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  1. #1
    Senior Member K & M McF's Avatar
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    Dec 2009
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    Kareela, NSW
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    Brake Booster Problem

    We went down to Brindabilla and Koscziusko National Parks over the Australia Day period and suffered a partial brake failure on the second day. Took two days to get out and to civilisation so not easy to get help.

    Anyway, the problem was that when applying the brakes (of course on a very steep downhill low range hill) the pedal went to the floor. If you pumped it, the brakes worked, but eventually the pedal went back to the floor. Once down, a check showed no loss of brake fluid. The next day it was a lot better so we put it down to perhaps contaminated brake fluid (water or air). However, it soon returned the same, so it was certainly not overheating. Still no loss of brake fluid. A check of the booster showed correct vacuum.

    We limped to Cooma eventually where we finally found a mechanic (most were closed even though a working day). Guess what, when they looked at it everything worked perfectly. We drove around town, refuelled and all was okay. We contemplated returning to finish the trip (and meet back up with our friends) but decided to drive back to Sydney.

    Sure enough, brakes ended up back as before. Not too bad on the Hume as no real need to stop, but had to use a lot of care going through Canberra and then into Sydney (picked the route we less need to stop!).

    Now back at home still cannot work out the problem, obviously a brake booster problem from what I can assess (and reading my Prado service and repair manual). Any ideas before I take it to the mechanics?
    Michael and Kelly

    1999 Prado Snowy 3.4L petrol, Ultimate Suspension 50mm lift (2013), BFG A/T, bull bar, winch, Twine hot water shower, home made rear drawers, Shippshape car top tent, UHF radio, tablet GPS & Navman GPS (both running OziExplorer), Spot 1, solar panel, second battery, inverter, Engel fridge and more

  2. #2
    Senior Member Leethal's Avatar
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    Aug 2008
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    Brisbane, QLD
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    Pedal going to the floor is more likely a brake master cylinder fault than a booster fault. A faulty booster tends to make the pedal harder to press as you loose assistance.
    If the brake master cylinder is by-passing internally it will sink to the floor. Try applying light pressure to the pedal and see if it slowly sinks to the floor.
    If you have water contaminated brake fluid it will boil very easily, I would change the fluid anyway if nothing else shows as brake fluid should ideally be changed every 12 months anyway.

    Lee
    02 VX, Toyota Alloy Bar, IPF 900XS with 50 watt HID, 50 mm Lift- Lovell Shocks n Springs, Safari Snorkel, large Pioneer tray, Pioneer In-dash, Alpine roof mount DVD screen -handled the Simpson and Innaminka roads, now with a little TRD blower & Unichip

  3. #3
    Member CoreyTroy's Avatar
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    Apr 2016
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    Illawarra NSW
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    I'd say you have a faulty master cylinder.
    You can buy a non OEM for <$100 on flee bay delivered.
    1999 Prado VX Grande White on Silver 3.4Ltr Auto

  4. #4
    Senior Member K & M McF's Avatar
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    Okay, thanks, the mechanics in Cooma seemed to think it was not master cylinder since it was not losing any fluid.
    Michael and Kelly

    1999 Prado Snowy 3.4L petrol, Ultimate Suspension 50mm lift (2013), BFG A/T, bull bar, winch, Twine hot water shower, home made rear drawers, Shippshape car top tent, UHF radio, tablet GPS & Navman GPS (both running OziExplorer), Spot 1, solar panel, second battery, inverter, Engel fridge and more

  5. #5
    Senior Member K & M McF's Avatar
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    Yes, it turns out it was the master cylinder. Like a new car now, amazing how much difference it has made.
    Michael and Kelly

    1999 Prado Snowy 3.4L petrol, Ultimate Suspension 50mm lift (2013), BFG A/T, bull bar, winch, Twine hot water shower, home made rear drawers, Shippshape car top tent, UHF radio, tablet GPS & Navman GPS (both running OziExplorer), Spot 1, solar panel, second battery, inverter, Engel fridge and more

  6. #6
    Member CoreyTroy's Avatar
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    Apr 2016
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    Illawarra NSW
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    Good stuff. Back to Prado-ing it again.
    1999 Prado VX Grande White on Silver 3.4Ltr Auto

  7. #7
    Senior Member K & M McF's Avatar
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    Dec 2009
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    Kareela, NSW
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    Well, towing boat, towed 2 tonne boat today and could stop!!
    Michael and Kelly

    1999 Prado Snowy 3.4L petrol, Ultimate Suspension 50mm lift (2013), BFG A/T, bull bar, winch, Twine hot water shower, home made rear drawers, Shippshape car top tent, UHF radio, tablet GPS & Navman GPS (both running OziExplorer), Spot 1, solar panel, second battery, inverter, Engel fridge and more

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