Expansion/Freeze Plug

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Expansion and Freeze Plugs


Nearly every engine is equipped with expansion plugs, also called freeze plugs or core plugs, as a by-product of the way the engine is manufactured. Water-cooled engine blocks, heads, and more are cast in a mold, and this sand-casting process leaves behind holes that must be filled to prevent cooling system leaks. Expansion plugs are installed in these holes to seal the water channel, and are also designed to push outward in the event of water freezing inside the engine. Though this can lead to leaks, it helps prevent a cracked cylinder head or engine block. If this has occurred, the freeze plugs on your engine will need to be replaced to restore leak-free performance.

Symptoms of Bad Freeze Plugs

Though expansion plugs can suffer damage due to coolant freezing in the water channels, it is much more likely that they will succumb to corrosion and rust over time. This can lead to pinholes or larger leaks, and you will likely notice coolant pooling below your vehicle or spraying in the engine compartment. If you notice any signs of coolant leaks or overheating, properly diagnosing the cooling system in your vehicle can help you determine the source of the problem so that it can be repaired. Freeze plugs are often straightforward to remove and replace, and can help solve cooling system problems before your engine overheats or experiences any long-lasting damage. Shop the selection of expansion plugs and freeze plugs, as well as freeze plug kits, at O'Reilly Auto Parts to make a complete repair.