How to Replace the Freeze Plugs on a GM 350 Truck


Freeze plugs are small plugs placed in the side of an engine block to prevent damage in extreme cold weather conditions. When the temperature drops too low, coolant with too much water can turn to ice. The freeze plugs are designed to push out of the engine block and allow the ice to expand naturally, preventing the engine block from cracking. The 350 engine found in many GM trucks has two freeze plugs located at the rear of the engine block beside the camshaft.

Things You'll Need

  • Hammer
  • Punch
  • Pliers
  • Emery cloth
  • Shellac
  • Seal driver
  • Place a punch on one edge of the freeze plug and tap it lightly with a hammer so it begins to rotate. Once the opposite edge protrudes far enough, grab it firmly with a pair of pliers and pull it free from the engine block.

  • Clean the inside of the hole with an emery cloth. Pull the cloth to the outside when wiping so that debris doesn't fall into the engine block.

  • Apply a light coat of shellac to the edges of the new freeze plug.

  • Insert the freeze plug into the end of a seal driver. Place the seal driver against the hole and twist clockwise until the freeze plug is in place.

Tips & Warnings

  • If the new freeze plug is a temporary rubber plug, do not use shellac to seal the plug.
  • Brass freeze plugs are more expensive than steel freeze plugs, but will not rust so they last much longer.


  • "Diesel Engine Repair Manual: General Motors and Ford V8 Diesel Engines : Gm 350 Cu in (Hayne's Automotive Repair Manual)"; Ken Freund; 1991
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