New Front Brakes won't release

QWERTYMage

QWERTYMage

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The parts list: New front brake master/lever, New lines/Banjos, new Calipers (Mike's XS 1975-matching).

It was working fine, but was spongy and needed a better bleed. I removed the front wheel while I was at it. The Pads/shims fell out, I put them back in, and pumped the brakes (pre-bleed), and they locked up. I had to pull the lower banjo bolt and wedge a thick ruler into the gap and prise the pads apart to get space.

I put the wheel back on.

I bled the brakes (fully drained with vaccume bleeder, added brand-new fluid (new bottle unopened), pumped the brakes to get the bubble out, and the brake is solidly engadged and not released.

I imagine I mucked something up somewhere because the sysem is clean and the old fluid was only in there 3 months.

Any guesses?

Thanks in advance.
 
Seems like you need to take the caliper apart and do a careful inspection.
If the pressure will not release, it may be the small pressure release hole in the bottom of the master cylinder is blocked.

For the pads to back off, 2 things must happen. The hydraulic pressure must bleed back to the master cylinder, and the the pads must retract slightly. The rubber piston seals are stretched as the piston moves, and once the pressure is released, the seals pull back on the pistons.
 
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First thing to try is just loosen the bleeder on the caliper. If the wheel then turns there are two main possibilities. First and most likely is the small return hole in the master is plugged or for some reason the piston is not coming back far enough to uncover it. Second would be there might be a problem in the hose going to the caliper restricting the flow of fluid when lever is released.

On the other hand if opening the bleeder does not let wheel turn the problem would appear to be in the caliper.
 
From My experience with my 82' xs650 Heritage special I had a similar lockup that would not release....
and after fighting it for about 2 weeks I was convinced the master cylinder was at fault I tore the mastercylinder appart and discovered there was NO second hole in the MC..... there was only one.... after checking the manual and verious threads on this site
I drilled a hole through the indent in the bottom of the MC that was supposed to go through, but didn't ..... with that 2nd hole now in the MC it started pumping up much better than it was.... after about 10 bleedings of the MC I still had air in it so I decided the air was traped at the hose connection at the MC..... I pumped it up and broke loose that hose connection to bleed the air there.... then things started working correctly.... I even tried laying the MC down on the floor to to get the air to rise in the line to no avail .... it seamed like it would begin to work but only add more air in the system..... but after I bled the hose connections (all of them) and then the brake calaper one final time it seamed to be working fine after that.
this hole in the MC is supposed to be next to the larger hole in the center of the bottom of the Brake fluid resivour, there was a indentation there but the hole did not go through.... so I drilled it out with my smallest drill bit ( 1/16")
one thing that lead me to the discovery that there was no hole was that the guys here told me that with the brake line at the calaper disconnected it should drip fluid....... mine did not.
because it didn't drip, the air would not be forced out of the brake line and filled with brake fluid , so I had a brake line full of air....
bleeding it was not enough to get the air out.... should have been but it wasn't i don't know why I bled it many many times.
with the hole drilled through like it was designed to be the fluid dripped from the line at the calaper....
attaching that and waiting a while allowed the line to fill for the most part .... then pumping and bleading worked....
then I bled the Bolts holding the lines and did one last final bleed..... it works fine now.
this may have relivance to your machine and it may not , so take it with a grain of salt !
....hope it helps !
Bob.........
 
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put a towel or protection over the paint when working on the brake MC as you will inevitably get squirts of brake fluid all over the place and if it gets on the paint it will eat right through it ! .... you have been warned !
LOL
Bob.......
 
Bob Kelly III said:
this hole in the MC is supposed to be next to the larger hole in the center of the bottom of the Brake fluid resivour, there was a indentation there but the hole did not go through.... so I drilled it out with my smallest drill bit ( 1/16")
one thing that lead me to the discovery that there was no hole was that the guys here told me that with the brake line at the calaper disconnected it should drip fluid....... mine did not.
Bob.........
Click to expand...

While 1/16 th sounds small and you say it worked for you I would not recommend it.

Just so happens this morning a guy over on the XS400 forum posted some nice pictures of his front master he is working on. It the picture below I have circled the small hole and you can see how small it is. Mine that I cleaned out just a couple weeks ago was very hard to see and took some time working with a very fine wire to open up. I can understand how someone might think it was not even drilled to begin with.

front master.jpg
 
yes that hole IS tiny so small that they don't use a small drill bit, they use a larger bit til the tip JUST breaks into the bore, ADD Chinese quality control and sometimes there's no hole at all! if you need to open one up, think wheat drill, or the smallest number drill at the auto store. be sure to get a bit of 1000 grit or finer in the piston bore, remove any burrs you may have created.
 
I rebled the brake, blew out the MC with compressed (canned) air... and it works... because suddenly I remembered I put on a longer chain last week and forgot to release the pressure on the rear drum brake.

I'm an asshole.

Thanks for all the awesome help tho.
 
UH ? what's the rear drum brake have to do with the front hydrolic brake ?
its very possable that the MC on my bike actually did have a hole in it at one time seeing as it's so extreamily small I might not been able to see it.... period the point is that the hole needs to be opened... if it's clogged I havn't had any trouble with the brakes at all except them being just a bit spungy , I figure I still have a tiny amount of air in it... but it will lock up the wheel at 40 mph.... i tried that.
so for me it's good to go and there is no leaks....
use your own judgment, I'm just throwing out possabilities for you to investigate so you can find the problem.
....
Bob........
 
lol so are you saying that it wasn't the front brake being locked up at all ? and it was the rear wheel all the time ?
time to start thinking cause and effect ! LOL
oooh boy ! that takes the cake QwertyMage ! but we all make mistakes ! it's things like that that make you smarter !
....
Bob..............
 
Yes, Mr. Kelly. It was the rear brake the whole time... actually it was me the whole time. The brake was just the brake doing it's job...

I only hope I remember this next time I fiddle with the bike.
 
lol No problem ! at least you learned something ! that's what it's all about !
we all make mistakes, we're human....well most of us ! anyway ! LOL
I had a rear brake on a bike that was working fine till I re adjusted it because the stroke was getting a bit long to make it stop right
so I adjusted it up and the next time I rode it coming to a stop sign it locked up and the peddle stayed down I reached down with my toe and pulled the lever back and it released .... when I got home I pulled the rear wheel and brake drum to discover the brake shoes were wore completely down..... almost to the metal and the actuating cam was going past it's Apex and locking the rear wheel ! LOL
I replaced the shoes and had to back the adjusting nut all the way back to the end of the threads ! .... that's the only machine I ever had to do that with .... I think it was my Kawasaki 350cc with rotary disk valves and 2 cycle engine.... It was a Wild thing ! it would wheelie in 1st. gear just by grabbing a handfull of throttle.... a really fun bike to ride ! evidently the previous owner only used the rear brake to stop.
I usually use both brakes.... but that depends on road conditions !
Have a good one !
Bob......
 

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