Engine: How to install the brass (moon shaped) freeze plug

[yepitsme]

I have never installed the brass (moon shaped) freeze plugs before now. I have always used the steel (cup shaped) freeze plugs in my old chevy's. Should I be using permatex on these brass plugs? And are there any tricks to installing them other than trying to fit them in straight and not too deep? Seems like it could be kind of tricky. Thanks.

[gordr]

By moon-shaped, you mean the brass discs, and not the cups, right? They make steel discs, too. Disc frost plugs are meant to be installed in stepped holes, which have a ledge for the disc to rest against when it is expanded by being flattened with a hammer and punch. If the holes have steps, you must use disc-style plugs. If the holes have no steps, you must use cup-style plugs. Assuming you have the holes with steps, first, scrape the steps clean of rust and crud with a sharp screw driver or utility knife. I would use Permatex, preferably the thick kind from a tube, but the liquid will work. Coat the ledge, and the sides of the hole outside the ledge. Coat the edge of the disc. With your hammer and driver at the ready, place the disc, convex side out, in the hole and rest it on the ledge. Center your driver on the disc, and administer a couple of sharp blows with the hammer. The disc should be noticeably flattened in the middle, but not turned inside-out, nor have a divot in it. Your driver should be a flat-ended punch about 2/3 the diameter of the disc. The head of an 8-ounce ball-pein hammer should be pretty close, and it comes with a convenient handle. Strike it with a 2-pound hammer. "They" will tell you not to strike a hammer with another hammer, and this is normally true, but you should not be striking so hard as to risk damage to the tools. Wear safety glasses in any case. If you can find a slug of steel or brass of suitable size, use that for your driver. Avoid using too small a punch. I would say a half-inch diameter is the smallest you should use.

[bezhawk]

Gasket shellac is what most engine builders use. Amazon.com: Permatex 20539 Indian Head Gasket Shellac Compound, 2 oz. : Automotive

[yepitsme]

Geordr......Thank you for detailed instructions. I've never heard this before. I did get it installed before I read this post. But I will now go back and give it a good whack in the center with a ball peen and another hammer. It makes sense. This Forum is awesome.

[StudeNorm]

Gordr's instruction are bang on. One thing to realize now since you did start the install without his instructions is Do Not give it TOO much of a good whack. You don't want to hit it hard enough to deflect the shape of the disc, as Gordr mentioned. I have seen it happen years ago. This can cause the disc to actually loosen in the hole. Perhaps modern disc design won't let this happen... You should notice when it is no longer moving as you whack it. It will be seated against the raised lip. Hope you understand what I mean here. Good luck and be patient.

[RadioRoy]

All this is assuming that the steps/ridges are still in the holes in the block and have not rusted away.

[Jeffry Cassel]

Not the best idea any engineer ever came up with. I use something bigger and flatter like a 1/2" or 5/8" bolt and give that a whack. Seems like it ought to expand the plug better. Great tip about Permatex.

[nvonada]

When I pulled my engine for new gaskets and cleaning on my Champion I failed to seat the disk-style core plug well. It popped out maybe 6 months later. I smelled a whiff of antifreeze and a minute later was sitting over a puddle by the side of the road. That is the only time the Studebaker ever had to get towed home. New one was seated a bit more aggressively

[tsenecal]

I had an old timer tell me a story about using a silver dollar for a freeze plug. The way he told it was that he set it over a round hole and put the dome in it, then installed it as usual. His joke was that "no matter how bad the car got, it would always be worth a dollar"! Of course this would have been when silver dollars were still in circulation.

[Andy R.]

Ledged or not, be sure to thoroughly clean the mounting surface.
A small brass wire brush on a Dremel works well without being too aggressive or causing a slight out-of-round situation.

If the mounting ledge is broken or deteriorated, there are shallow cup brass plugs that will work.