This video will show how to replace a freeze plug. Freeze plugs, core plugs or casting plugs...whatever you call them, they will eventually need replacing due to corrosion or leaking. Replacement can be done with the engine in the vehicle, but it's obviously a much simpler job to do if the engine is out. Although these plugs were in good shape, I figured it was good preventative maintenance to do a replacement before I installed this engine in our 4x4 Square body truck.