Chevrolet Full Size Cars 1979-1989

Freeze Plugs


On most cast iron blocks, round metal plugs are used to seal coolant jackets. These plugs allow for a certain amount of water and block expansion should water (without anti-freeze) ever be left in the coolant system. Although the cooling system should NEVER be filled with plain water only, an emergency and unavailability of coolant could force the situation to occur.

In the event that water only is placed in the cooling system and the engine is subject to sub-freezing temperatures, it is likely that the water will freeze and expand. It is also quite possible that the block will expand and crack. If you are lucky though, the expansion may only cause freeze plugs to become dislodged.

During engine block overhaul, it is often standard procedure to remove and replace all of the freeze plugs.


  1. If necessary, remove the engine from the vehicle or remove the interfering components, in order to access the freeze plug(s).

Always wear proper eye protection when using a chisel, especially when attempting to dislodge a freeze plug.

  1. Using a hammer and a suitable chisel, cock the plug in the bore.
  3. Using the chisel or a small prybar, drive/pry the freeze plug from the bore. Be careful not to score the block or the new freeze plug may not fit well.

To install:

Some auto part stores may offer easy to install freeze plugs consisting of a grommet with metal plates and an adjustment bolt. These plugs are positioned, then the bolt is tightened to expand the grommet sealing the block bore. Although these might be handy to get the vehicle home quickly, they should not be installed as a permanent fix.

  1. Freeze plugs are interference fitted to the block. Make sure you have the proper plug size and an equalled sized driver. The proper sized driver will ease the installation process by preventing the plug from cocking in the bore as it is driven into position.
  3. Position the plug to the bore and drive into position.
  5. Install the interfering components or the engine, as applicable.