No breaks

a couple of weeks ago my beaks started loosing pressure. the pedal would go all the way to the floor and nothing would happen. i could pump them hard again but a second later the pedal would again hit the floor. i was informed that the problem was more than likey the master cylinder so i changed it. spent about 3 hours bleeding the breaks and still nothing. i can't see it leaking anywhere.
have it booked into my local at the end of the week but i was just wondering if anyone has experienced this before.
it's a S7 STI.
i'd appreciate any help

sometimes when bleeding a cars breaks you need a machine its a vacuam and pumps fluid in so loses no presser when opening one of the nipples not much help but i would say this is y still no breaks if your master cylinder was gone

i brought it into the garage yesterday and they haven't got it completely figured out yet but the recon theres a problem with the hub and it's pushing the pistons out of place when the disc is spinning and thats why it takes a couple of pumps to get them back into place.