Adventures in Hot Metal – Part 2

After all my hard work, it was time to pressure test the exhaust pipe!

I found some thick Playmobile toys that I though would work to plug the ends. I cut them out and drilled the appropriate holes. I then screwed in the air connection fixture for my shop compressor.


I fired up the compressor and tried it!


The plastic blocking plates and the vinyl shower pan liner weren’t even close to strong enough for a complete seal to 30 PSI, but even at slightly over 20 PSI, I could tell air was coming through the repair! Drat!

So after all my hard work, the part leaks. 😦 Ironically, I think I fixed the original leak pretty well, but the huge hole I blew in the pipe wasn’t sealed by the coil of stainless wire and very expensive SSF-6 silver solder.

The are two main problems with this otherwise brilliant idea. First it’s *very* hard to heat the thicker pipe (still pretty thin) without totally destroying the thin wire on top. Maybe someone better than me could pull it off, but I actually melted through the wire several times. Everything has to be evenly hot for the SSF-6 to do its capillary flow action to the right place. Second, the SSF-6 is $30 a rod, so while with proper heating it might be theoretically possible to seal the entire coil, it would super expensive.

So, back to the drawing board. This time using a carbonizing flame instead of a neutral flame (not as hot, better for brazing), I painstakingly re-melted the silver and pulled off the stainless wire in little bits. I then used a wire brush to brush off the silver while it was still liquid. My friend Tyler warned me that I might be compromising the stainless pipe’s corrosion resistance by using a mild steel brush, but 1) the parts of the pipe I’m re-working a shitload of times are already probably altered anyway and 2) I was only heating to the melting point of the SSF-6, which is 1150 o F, and not the melting point of the stainless.

After I got done with that, I sanded down the surface a bit with sanding cloth, especially to get the big hole level with the rest of the surface:

Sanding off the Bad Stuff                                     Not Perfect, But Better!

Next I cut a piece from a stainless hose clamp that was long enough to go all the way around the pipe with a little to spare. This collar will cover the big hole I blew into the pipe and was cut from a much longer clamp so there were no holes. I then used vice grips, pliers, and another hose clamp to gently form the collar into a perfect fit for the pipe. My intention was to try using the SSF-6 the same way that silver solder is used for joining copper pipes in plumbing. Note how I only covered half the collar with the hose clamp. I brazed the opposite end of the collar *first*, then I was going to move the clamp to the other side and do it again.


I fired up the torch, and was successfully able to get the SSF-6 to slurp into the gap! I let it cool down a bit, then took off the hose clamp. At first it seemed like the clamp had been successfully joined to the pipe, but a little bit of wiggling and it popped off. Shit!


The gap was too big, and I’m also guessing that there wasn’t enough flux inside the join. I should probably have brushed it with flux before putting the collar all the way on. You can see the shiny part where the silver did exactly what I wanted it to do, but it would have taken a *lot* more of the SSF-6 to get this right, so I decided to save what was left for fixing the pipe that’s still in the van. It has only a hairline crack right at the flange, and that’s perfect for the SSF-6’s capillary action.

Getting My Bronze On

It was time to learn how to work with bronze. I had originally though it wasn’t high temp enough for this application, but bronze’s melting point is actually much higher than the SSF-6. It doesn’t capillary quite as nicely, but it *can* be used to actually add material if done correctly instead of only flowing into tiny gaps. I had already picked up some flux coated bronze rods from Home Depot the day before, so I was ready. I had tried them the day before using my little propane plumbing torch, but it wouldn’t melt the rod even directly in the hot tip of the flame. It would have to be oxyacetylene again.

I put the collar and hose back in place over the hole and started again, this time with the bronze. It took some finagling, but I could already tell I was getting better with the intricate hand dance. I angled the work piece so that the bronze would tend to flow downward slightly into the join. I moved it when necessary to keep the working edge pointing upward. Here it is after the first go round. In this picture you can also see the original rip that started this whole process. I was fixed by the silver, but got un-fixed when I pulled the wire coil off.


This time it sealed a lot better! I took the hose clamp off, and it was still stuck on there!


I moved the clamp to the side I just brazed, and repeated the process for the other side. I also did a little dab-dab to seal one tiny hole I had made for the wire, the original tab tear, and the gap where the flange meets the pipe. I found that it was *much* harder to do this than to just get the bronze to flow. It would have helped more if I had oriented the workpiece so that it was perfectly horizontal to discourage the bronze droplets from running off.

Once everything cooled off, I did another pressure test, this time with soapy water. Success! No bubbles were visible on the repaired side!


This is all very crappy workmanship, I am a rank beginner, and I am desperately hoping that I don’t have to use this pipe in my van. However, I do *not* want to take the newer pipe, which *also* has a hairline leak where the flange meets the pipe, out of the van until I have a viable replacement. My plan is to remove the newer pipe, fix it now that I’m more competent and because it’s far less damaged and an easier repair, then put that same pipe in the same day.

Wish me luck!

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