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replaced the brake master cylinder bench bleed it.... installed it did a brake bleed evacuated all the air from the system... pedal was firm...however....when I started the vehicle the pedal droped to the floor and is not firm whatsoever...is it possible I still have air the the system even though the pedal is firm before starting the car?...The idle revs fluctuate (250rpm) a little when applying and releasing the brake....could it be the brake booster?

any help would be appreciated?

CHEERS...