Freeze plugs are small, cylindrical-shaped plugs that are used to fill the passages in an engine created by the sand cores. During production, passages are created in engines that allows for the removal of casting sand. ... When the water coolant inside a vehicle's engine froze, its freeze plugs would push out.

What happens when a freeze plug goes bad?

If you have a bad freeze plug, your vehicle will leak coolant. If you have a slow cooling system leak that comes and goes, you may have a pinhole freeze leak.

How much does it cost to replace freeze plugs?

Researching online, an easy to reach freeze plug could cost anywhere from $200 to $400, whereas a freeze plug that requires the mechanic to lift the engine or transmission out can cost anywhere from $900 to more than $1,800.