blackrandomapple Posted May 28, 2009 Report Share Posted May 28, 2009 Hello, Im looking for some big help here, My bro's bike has had a spongy front bike since he had it, i i though i would take caliper of and do the usual strip down rebuild kinda thing! Im still in the garage 5 hours later. The brake is now worse than when i started but i just can pinpoint a problem! So far i have: Striped and rebuilt caliper, Unstuck pistons Clean all holes Bled brake with no syringe Bled brake with syringe Bled from top Bled from bottom I have even striped it all down and rebuild it on the bench, once with caliper highest and once with lever highest!!! Brake worse than when i started......... rrrgghh Really what could be the problem here, It was working ok ish before i started so im sure all parts are working?!?! Help Quote Link to comment Share on other sites More sharing options...
sdeane01 Posted May 28, 2009 Report Share Posted May 28, 2009 Could be the seals in the master cylinder. Or the issue could be with pads or the disc. Quote Link to comment Share on other sites More sharing options...
blackrandomapple Posted May 28, 2009 Author Report Share Posted May 28, 2009 Could be the seals in the master cylinder. Or the issue could be with pads or the disc. i think i can count the pads and disc from being the problem because the pads are really good and the disc seems ok, also not sure that this would cause it to be spongy! even tho im sure it is bled properly i can still pull the level all the way in no matter what adjustaments i make on the lever?!? would master cylinder seals cause it to be spongy? and would they leak if they were gone?? Quote Link to comment Share on other sites More sharing options...
b40rt Posted May 28, 2009 Report Share Posted May 28, 2009 How old is the brake fluid that your using ? Quote Link to comment Share on other sites More sharing options...
blackrandomapple Posted May 28, 2009 Author Report Share Posted May 28, 2009 How old is the brake fluid that your using ? Its pretty old a think, maybe 2-3 years lol, I just been back out to the garage (again) And i took the seals out from the master cylinder and gave them a clean, There is a def improvment but still a little spongy! i wont be able to test performance till the morning! Dam its 11:30pm Quote Link to comment Share on other sites More sharing options...
axulsuv Posted May 29, 2009 Report Share Posted May 29, 2009 If you can pull the lever all the way in , like you stated , and there are no external leaks , the master cylender is bypassing internally . Get some new rubber bits for the master cylender and some new brake fluid and you'll be fine . And if Brake fluid has been laying about in a opened container for more than a week or two , throw it out and get some from a sealed container . Brake fluid is very hydroscopic (absorbs moisture ) and old brake fluid will corrode the bores in the hydraulics . Fresh fluid is cheap insurance ... Glenn Quote Link to comment Share on other sites More sharing options...
blackrandomapple Posted May 29, 2009 Author Report Share Posted May 29, 2009 If you can pull the lever all the way in , like you stated , and there are no external leaks , the master cylender is bypassing internally . Get some new rubber bits for the master cylender and some new brake fluid and you'll be fine . And if Brake fluid has been laying about in a opened container for more than a week or two , throw it out and get some from a sealed container . Brake fluid is very hydroscopic (absorbs moisture ) and old brake fluid will corrode the bores in the hydraulics . Fresh fluid is cheap insurance ...Glenn Ok im off to bvm this morning before work to buy a master cylinder seal kit. Is it worth me getting a new piston set on sale or return or is it def gunna be matser vylinder Quote Link to comment Share on other sites More sharing options...
blackrandomapple Posted May 29, 2009 Author Report Share Posted May 29, 2009 This is atatring to anoy me know, Bought new pistons and master cylinder seal kit, I have even tried new discs and pads! The brake does work now put its very poor, 3 fingers are needed to stop, Quote Link to comment Share on other sites More sharing options...
copemech Posted May 30, 2009 Report Share Posted May 30, 2009 (edited) This is atatring to anoy me know,Bought new pistons and master cylinder seal kit, I have even tried new discs and pads! The brake does work now put its very poor, 3 fingers are needed to stop, So if you have good lever pressure now, just poor stopping ability, take your liter bottle of water with you, go run down the street and back making a couple of good hard stops with the front from 5th gear to warm up the rotor and pads, then quickly douse the disk with the water to shock cool it. Do this a couple times, then resume normal operation or let set a bit. Try it again later and re- douce it if needed. New pads need to thermo cycle a bit to firm up, and disk need a good steam clean. Edited May 30, 2009 by copemech Quote Link to comment Share on other sites More sharing options...
axulsuv Posted May 30, 2009 Report Share Posted May 30, 2009 Copey ; Do you mean like burnishing the pads to ensure 100% surface contact ? aka a serious test drive ... Glenn Quote Link to comment Share on other sites More sharing options...
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