Brake Master Cylinders
After a brake master cylinder was installed, the technician was unable to bleed the brake system. Fluid pulled from reservoir would return to reservoir through the same line as the internal bypass was not functioning properly. Master cylinder was disassembled and bypass was found stuck and unable to move. Metal shavings were found inside, and an O-ring was torn, with black specks mixed in with the shavings. Part replaced with new master cylinder.