New Sidecar Brake - Trouble Bleeding - Too much air

Discussion in 'Hacks' started by tjlyons1, Sep 7, 2018.

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  1. tjlyons1

    tjlyons1 n00b

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    Hello Everyone,
    If any one has any suggestions please let me know. I just bought a new DMC sidecar and installed it. Last step to complete is the brakes. I had some trouble with the line because it was made with compression fittings that sort of fell apart, so I had the line completely repaired with crimp fittings and tested for up to 3,000 PSI. So I know the line is good. The line is very long and braided, not hard metal like car brake lines. I have it installed and do not see any leaks. I am able to pull plenty of fluid through the lines with the vacuum pump gun tool, which seems to work great. The problem is I continue to see a lot of air coming through to the caliper. I do not know if I just need to keep bleeding since it is such a long line, if the tube I am using on the bleeder is not tight enough, maybe the brake pedal needs adjusting. I am having trouble figuring it out. Any suggestions would be greatly appreciated. Thanks!
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  2. jaydmc

    jaydmc Long timer

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    First as we are tied to the rear brake pedal with its own master. Disconnect the linkage to the bikes factory master. This way you are only moving the sidecars master which gives you a longer stroke. I have found the best way to blead these brakes is a bit backwards from normal. First open the blead screw. Press the pedal down, with the pedal still down tighten the screw. Repeat until you have mainly fluid then blead normally. My "theory" as to why this works is that we are moving the fluid quicker in the line pushing air bubbles along rather then letting them "peculate" in the same spot.
    Another way that some times work but is VERY slow. Remove the caliper, put it on the ground (so that it is lower then the master) open the bleed screw and wait making sure that the reservoir does not go empty. Let gravity do the work. This can take hours.
    Jay G
    DMC sidecars
    866-638-1793
    #2
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  3. Strong Bad

    Strong Bad Former World's Foremost Authority Supporter

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    Most of the time when bleeding with a vacuum pump the air seen is from the threads of the bleed fitting, not from the line itself.
    #3
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  4. usgser

    usgser Long timer

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    I don't know what system DMC/Jay uses but IMHO vacuum bleeders like MityVacs are randomly hit-or-miss functional. For years now for bikes,cars,trucks I'm a huge fan of reverse pressure bleeding using a DIY pressure bleeder made from a 1/2 gal garden sprayer. Air bubbles inherently travel upwards so pressure bleeding toward the master cylinder allows the air bubbles to naturally move to the higher mc rather than forcing it downward to the bleed nipple. If it's a really short run some folks have used a large (100cc ?)veterinarian syringe. Force the air up not down.
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  5. DRONE

    DRONE Dog Chauffeur

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    Force the air up not down - brilliant! I've had two DMC sidecars and have had trouble using a Mity Vac, a reverse bleeder, and doing it the traditional way just using the pedal. But that's with the caliper installed. If you remove the caliper from the rotor, clip the various cable ties holding the brake line, then elevate the rotor and hang it on something so that the brake line is uphill all the way from the master cylinder to the caliper, then the bleed is done in a flash. "Up not down." Pain in the ass, but it's done. However, I can't imagine this problem is peculiar to DMC. Seems like anytime you have a long line from the bike to the car the bleed will be difficult simply because of the length, the elevation changes, and the curves in the line.

    To help prevent the Mity Vac problem that Strong Bad pointed out in Post #3, I use a thick grease on the bleed screw threads. The kind I use is lithium based but I'd guess that any sort of grease would work if it's thick enough to prevent air getting sucked up from around the threads.
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  6. Bobmws

    Bobmws Curmudgeon At Large

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    I do this also, then do one or two normal bleeds using the master cyl.
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  7. 3legs

    3legs Real men ride sidecars Supporter

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    If it's at all possible take the whole brake system off and hang the lot from the m/c down (but take the pressure off the calipers so they don't hang completely off the ground).

    Then run a clear tube from each bleed nipple to a 1/3 full jar of brake fluid (making sure the end of the tube is in the fluid) and just keep pumping fluid through until no more bubbles (make sure you keep topping the m/c up).

    Also make sure you bleed the banjo bolts as well starting from the top and work your way down.

    No need to close the bleed nipples every pump.

    Works for me every time.

    Note mine is tied in to my rear brake m/c (double banjo bolt) and i've set mine up to easily take the whole system off in one lot.

    Hope that makes sense.


    3legs
    #7
  8. Strong Bad

    Strong Bad Former World's Foremost Authority Supporter

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    Now this is brilliant! Never thought of it, I will give it a try next time!
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  9. Bobmws

    Bobmws Curmudgeon At Large

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    I think this became popular when speed bleeders hit the scene. They use a sealant on the threads so when the bleeder is opened air isn't sucked back in or fluid doesn't ooze out of the threads.
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  10. FR700

    FR700 Heckler ™©®℗

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    [​IMG]
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  11. Strong Bad

    Strong Bad Former World's Foremost Authority Supporter

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    Oh that's just what I need another gizmoe! I've already got a garage full of those little "Uni-taskers". :lol3
    #11
  12. Railbender

    Railbender Long timer Supporter

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    The sealant SpeedBleeder uses is available. I got a bottle of it on fleabay a few years ago. It is baked on and works great.
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  13. FR700

    FR700 Heckler ™©®℗

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    I've had one for years. No constantly opening and closing the bleed nipple.

    For the really PITA jobs I just use a 4' piece of clear tubing on its own. Zip tie it to the top of a broom and rest it against the vehicle so the tube is higher than the master.

    One man job to do a car.


    .
    #13
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