MTFCA Forum

I was looking my T over yesterday and noticed that the left rear half of the engine block was wet. It has always been a little moist near the bottom and since it never caused an issue, I just left it be. This time however, it was the whole side, up close to the head. I cleaned off the moisture and waited 20 or 30 minutes and noticed that it was seeping from below where the headbolts mount amd above the 'open' cylinder shaped part of the block. I wire-brushed the area and found a crack about an inch and a half long! Im confused on how, and why it appeared. This winter it got quite cold, aout 10 or 15 below at its coldest, however all fluid was drained and the head was off while I was replacing the valves. I just recently got the head back in and filled the cooling system with 50/50 antifreeze and water. I ran the car and have left the coolant in the engine. It has only gotten down to the teens some nights so it did not get cold enough to freeze the coolant. I tested the fluid and it was fine. I plan on just patching it with JB weld, or some sort of epoxy. I plan on replacing the engine regardless hopefully sometime later this year.
My concern is how and why it formed. It is below the headbolts and they are the only thing that I can think of that might have caused it. The headbolts are new, same as the old ones and I checked the head to make sure they didn't bottom out without the gasket on.
Anyone have any ideas on what may have caused this?

Red mark is the approximate location of the closest head bolt. I can get more pictures this evening.

Probably was cracked by ice years ago.

That looks like an old crack to me. It was probably sealed off with with rust or paint or grease. Doing the head work and putting clean coolant in the engine probably disturbed the debris in the crack, allowing it to leak. Antifreeze will leak more easily than plain water. I'd clean it up and put a thin coat of JB KwikWeld on it since you plan to replace the engine soon. That crack could be stitched to make a permanent repair if the block is otherwise good.

People used to "rust up" cracks in cast iron water jackets by putting a chemical in the cooling system that promoted rusting. It could make a lasting repair in many cases.

i would clean the area well and then block off the lower water inlet and hook a shop vacuum to the upper water outlet ... apply vacuum and add either locktite weld porosity filler or simple super glue to the crack ... the vacuum will draw the sealer into the crack and give a very good long term seal ... DO NOT use a combustible cleaner if you are applying vacuum ... most shop vac. units will ignite the vapor ...this has worked well for me on several occasions , hope it works for you ...Gene French

I can pretty much promise you it's been cracked for a long time. You've gotten some good advice already. I'd say go with the solutions above and don't worry too much about it. Mt roadster has a couple of cracks too. Every so often I see a wet spot on the block. It never leaves a drip on the pavement, so I just ignore it.

Thanks all.
Im glad that it is probably an old crack that reopened. I have noticed that it is quite Rusty in the water jacket and I have been progressively taking chunks of rust out and flushing the system.
Hopefully, its been that big since it froze, and I dont have to worry about it getting bigger.

It CAN expand unless you "stop" drill each end of the crack !

You might want to just throw a bottle of "Bars Leaks" in, and see if it stops on it's own. You might never have to mess with it again, until you overhaul the engine. At that point you can get it weld-repaired, and be done with it. I agree with all the others that it is an OLD failure, perhaps 50-75 years. Bars-leaks is a fast, cheap and easy solution, if it works. Which it probably will. That is just a TINY crack you have there! My bet is if you throw a bottle of Bars-Leaks in, it will stop it right there.

It can be repaired permanently by metal stitching if you ever decide to rebuild the engine.
Only problem is that may not be the only crack on the block.
Example shown is crack in similar location along with others due to ice damage.
https://jandm-machine.com/crack_repair.html

RajoRacer is CORRECT.....You will need to clean it down to bare metal. Find the ends of the crack and drill a SMALL hole at each end. I prefer to take a STIFF, as in REALLY STIFF wire brush and rough up the crack and drilled holes. The holes with stop the crack from promulgating farther.

JB Weld IS epoxy with metal added for some strength. Since the epoxy is the strength member, I can NOT see how adding metal dust will strengthen it, but it will make it look more like metal.

The vacuum cleaner advice is good as long as you do not suck the JB Weld completely into the block. You want it to move just inside of the crack, so as to add "backing strength" and "holding strength", inside the crack. I have used a tooth pick to "push" the JB Weld in, with excellent results.

Good Luck

As mentioned use a SMALL drill and drill a hole each end of the crack, Wire brush it well and clean the area as best you can then coat the area with JB Weld. Use a small flat spreader such as used with body filler. That will press in the JB Weld. Remove the excess and recoat again. Let dry and that should take care of it. It will last as long as you own the car and thereafter.

An observation from an old hand on coolant. He suggested it should be called crackant. If there is a crack anywhere, crackant will find it.

I agree withe metal stitching it as a permanent repair. The best part is it is in about the most accessible spot there is to make the repair with the motor still in place. Just drive down to the shop and have done with it.

Allan from down under.

Flame spray welding works well on cast iron and is barely noticable. Since it out in the open you may be able to have it done without removing the engine.

Lock N Stitch. Like J&M says. Google it.
Not cheap but the best. Dan

Stitch it! Gotta be somebody local to you
that does it. My guy is in Milbury Massachusetts.

Hi Austin,
My first T had several cracks like that show up I think because the antifreeze seeped through the rust in the block. I used KW block sealer for
years to keep the cracks @ bay. when I had to rebuild the engine it was time to do something more permanent. Cleaned the block & head out
with Zepp Calcium, Rust & Lime remover ( that made it leak real bad ) When I drilled the ends of the cracks it became apparent that the block
was pretty thin & Lock & Stitch would not be a option. I ground out the cracks & filled with PB weld, ground it smooth & JB welded two
aluminum plates over the sides of the block. ( used to do this to repair broken kart race engines ) Then back filled the bottom after a couple
of days. that was 7 years ago so far no leaks.
Craig.

Really surprised noone has recommended the Famous Ultra Black!! My couple of patches are going on 10 years now and no seeping! What I found with the JB which I tried first is it's not flexible and started seeping after mnay heat and cooling cycles.. Now maybe there was an adhesion issue. Back then I didn't think of the vac trick. The Ultra Black or Right Stuff stays flexible and adheres Very well after cleaning the oily surface! A bit of paint and it's hard to see!

Professor Fate wrote: ↑

Mon Mar 17, 2025 7:55 pm

Stitch it! Gotta be somebody local to you
that does it. My guy is in Milbury Massachusetts.

Frank Casey Died in 2023, so I guess you'll be coming to us.

How's this for a crack ? Was forever weeping & the fella wanted me to see what was going on - found the cause !!!

Steve,
Did you fix it? And how if you did?
Craig.

No - it got scrapped. We have a really competent cast iron welder in Western Washington but couldn't justify the cost.

We are talking about two different things here - cracked or rusted through - and repairs might be different. If rusted through, you might have to go a long way to get enough purchase for metal stitching. In those cases, "temporary repairs" using JB or other epoxies may last a very long time. A shop here uses a special procedure that involves soldering the crack and he has had very good luck with that on cracks with good metal around them.

The cracked block above was soldered.

Rajo's block would make a good anchor for a buoy of small boat!
Norm

Steve that block could have been repaired fairly inexpensively. Cast CAN be welded one of two ways. Arc welded with nickel rod, implementing both preheat and post heating. The second way, in the case like your pictured block where rust is more the case. Preheat the cast and gas weld it. Brazing it using silicon bronze filler rod and post heat. The main factor to success is clean it well before and cool it as slowly as possible. Silicon Bronze will expand and contract at temperature very close to cast, thus making this an excellent way to repair cast. In the last 40+ years I have successfully repaired countless cast blocks, cylinder heads, and transmission cases.