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Master Cylinder

Discussion in 'The DIY Room' started by papadave, Apr 9, 2014.

  1. papadave

    papadave

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    So, local mechanic thinks it may be going bad.
    Doesn't look too tough. Do these come with the bleeder kit?
    I've been losing fluid in a come and go way, and he says it's probably in the booster.
    If true, what needs to be done to that?
    Thanks for any ideas/help.
     
  2. gmule

    gmule

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    If you have fluid in the booster soak it up with rags or paper towels.
    Just make sure you bench bleed the master cylinder before you put it on. Some will come with the bleeder kit some won't.
    You can also install the master cylinder, connect the lines pump the brake pedal until you have pressure, hold it and crack open the lines on the master cylinder as if you were opening a bleed screw on a caliper or wheel cylinder. Once the master is bled you can gravity bleed the brakes start with the RR on to the LR then RF and finally LF.
     
  3. papadave

    papadave

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    Thanks gmule.
    Pretty much what I thought, but I've never messed with a MC so I wasn't sure.
    One other question.....even if I do the bench bleed, since the main lines are open I presume I'll still need to bleed everything else, right? Wrong?
     
  4. gmule

    gmule

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    Yes you still need to bleed the entire system.
     
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  5. chris

    chris

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    Booster and master cylinder 2 different animals, Booster vacuum operated, check vacuum lines. loosing fluid- has to be going somewhere that means a leak . You will have to go under unit to check all the lines, as most units no longer have chromium plated lines they rust pretty quik depending on your area. You will need to follow the brake lines along the frame rails looking for an oily spot. Generally when a Master cylinder goes it is internal, allowing fluid to bypass the piston. Ain't no expert just past experience.
     
  6. papadave

    papadave

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    Thanks chris. Here's the weird thing......no leaks for about 2 weeks now. I was adding fluid every couple days when it was cold out.
    Also don't see any signs of leaks, other than the missing fluid. Brakes sometimes feel good, then get slightly "soft"/spongy.
    When I first noticed this last year, I grabbed a bottle from the local AutoValue and it was synthetic (didn't notice until after I used it)......problem seemed to get worse.
    After going through that bottle, I went back to non-syn, and once I used about 1/2 that bottle, loss all but stopped.
     
  7. papadave

    papadave

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    The thought was the seal (s) was going bad, and got worse because of the syn. fluid.