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Thread: Braking increasing RPM's?

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    Default Braking increasing RPM's?

    Hi everyone, My name's Ryan and pretty new to the Z-world and loving it though. A friend of mine bought 2 1972 240z's and they both need a little work. The problem presently is that when I press the brakes on one of them it increases the RPM's. I'm not sure if any of the hoses might be hooked up wrong or if something is just going out. Thanks for any Help.

    Ryan

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    Semi-retired admin Arne's Avatar
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    Sounds like a power booster problem to me. When you step on the brake pedal you are causing a vacuum leak that lets the idle increase. Try disconnecting and plugging the hose to the power booster and seeing if that makes a difference.
    Arne - Former owner, HLS30-37705, 7/71, 905 Red
    Car blogs - 240Z - Porsche 911

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    240Z Elec. Upgrade guy Zs-ondabrain's Avatar
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    also sounds like the booster valve is possibly backwards. The valve in question is located on the firewall inbetween the booster and the intake. just follow the hose.

    The valve only lets air go one way and if it's backwards, it'll push air into the intake and make your RPM's go up.

    my $0.02 worth.
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    Thanks guys, I'll give those ideas a try. I tried disconnected a couple other hoses with no luck, but I'll check that booster valve too.

    Ryan

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    Default Another brake question

    Ok I tried checking the booster valve and that seems to be hooked up right, but I do notice that when I press the brake pedal I can hear a little air leak. This is when the engine idle increases...The same thing happened when I unhooked the check valve and didn't have the end covered leading to the intake. So do you guys think I need to rebuild or replace that vacuum on the brake system?

    thanks again
    Ryan

  6. #6
    beandip beandip's Avatar
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    If you disconnected the vacuum line from the manifold and plugged it off , then started the engine . Then applied the brakes and the engine did not react. If the vacuum line is not leaking and as you say the valve is installed correctly . You have a faulty vacuum booster. I don't believe kits are available any longer, I haven't seen one in years . Gary
    I'd rather die while I am living than live while I am dieing. CZC 1887 IZCC 12602 Member of NorthWest Z Car Club

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