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So I just had a stroke whilst bleeding new lines

Discussion in 'Technical and Troubleshooting Torque' at netrider.net.au started by Azamakumar, Jan 19, 2011.

  1. New HEL lines came in on monday so I figured I'd whack em on today being my day off. Cut forward a good 5hrs and I can't get pressure on the lever. Doing the whole "open bleed valve, squeeze and hold lever, close valve, release lever" was working fine but after I got a bit of fluid out of the calipers, opening the bleed valve would suck some of the fluid back in.

    Stumped I turned to google which suggested to crack the banjo, squeeze so some fluid comes out whilst tightening it back up (with the valves closed of course). Going back to opening/closing the valve pulled out some air then fluid at a steady rate but then it was back to getting sucked back in when I opened the valve.

    Obviously I have some air somewhere in there but I have nfi where. I've cracked all 3 banjos (master cyl, left and right calipers) and let a bit of fluid dribble out which helped a bit but still nothing. Every walkthrough/youtube vid I've seen says to start at the cylinder's bleed valve, yet I don't have one so the next step is the calipers. Also I've been really anal and kept the reservoir near full the entire time so as not to get any air in. Is there something wrong with the way I was priming? Or is there a diff method that works better when you've just replaced the lines? Saw one suggestion of attaching a decent length of hose and just sucking the fluid through which doesn't seem too stupid but I'll have to leave it for tomorrow (or friday).

  2. Use a cable tie or similar to hold the brake lever on and try again in the morning.

    Edit: Oh and gently tapping the calipers/brakelines might also help move any stuck air bubbles.
  3. tried reverse bleeding?
    use a syringe with a short length of vinyl tube to blow fluid BACKWARD up the line to the res.
    no promises, but it's a thought
  4. I cant understand how the bleed valve would suck fluid back in as you opened it if you had pressure on the lever. Before you cracked the bleed nipple there should have been pressure there from pumping the lever a number of times so that when you crack the bleed nipple that pressure is released out of the bleed nipple and you continue hoding pressure on the brake lever. Then once the bleed nipple has benn tightened you release and pump the lever again. I have no ide how fluid/air can be sucked back in the nipple if there is pressure on the lever.
  5. You might try the correct way:

    Squeeze, open bleed valve, continue squeezing, hold lever and close valve, release lever.

    I actually prefer to close the bleed valve while the lever is still moving, so that there is no chance of air being sucked back before I close the bleed valve.

    If you want to be very sure, sqeeze the lever a few times between each opening of the bleed valve. You can also use a large rubber band or similar to perform the initial squeeze, if there are issues in reaching the bleed valve.

    When you release the lever a small reduction in pressure can be created when the piston in the master cylinder returns to its normal position, especially if things are a little worn in the master cylinder.
  6. +1...Always pump it a few times and crack open with pressure on the lever and close while it's still moving.
    If you've cracked the bleed valve open and the lever is all the way down, there is no longer pressure in the line.
  7. Hmm thanks. Will try a fresh flush first thing tomorrow morning.
  8. if that doesnt work, try cracking open the top banjo bolt , as sometimes gets air in there as well..and yes, each time you do it, tap the lines , and do one caliper at a time.
    Im waiting for my hel to come, so just do one line at a time. Dont worry about brake oil, i sometimes nearly use a whole bottle doing the front to get it right and it can take that much to get it all air out...
    Another trick to try is, put a tubing on the nipple and into a bottle for the excess, but never let the tube get open to the air, another words, pour some brake fluid in the bottle to cover the end of the tube and dont let it come above the oil,. if its sucking, it will only suck in oil and no air..works a treat
  9. I had a similar problem when I swapped over to braided lines on the track bike with the front brakes taking ages to get pressure. What I did was get one of those one man brake bleeding kits, which is basically a tube with a one way valve, that way you dont have to continually tighten and untighten the bleed fitting.

    However it still took ages to get pressure and bleed the front brakes, reverse bleeding like the forgotten suggest is better as you can move more brake fluid than you would pumping the brake lever.
  10. Ok huge improvement but still not happy. Tapped the lines then pumped the air out via the reservoir. Bleeding was much easier (was using Roderick's method - thanks for that tip). It's still not quite as firm as before but after going through about 3/4 of a 500ml bottle I'm only pushing out fluid at each caliper.

    Where is the fvcking air ](*,). Cable tie the lever off and let it sit a while then try again?
  11. Yep, cable tie overnight if you can.

    I think it took three bleeds over three weeks to get all the air out of mine when I put the HEL lines on.

    Just keep at it!

    Moving the wheel side to side or riding the bike (If you've got enough brake!) can get the air bubble moving, as well as tapping the calipers & lines.

    The last thing I did was crack the banjo at the master cylinder cos that's where the air collects on my system.

    Makes a vacuum bleeder an attractive option if you ever need to do it again...
  12. Isn't cracking the master a step back?

    EDIT: disregard that I suck cock. Just figured that one out. Onto my next question - how do you get brake fluid off tyres. Couple of spots on the sidewall afaik but just to be sure...
  13. hmm just took it for a spin around the block, still not the same feel as the old ones but i managed to get my arse up in the air for the first time on the stock pads

    faaaaaaaaaaaaaaaaaaaaaaaaaark can't wait til this is done properly
  14. Soapy water. Your other statement could used against you... :angel:
  15. was wondering and its just a thought as ive got new hel lines and need to put them on, but has anyone tried to heat the brake fluid to a warm temperature? Surely by heating it , would it thin and be able to be pushed through easier? never tried it or herd about it, just a thought. but when you are riding etc, does the oil heat up, i actually dont know the answer to this one!
  16. Rode to lidcombe then back to blacktown for work. Cable tied off the lever during my shift, and gave the bike a good hammering on the way home (there should be more wide roads with giant roundabouts). Much better bite than the stock lines, but I'll give it another quick look tomorrow to see if I can push it just a bit more.

    And moyston, depending how much it thinned out after bleeding, you'd be left with a spongey lever once it cools down (I think).
  17. Just read this trick in 2 wheels....

    Remove the caliper, hang it up somewhere so it is the highest point in the system, then bleed. Repeat for 2nd caliper. Makes sense when you think about it as air will naturally want to move to the highest point in the system.

    Its not uncommon for brakes to take a lot of bleeding when you have completely emptied the system. Also make sure you're working out to in, furtherest caliper from m/c first.
  18. Shouldn't it be nearest to furthest? Everyone (I've read, at least) suggests to start with the valve on the reservoir, then right caliper, then left, and so on. Same principle holds for the ones I've read for cars too.

    EDIT: and the caliper at the highest point doesn't seem like a bad idea but methinks if you actually did that you'd get air trapped in the banjo at the master, but that should be heaps easier to fix.
  19. edit: Pretty sure I've always done it out to in....at least on cars. Have done my bikes this way as well and never had a problem. A google search is inconclusive....some say furtherest to nearest, some say the reverse.
  20. I've always found the plastic tube trick is very useful too aza.

    3mm will need to be heated up and stretched to the nipple size, 5mm might be a bit loose. I use an old windscreen washer line out of an oooold car for it (3mm) and I can see when any bubbles come out of the line.

    It also helps keep the mess in one location as you point the tube into a little jar ;)