By Staff
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This month, I’m passing on some varied advice from
contributors to the internet Stationary Engine Mailing List to
solve the problem of a cracked water jacket.

The initial question: We’ve had numerous discussions on
welding cast iron in the past. People that I know to be
knowledgeable have posted detailed descriptions on what to use and
how to use it. All that aside, I still don’t feel enough
confidence in my ability to tackle an engine. We’ve got a 6 HP
FM Z with a thin crack in the water jacket that extends from the
head back to the base directly below the cylinder. It’s
virtually non-existent when cool, but as the engine runs, a
steadily increasing stream of water begins to make its appearance.
It’s pretty bad after a while. Anyway, because it’s in a
high-stress area, I figure it will have to be welded. My problem is
that I haven’t had much luck locating someone in my area that
is experienced in welding cast.

And in response: For the last seven or eight years I have been
using a welding rod designed for dirty castings. No preheat, no
grinding or cleaning, no stress relieving, machinable (unlike Ni)
and it welds right through rust and dirt!!!

It takes a different technique but saves a lot of work and has a
higher success rate. I have had great luck with it. The rod is Weld
Mold 706the manufacturer is in New York but I get mine from a small
specialty weld supplier.

This rod seems to burn right through the rubbish. I have done as
much as six inches of continuous weld without trouble. The only
place I have had much trouble is right next to the exhaust valve or
on an exhaust manifold. The first pass always looks a little
bubbly, but just chip and brush and weld right over it. Comes out
smooth as satin. The results are the same color as iron and can
easily be drilled and tapped. I think the reason it works so well
is that the expansion and contraction of the weldment matches that
of iron. (Ni and stainless contract so much during cooling that the
weld pulls from the iron.)

The best cast iron rod that I have ever used is the Palco 808
rod made by Precision Alloy Company of Scottown, Ohio. They really
‘flow’ well and are easily machinable. You can use them to
weld steel to cast with good results (those of you that are
familiar with alloys know that this can be difficult).

The primary concern of welding such a project is the condition
of the metal. I’ll bet it’s rusty, thin, and most likely
will be difficult to weld.

I have used radiator repair epoxy putty successfully, I have a
particular patch on my car radiator that is going on four years old
and doing fine. It is on the top (hot) tank, and goes through a lot
of expansion and contraction cycles plus vibration. It cost less
than $3 for material, and it took about an hour to prepare the
crack and apply the stuff. Almost all the different brands and
kinds of patching materials available are all the same basic epoxy;
they add fillers, colors and perfumes to fool you into thinking
they are all different and unique from each other when they are
not. I would try radiator epoxy first, because it won’t keep
you from welding it later if it comes to that. As far as welding
goes, ask the welder to consider either Ni-Rod or a stainless steel
rod meant for thin cast iron sections, with a preparation of
grinding out the crack to a shallow depth. Follow the welding with
thorough peening of the bead to eliminate all stresses from

Depending on how big the crack is, you can open it up with a die
grinder and a cone-shaped carbide burr. Knead up a batch of the
epoxy putty as mentioned in the previous post. With the tiniest bit
of effort you can fill the crack, smooth it out and have a nice
smooth homogenous surface. It’ll set up in 10 minutes and will
take paint readily.

We used Araldite (epoxy) to repair the leaking water jacket on
my father’s A Model Ford about 20 years ago. We ground out a
groove where the block was cracked and filled it with Araldite.
Once it had set we ground it smooth with the block and painted over
it. The car has done a LOT of mileage (it has been ’round
Australia) and has had the engine rebuilt recently. We are still
using the same block we repaired all those years ago and it has
never leaked.

The heating and cooling on the water jacket is minimal about 200
degrees. Epoxies are somewhat plastic, allowing the expansion and
contraction of the metal, so I don’t think that’s a big

I have an engine with a crack in the bottom of the water jacket.
Several years ago I put radiator stop leak in the water and finally
the leak stopped and hasn’t shown back up for a few years

If you don’t want to or can’t weld it, metal stitch it.
This works as good or better than a weld.

Metal stitching is an old art of repairing cast iron before the
days of welding. Small holes are drilled along each side of the
crack and from side to side a slot is cut in. The side holes are
fairly close together, something like this:

At each end of the crack, a small hole is drilled through to
stop the migration of the crack.

The end holes are plugged and peened. In the side holes, a
bowtie or staple-like item is inserted and also peened in, then the
length of the crack peened to seal it. I’ve seen some of the
old big engines and compressors repaired this way and with
excellent results.

I have two cracks in my 6 HP Z on the bottom side of the head
that I vee’d out with a small dental grinder, cleaned very good
and put JB Weld in them. It is the engine I once used to pull a
molasses mill for two days, full rolling boil most of the time, and
never leaked.

In my reproduction copy of the McCormick-Deering operating
instructions, under ‘repairing water jackets,’ it says
‘Where the crack is a very small one, not over a thirty-second
of an inch in width, the patching can be done by means of what is
termed a ‘rust joint.’ Drain the jacket. Put a coat of
putty or tallow over the crack, being careful not to fill the crack
with it. Fill the jacket high enough to cover the crack with
salamoniac solution (salamoniac is ammonium chloride; one pound to
a gallon of water), let stand thirty minutes, drain, and run engine
five minutes to warm jacket. Stop engine, put solution back into
jacket and repeat process three or four times. If the crack is not
too wide, you will thus form a rust joint that will never

So there was a good variety of solutions to the original
question, and hopefully the outcome will be as positive as the
engine owner’s response, which follows:

Thanks to all who responded on and off-list concerning my
‘crack problem.’

Everyone seems to recommend an epoxy without hesitation, but I
still have my doubts in this case. I mean it is just below the
cylinder after all. Those of you who have a 6 HP FM Z probably know
that they do tend to get pretty warm.

Prior to posting my question I was concerned with the stress of
expansion breaking up the epoxy fairly quickly, but maybe not.
Perhaps I’ll try some of my favorite epoxy on the outside and
try to get a liquid epoxy settled into the crack from the inside.
I’ve just never had this exact problem before, so I’ll
defer to your collective judgment and give it a shot.

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