VW_OwneR_85 2 Posted April 30, 2013 is there a way to know 100% that the master cylinder seals are gone? my brake system was dry as i re newed the rear brake pipes, i have pure clean air free fluid at all bleed points , 2 on the pump , 1 on the master cyclinder and at all four wheels, yet the pedal is spongey as hell! also abs pump seems to be makeing an unusual noise upon start up which it didnt do before so im thinking maybe theres still air trpped inside? but if theres pure air free fluid at the bleed skrews what more can i do? cheers. Quote Share this post Link to post Share on other sites
16VG60 1 Posted April 30, 2013 If your master cylinder seals fail then your pedal will sink under pressure as fluid will be blowing past the piston seals. To test the cylinder you can detach the brake pipes and replace with bleed nipples into the pipe ports onto the master cylinder. Bleed the cylinder of air and the depress the pedal. Your pedal should be solid and hold position under full pressure. Quote Share this post Link to post Share on other sites
VW_OwneR_85 2 Posted April 30, 2013 (edited) i like your thinking!! blady good idea that, i drove it down the road with caution and it does stop with only one push needing to stop, if fluid was to pass the seals you would need to pump the pedal several times right? so maybe i just need to bleed it some more although i think i have enough , also i have a sealey vacum bleeder but its letting in air at the nipples im guessing thread tape is the only solution to fix this? thanks very much p.s the system was bled useing pedal method with caution, Edited April 30, 2013 by VW_OwneR_85 Quote Share this post Link to post Share on other sites
VW_OwneR_85 2 Posted May 1, 2013 right! think i can rule out the master cylinder seals as the pedals realy firm when ign off and doesnt loose any travel if held down , i have bled some more fluid useing a sealey pressure bleeder, works an absolute treat!! imo better then the vacum bleeder as that just sucked in air from the bleed nipple threads aswell as fluid from the system, abit of air came out from the front right caliper but i ran out of fluid so i cant finish it off this evening :( but the abs pump no longer makes that noise upon start up! so i think i just need to bleeed more through the fronts :) cheers Quote Share this post Link to post Share on other sites
