So I just can't seem to bleed the damn rear system. It’s on my 2000 748. I've used a mighty vac bleed tool, it works @ first, but after 30 minutes or so its flat again, lever goes all the way down with no brake engagement. I've even taken off the caliper and held it up in the air while bleeding and same result. I don't see any evidence of the caliper leaking oil or any other signs of leakage. Anyone else have this issue?