This post might be on the longer side but I like to provide the background leading up to my question/concern. As always, would appreciate any guidance and advice. Particularly since brakes are not something I feel I should be careless about.
A couple months ago, after considerable research through threads and posts in the forum I decided to run my plumbing with stainless steel tubing and with AN single flares. I understood this was a "delicate" process that had to be done right, so I got the right tools and material (soft-annealed, seamless, 0.028'' thickness) and made sure to DM some of the SS experts in here to check that I was doing my flares correctly. During my bleeds there were no leaks, if I rolled the car and hit the brakes it would stop, and I could slam on the brakes hard and no fitting busted open. Still, I left paper diapers under every fitting and every time I worked on the car, I would pump the brakes a bit to keep testing.
Here is where it began to become somewhat frustrating. Weeks would go by where I would hit the brakes and rub pieces of paper against the fittings and all clean, but then on seemingly random days, one of the diapers showed a tiny brake fluid stain. I was stuck in this cycle of tightening, loosening, re-tightening, bleeding, testing, days without any weeping, and again at random, one day I'd see a bit of brake fluid when rubbing the fitting with paper. I re-did that problematic line 3 times. Thankfully it was the shortest of my SS lines and without any bends. The last time I tightened more than I believed it was recommended and that seemed to have stopped the issues but given the randomness of when I would find the fitting weeping a bit, I realized I needed a more reliable test.
I followed Mike Bray's procedure to modify a cap for the brake reservoirs and hooked it to a Motive Power Bleeder, that way I can pump it to something like 10 PSI and force any leaks to show themselves instead of waiting, as well as checking if the pressure drops. Here is where it gets confusing. My first day, I find that for both front and rear brake systems, I'm dropping around 1 PSI every 9 to 12 minutes. I finally find some fittings actually wet, so I tighten those, and I rub paper on all fittings and found small weeping in one of the master cylinders and then on 2 different bleeder screws (not the nipple where you bleed but where it bolts to the caliper) of the Wilwood brakes. I decide to get an AN cap to seal one of the lines that kept giving me issue, to try to find if the problem was my flare on the line or if the surface of the T fitting was compromised. I re-do my tests, I find absolutely no leaks or weeping on the rear brakes, and yet I'm still dropping about 1 PSI every 9 to 12 minutes. I suspect that the Motive is leaking somewhere, so I created a little jig with the problematic line. I cap one end and hook up the other directly to the Motive Power Bleeder while all the connections are underwater. The first time there were plenty of bubbles, so I tighten everything until I get no bubbles. However, I still got about 1 PSI drop in 11 minutes. Seems that this Motive Bleeder will always have that pressure drop, the leak must be in the bottle's pump or where it connects to the vinyl tubing since I had every other connection underwater.
What confuses me is, what about those micro-leaks/weeping that I found when I pressure-tested the lines on the car? I re-did the tests, rubbed paper against the fittings, and again found nothing on the rear brakes, and micro-weeps if I jammed the edges of paper into the fittings, but still for both between 1 PSI drop between 9 to 12 minutes. If I test the one with the micro-weeping with soapy water, no bubbles are created. As I mentioned in the beginning, I don't want to be careless with the brake system but I don't know what else to do other than continuously re-doing lines until there are no micro-weeps. Even if the Motive Power Bleeder can't maintain pressure for more than 10 minutes, if anything in the actual lines had a leak, I should be dropping pressure faster. Is this acceptable? Can I continue? The bleeder screws and master cylinder didn't weep these last few pressure tests, not sure how they "fixed" themselves. My next step is to get a pressure gauge and test on every caliper if I'm getting +1000 PSI when I slam on the brakes. Would these two tests combined provide enough proof of a brake system that will stop a car at any speed? I feel the answer is "nope, there can't be anything wet at all, re-do this".
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Brake Lines - Testing & Issues
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