GM Astro/Safari 1985-1996 Repair Guide

Engine Block Heater and Freeze Plugs

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REMOVAL & INSTALLATION



See Figures 1, 2 and 3



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Fig. Fig. 1: Engine block heater-located in the engine block freeze plug bore



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Fig. Fig. 2: The freeze plug can be loosened using a punch (or chisel) and hammer



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Fig. Fig. 3: Once the freeze plug has been loosened, it can be removed from the block


CAUTION
Removing the block heater or freeze plug may cause personal injury if the engine is not completely cooled. Even after the radiator has been drained, there will be engine coolant still in the block. Use care when removing the assembly from the block.

To remove an engine freeze plug or block heater, accessories may have to be removed, such as the starter motor, motor mount, etc. Remove an obstruction before attempting to remove the freeze plug. In the worst case scenario, the engine may have to be removed from the vehicle if the suspension or frame prevent access to the plug.

  1. Disconnect the negative battery cable for safety.
  2.  
  3. Raise and support the front of the vehicle safely using jackstands.
  4.  
  5. Drain the engine cooling system from the radiator. If possible, remove the engine block drain plug(s) to drain as much fluid as possible from the block itself.
  6.  


CAUTION
When draining the coolant, keep in mind that cats and dogs are attracted by 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. Locate the plug or heater which must be removed and determine what steps will be necessary to access it.
  2.  
  3. To remove the block heater, disengage the electrical connector, loosen the retaining screw and remove the heater from the block.
  4.  
  5. To remove the freeze plug, drive a chisel through the plug and pry outward. Or drill an 1 / 8 in. hole into the plug and use a dent puller to remove the freeze plug.
  6.  

To install:
  1. To install the freeze plug, coat the new plug with silicone sealer and clean the block mating surface free of rust and corrosion. Using a deep socket the size of the interior of the plug, drive the plug into the block until the plug lip is flush with the cylinder block. Run silicone sealer around the mating area.
  2.  
  3. To install the block heater, coat the O-ring with engine oil and clean the block mating surface free of rust and corrosion. Install the heater and tighten the retaining screw. Engage the wiring to the heater.
  4.  
  5. Connect the negative battery cable.
  6.  
  7. Properly refill and bleed the engine cooling system, then run the engine and check for leaks.
  8.  
  9. Shut the engine OFF , then remove the jackstands and carefully lower the vehicle.
  10.  

 
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