How to Install Concave/Convex Disc Type Freeze Plugs

Written by timothy burns | 13/05/2017
How to Install Concave/Convex Disc Type Freeze Plugs
While freeze plugs are simple to replace, gaining access can be quite difficult. (car engine image by itsallgood from

Water expands when it freezes, and freezing water can crack solid metal containers if no expansion room is available. For this reason automotive engines contain replaceable "freeze plugs" which allow water to expand and freeze without damaging the engine block should adverse conditions arise. These plugs are made from thin stamped steel or brass, and occasionally must be replaced.

Locate the freeze plugs on the automotive engine block. These small stamped plugs look a bit like smooth inverted bottle caps inserted in engine block holes. The freeze plugs are typically located underneath the intake and exhaust manifolds, directly adjacent to each piston. In other words a V6 motor has at least six freeze plugs. An eight cylinder motor has eight cylinder freeze plugs, plus a large one near the crank shaft.

Pry the existing freeze plug out of the hole using the needle nose pliers and the small flat head screwdriver. The freeze plug will be damaged as it is removed. These parts must be replaced once removed.

Lightly sand the side of the freeze plug hole with steel wool. Remove any burrs, metal shards or corrosion which exists on the side of the freeze plug hole.

Place a light coating of silicone gasket material around the perimeter lip on the new freeze on plug. Do not put gasket material on the engine block hole. This seal it should only used in the exterior of the engine block.

Press the new freeze plug into each hole using a socket from a socket wrench set which exactly matches the size of the freeze plug. The socket should neither be larger or smaller than the freeze plug, the socket should fit perfectly into the concave freeze plug in order to press the freeze plug in place without damaging the new part.

Things you need

  • Freeze plug replacement kit
  • Needle nose pliers
  • Steel wool
  • Small flat head screwdriver
  • A hex head socket which matches the size of the new freeze plugs
  • Small ball peen hammer
  • High-temperature silicone gasket material

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