Hayes HFX-Mag leak- Mtbr.com
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  1. #1
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    Hayes HFX-Mag leak

    I have a new Hayes HFX-Mag that's leaking at the point where the hose nut connects to the master cylinder cartridge. Or, less precisely, it's leaking at the point where the hose connects to the lever assembly. I'll provide a somewhat lengthy explanation of what I've tried. Hopefully some of you reading this will be able to provide some suggestions of what to try next.

    I've had a heck of a time with the bleeding. I've probably been through the bleeding process 30-40 times by now. I ended up taking the entire brake system (lever assembly, hose, and caliper) off the bike and have situated the lever on a suitably sized dowel held up at various angles by a spare bike stand. It's easier to experiment without having to worry about brake fluid getting all over the rest of the bike... The caliper is dangling free and I'm able to turn it in various directions in order to get the last little bit of air out of the caliper. I've tried holding the lever assembly up at various angles too (though always with the overflow port on top). I'm using the Haye's bleed kit. On my last 5 or 6 tries at bleeding, I haven't seen any new air come out.

    Each time that I test after bleeding, the lever goes to the bar. There is some slight resistance, and the caliper pistons move slightly, but not much. If I remove the pads and put my finger in the calper where the pads would go, I can feel the pistons pressing on my finger slightly when I stroke the lever quickly. If I do a slow squeeze of the lever, the pistons move even less, if at all. (If it were working properly, the pistons could probably crush my finger!) Most of my tests are performed though with the brake pads installed with that nylon spacer that comes with the brakes placed between the pads.

    On two occassions after the bleed, I've closed the overflow port, and have added extra fluid to the system via the caliper's bleed valve. (Actually, I've done this more than twice, but there are two particularly noteworthy occassions...) After addiing the extra fluid, I tested by squeezing the lever. Lo and behold, I actually encountered the resistance expected from a normally working brake! However, on these two occassions, as I squeezed the lever further, fluid started leaking from around the nut that attaches the hose to the lever.

    When the leak occurred the first time, I disconnected the hose, snipped a small bit of hose off, and reinstalled using a new compression bushing (olive). I then bleed and rebleed, ad nauseum, until it failed again (with added pressure) in an almost identical manner.

    So far, I have two hypotheses for the cause of the leak" 1) Incorrectly torqued hose nut, and 2) Leak from inner lining to outer lining of hose.

    With regard to (1), Hayes' instructions say to torque the hose nut to 60 in-lb. You have to use an open end wrench for this and I don't have a suitable fitting for my torque wrench. So I just used an open ended wrench and guessed. When the leak occurred the first time, I speculated that I had either not torqued the hose nut enough or perhaps even too much.

    Regardless, on my second try (with a new compression bushing), I did use my torque wrench. (I connected my torque wrench to the box end of my 10mm wrench via a 10mm hex bit. I measured the lengths of the two wrenches and made a simple calculation to give me the 60in-lb equivalent with my now longer torque wrench. Assuming my calculations are correct - and I believe that they are - the hose nut should now be torqued properly.

    With regard to (2), I've read elsewhere (see http://www.ridemonkey.com/forums/arc...p/t-82571.html) that a hole in the inner lining can allow brake fluid to leak in between the two linings. This could be happening with my brake, but if so, why does the fluid leak out of the end of the fitting that is closest to the lever body?

    I thought too for a time (just prior to the second leak incident) that perhaps the master cylinder was bad. After all, the lever was moving freely (with some amount of damping) to the bar and back. However, after encountering the normal expected resistance (a victory of sorts) and then the leak, I think the chance of it being a bad master cylinder are less probable.

    Ideas, anyone?

  2. #2
    Meh.
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    Forget the Hayes bleed kit. Use a big syringe at the caliper end and push fluid to the top while tapping the caliper and lines.

    Sounds like either way the hose is fubar.

    Make sure that the cuts are nice and clean and straight. A sharp razor blade usually does the trick just fine.

  3. #3
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    Quote Originally Posted by XSL_WiLL
    Forget the Hayes bleed kit. Use a big syringe at the caliper end and push fluid to the top while tapping the caliper and lines.
    Yeah, I've been meaning to try this.
    Sounds like either way the hose is fubar.
    I'll start over with a new hose.
    Make sure that the cuts are nice and clean and straight. A sharp razor blade usually does the trick just fine.
    Ah! I was using some shop scissors. The Hayes instructions say to use either some good scissors or a cable cutter. The cable cutter that I have isn't very good; when I did a test cut, the scissors definitely gave a better looking end. However, the end wasn't perfect, and there was a bit of crushing going on too. Anyhow, I'll give the razor blade a try.

    Thanks for all of the advice.

  4. #4
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    Hey Will, another question:

    When threading the hose nut onto the lever assembly (sandwiched underneath is the compression bushing), does the hose nut typically "use" up all of the threads on the lever assembly? On my first attempt, I hit significant resistance early on, but I think this was due to the compression bushing deforming. On my second try (with new compressioin bushing), I didn't worry about it as much since I had a torque wrench. Nevertheless, I the hose nut is still several mm away from the end. I ended up at about the same point each time.

    Thanks again,

    Kevin

  5. #5
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    Tighten the nut till you can see the tip of the compression bushing, no further or you'll damage the threads on the cartridge.

  6. #6
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    An update...

    I got the new hose today. I ordered a front hose from Jenson and it was pretty close to the length that I had previously chosen, so I didn't bother cutting it.

    I did a bleed, this time using a syringe. Will was right; it's a lot easier. I used the MixMizer from Enduro Fork Seals. If you use one of the hoses from the Haye's bleed kit and snip a tiny bit from one of the ends at a diagonal, it's possible to insert that now (sort of) pointy end into the nozzle of the MixMizer. It's tight, but that's good because it prevents the DOT 4 fluid from leaking.

    Bleeding the brake using the syringe was much, much nicer. Getting the initial air bubble out of the hose was easier. (Just point the nozzle up and push on the plunger until the brake fluid is at the end.) Sucking air out of the caliper was easier; no squeezing and releasing as with the bottle. Instead, you just inject a bunch of fluid and then draw some of it out. Let the bubbles float to the top (non-nozzle end) of the syringe and repeat a few times. Once the air is out of the caliper, shoot the brake fluid through until it comes out of the overflow hose. The plunger stays put, so you can set it down - I had arranged things so that I had a nearby table - and come back to it as needed.

    But, alas, I'm still seeing a leak. I thought at first that it was from the hose, but I wiped the fluid away and observed more closely that it's actually coming from in between the cartridge and the master cylinder body. So I guess it's time to call Hayes and ask them to fix it under warranty.

    One thing I found curious: The instructions that came with the brakes said to torque the hose nut to 60 +/- 5 in-lbs. However, the instructions that come with the replacement hose said to torque the hose nut to 40 in-lb plus one full rotation. Could something in the master cylinder assembly have been damaged by using the higher torque value? For my most recent effort, I decided to follow the instructions that came with the replacement hose. The hose nut is not screwed on as far as before; before, I was able to see the end of the compression bushing poking from under the hose nut; now, using the lower torque value, I do not.
    Last edited by KevinB; 09-27-2007 at 08:13 AM.

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