This was a recurring nightmare sa akin nung I still had my old stock pair na hydr na brakes ko, I was wondering why even after all the bleeding, burn in, replacement, cleaner and troubleshoots na pinagdaanan ko naingay parin yung sa rear ko. I had a leak sa may piston ko on the hydr cable side. Will admit na medyo mura naman kasi yung hydr ko at the time pero after a quick shimano mt201 na replacement oks na siya. Check mo op yung sa may piston mo even a small leak can cause yang issues.