GM Astro/Safari 1985-1996 Repair Guide

Heater Core

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REMOVAL & INSTALLATION



Front Core

See Figures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 and 11



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Fig. Fig. 1: The heater core has its water connections in the engine compartment



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Fig. Fig. 2: With the engine cover off, the trim panel bolts are accessible



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Fig. Fig. 3: Remove the trim panel to access the heater box



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Fig. Fig. 4: The air distribution duct is mounted in front of the heater box



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Fig. Fig. 5: Note the seal at the top of the duct. Make sure it is in place when assembling the duct



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Fig. Fig. 6: The side cover is held by 2 bolts



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Fig. Fig. 7: The side cover is also gasketed. Check its condition once removed



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Fig. Fig. 8: The heater core is held by small bolts and molded-in brackets



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Fig. Fig. 9: In most cases, the core can be separated from the heater box without removing the entire assembly



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Fig. Fig. 10: Mounting scheme of the front heater module



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Fig. Fig. 11: Exploded view of the front heater module

The front heater core is located on the right side of the passenger compartment, under the dash.

  1. Disconnect the negative battery terminal from the battery.
  2.  
  3. Place a catch pan under the radiator, open the drain cock and drain the coolant to a level below the heater core.
  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. Remove the radiator overflow coolant bottle and the windshield washer fluid bottle.
  2.  
  3. In the engine compartment, remove the inlet/outlet hose clamps from the heater core. Remove and plug the heater hoses to prevent coolant spillage.
  4.  
  5. From inside the vehicle, remove the engine cover to provide extra room.
  6.  
  7. From under the dash, remove the lower right filler panel.
  8.  
  9. Remove the distributor duct, for extra room.
  10.  
  11. Remove the heater-to-cowl bolts and the heater assembly from the vehicle. In some instances this may not be necessary.
  12.  
  13. Separate the cover plate and the heater core from the heater assembly.
  14.  

To install:
  1. Assemble the cover plate and the heater core to the heater assembly.
  2.  
  3. Install the heater-to-cowl bolts and the heater assembly in the vehicle, if the entire assembly was removed.
  4.  
  5. Install the distributor duct.
  6.  
  7. From under the dash, install the lower right filler panel.
  8.  
  9. From inside the vehicle, install the engine cover.
  10.  
  11. In the engine compartment, install the inlet/outlet hoses on the heater core tubes.
  12.  
  13. Install the radiator overflow coolant bottle and the windshield washer fluid bottle.
  14.  
  15. Refill the coolant to the proper level and check for leaks.
  16.  
  17. Connect the negative battery cable to the battery.
  18.  
  19. Start the engine and recheck for leaks after it has reached operating temperature.
  20.  

Rear Core

See Figure 12



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Fig. Fig. 12: Rear heater components

A rear heater core provides heating to the rear of the vehicle. It is located on the left side of the vehicle, in front of the wheel fender and is concealed behind a cover.

  1. Disconnect the negative battery terminal from the battery.
  2.  
  3. Place a catch pan under the radiator, open the drain cock and drain the cooling system.
  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. From under the vehicle (at the rear heating unit), remove the inlet/outlet hose clamps from the heater core. Remove and plug the heater hoses to prevent coolant excess spillage.
  2.  
  3. From inside the vehicle, remove the heating unit cover.
  4.  
  5. Remove the heater core from the blower assembly.
  6.  
  7. Inspect the heater hoses for deterioration, then replace (if necessary).
  8.  

To install:
  1. Install the heater core into the blower assembly. Make sure all the seals are positioned properly.
  2.  
  3. From inside the vehicle, install the heating unit cover.
  4.  
  5. From under the vehicle (at the rear heating unit), install the inlet/outlet hoses on the heater core tubes.
  6.  
  7. Refill the radiator to the proper level.
  8.  
  9. Connect the negative battery terminal to the battery.
  10.  
  11. Start the engine and check for leaks.
  12.  

 
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