Brakes - Master Cylinder | Ford Escort Owners Association (FEOA)

Brakes Master Cylinder

Discussion in 'Wheels/Tires/Brakes' started by SoccerStar146, May 11, 2018.

  1. SoccerStar146

    SoccerStar146 FEOA Member

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    I think my master cylinder is leaking, when I'm at a complete stop I can still press my pedal down more. I found a new master cylinder, but I'm just wondering if I'll have to replace my booster too? I'm pretty sure the leak is from a bad internal seal on the master cylinder so brake fluid would be leaking into the booster. Can I get away with just trying to dump the fluid out of the booster or should I replace it?
  2. denisond3

    denisond3 Moderator Staff Member

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    Vacuum Boosters seem to last much longer than master cylinders. With my leaky master cylinders, there was a wet trail of brake fluid down the outside front of the booster. The problem was having to top-up the fluid in the m.c. reservoir now and then. I fixed the problem I had by just replacing the master cylinder and its reservoir; and bleeding all the brakes (and clutch). I didnt touch the booster.
    I dont know any quick way to check the health of a vacuum booster, except by either replacement or opening one to look inside. At which point I would likely replace it with a new or rebuilt anyhow.
    If your brakes have not been bled in the last year - then its a good idea to do so anyway. And what you want to see coming out at the bleeder screws, is nice clean clear fluid; not brownish or dark gray! ...And with no bubbles.
    You could look into the vacuum hose that connects to the top of the intake manifold. If there had been a fluid leak into the booster, it would have eventually gotten sucked into that hose, and it would be wet inside the hose.

    Replacing the vacuum booster still appeals to me; since while I know the booster can fail, none of mine have done so .....yet. I wish there was a source of OEM style vacuum booster hoses; the kind having the one-way valve in the middle of the hose. Its almost invisible, just showing up as a lump in the hose, like a snake that has just swallowed a mouse.

    If/when you are looking for fluid leaks, dont forget to look on the inner sidewalls of the tires. The fluid leaking from a caliper or wheel cylinder will stream down the sidewall, all around the tire. The evidence also doesnt get rinsed off by driving in most rainy weather.
  3. SoccerStar146

    SoccerStar146 FEOA Member

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    Bad news, it seems that my fluid leak is coming from my pressure differential valve. My research shows that is behind the intake manifold bolted to the firewall. If that's not the correct valve please let me know. I had cleaned off a bunch of sludge on it a few months ago, but now there's more sludge on it. Any info?
  4. denisond3

    denisond3 Moderator Staff Member

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    I dont recall anyone having had a failure of one of those. I would imagine there may be a rusted brake line close to it, which could be the source of the leak. I also dont know offhand where you could buy a replacement, but I would start by asking at an auto parts place. One of the best auto parts places is a NAPA outlet.
    zzyzzx likes this.

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