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Brake Bleeding!

Discussion in 'Technical and Troubleshooting Torque' started by DenholmReynholm, Apr 15, 2013.

  1. I've put my brakes back together and connected it all up, now I'm trying to bleed them. The system was empty when I started and I'm getting very little fluid through the bleeder. Was getting zero fluid for a while and now getting a small trickle if I hold down the lever. I imagine there was a lot of air in the system as there was no fluid, and the master cylinder is draining as I pump the brake lever, so I assume fluid is getting in the system, but I'm not sure if I'm doing it right, having never done it before.

    Is it normal for an empty system to take forever to start pumping out fluid? If so are there any tricks to make it easier, like holding the lever closed for a couple hours?

    Thanks in advance!

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  2. #2 NSSherlock, Apr 16, 2013
    Last edited: Apr 16, 2013
    It's normal. Pump pump pump.
    You can hook up a hand vacuum pump to the bleed screw and suck fluid from the reservoir in.
    Last time I opened the bleed screw and kept pouring fluid into the reservoir until it trickled out then closed it. Eventually got there.
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  3. Cheers, just wanted to make sure i wasn't completely wasting my time!
  4. Or maybe I am, still nothing and something which is either spillage or a leak, which would mean its not properly put back together.

    Will leave the lever held in overnight and if not much more luck in the morning ill trailer it to a mechanic :(
  5. You should pump a couple times then hold firm with the bleed screw shut. Get a friend to open bleed screw and lever should pull all the way back to the grip. Close bleed screw before releasing lever otherwise the system will suck air back in through the bleed screw. Repeat until nothing but clean fluid comes squirting out when the bleed screw is opened. So to repeat only ever open the bleed screw with pressure on the lever and dont let the lever go until screw is closed
  6. I've got some thingy with a one way valve, the instructions that came with it say no need to open and close the bleed valve as the inbuilt valve takes care of it ?
  7. Fair enough. Didnt read that earlier. Well jist pump away then
  8. You are actually pumping the brake lever aren't you? You can't just pull the lever in and leave it. Keep topping up master cylinder and keep pumping.
  9. Have the same but usually still pump with bleed shut, hold handle in then open bleed.
    I think I found this a little quicker since you get more pressure behind it.
  10. I find that filling the calipers from the bottom through the bleed nipple using a big syringe much more effective. If you are pumping the fluid down from the master cylinder, it is against rising bubbles. Even so, an overnight wait and a second bleed is in order. The second day, fit the syringe, release the nipple valve and suck the air (from the hose you used) into the syringe first, you will get a few bubbles from the calliper. Wait until all that air is in the top of the syringe. Hold it vertically, then push only fluid in. Watch the level in the master cylinder reservoir, you don't want it overflowing. (damage to paint) Push a bit of fluid up, then pump it back into the syringe. I always manage to get a few bubbles the second day after the system has settled a bit, and I always finish with a rock hard system. Using a syringe makes it easier to get the little air bubbles out the top. It makes more sense than pumping them all the way through to expel, and gives excellent control of the level of the fluid in the reservoir. I spill a lot less fluid this way, and waste less in the process.
  11. Oh I left out one thing - the syringe - Plain Jane engine service syringe, plastic, 80-100 ml. capacity. Made for whatever plastic and rubber is completely compatible with oil or brake fluid. any supercheap auto or similar should have them.
  12. Cheers all, I've got myself a vacuum bleeder from repco, doubles as a vacuum gauge so will probably be useful for more than just brakes, but gonna give that a go. Will try the syringe if no luck!
  13. I like to wedge all but one of the pads back before I begin pumping. This will see the first one seat and then I remove one of the wedges and repeat.

    Master cylinders often don't have enough volume to get all four sets of pistons to slide significantly at once. Instead they just sit there rocky back on forth on the seals.
  14. How much did the vacuum cost you?
  15. +1 to that. I got a syringe from work and some chemical hoses. Just make sure when you do this, the hoses are TIGHT on the nipple and syringe. The first time I did it, the hose wasn't on properly, the pressure pushed the hose off and I got brake fluid flicked in my eye...caustic = burns like a motherfcuker in the eye.

    You can follow this clip...

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  16. Even $100

    I'm now rocking slowly in the fetal position trying to convince myself that this was a good idea and I definitely shouldn't have just got a mechanic to do it in one day.

    Vacuum helped a lot, still having issues with the left caliper but the right one has the right flow of fluid, just need the left one working then I can focus on getting the liittle bubbles out.

    As it stands the right looks fine, I suspect I was drawing air into the hose around the bleeder screw on the left, think I fixed it and was on the way to working but ran out of fluid so will have to wait till I can get some more tomorrow. Still no real pressure at the lever, its firmer than it was before but still comes all the way back to the bar.

    I cant wait till my only problem is what to do with all the old fluid. Fire seems good at this point haha
  17. You are only trying to bleed one side at a time right? ie. not having both bleed nipples open at once?

    Not sure if you're still trying to pressure bleed or if you're using the vacuum pump kit now, but assume I'm talking about pressure bleeding here. 'bench bleeding' master cylinders is always good practise to get them to start pumping fluid again (google 'bench bleeding mc').

    Try cracking the line(s) slightly at the MC and pump a few times, it should help to expel some air and get things flowing - put a rag around the line so brake fluid doesn't make a mess and get on your paintwork etc.

    Tighten up the line then give it 5 - 10 pumps with the bleed nipple shut to build up pressure, hold lever in while opening and closing the bleed nipple. Repeat about 50 times and eventually you should get some pressure on the lever again - don't be disheartened if nothing seems to come out the first 20 times.

    As long as you don't release the lever while the bleed nipple is open the system can't draw any further air into it so it WILL eventually come good. I did a set a few days ago and it wore my hands out from all the pumping lol... but after about 20 - 30 mins the brakes came good again and I was glad I bothered!

    The one-way-valve/one man kits I find not too useful on bikes - especially with dry systems. A bit of clear tube is good enough as generally I can contort myself to perform both tasks of pumping and opening/closing bleed nipples at the same time :sneaky:
  18. Yep, one side at a time, have switched to vacuum bleeder now.