Brake Booster Testing Procedures

Brakes, Steering & Suspension

  1. JedIEG

    JedIEG Well-Known Member

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    I have been having issues with keeping my engine running and having it stall when stabbing the throttle and even after idling for a couple of minutes. I started clamping off vacuum hoses to see if I could find a leak. When I clamped off the hose for the brake booster the engine idle slowed down 100 rpm and vacuum reading smoothed out. I can blip the throttle with no hesitation now... that leads me to believe my booster has an issue. The FSM doesn't have much in ways of testing the booster. Does anyone have an idea on what to do to test if the diaphragm is blown? I tries a vacuum hand pump, but i think its too small to pull enough vacuum.
     
  2. 69L48Z27

    69L48Z27 FBBO Gold Member FBBO Gold Member

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    You can pull a vacuum with a hand pump to check it.

    The other way I’ve tested mine... Place your foot lightly on the brake pedal with the engine not running, make sure all the residual vacuum is out of the booster. Now, start the car and your foot should fall with the pedal a little bit.

    Also, as soon as you stop the engine pull the hose off the booster and you should hear a whoosh of air.

    Sounds to me like your booster is not holding causing a vacuum leak.
     
    • Agree Agree x 1
    • JedIEG

      JedIEG Well-Known Member

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      If this booster is bad, where do I get a rebuild kit or new booster? I have the stock disc/10" drum booster and 4 bolt master cylinder. I cannot find anything for the single diaphragm boosters at the normal speed shops (only lots of stuff for dual diaphragms). Am I missing some key word for the single dia boosters?
       
    • 69L48Z27

      69L48Z27 FBBO Gold Member FBBO Gold Member

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    • Sixpactogo

      Sixpactogo Well-Known Member

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      Did your car come from the factory with front discs? Or have you upgraded? Are we dealing with a B body? IMO, If you have disc brakes up front, you probably should have the dual diaphragm booster. I know there are a couple guys on here that say you can get by with the single but my experience says no. If yours in fact has failed, I agree with 69L in post 4. According to my 68 parts book, Disc brake cars got the dual diaphragm. Another thing to check.....how about the check valve? I have seen them fail too.
       
    • JedIEG

      JedIEG Well-Known Member

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      It is a 72 Satellite Sebring Plus with the factory power disc/drum set up a single diaphragm booster. I believe it is a Midland Ross booster since my dad's 74 Cuda has Bendix stamped on it and is crimped where mine is a v band.
      From my 72 service manual it appears to be the correct booster for the factory. I have not verified the check valve though.
       
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