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Disc brake leak

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Old 08-17-10, 10:07 PM
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wondermoose
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Disc brake leak

I just got a new bike and was adjusting its disc brakes when I noticed hydraulic fluid was dripping out. I was pretty sure I only loosened the adjustment bolts, but checked and tightened everything back up and now when I pull the lever, nothing happens. I pull it all the way in and nothing. What did I do? And I still haven't figured out how to adjust the brakes properly!

The brakes are Hayes, though I'm not sure which model.

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Old 08-17-10, 10:48 PM
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zjk
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Did they only start to drip after you started adjusting the brake? Rebleeding will probably solve the problem
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Old 08-17-10, 10:56 PM
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Yes. The brakes were working fine, aside from the alignment of the calipers, and were not leaking before this. What could cause the whole system to fail like that though? Just a little leak doesn't sound like it should shut down the entire system to the point where nothing happens when I pull the lever.
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Old 08-17-10, 10:57 PM
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You may've loosened the bleed screw, and let air into the lines. With air in the lines, the levers would feel mushy and allow the brake levers to travel all the way without providing any stopping power. If so, you'll need to bleed the system, which is not difficult. Hayes sells a brake bleed kit. Also, I believe Hayes brakes use regular, automotive quality brake fluid, which mean you can buy this fluid fairly cheap at auto stores, x-Mart, hardware stores...

Did the leak occur in the lever caliper area?
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Old 08-17-10, 11:02 PM
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Yes. Maybe I got the bolts wrong. I was under the impression the bolts on the side were for adjustment. If that's not how to adjust them, then how? Loosening the mounts and aligning them manually? Appreciate the help, guys.
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Old 08-17-10, 11:10 PM
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Torchy McFlux
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I think you should strongly consider just taking your bike into the shop you bought it from and letting them take care of it. It's under warranty and they might cut you some slack for screwing it up.
By the way, Hayes brakes use DOT 4 fluid which is reactive enough to remove paint. Try not to get it on your skin, and make sure you thoroughly clean up anything it came into contact with with isopropyl alcohol.

Last edited by Torchy McFlux; 08-17-10 at 11:33 PM.
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Old 08-17-10, 11:17 PM
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Yeah, planned on hitting up the shop first thing tomorrow. For future reference, though, do I only do adjustments by loosening the mounts? Thanks.
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Old 08-17-10, 11:29 PM
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Torchy McFlux
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Yes. Loosening the mount bolts will allow for big adjustments. Since Hayes brakes have an overflow resevoir built-in to the master cylinders, they self-adjust - so they're virtually maintenance-free for long periods. The most you might need to do is force the pistons back into the caliper bores to "reset" the pad return distance and centering. You do this by removing the wheel and jamming a plastic wedge (that should have come with your brakes) between the brake pads. Then re-install the wheel and squeeze the lever a few times.
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Old 08-18-10, 12:58 AM
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Originally Posted by wondermoose View Post
Yes. Maybe I got the bolts wrong. I was under the impression the bolts on the side were for adjustment. If that's not how to adjust them, then how? Loosening the mounts and aligning them manually? Appreciate the help, guys.
You loosened the bolts that hold together the two sides of the caliper. There's an Oring sealed joint in there that opened up and let out the fluid as well as air into the caliper. As Torchy has already mentioned you adjust then only with the mounting bolts.

Again as Torchy mentioned the DOT 4 is very nasty on paint but it's no more harmful to skin than any other car oil or fluid other than battery acid. I wouldn't bath in the stuff but a little on your skin is no need to panic. If you get some on you just don't touch anything painted until you wash it off well.

An "upgrade" would be to switch to DOT 5.1 which has an even higher boiling point. Great stuff if you're a downhill racer or serious downhill rider. But totally not needed if you're just a regular joe that has some shred of a sense of self preservation. If you do upgrade do NOT go for the DOT 5. The ".1" makes a huge difference. 5.1 is a glycol based fluid same as the DOT4. DOT 5 is silicone based and if mixed with any of the other glycol based fluids will turn both of them to nasty Jello like muck. So just keep that in mind that 5 is bad.
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