I have a 95 Accord with abs. Brakes were sinking during stop and only occasionally, but never great. We've only had a few months and I just started driving while my Civic was in shop. The brakes on the Accord finally started going to floor completely, so booster was replaced. And bled twice. Then MC replaced. Brakes work now, but pedal isn't hard. Goes about halfway. 3rd day since MC and 2nd bleed from that, and pedal is slowly starting to sink when stopped at a light. Not enough to move car yet, but I'm afraid it's coming. Car was never losing brake fluid, but now both parts have been replaced and bled 4 times by mechanic. What in the world? Please help. Booster was off wrecked car and MC from Auto Zone. This is supposed to be my back up car, but right now is my only.

 

As far as I know the only way the pedal should sink is either because of a leak, or bad master cylinder. I would bring the MC back to Auto Zone.