I put new brake pads in my MTB and when I went to test the front brake it completely failed. I then noticed brake fluid had leaked from the master cyclinder. As it turned out the bleed plug thing had some how fallen out. I did not touch the master cyclinder at any point. How is it possible for the bleed plug (or what ever its called) to fall out?
How the hell did that happen?
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Cameronmu917772
Well-Known Member
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- Fife
Did you pull the brake leaver when the pads were out?
Not that I remember, I have no reason for doing that. How would pulling the brakes without the pads in cause this?
Cubist
Still wavin'
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- Ovver 'thill
Hasyour missus been checking your life insurance recently?
mrandmrspoves
Middle aged bald git.
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- Narfuk
If you are referring to the bleed nipple it is hard to imagine it unscrewing itself and coming loose - but it is possible that it fractured and the end snapped off. IF it is just slightly loose you can easily bleed the system and re tighten.
Cameronmu917772
Well-Known Member
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- Fife
More pressure than required going through your calliper will cause it to want to escape some where. Although your bleed nipple should hold that pressure. I have looked over your post a few times and struggle to understand what has happened my self. If you had fluid leaking from the master cylinder ther should be good reason for this. Burst seal or damage? The bleed nipple it's self is screwed in befor it becomes air tight. And a fraction of a turn the other way would cause it to exspell all of the excess air in the system along with fluid. So your brakes would of failed before you changed them. In all honesty man it seems totally weird from your description. If you can upload a pic it may help. Or let us know what make and model it is you are running?
Cubist
Still wavin'
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- Ovver 'thill
He means the bleed port on the lever reservoir as far as I can tell. I have no idea how it could work loose.
I like Skol
A Minging Manc...
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Simples, I am Sherlock Holmes AICMFP 
It's something I have done with cars a couple of times over the years. Brake pads are low so pop them out, squeeze back the caliper pistons to make room for the meaty new pads plus a couple of mm working space.... Bingo, brake fluid is leaking out of the filler cap and running down the servo and bulkhead. This is due to the fluid being topped up between pad changes in a car but on a bike it may just be down to fine tolerances/small capacities. I'd take a wild stab and guess maybe the OP was working on the bike upside down? The filler plug was probably never tight and until it was put under some pressure or the bike turned over it didn't matter. The fluid from the caliper has to go somewhere when you fit new pads.
It's something I have done with cars a couple of times over the years. Brake pads are low so pop them out, squeeze back the caliper pistons to make room for the meaty new pads plus a couple of mm working space.... Bingo, brake fluid is leaking out of the filler cap and running down the servo and bulkhead. This is due to the fluid being topped up between pad changes in a car but on a bike it may just be down to fine tolerances/small capacities. I'd take a wild stab and guess maybe the OP was working on the bike upside down? The filler plug was probably never tight and until it was put under some pressure or the bike turned over it didn't matter. The fluid from the caliper has to go somewhere when you fit new pads.
Simples, I am Sherlock Holmes AICMFP
It's something I have done with cars a couple of times over the years. Brake pads are low so pop them out, squeeze back the caliper pistons to make room for the meaty new pads plus a couple of mm working space.... Bingo, brake fluid is leaking out of the filler cap and running down the servo and bulkhead. This is due to the fluid being topped up between pad changes in a car but on a bike it may just be down to fine tolerances/small capacities. I'd take a wild stab and guess maybe the OP was working on the bike upside down? The filler plug was probably never tight and until it was put under some pressure or the bike turned over it didn't matter. The fluid from the caliper has to go somewhere when you fit new pads.
That sounds the most likely. My bike was indeed upside down and I also did have the brakes bled and topped up a while ago. Its one of these that popped out the master cylinder:
http://www.chainreactioncycles.com/hayes-master-cylinder-bleed-plug-hfx-9-so1e/rp-prod20129
My brake is the Hayes s01e. To make room for the new pads I had to adjust the brake piston using a hex wrench.
Cameronmu917772
Well-Known Member
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- Fife
Yeah that works for me
lpretro1
Guest
Its nothing to do with bike being upside down or otherwise. It is not uncommon for the Hayes HFX9/Sole1 brakes to shed the bleed plug for no apparent reason. We have seen this several times in our workshop. Even on brand new bikes. It is a really bad design as it simply pushes into place unlike most brakes which have a proper screw in plug. In one instance it happened by leaving a bike in the sun so the fluid heated up and it popped out, another was left in a hot shed - same result, another was a brand new bike on it's first outing just shed it and the poor lady riding it hit a tree - unhurt if a little shaken. Personally I'd ditch them for that very reason.
I like Skol
A Minging Manc...
- Location
- Sunny Ashton-under-Lyne
People don't normally bleed or otherwise work on the braking system of their cars while they are resting on their roof! It's simple, the air will rise to the top. This should be the reservoir but, if it is all inverted then this is the caliper, and air in the caliper is not good.
Managed to obtain the parts needed and bled the brake. The brake is now working brilliantly (for now). However the instructions that came with the bleed kit said to clean out the syringe and tube by sucking in and forcing out warm soapy water. After this it said to take apart syringe and leave to dry. I never bled brakes before but wont this leave some sort of residue inside the tube and syringe?
It's good to read all this stuff because it just confirms my determination to stick with cable operated discs when I finally do make the swop to discs. Anyway, I expect this technology is just about to be replaced by electrically operated brakes, finger light and more powerful than pushing a stick through the spokes on the back wheel.
