Quote Originally Posted by Benson View Post
Re-bleed the brakes properly... sounds like there is still air in the system
If the problem is caused by an internal MC leak, then bleeding the brakes will make zero difference (unless you also happen to have air in the system). A pedal that sometimes sinks slowly to the floor and sometimes doesn't doesn't sound like air in the system to me. Brakes that need bleeding have a soft / spongy pedal, but it doesn't usually go all the way to the floor unless there is quite a lot of air, and it's usually consistent, not inconsistent as the OPs problem seems to be...