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My master cylinder has a vaccuum leak! Not a misprint! Read on-

Discussion in 'The Garage' started by diesel4me, Apr 12, 2004.

  1. diesel4me

    diesel4me 1 ton status Premium Member

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    My 79 C-10 was idling poorly so I investigated and after a whole can of carb cleaner was squirted on all the base gaskets and hoses,etc,I finally found the source of the leak.The master cylinder has a bolt hole at the rear bottom of it--they used to bolt the proportioning valve there on the early (68-72) trucks.Vaccuum was coming out of this hole!!.My power brake booster has had me wondering if that was the source of the leak,because you can hear vaccuum noises under the dash that vary with the intensity of your foot pressure on the pedal. Also if you hit the brakes hard and fast you hear a "hawww" sound and there is a slight hesitation in the pedal travel(makes you think your going to hit the car in front of you) /forums/images/graemlins/yikes.gif.I assume the booster is junk??.This happenned to me on other GM trucks I've owned too. /forums/images/graemlins/angryfire.gifFor now I stuffed a peice of rubber in the hole,and it now idles much better--even the brakes seem better.I'm hoping this hasn't trashed my master cylinder,since its a recent rebuilt from autozone--guess I should have replaced them both. /forums/images/graemlins/angryfire.gifHas anyone here ever had this weird source of vaccuum leakage??. /forums/images/graemlins/1zhelp.gif /forums/images/graemlins/1zhelp.gif /forums/images/graemlins/ears.gif /forums/images/graemlins/ears.gif.This is my only current daily driver--3 trucks registered and insured,and now after paying those bills,cant really afford to fix them all--getting tired of giving all my $$$$$ to the government to keep them legal,and not having enough to maintain them properly!!!Sorry for the rant--but being unemployed and having no dependable wheels is getting to me---no sense in even looking for a job--I have plenty of work waiting in my garage! /forums/images/graemlins/blush.gif /forums/images/graemlins/blush.gif Also,does anyone know if you donate a vehicle to charity for a tax credit,and your unemployed,can you get a tax refund check??? It would be nice to get some cash right now,and my van is off the road--just wondering. /forums/images/graemlins/ears.gif /forums/images/graemlins/thinking.gif /forums/images/graemlins/dunno.gif
     
  2. m j

    m j 1/2 ton status

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    [ QUOTE ]
    Vaccuum was coming out of this hole!!

    [/ QUOTE ]

    /forums/images/graemlins/whistling.gif
     
  3. 84_Chevy_K10

    84_Chevy_K10 Banned

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    [ QUOTE ]
    [ QUOTE ]
    Vaccuum was coming out of this hole!!

    [/ QUOTE ]

    /forums/images/graemlins/whistling.gif

    [/ QUOTE ]

    Lol, vacuum coming OUT. /forums/images/graemlins/rotfl.gif /forums/images/graemlins/rotfl.gif /forums/images/graemlins/thumb.gif
     
  4. justhorsinaround

    justhorsinaround 3/4 ton status

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    Yes, I'm thinkin it's your brake booster. Replace that thang and I'm sure you'll be much happier.

    Good luck to y'all in the future.

    Allan
     
  5. Triaged

    Triaged 1/2 ton status

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    Why not just seal it up with some RTV /forums/images/graemlins/confused.gif
     
  6. BAJA_BLAZER

    BAJA_BLAZER 1/2 ton status Author

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    Because it is the Brake Booster Diaphragm that is torn and and the hole is the vent to the outside. Plug the hole and the diaphragm is still bad, and braking will suffer. Get a new Booster.
     
  7. 4xcrazy

    4xcrazy 3/4 ton status

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    Yes, and to add, your master cylinder you bought is most likely still good, as these are basically two different units, Just don't disconnect the brake lines, just remove the MC from the booster and replace.
     

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