[Land-speed] Brake Question

[Dick J]

After fifty-plus years of playing with old cars, it would seem that I should have more answers than questions, but here goes, another stupid question.  
   
  I decided that while the motor was out of my car (77 Pontiac Firebird), I'd detail the engine compartment, and replace both of the old, bent-up front brake lines.  When I got ready to bleed the front brakes, I removed the bleeding nipples to clean them up a bit, and noticed bubbles streaming out of the caliper fitting.  After a moment, the bubbles stopped and a solid flow of fluid started leaking out.  I screwed the nipples back in and snugged them down.  I checked the master cylinder, which had just been filled, and the front bowl was about half empty.  I topped it off, got into the car to feel the pedal, and the brakes were fine.  The system had "bled itself" ? ? ?  
   
  I've done that with hydraulic front disc brakes on motorcycles before, helping along by tapping on the brake line, but I've never had it happen with a car.  
   
  Any comments??
   
  DickJ
  In East Texas

  
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