The only time I've ever experienced what you are describing, besides being a defective master cylinder or air in the brake lines, is when one of my front pads wasn't properly seated in the caliber assembly. The brake pedal had too much travel after bleeding the brakes.
Upon further inspection I found the problem, replaced the pads, and since then the brake pedal has very little travel.

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1993 190E 2.3
2001 SLK230
1971 LS5 (454) Corvette Convertible