I found a way to independently test the bolts for leakage:



The results are in:



So it's confirmed. I somehow managed to destroy my brew boiler during a preventive gasket change. I have two other observations to corroborate this: the affected bolt is about 1 mm longer than the others, and sliding my finger inside the boiler, contrary to the two other bolts, I feel a depression at its position.

I now realize that when the nut cannot go further because the element flange is in contact with the boiler, then applying further torque actually unscrews the bolt from the boiler (despite the welding spot).

Let my experience be a warning to others...

Now that the problem has been identified, I can think of the remediation. Obviously I can buy a new boiler (which incidentally would also solve my thermostat issue). I see that Clive Coffee has it listed for USD 150.00 but is out of stock; I'll see if any Canadian retailer has it. Hopefully it would be under CAD 200.00.

But is there anything else that is worth attempting? Perhaps RTV silicone around the edges of the bolt? What are the chances that this kind of fix would hold up for the long run? I think I know the answer but I would still value your opinion...

There is maybe a way to repair it or at least a tentative, at your risk, but it require great attention to avoid any sealant to get in contact with the boiler water, or if you can find a NSF product is better....otherwise a new boiler is the simpler / faster / safe solution.
1) remove the screw...if possible.
2) reinserts the screw, just 1 turn, then apply, form the outer side of the boiler flange, some heat resistant thread locker sealant onto the screw thread and go ahead to screw in until the proper length is reached, if the sealant it works quick ( few seconds in some case) be sure you are fast enough.
3) let the boiler rest dry for 24 hours
4) good luck

Thanks @Giampiero -- I'll see how mobile is the boiler bolt, but without a bolt head, I fear damaging the threads if using a plier or wise-grip.

I was thinking perhaps using superglue and letting it drip in the bolt hole. I doubt this would flow all the way inside the boiler, and my hope is this would form a solid barrier. Then gain, thermal expansion might break the bond between glue and metal, especially after dozens of thermal cycles.

So as you said, a high-temperature thread sealant might be best, perhaps coupled with RTV silicon around the junction of the bolt and the boiler base.

I have little to lose at this point, so if it doesn't work I can look for a new boiler.

Are you able to turn it? Is the weld completely broken? I was imagining just a tiny crack, but if you can move the bolt, you can get it out of the hole. If the inside is smooth enough, you could possibly use a fibrous gasket around the bolt on the inside of the boiler, the element flange on the outside holding it tight. (I dunno, just grasping at straws, here). I am assuming that the bolt is just a carriage bolt, but it it has enough head to hold a gasket in place it might work.

JRising wrote:Are you able to turn it? Is the weld completely broken?

I just checked this and no, I cannot turn the bolt with a plier, and applying more pressure (e.g. with a wise grip) to hold it will probably damage the threads. Not sure how broken is the weld -- I'd need some sort of fiberscope / endoscope / inspection camera for that.

JRising wrote:I am assuming that the bolt is just a carriage bolt, but it it has enough head to hold a gasket in place it might work.

I don't think it's a carriage bolt, probably just a threaded stud in fact. The size of the depression (feeling with my finger) on the inside of the boiler seems to match the diameter of the bolt. So a washer inside would have been a good idea, but I don't think there's a head to hold it in place.

I'm also wary of introducing anything inside the boiler. I also kind of doubt that anything I do on the outside will hold for long, but I'll probably try something before ordering a new boiler -- if this is available anywhere.

If I had no choice but to try to repair it, I suppose I might try to drill out the leaky stud, thread the hole very slightly larger and fit it with a bolt from the inside on a fibrous gasket. Then swear a lot when it still leaked, then replace the boiler.

I wish I had a boiler in hand that I could study to give you any better advice, the idea of drilling out the old stud may be stupid, depending on how close it is to the cylindrical boiler wall. But if that drain plug isn't touching the wall, there could be room for a new bolt.

coffeedog wrote:I'm not sure if this applies but you can turn a stud by putting two nuts on the threads. Tighten them against each other and use a wrench to turn. Outside nut for clockwise, inside nut for ccw. When
done use two wrenches to separate the nuts. I may misunderstand but it sounded like you were using vice grips on the threads and for me that always ends in stripped threads and swearing.

Well, that's basically how I ended up unsealing the bolt in the first place. The nut was held in place (by the element flange), so the counter action was the bolt unscrewing from the boiler's bottom plate.

Thanks for the tip, I could try that. But I wonder if it has more chance to get sealed if I unscrew it completely, add thread sealer, and screw it back, or if I keep it as intact as possible and add a sealant from the outside.

JRising wrote:Then swear a lot when it still leaked, then replace the boiler.

I will probably end up like that even whitout having to drill out the bolt. That's a lot of metal to drill out, and the boiler itself is stainless steel, very hard as I found out trying to tap an M4 thread on the top. I won't go there with the bottom plate for sure, and I'm not equipped for that kind of work.

I thought of some sort of adhesive patch on the inside of the boiler, but having foreign material of any sort basking for a long duration in boiling drinking water seems like a particularly bad idea.

The only thing I can think of is to back out the stud if you can, wrap with high temp, potable water ptfe tape and reinstall. Otherwise new boiler.

Well I think this will be "new boiler".

I managed to get the stud out by using that trick (just tightening a nut around that stud).



However, the hole... has no thread:



So in my case, the stud was just welded on the inside of the boiler. I won't attempt to enlarge the hole, put a threaded insert, re-tap a new hole, etc. This is totally out of my expertise. The only way to correctly fix this would be to ask a metal shop to somehow separate (cut?) the boiler bottom, re-weld the bolt, and re-weld the bottom, and test for leaks. I don't think that will be competitive with buying the part though.

I'm now looking for a new boiler. IDC have one in stock, but it's quite expensive (CAD 342.89). I've begun to ask around to see if any other Canadian shop has a boiler in stock.