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 antifreeze or enough antifreeze) 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 then subjected 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.
REMOVAL & INSTALLATION
See Figures 1 and 2
- Disconnect the negative battery cable, then properly drain the engine cooling system.
- If equipped, remove the engine coolant drain plugs (located at the bottom of the block usually near the oil pan rail) and drain the coolant from the block. If the engine is not equipped with coolant drain plugs, drill a small hole in the leaking freeze plug and allow any remaining coolant to drain.
- Remove any components that restrict access to the freeze plug or, if necessary, remove the engine from the vehicle for access to the freeze plug(s).