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    #1

    Brake check valve question

    I'm trying to troubleshoot a braking problem. Does this check valve look correct? Realoem shows one in from the booster and 2 out to the manifold. Mine only has one in and one out, leaving a fitting open on the manifold.

    Just wondering if I'm not getting vacuum assist because of this.



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    '90 325is
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    #2
    BMW used two systems for the vacuum hose. One is the single connect, like you have and the other is a dual connect.

    No vacuum boost, especially with the engine idling, will be a major leak between the intake and the booster or a bad booster.
    The car makes it possible, but the driver makes it happen.
    Jim Levie, Huntsville, AL

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      #3
      I notice oddly that 40mph and under I can lock them up. Anything over 40 it takes tons of pressure just to slowly stop. Could a leak between the MC and booster be the cause? Can I use copper gasket between the 2?

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      '90 325is

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        #4
        The pedal going hard usually means a lack of vacuum in the booster. You could have a bad check valve, leak in the hose, or a leak in the booster. If the hoses look good and the check valve works, you can use a hand held vacuum tester to check the booster.
        The car makes it possible, but the driver makes it happen.
        Jim Levie, Huntsville, AL

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          #5
          Originally posted by jlevie View Post
          The pedal going hard usually means a lack of vacuum in the booster. You could have a bad check valve, leak in the hose, or a leak in the booster. If the hoses look good and the check valve works, you can use a hand held vacuum tester to check the booster.
          I replaced the brake booster and the hose from the booster to the check valve is new. I can suck a little bit of air from the line that comes from the check valve to the intake manifold and can't blow back to the booster. So that means the valve works right? Where would I hook up the vacuum gauge on the booster?

          Btw thanks for the help. I have replaced the booster, flushed the system 2x, replaced the pads 2x, taken it to a shop, and still have the problem. but I feel like I'm closer.

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          '90 325is

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            #6
            To test the whole system, connect the pump/gauge to the line that connects to the throttle body. To check just the booster, connect to the nipple in the booster.
            The car makes it possible, but the driver makes it happen.
            Jim Levie, Huntsville, AL

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              #7
              Ok thanks. Just have to get my hands in a mity vac now

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              '90 325is

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