Thanks again drgary. I was able to pull apart the electro hx block and it is exactly as you suspected.

The crack does go all the way through at that junction but it's not very deep. Water is coming in through that block from the pump but the stress crack is only on that outside corner of the threads so I don't think it's an issue. Nonetheless I would like to have it repaired but don't know where to start or whom to call to even attempt to braze it. I think it's superficial.

Thoughts ?

I would think the right way to fix that would be to have a professional braze it. Otherwise you have three fasteners holding the cap onto the seal on top of a pressure vessel. The existing crack may allow the machine to continue to run without a leak for now, but a gasket might fail to hold back a leak sooner than otherwise. Maybe I'm nitpicking, but I would want to see a permanent repair to that. Another option some might use would be silver solder. That requires more heat than regular soldering. If you tried to patch it with something like JB Weld I don't think you would have sufficient tensile strength across the hole.

Pro job due to tools and expertise required.
Grind out from the outside, clamp to tightly close the crack after chemically cleaning it and then either use a high strength high percentage of silver bearing rod or one of the high strength brass rods. This is a gas welding/brazing job.

Silver soldering is actually a brazing process and will hold this fine. The benefit of using silver braze is it operates at a slightly lower temperature in the brazing process. Finished repair will have to be re-tapped and it is metric. It is critically important to use the correct material for the replacement gasket so as to minimize the torquing requirements. Be sure that the material temperature rating exceeds the normal operating temperature by 50F minimum.

Thanks. Tons of sheet metal/metal fabrication/brazing companies near me but I doubt any of them would want to take on a small job like this. I could bring it to cerini's for sure and I'm with you DrGary I'd want it brazed/repaired at that joint.

At this point I'm not sure whether to abandon this project or not depending on how much brazing is going to cost. Anyone out there with a range of what it might cost? I can't imagine that it would be super costly. I'm thinking $100 to have it professionally repaired but I could be wrong.

Thanks for your input OldNuc and DrGary.

If I abandon I'll probably end up parting it out but maybe I can come up with a resolution with the seller of the machine but sometimes you can't catch everything until you start taking it apart.

Look at local weld shops, call and ask them. They may be willing to do this inexpensively. You may be able to tap it yourself.

Added: I also wonder whether there's another option, which would be to fill in the tapped hole with a hard and heat resistant material, drill and retap a hole into that material at the next smaller gauge? We are only looking at one of four holes that fasten down to a rubber gasket.

In any case I don't think the boiler is toast because of that one external crack on a fitting flange.

Thanks DrGary. Going to call some weld shops and will post what I find in case anyone in my area has the same issue.

Boiler is not toast but I think something like that probably should have been disclosed in a listing.

Ok shouldn't there be a seal between the hx block and boiler ?

No seal on bottom of hx block (electro block) either

I would leap to the conclusion that someone lost thee seal and then torqued on the bolts until something broke. In most cases you would find a high temperature fiber gasket with a large central hole and 4 bolt holes.

Post a picture of the face of the mating part and what it is supposed to look like will be apparent. That is clearly not a leak tight metal to metal closure.

The lower left bolt hole in your pix above does not look real healthy either.

Thanks OldNuc. I noticed the left flange as well. That has a hairline crack and with due time I suspect could have developed into something a bit deeper.

Bottom side