How do you change freeze plugs on the engine?

Answer 1

Can a freeze plug be changed in the driveway? Yes & No. You may have a hard time even getting to the plug, and then being able to remove and re-install. The worst of the lot to change is the one on the rear of the engine.

Freeze plugs are normally something you change at overhaul time when the block is stripped, it has been through the acid bath, and the core is clean. Changing one on the fly is hard because you often end up with leaks worse than you had before you changed the plug. Since they are a press fit, the mating surfaces have to be in good shape. First, the only reason I've ever seen one go bad is by corrosion from using tap water in the cooling system. That is bad news because it causes widespread corrosion. Never ever use tap water in a cooling system. Use distilled water. As for the freeze plugs - when one fails, a hole will have corroded through it, usually at the edge.

Replacing freeze plugs can be a real headache. It's easy once you get enough room to swing a mallet, but very often that means removing the engine. Don't even think of using stop-leak products to try to patch a leaking freeze plug. I have successfully used another technique, though. If you have identified a leaky freeze plug, you can: (1) drain the system, (2) clean the depression in the freeze plug with Scotch-brite and a cleaner like Simple Green to remove both grease and water-soluble deposits, (3) after it dries, apply a liberal amount of putty type steel filled epoxy to the inside of the freeze plug. If you aren't familiar, they are shaped like shallow flat-bottomed cups with an inside diameter about the size of a quarter. What you want to do is to cover the hole with the epoxy from the bottom of the cup up all the sides to the rim, where there is no corrosion. This isn't foolproof, because sometimes the leak is actually not through the plug but around it. Still, it is cheap, fairly permanent, and about the easiest thing to try. Don't worry about making the plug hard to remove if/when the time comes - they are removed by placing a punch in one edge and whacking it with a mallet to knock the plug sideways. The epoxy won't get in the way of that at all. Warning - don't remove a plug unless there is room to use the mallet to seat a new one! If you do, count on removing the engine to get to it. Once it is removed, clean the area thoroughly with a wire brush, (Warning, do not use a grinder or sand paper). After the area is clean, you install the new plug by placing it inside the hole and hitting it dead center with a mallet and flat punch. This causes the plug to expand and seat itself. But you must have room to be able to do this. This is where the job becomes difficult most of the time. No room!