I changed the brake fluid on my 94 Integra twice in two weeks and have notice the same problem. Whenever I start the car, drive a few minutes, and step on the brakes, it goes all the way to the ground. But the brakes will be fine like 10 minutes later. The first time I did this, I thought I may had gotten air in they lines so I bleed it again(*till I saw no air bubbles in the line*), and still the same problem.

I follow the sequence to bleed the brakes: RR, LF, LR, and RF. Attached a hose with line, had my friend pumped the brakes till it was hard before I opened the bleeder valve to let the brake fluid out. Closed the bleeder valve while my friend had the brake pedal pressed and repeated the process. I never let the brake fluid go below the MIN line and made sure the lines were free of air bubbles before going to the next.

So what is the problem??????????????