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Thread: General Brake Bleeding Question

  1. #1
    Purist, whats that? Jason Broadhurst's Avatar
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    General Brake Bleeding Question

    On a 2 output master, one circuit feeds the front wheels and the other circuit feeds the rear wheels. Both using a T piece.

    With completely dry lines, the rears bled up nicely and are free of air.

    The fronts now can't bleed because depressing the pedal is impossible as it hydro-locks and clamps the back brakes.

    Is there something I'm missing, either procedural or mechanically/hydraulically?
    Jason Broadhurst

    Someone once asked me if they could use my mower. I said "sure, so long as it doesn't leave my yard"

  2. #2
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    are all the brake lines OEM ? or has someone made changes?

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    Opens GAZ914's Avatar
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    I take it the rear circuit is also the rear part of the M/C.

    Although the rear circuit 'locks up' - the piston should still push on the front piston in the M/C until it stops at the end of the M/C. See diagram

    https://en.wikipedia.org/wiki/File:M...er_diagram.svg

    Something doesn't sound right with the M/C - have you tried undoing the line at the M/C and see if any fluid being pushed?

    cheers
    Gaz
    Race Car: VT Commodore (Murray) coming soon!
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  4. #4
    Non Compos Mentos Gammaboy's Avatar
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    Let me guess, it's got a switch mounted between the line ports on the master? Bled it with a dry master cylinder? Rear circuit is closest to the booster?
    When you went full metal jacket on the pedal it pushed the shuttle valve that operates the master warning switch all the way down the bore and has closed off the port on the other circuit. Been there, done that. Had to pull the master back out, unscrew the closure plug on the shuttle valve and belt the thing against a bench to get the shuttle valve to unseat and return to centre.
    "Where can we get hold of a Vincent Black Shadow?" "Whats that?" "A fantastic bike," I said. "The new model is something like two thousand cubic inches, developing two hundred brake-horsepower at four thousand revolutions per minute on a magnesium frame with two styrofoam seats and a total curb weight of exactly two hundred pounds."

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    ^^^ what he said

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    Resident Oaf Jim's Avatar
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    Yep for sure.
    When bleeding only use a 1/4 of the pedal travel to do it and bleed at the MC first.
    Turns out, far too much has been written about great men and not nearly enough about morons


    Quote Originally Posted by seedyrom
    my neighbours called the cops...... not because of the sound of me working in the garage was too loud, but because i taped a cardboard box to my back, covered my self in vaseline and pretended i was a snail on their lawn

  7. #7
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    Also you can gravity bleed the system before attempting to bleed the normal way, and that helps when you've got the shuttle valve in there. Also another way is to gently apply compressed air to the front brake circuit via a front bleeder, usually 5 or 10PSI is enough to shuttle the ball back enough to let you bleed fluid through. COVER THE MASTER! Not sure if the air trick works on modern shuttle valves but it's worked on the ones I have encountered on a few random 1969-1994 vehicles. Also didn't work on a few random vehicles in that range as well...call it a first attempt.

  8. #8
    Purist, whats that? Jason Broadhurst's Avatar
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    Handy shit fellas.

    The pedal basically goes 20% down with little resistance and then is rock hard.

    Worst case gotta pull the master off and have a play by the sounds of things but will try the others first.
    Jason Broadhurst

    Someone once asked me if they could use my mower. I said "sure, so long as it doesn't leave my yard"

  9. #9
    Down with ma homies Greg Rust's Avatar
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    Just crack the lines 1/2 turn at the master cylinder and put a rag around it to stop the dribble on your paint.
    xw Falcon 393 full race cam, NGK spark plugs.

  10. #10
    Resident Oaf Jim's Avatar
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    Did you take the brake clamps off?
    I may know someone that forgot to take the brake clamps off one day...
    Turns out, far too much has been written about great men and not nearly enough about morons


    Quote Originally Posted by seedyrom
    my neighbours called the cops...... not because of the sound of me working in the garage was too loud, but because i taped a cardboard box to my back, covered my self in vaseline and pretended i was a snail on their lawn

  11. #11
    Į\_(ツ)_/Į burn is weird's Avatar
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    http://www.ebay.com.au/itm/Hand-Held...g/162639571615

    or

    https://www.ebay.com.au/itm/Hand-Hel...p/172810521685 (supercheap want $202 for that exact model "bikeservice vacuum pump")

    pull instead of push. also awesome for pulling pistons back in multi piston calipers when changing pads by clamping the line.

    all Master cylinders are designed to feed from reservoir so will have no issues this way, added bonus is bubbles get bigger under vacuum.

    also good for calibrating absolute pressure sensors.
    Last edited by burn is weird; 11-01-18 at 10:23 AM.

    Oo___oO


  12. #12
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    My pressure bleeder is awesome.

  13. #13
    Compulsive modifier awdmoke's Avatar
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    Vacuum bleeder is great, just remember to grease your nipples.
    Google it.
    Lots of minis & mokes including a G13b powered Sports Sedan, a couple of Swift Gtis, a Goggomobil, Porsche 928S, Polo Gti, BMW 540i, a WRX and a few others.

  14. #14
    Down with ma homies Greg Rust's Avatar
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    Jason Bleedhurts.
    xw Falcon 393 full race cam, NGK spark plugs.

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    What one do you use Tim?

  16. #16
    Resident Oaf Jim's Avatar
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    Iíd use a pressure bleeder over a suction type.
    Good old clear tube into a bottle has served me well for 30 years and I donít see the value in other methods.
    Last edited by Jim; 11-01-18 at 05:55 PM.
    Turns out, far too much has been written about great men and not nearly enough about morons


    Quote Originally Posted by seedyrom
    my neighbours called the cops...... not because of the sound of me working in the garage was too loud, but because i taped a cardboard box to my back, covered my self in vaseline and pretended i was a snail on their lawn

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    Quote Originally Posted by Jim View Post
    Iíd use a pressure bleeder over a suction type.
    Good old clear tube into a bottle has served me well for 30 years and I donít see the value in other methods.
    You know what vacuum bleeders are good for? When you have finished pumping the pedal into it you close the nipple pull the trigger and lock it so it sucks all the fluid out of the hose so you don't drip it all over the floor.

  18. #18
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    Quote Originally Posted by garvice View Post
    What one do you use Tim?
    Ive got one of these


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    Cheers Tim.

  20. #20
    Resident Oaf Jim's Avatar
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    Quote Originally Posted by S View Post
    You know what vacuum bleeders are good for? When you have finished pumping the pedal into it you close the nipple pull the trigger and lock it so it sucks all the fluid out of the hose so you don't drip it all over the floor.
    Amazing. Are you saying they have invented a machine that can replicate the effects of gravity in fluids? Iíve always just held the hose up.
    Turns out, far too much has been written about great men and not nearly enough about morons


    Quote Originally Posted by seedyrom
    my neighbours called the cops...... not because of the sound of me working in the garage was too loud, but because i taped a cardboard box to my back, covered my self in vaseline and pretended i was a snail on their lawn

  21. #21
    Non Compos Mentos Gammaboy's Avatar
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    Quote Originally Posted by Jim View Post
    Amazing. Are you saying they have invented a machine that can replicate the effects of gravity in fluids? Iíve always just held the hose up.
    I think he also uses it on his cock to, errr, suck the fluids out.
    "Where can we get hold of a Vincent Black Shadow?" "Whats that?" "A fantastic bike," I said. "The new model is something like two thousand cubic inches, developing two hundred brake-horsepower at four thousand revolutions per minute on a magnesium frame with two styrofoam seats and a total curb weight of exactly two hundred pounds."

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