W204 c250 cdi brake pedal hits the floor

[Redfaced]

I've just had all my brake lines replaced as I had a leak (brake pedal was still hard) and now I've got it back the brake pedal is very soft and hits the the floor. They used a pressure bleeder to change the fluid. What's happened here? I have a fault regarding brake vacuum before this but as far as I've found out that only effects stop start. The pedal also makes a feel feeling/vibration when pressed padr a certain point ( about 80%) that feels like air squeezing/bubbling past something. Also the airbag light is now flashing. Can anyone shed some light on this before I start complaining, have they damaged the master cylinder?

 

[Redfaced]

I will like to add that when engine is off the pedal Is rock solid, pedal only goes soft after the engine is running

 

[AlanGunn]

Who did the work.
Can't you take it back to them.

 

[brandwooddixon]

Master cylinder seals could be an issue, if the brake pedal sinks to the floor when pressed.
As regards the flashing light and the vibration, are you certain that it's not the ABS cutting in? Airbag light should come on and then go out when the ignition is first turned on.