Brake pedal to the floor

[rikgerards]

After overhauling the master brake cilinder of our GMC we have the problem that the first push of the brake padel goes to the floor.

Brakes are bled, reservoir is full, only the first stroke goes to the floor, the second push brake feels good. After releasing the brake padel and waiting a few seconds the brake padel goes to the floor again.

Any sugestions what cloud couse this problem? No alternations where made in adjustment screws. Onley seals, and spring are replaced.

Thanks for you help,

Rik