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82 Maxim Master Cylinder Cleaning

Discussion in 'XJ Technical Chat' started by eigenseca, Jun 14, 2019.

  1. eigenseca

    eigenseca Member

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    I'm currently trying to prep front brake systems for rebuild. I've gone through the Mc and the bore looks smooth but I'll probably smooth it a little more just to be sure. But it seems to have some gunk that is giving me a lot of trouble. This white residue inside the m/c itself will not go away. I've soaked it twice in carb dip, twice in purple power and scrubbed it multiple times with a tooth brush and a nylon brush on a impact. I always rinse with brakeleen. Another thing I'm wondering about is what this rust colored stuff is on the edge of the bore. I didn't think aluminum would rust so it must just be some form of corrosion but it's a pain to remove. Does anyone have any tips for removing the gunk from the sight glass window as well?
    20190612_215211.jpg 20190612_215218.jpg 20190612_215227.jpg 20190612_215237.jpg
     
    eigenseca, Jun 14, 2019
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  2. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    That white stuff is aluminum oxide. Don't bother trying to get rid of it.
    The rust looking stuff is rust. The spring and piston screw are both steel, and will tend to rust when in contact with brake fluid (when the brake system is neglected). The mounting hardware is also steel, and can rust as well. The rust does not need to be removed either. It's embedded into the aluminum.
    Be careful when polishing the bore. You can cause it to become oval, or go oversize, and then you'll need a replacement master cylinder.
     
    k-moe, Jun 14, 2019
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  3. eigenseca

    eigenseca Member

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    Thanks for the info, what would be the best way to hone the bore?
     
    eigenseca, Jun 14, 2019
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  4. XJ550H

    XJ550H Well-Known Member Premium Member

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    you could use a flex hone made for the job.

    or use a dowel with wet/dry paper wrapped loosely on it and a drill spin it a few times with an in and out motion and your done. wet paper with brake fluid
    paper will expand when spun. it does need to be secured to dowel. I cut a slot in dowel when I do this. in out 2 or 3 times that's it and not to fast
     
    XJ550H, Jun 14, 2019
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  5. XJ550H

    XJ550H Well-Known Member Premium Member

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    [​IMG]
     
    XJ550H, Jun 14, 2019
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  6. Polock

    Polock Well-Known Member

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    don't you think that hone is a bit drastic ? 000 or oooo steel wool on a wood dowel would shine it right up
     
    Polock, Jun 14, 2019
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  7. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    I would avoid using a ball hone. I know they are meant for the job, but the bore is aluminum and won't be so bad that it needs much more than a light dressing. If it does need more than that it would be preferable to source another.
     
    k-moe, Jun 15, 2019
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