Sometimes, when you push the piston outside of it's normal travel range, crud, scratches or ridges within the master will damage the seals.
Scott
How true that is! And depending on how the lines were run it becomes almost impossible to get the air out with just the volume of oil created by using the master cylinder. I always hook a vacuum up to the bleeder an suck the air out and oil through the lines. Then finish with just a couple pumps…….
