MTFCA Forum

Was driving down the road when the engine began to stutter. Looked out the back window and saw steam billowing out the back. Turn the idle down, engine off, and placed in neutral, coasting to side of road all about the same instant. Opened the hood and saw liquid coming out the right side of the engine, toward the rear. Saw a missing freeze plug hole and the 1926 Indian was sitting on the hood shelf, which I was happy to find. The two bison must have scared him off. Called for a toe.

Back at the show, I already knew that the overflow tube from the radiator was not clogged recently but maybe a mud dabber got to it. Hooked up a vacuum pump but could not get a vacuum nor even see the needle move (because it is clear and not clogged). Also ran air pressure thru the tube freely. So, the JB weld did not hold the plug. Even cold, there is 1 to 1-1/2 lbs psi just from the height of coolant/water in the radiator.

Cleaned the hole with a Dremel bit, used high temp silicone, pressed the nickle back into place and placed three tack welds each around the Indian and the two bison. I don't think they appreciated the close lightning strikes but so be it.

The way the nickel is used is like a welch plug. You put the nickel in a socket almost as large as the nickel. Then with a ball peen hammer make the nickel a bit cupped shape, enough so that the od of the nickel is slightly smaller then the hole in the block. Put some RTV around the hole for good measure then place the nickel into the hole so it is convex rather than concave. Put a flat head hammer on the face of the nickel and tap the hammer to push the nickel against the shoulder in the block and to flatten the face of the nickel. This will cause the od of the nickel to expand and seal the hole. No weld necessary.

varmint wrote: ↑

Mon Oct 27, 2025 1:03 pm

Saw a missing freeze plug hole and the 1926 Indian was sitting on the hood shelf, which I was happy to find. The two bison must have scared him off. Called for a toe.

And that's where the novelty of using coins instead of the proper Welch plug wears off.

That nickel thing never appealed to me for reasons others have stated. There's something about hammering a rigid, coldworked slug of metal into a hole in a 100+ year old casting to make it watertight that seems just plain wrong. jb

I don't know if it's true but the welder that was repairing a long crack in the top of the valve galley in my 26 block (in the usual place) told me there was a small crack above my freeze plug. He assumed it was from the nickel being harder than the block and cracking when the nickel was straightened.

Steve Jelf wrote: ↑

Mon Oct 27, 2025 1:48 pm

After a plug sealed with original Permatex fell out, I switched to Ultra Black. That proved quite adequate.

Permatex Right Stuff is incredibly tough. But it's not cheap.

Steve Jelf wrote: ↑

Mon Oct 27, 2025 1:48 pm

After a plug sealed with original Permatex fell out, I switched to Ultra Black. That proved quite adequate.

Permatex Right Stuff is incredibly tough. But it's not cheap.

The high temp silicone dried for 24 hours but failed when I added coolant, and I made sure it was clean.
Had to drain the coolant, clean again and this time I'm using Ultra Black.

Clean it real well and use loctite.

Had an issue with a club members T were when the block was cleaned out the recess for the plug was to large & out of round for a freeze plug or even a nickel. I ended up tapping & installing socket head pipe plugs then filling the socket with couching so you didn’t notice. If I remember correctly you have to cut down a tap to get the threads deep enough.
Craig.

The Ultra Black cured and it runs fine once again. I have stainless sheet steel if I needed to cut a thin metal plug to a custom size. They are available new if you can wait a week. I typically cannot. All kinds of brass Dorman freeze plugs are sitting at the auto parts store if I need one immediately and am willing to cut it. Seems like I should go ahead and order a real set and keep it in the tool box with some quick drying gasket maker. I didn't even have a jug with me to fetch water. Now I do. Yes, the Nickels were cupped already. After the four mile run, the only leak under the engine bay was a fresh drop of oil.