Am I imagining this or did I read a post about a insert to cure AN fitting seapage? I did a fruitless search and now I'm starting to think it may have been a wishful dream.
there are tin (very thin) seals that go on the fitting usually on the larger sizes. Just a note here do you have the right flare angle on the tube & is there damage to either the tube or fitting? These should be able to withstand several thousands pounds of pressure.
I bought a 37 degree flaring tool and practiced. I learned that cutting the tube can work harden ss and cause splits in the flare. I learned that over tightening a pipe fitting into a through frame fitting can split it. also know how important it is to have a square cut. I learned that ss tube can gall the seat on fittings and cause leaks. I even played with trying to anneal the tube. I have the car plumbed now in ss but can't seem to cure one place that gets a drop on the line. I built a couple of my race cars with aluminum lines and fittings which are unbelievably ez to use but just couldn't bring myself to use on the street. Next project will either have mechanical brakes or steel lines.
I buy used AN fittings from NASCAR teams on E-Bay...MUCH CHEAPER! They're kinda rough sometimes... Sometimes the cone is out of round or have a nick in it. Use a Center punch or driver...anything with a nice taper on it. Tap it in the center of the cone (flare it out / make it round) It's worked great for me!
You can try a couple of things, make sure the surfaces are clean. If there is any damage take some really fine sand paper and polish the nicks or scratches. If all else fails try Racer warehouse for your fittings, I only use Aeroquip ! Never had a leak.
Are you using steel fittings? Years ago, when most fittings were aluminum on aluminum or steel on aluminum, conical seals were never required. A conical seal places a soft surface between our two hard sealing surfaces. This soft material deforms and fills in the voids.
A do it yourself remedy is to make a 37* flare on a copper tube. cut off the flare and file it size like the store bought insert in the picture above. First thing to do tho is to inspect what you have and make sure there is good seats and fix it gently if it's bad. The best thing for good connections is using steel fittings and nuts and inserts. Mcmaster-Carr sells them in the sizes we use for brakes -3 and -4. We have had a lot of issues in the past with the alluminum stuff on race cars and now use steel componants with the stainless steel brake lines.
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