June 28, 201511 yr Just taken my front disc off for the first time (bought the bike used) and found some silicone around each of the bolt spacers. Would this be to stop squeak/vibration? Basically I went to take my bike out yesterday and found my front brake had no pressure at all even though it was fine when I last rode it a few weeks ago. So I bled it out but in the process the hose popped off and spilt fluid on my disc and pads! So, had a go at them with some wet and dry but they are squeaking real loud and not gripping so I got in a mood and ordered a new disc and a set of pads. So what can I check when rebuilding with regards to the fact the whole system just lost pressure and also should I be adding silicone to the disc bolt spacers again? FYI the brake was super strong before it lost pressure.
June 28, 201511 yr Author While on the subject what's the best method of bleeding the front using a syringe? Pretty sure I've don't it OK but never hurts to see what other people are doing.
June 28, 201511 yr Author No I've not found the issue yet and yes good shout about sorting the system with the old disc and pads in I'll definitely do that. Just checked the bike and its still heing pressure from when I bled it yesterday, going to be pretty hard to diagnose a leak that only sometimes leaks.
June 28, 201511 yr Author One thing you could try is to put paper towel around the caliper and master cylinder and cable tie the brake lever to the handlebar so the system is under load. Leave it overnight and check the paper for any signs of a leak the followng day. When you noticed the problem was there any fluid on the floor or on the bike anywhere? Also did you notice if the reservoir level had dropped much? That's a good idea, didn't notice any oil no as my garage is carpeted so the carpet would have soaked it up also reservoir was pretty full tbh.
June 28, 201511 yr Author OK, have cabled tied the front brake on tight and covered all the hydraulics joints with paper towel, will check on it again in about 20hrs from now.
June 28, 201511 yr Depending on year/master cylinder type, some used to have a poor finish to the master cylinder bore ports, the rough edge would cut the seal, the fluid would by pass the seal so would not build pressure, there would also be no leaks externally. I've had a few occasions after dropping a bike the brake or clutch become inoperative due to me pulling either lever when picking the bike up, this was because the fluid was below the inlet port so only gulped air into the system.
June 29, 201511 yr Author Depending on year/master cylinder type, some used to have a poor finish to the master cylinder bore ports, the rough edge would cut the seal, the fluid would by pass the seal so would not build pressure, there would also be no leaks externally. I've had a few occasions after dropping a bike the brake or clutch become inoperative due to me pulling either lever when picking the bike up, this was because the fluid was below the inlet port so only gulped air into the system. It's a 2012 with AJP master cylinder, that likely to have that issue?
June 29, 201511 yr Author OK it's been pressurised for over 22hrs now and no leakage anywhere?! I guess all I can do is fit my new disc and pads when they arrive and see what happens.
June 29, 201511 yr Dont see a reason to replace the disk. I would try a new plunger, these wear over time and is an easy fix.
June 29, 201511 yr Author Dont see a reason to replace the disk. I would try a new plunger, these wear over time and is an easy fix. TBH I got annoyed with it honking so just saw red and ordered a new disc and pads. By plunger which bit do mean?
June 29, 201511 yr Author I mean the part that pushes the fluid, inside the master cilinder. Awesome thanks.
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