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Thread: Losing Brake Boost

  1. 16th January 2012, 12:55 PM #1
    brno465's Avatar
    brno465
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    Losing Brake Boost

    Hi Guys.
    A question for the experts before I go see a mechanic.

    Having issues with my Disco 300Tdi's brakes.
    You get full power assist when you first push the pedal, but you only get one go - feather the pedal pressure, or release the pedal and put your foot down again and all boost is gone.
    It still stops, but it takes a bit of effort.

    No brake fluid is being lost, vacuum pump was replaced 12 months ago, can't hear any hisses under the bonnet when the brake is applied.
    There is the hiss in the footwell (booster equaliser valve ?? ) but it has always been easy to hear.

    As always, any info greatly appreciated.
    Tim
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  2. 16th January 2012, 03:38 PM #2
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    Blknight.aus
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    Vac leak from the piping, or the boosters leaking.
    Dave

    "In a Landrover the other vehicle is your crumple zone."

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    Fozzy, 2.25D SIII Ex DCA Ute
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  3. 16th January 2012, 05:39 PM #3
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    Thanks Dave.
    Any easy way to tell which is leaking?
    Can't see any cracks in the pipe, or hear anything hissing, so guess it's more likely to be the booster ?
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  4. 16th January 2012, 07:45 PM #4
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    To diagnose the vac system remove the hose and fit a tee piece to the vac pump inlet. Use some soft hose each side you can clamp shut. Use a vacuum gauge on the tee. Run the engine with the booster clamped off, see how good the pump is, then see how high the vacuum goes with the booster connected, then clamp off the vac pump side and see how long it holds vacuum.
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  5. 16th January 2012, 09:08 PM #5
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    thats more or less how I'd do it but I have a seperate vac pump with a flow gauge to test the booster.

    If i get flow after 30 seconds its a booster leak
    Dave

    "In a Landrover the other vehicle is your crumple zone."

    For spelling call Rogets, for mechanicing call me.

    Fozzy, 2.25D SIII Ex DCA Ute
    Tdi autoManual d1 (gave it to the Mupion)
    Archaeoptersix 1990 6x6 dual cab(This things staying)


    If you've benefited from one or more of my posts please remember, your taxes paid for my skill sets, I'm just trying to make sure you get your monies worth.
    If you think you're in front on the deal, pay it forwards.
    Reply With Quote Reply With Quote
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