Results 1 to 9 of 9
  1. #1
    mtbr member
    Reputation: downhill2004's Avatar
    Join Date
    May 2004
    Posts
    36

    can't bleed HFX 9?

    Hi All: I'm trying to bleed my year-old HFX 9 rear caliper using the Hayes kit for the first time. I discovered that my braking power had suddenly diminished and I was able to fully depress the lever without much braking force being created. I also noticed today, before working on it, that the rear caliper was not fully releasing after letting go of the lever, and there was a lot of intermittent brake drag on the disc. So...

    I pulled the pads out and forced the pistons all the way in.

    I pulled the pin on the master cylicnder and placed the aluminum ferrule in it with the hose going into a catchcup.

    I filled the squeeze bottle with fresh fluid, placed it over the nipple and worked all the air out of the tube. I then opened the nipple 1/4 turn and squeezed for 5 secs...I noticed that a lot of fluid started coming out of the base of the nipple and dripping down over the caliper. When I let go, a lot of bubbles came back up the tube into the bottle. After a few more squeezes, I realized the air was coming back in through the base of the nipple.

    I opened up the nipple again and squeezed really hard, but no fluid ever came out of the master cylinder. I even pumped the lever a few times while squeezing the bottle, and felt little resistance in the lever, and didn't notice the piston moving in response to the pumping of the lever either.

    WTF?

  2. #2
    mtbr member
    Reputation:
    Join Date
    Nov 2006
    Posts
    141
    Quote Originally Posted by downhill2004
    Hi All: I'm trying to bleed my year-old HFX 9 rear caliper using the Hayes kit for the first time. I discovered that my braking power had suddenly diminished and I was able to fully depress the lever without much braking force being created. I also noticed today, before working on it, that the rear caliper was not fully releasing after letting go of the lever, and there was a lot of intermittent brake drag on the disc. So...

    I pulled the pads out and forced the pistons all the way in.

    I pulled the pin on the master cylicnder and placed the aluminum ferrule in it with the hose going into a catchcup.

    I filled the squeeze bottle with fresh fluid, placed it over the nipple and worked all the air out of the tube. I then opened the nipple 1/4 turn and squeezed for 5 secs...I noticed that a lot of fluid started coming out of the base of the nipple and dripping down over the caliper. When I let go, a lot of bubbles came back up the tube into the bottle. After a few more squeezes, I realized the air was coming back in through the base of the nipple.

    I opened up the nipple again and squeezed really hard, but no fluid ever came out of the master cylinder. I even pumped the lever a few times while squeezing the bottle, and felt little resistance in the lever, and didn't notice the piston moving in response to the pumping of the lever either.

    WTF?
    I have only worked on hayes Mags and Soles but I have always had to open the bleeder screw way more that 1/4 turn. I have also had mags where a previous owner/wrench tightend the bleeder too much and pinched the hole shut.

    Try to get your hands on a 60cc syringe, connect a small piece of hose, use the Hayes bottle with a small weep hole in the top , also cut off the end of the bottle just enough to get the hose to go to the bottom as your catch resevoir. You can then push and pull fluid through the brakes until you have no air in the line.

    But I would also check for sticky piston seals it sounds like your pistons are not retracting properly and you may have a small leak around a piston seal. last I would check the MC to besure the seals are good on that, I had 2 9/sole levers blow the seal and with hits to the brake handle.

    Good luck

  3. #3
    mtbr member
    Reputation: downhill2004's Avatar
    Join Date
    May 2004
    Posts
    36
    Quote Originally Posted by new2this
    I have only worked on hayes Mags and Soles but I have always had to open the bleeder screw way more that 1/4 turn. I have also had mags where a previous owner/wrench tightend the bleeder too much and pinched the hole shut.
    Thanks for that suggestion...I backed it open quite a bit more, and still the same...just more fluid leaking from where the nipple threads into the caliper.

    I installed these brakes and they came pre-bled, so this is the first time I've tried to bleed them. I could just remove the nipple and see if it's blocked I guess, but I think not because the fluid is going through the nipple and backing out of the threads from the caliper.

    Quote Originally Posted by new2this
    Try to get your hands on a 60cc syringe, connect a small piece of hose, use the Hayes bottle with a small weep hole in the top , also cut off the end of the bottle just enough to get the hose to go to the bottom as your catch resevoir. You can then push and pull fluid through the brakes until you have no air in the line.

    But I would also check for sticky piston seals it sounds like your pistons are not retracting properly and you may have a small leak around a piston seal.
    There's definitely no fluid leaking from around the pistons...

    Quote Originally Posted by new2this
    last I would check the MC to besure the seals are good on that, I had 2 9/sole levers blow the seal and with hits to the brake handle.

    Good luck
    I'm wondering now if the line is damaged, maybe kinked internally? It looks a little banged by the caliper?
    Attached Images Attached Images

  4. #4
    mtbr member
    Reputation:
    Join Date
    Sep 2007
    Posts
    1
    A common problem with the HFX9s (particularly OEM units). The solution is to remove the bleed screw and carefully apply Teflon thread tape to seal the threads. The original thread seal 'paint' that Hayes uses quickly wears away as you bleed the brakes. I've tried a number of different thread-seal compounds but none seem to last (the glycol based fluid strips it off quickly). The teflon tape works OK but you need to be patient and apply evenly. Do not use Loctite type thread compound.

