Front Locking Up - Help Please!
Thread Starter
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5th Gear
Joined: Mar 2011
Posts: 9
Likes: 0
From: NY
Front Locking Up - Help Please!
Hi, I have a 2003 833 custom. At the end of last season my front brake locked up on me while riding. I bled the brake, which released the pressure, and I was able to make it home just using the rear.
Recently I have been working on the problem, and figured it would be the master cylinder to blame. There were a couple o-rings in the master that were questionable, so I rebuilt the entire thing. Put it back on, and the brakes still locked up.
Next I rebuilt the caliper, still locked up.
So I figured it could be the line because I have heard that they can fail internally causing a check valve situation which doesn't let the fluid back up. Replaced the line and still locking up.
I'm at a loss for what to do. Am I missing something simple? Can there be something wrong with the lever itself? Any help is greatly appreciated.
Recently I have been working on the problem, and figured it would be the master cylinder to blame. There were a couple o-rings in the master that were questionable, so I rebuilt the entire thing. Put it back on, and the brakes still locked up.
Next I rebuilt the caliper, still locked up.
So I figured it could be the line because I have heard that they can fail internally causing a check valve situation which doesn't let the fluid back up. Replaced the line and still locking up.
I'm at a loss for what to do. Am I missing something simple? Can there be something wrong with the lever itself? Any help is greatly appreciated.
Road Captain
Joined: Sep 2010
Posts: 574
Likes: 3
From: AB Canada
Not sure how you are bleeding your brakes, but if you are 'pumping' the lever and the master cylinder piston is returning and exposing the relief port then it's most likely not your master. Where is your caliper piston, ie are your brake pads worn and your piston at the end of it's travel, pins in good shape? Are you using compatible brake fluid for the 'rubber' items in your system? Was the bike worked on prior to the brake failure?
Thread Starter
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5th Gear
Joined: Mar 2011
Posts: 9
Likes: 0
From: NY
the rotor looks good...there is no pulse before they lock up, I use the brake a couple times and then they lock as I am riding, kind of gradually, until it becomes completely locked. The locking usually occurs when I am NOT pulling the lever in
Last edited by tony2x; Mar 28, 2011 at 12:33 PM.
Thread Starter
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5th Gear
Joined: Mar 2011
Posts: 9
Likes: 0
From: NY
Not sure how you are bleeding your brakes, but if you are 'pumping' the lever and the master cylinder piston is returning and exposing the relief port then it's most likely not your master. Where is your caliper piston, ie are your brake pads worn and your piston at the end of it's travel, pins in good shape? Are you using compatible brake fluid for the 'rubber' items in your system? Was the bike worked on prior to the brake failure?
this bike takes Dot 5 and that's all I have put in there when I flushed the old stuff out
Not sure about the history...bought the bike used with 3000 miles on it about a year ago
Road Captain
Joined: Dec 2009
Posts: 540
Likes: 3
From: Nooga, TN
You might try filling the master cylinder from the bleeder using a syringe. Lower the level in the master cylinder and force fluid through the bleeder. This should tell you if you have an obstruction somewhere. Sounds like the relief port may be clogged. Sounds like as the brake fluid heats up and expands it has no where to go and causes a hydraulic lock. DOT 5 will expand with heat more than DOT 3 or 4. This method might also help clear any gunk in the relief port.
Former Sponsor
Joined: Jan 2009
Posts: 19,364
Likes: 40
From: Los Angeles, CA
I had the same problem on another brand bike I owned and it was a hairline crack in the MC. New master cylinder fixed. I am not saying this is your problem, but something worth checking for.
Drew
Drew
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Thread Starter
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5th Gear
Joined: Mar 2011
Posts: 9
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From: NY
You might try filling the master cylinder from the bleeder using a syringe. Lower the level in the master cylinder and force fluid through the bleeder. This should tell you if you have an obstruction somewhere. Sounds like the relief port may be clogged. Sounds like as the brake fluid heats up and expands it has no where to go and causes a hydraulic lock. DOT 5 will expand with heat more than DOT 3 or 4. This method might also help clear any gunk in the relief port.
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Thread Starter
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5th Gear
Joined: Mar 2011
Posts: 9
Likes: 0
From: NY
I'll try to take a look at it tonight....where was your crack? was it easy to see with the naked eye?
