Hydro's generally can have 3 functional issues (i.e. not related to pad or fluid contamination) and if no leaks are present: Bad bleed, ruptured brake line, or blown master cylinder piston.
It's easy to test for all 3 in one go. Hook up an overflow bottle (syringe without a plunger will suffice) to the master cylinder with the MC in the bleed position. Insert a pad spacer/bleed block at the caliper, slowly pull the lever. Watch the fluid rise up into the overflow as how it behaves tells you what you need to know. If the level spikes up consistently with no engagement, likely a MC piston. If the height that it rises decreases with each lever pull, likely a brake line issue. In both of those instances, the lever will travel to the bar as long as it's pulled slowly. It may begin to engage if you pump it fast. For the final scenario, if minimal to no fluid rises up but the brake engages then it's likely a bad bleed. If you want more info, PM me and I'll be happy to break down the why's of it.
Aug. 29, 2018, 7:37 a.m. - JT
Hydro's generally can have 3 functional issues (i.e. not related to pad or fluid contamination) and if no leaks are present: Bad bleed, ruptured brake line, or blown master cylinder piston. It's easy to test for all 3 in one go. Hook up an overflow bottle (syringe without a plunger will suffice) to the master cylinder with the MC in the bleed position. Insert a pad spacer/bleed block at the caliper, slowly pull the lever. Watch the fluid rise up into the overflow as how it behaves tells you what you need to know. If the level spikes up consistently with no engagement, likely a MC piston. If the height that it rises decreases with each lever pull, likely a brake line issue. In both of those instances, the lever will travel to the bar as long as it's pulled slowly. It may begin to engage if you pump it fast. For the final scenario, if minimal to no fluid rises up but the brake engages then it's likely a bad bleed. If you want more info, PM me and I'll be happy to break down the why's of it.