  5. #5
    mtbr member
    Reputation: downhill2004's Avatar
    Join Date
    May 2004
    Posts
    36
    Quote Originally Posted by El prez
    A common problem with the HFX9s (particularly OEM units). The solution is to remove the bleed screw and carefully apply Teflon thread tape to seal the threads. The original thread seal 'paint' that Hayes uses quickly wears away as you bleed the brakes. I've tried a number of different thread-seal compounds but none seem to last (the glycol based fluid strips it off quickly). The teflon tape works OK but you need to be patient and apply evenly. Do not use Loctite type thread compound.
    Thanks for that. Since my orig. post, I've been in touch with Hayes and they've been extremely helpful and encouraging...bravo. Hayes also recommended teflon tape, but the real problem for me was that indeed the hose had been kinked/damaged at the caliper. I traced this back to the position of the first hose guide, which is positioned too low on the chainstay and forcing a radical bend in the cable, which resulted in it getting kinked when it was pulled forward when twisting the handlebars (like when carrying the bike and having the handlebars rotate 180 degrees to the right).

    This bike originally came with Avid BBs, so the cable routing was less of an issue before I put the hydros on.

    Hayes suggested I order a Stroker/Camino hose kit, which has a bend in the caliper fitting, instead of the HFX-9 hose's straight fitting. It was either that or route the host differently. When I get the new cable on and fill the bleeder threads, I'll post a follow up and close the thread.

    Thanks for all the help on the list!

  6. #6
    mtbr member
    Reputation: downhill2004's Avatar
    Join Date
    May 2004
    Posts
    36

    Fixed: New hose with better routing

    Just to follow up, I ordered a Stroker hose kit which has the 90-degree banjo fitting on the caliper instead of the straight fitting, and this allowed me to properly route the hose.

    The old hose definitely was damaged by flexing at the caliper, caused by improper routing. Hopefully this will help anyone contemplating upgrading or changing hydraulics...make sure the hose has as straight a path as possible, or change the fitting at the caliper!
    Attached Images Attached Images

  7. #7
    mtbr member
    Reputation: fawndog's Avatar
    Join Date
    Nov 2007
    Posts
    109
    Quote Originally Posted by El prez
    A common problem with the HFX9s (particularly OEM units). The solution is to remove the bleed screw and carefully apply Teflon thread tape to seal the threads. The original thread seal 'paint' that Hayes uses quickly wears away as you bleed the brakes. I've tried a number of different thread-seal compounds but none seem to last (the glycol based fluid strips it off quickly). The teflon tape works OK but you need to be patient and apply evenly. Do not use Loctite type thread compound.
    the bleeder is a compression fitting and in order to work properly it has to be clean.

    The threads on any compression fitting are NOT meant to be air tight, what is meant to be airtight is the fitting (male and female sides).
    So you are going to get fluid past the threads no matter what. The trick is to not draw air in past those threads. To do this you must push fluid into the caliper and up the system, I go through about 3/4 of that Hayes squeeze bottle on a rear system (squeezing 1/4 bottle in at a time). If you ever stop putting positive pressure into the system close the bleeder before you stop squeezing. Dont pump the lever until you close up the entire system.

  8. #8
    mtbr member
    Reputation:
    Join Date
    Sep 2007
    Posts
    49
    Quote Originally Posted by fawndog
    The threads on any compression fitting are NOT meant to be air tight, what is meant to be airtight is the fitting (male and female sides).
    So you are going to get fluid past the threads no matter what. The trick is to not draw air in past those threads. To do this you must push fluid into the caliper and up the system, I go through about 3/4 of that Hayes squeeze bottle on a rear system (squeezing 1/4 bottle in at a time). If you ever stop putting positive pressure into the system close the bleeder before you stop squeezing. Dont pump the lever until you close up the entire system.
    It would have been nice if the hayes bleed instructions included that bit of info. I also had a particularly hard time keeping air from being drawn through the bleed port threads. It leaked terribly when open 1/4 turn, but teflon tape slowed down the flow enough to manage.

    It sounds like i had issues very similar to the OP. My line was crushed between the fork and frame months ago, but only recently did the lever lose all ability to move the pistons (happened over the course of 10min of riding). The leaking bleed port issue along with my general newbness prevented me for getting a good bleed for a while longer, but when i finally was albe to bleed it properly the hydraulic line blistered and burst in my face at the damaged place (laugh).

  9. #9
    mtbr member
    Reputation: fawndog's Avatar
    Join Date
    Nov 2007
    Posts
    109
    Quote Originally Posted by roku
    It would have been nice if the hayes bleed instructions included that bit of info. I also had a particularly hard time keeping air from being drawn through the bleed port threads. It leaked terribly when open 1/4 turn, but teflon tape slowed down the flow enough to manage.

    It sounds like i had issues very similar to the OP. My line was crushed between the fork and frame months ago, but only recently did the lever lose all ability to move the pistons (happened over the course of 10min of riding). The leaking bleed port issue along with my general newbness prevented me for getting a good bleed for a while longer, but when i finally was albe to bleed it properly the hydraulic line blistered and burst in my face at the damaged place (laugh).
    That would make me chuck it, brake fluid is really one of the worst chemicals a mechanic comes into contact with. 15 years is how long I've been wrenching, bleeding is no job for someone alone or a noob. It takes a lot of work to keep air out of a closed system.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •