118d - Weird brake fault? - Benjamin Knight

So I'm hoping someone really kind could advise me on this, I have a 59 plate 118d which I was driving and started to smell a burning rubber smell it was the pad so i got a new caliper from a reputable BMW breaker. After having the caliper fitted my brakes are now soft to the floor unless pumped? Was told mechanic had manually bled the system 3 times and was determined there's no air in there? Can anyone advise I would be very thankful.