When it comes to building stainless steel braided lines with aluminum hose ends, it’s a polarizing task. Some love doing it, and some hate doing it. While we fall into the former camp, we recently ran into some real-world struggles while helping out with a project for one of our sister magazines. We were building some PTFE AN lines for the fuel system of a Chevelle on the car when our typical “engine dyno privilege” popped up.

See, here at EngineLabs, we typically have the luxury of building our lines on the bench in the shop and simply turning around to fit them, since the engine is sitting on a stand right there. Once at the dyno, a leaky fitting is no big deal, as we can easily fix it and get back up and running in minutes. However, in the real world, on our backs under the car, running lines from the tank up to the engine, we realized that a leaking assembly could result in hours of work just to get at the offending fitting.

While a leak is rare for us, it does occasionally happen, as we’ve seen at the dyno. It can be a poorly assembled fitting, a non-concentric flare (male or female), a loose swivel assembly, or even a cracked fitting that causes a leak, but as with anything made by a human, stuff happens. There are a variety of fixes to all those problems thanks to products like the Koul Tools hose end assembly tools, the P-51 Sureseat female flare lapping tool, and the Fitting Fixer male flare lapping tool. However, the fix might be easy, but in the real world, getting to the fitting to fix them can be an arduous task.

So, with that in mind, we decided it would probably be best to actually pressure test each fitting before installing the line into the car. How, you ask? With a little thinking and a quick order from Summit Racing. Our first attempt was to cobble some brass fittings together from the plumbing aisle of the local hardware store, only to realize that none of the plumbing flare fittings fit a -6 AN fitting properly. The 1/4-inch MIP fittings thread in, but don’t have the proper flare (so don’t try to just crank it down; you’ll wreck your AN fitting that way).

With that, it was off to Summit’s website, where we ordered an Earl’s Performance -6 AN male plug fitting and a -6 AN to 1/4-inch NPT adapter. In fairness, we were already making an order for parts, so we just added them to the cart on that order. But, either way, they arrived in a couple of days, and we assembled our new pressure-testing rig.

To be fair, “assembling” is a bit of a stretch. All we did was thread the 1/4-inch NPT adapter into a brass female air-hose quick disconnect fitting we had lying around with a little Teflon tape, and that was it. From there, we set the air compressor to a mild 80 psi of tank pressure and then capped off one end of a line, threaded in our quick-disconnect assembly to the other side of the line, and plugged it all into the air hose.

Here is the setup installed. The plug goes into one end of the line (left), while the quick-disconnect fitting with the AN adapter screwed into the other fitting (right). The line is then plugged into the air hose to pressure test.

From there, we learned a couple of tricks. First, you can’t just listen for leaks, because our quick-disconnect has some slop in it, and hisses a little bit. Our first attempt to check used soapy water sprayed onto the fitting to look for bubbles. The problem with that is two-fold. One, you make bubbles in the solution when you spray it. Two, on the side with the quick disconnect, the leak was enough to blow onto the fitting and make bubbles where no actual leak existed.

The solution we came up with was highly technical: full submersion of the assembly at a static internal pressure in a translucent observation vessel containing a dihydrogen monoxide solution… We dunked it in a glass of water. Not only did that method make it extremely easy to see whether there was a leak or not, but it was also readily apparent where the leak was coming from (like when we didn’t tighten the plug). Another benefit to the water test, was that we were able to easily submerge the ends of the hoses that were already run and mounted under the car by simply using a pub glass.

While this won’t prevent 100 percent of potential leaks in the system, we know for sure that not only are none of our AN line fittings going to leak, but that our assembly of the hose ends onto the AN lines is rock-solid as well. Not bad for less than the cost of a trip to Starbucks.