engage the electrical connectors and components to the module cover, as applicable.
  8.  
  9. If removed, install the right wiper arm.
  10.  
  11. Install the module screen and rubber seal. If removed, install the washer nozzle to the cowl.
  12.  
  13. Remove the plugs and reconnect the heater hoses to the core tubes.
  14.  
  15. Connect the negative battery cable, then properly refill the engine cooling system and check for leaks.
  16.  



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Fig. Fig. 3: Loosen the clamps, then disconnect the hoses from the heater core tubes



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Fig. Fig. 4: Remove the rubber seal from the module top cover



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Fig. Fig. 5: Loosen and remove the module cowl screen retainers



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Fig. Fig. 6: Make sure all of the screen retainers are removed, some like this one, are on the side of the screen



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Fig. Fig. 7: If necessary, remove the retainer and reposition the washer nozzle



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Fig. Fig. 8: Some retaining bolts may be partially hidden, check under the wiper arm



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Fig. Fig. 9: With all of the fasteners removed, carefully lift the screen from the top of the module



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Fig. Fig. 10: Disengage all electrical wiring and components from the top of the module



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Fig. Fig. 11: Loosen and remove the module top cover retaining bolts



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Fig. Fig. 12: As with the cowl screen, the top cover bolts may be difficult to find



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Fig. Fig. 13: If the windshield's chrome trimplate interferes with cover removal, it will have to be loosened or removed for additional clearance



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Fig. Fig. 14: Remove the bolt and bracket from the passenger side of the trim plate



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Fig. Fig. 15: With the bolt and bracket removed, the trim plate support may be removed for clearance



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Fig. Fig. 16: Once all of the bolts are removed, break the seal by lifting the top cover from the module



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Fig. Fig. 17: Remove the core retaining bracket; in this case by loosening the retaining bolt



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Fig. Fig. 18: Lift the heater core from the module, but remember it still may contain a fair amount of coolant

 
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