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Thread: Vacuum pump / Brakes Issue

  1. #1
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    Vacuum pump / Brakes Issue

    Thought I would put up a thread of how this headache gets resolved.

    Background - I had a perfectly good 402ci motor in my Monaro, and brakes were first class.

    Changed motor to one from my old drag car - big solid cam, and made fuck all brake vacuum in drag car.

    Exactly the same issue now in Monaro

    Talked to a lot of people about my problem, and was assured a vacuum pump would solve it for me.

    Bought CVR VP-555 for just over $550.00

    Fitted it up according to instructions

    Tee it into brake booster line, and install check valve on engine side of line.

    Pump fires up, sucks fine, and cycles on and off when you block off line/ unblock line.

    Ok - so I sucked on check valve and it works perfectly.

    Replumbed so only vacuum pump supplying booster - no change, still one pump then no more assistance on brakes.

    Then bounce this off a few people, and condenses is, I need a vacuum tank as well (fuck me how hard can shit get overnight??).

    Decided to look on net at tanks to get an idea - most look to be around 2l capacity, but sizes dont match spaces in engine bay for me.

    Friend suggests try one out of pvc to make sure it solves problem first - great idea.

    Only had 90mm pvc stormwater kicking around - vacuum pump collapsed that!! - therefor I know pump sucks well!!

    Will make one from 100mm tomorrow night and try that.

    If that works, I will get a custom one made up so vacuum pump mounts on top, and mount it all where original air box was.

    Not convinced this is the issue though.

    Unfortunately, I think this rules me out of Collie on Saturday

  2. #2
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    Quote Originally Posted by heavyduty1340 View Post
    Replumbed so only vacuum pump supplying booster - no change, still one pump then no more assistance on brakes.
    Does it recharge over time? If it's got good pedal once then it's obviously working, but it sounds like the rate it's drawing down is way too slow. A quick look online and everyone using them loves them, so maybe you have the 1 in 10,000 that's dodgy?

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  4. #3
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    I have a 2L steel vacuum tank if you want to borrow it for this weekend, has hose and check valve on it.

    Also check your booster, engine off and push pedal, should hear rush of air. Get your head up under dash with a bit of hose to your ear.
    Now turn on your Vac pump and listen again for any air rush under dash but don't touch the pedal.
    xw Falcon 393 Full race cam. NGK plugs.

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  6. #4
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    Not something stupid like throttle still stuck on?

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  8. #5
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    This is the biatch from hell.
    There is zero room in bay now - I need to dummy test tank to ensure this is the fault.

    Time to take a step back and sort properly so I dont bin the old girl.

    Reckon 100mm pvc will do the job as a test tank - thanks for the offer Greg Rust.

    Gotta be an underlying issue I think - will resolve or burn!!

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  10. #6
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    were allowed to have passengers at collie yeah? just pick up a bunbury slapper on the way to collie. strap her in and give her the brake booster hose and get suck en.

  11. #7
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    Wired it to constant power to see if it works like that?

    You mention in other thread its off fuel pump relay?

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  13. #8
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    Pump works fine, but just doesnt seem to suck enough.

    I will try my accumulator tank tonight and see how it goes.

    If that doesn't help, then I'm stumped.

    Once engine starts, fuel pump relay has constant power, and pump will cycle on and off.

    When you put your finger over the end of pump, vacuum isn't super strong - I would have thought it would suck like a two bit hooker

  14. #9
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    Two really dumb questions....is the polarity correct? and are the inlet/oulets on the pump plumbed to the correct ports?
    I drive a Prius cause I'm dead inside.

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  16. #10
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    Quote Originally Posted by -Luke- View Post
    Two really dumb questions....is the polarity correct? and are the inlet/oulets on the pump plumbed to the correct ports?
    DC voltage

  17. #11
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    ^?
    I drive a Prius cause I'm dead inside.

  18. #12
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    Quote Originally Posted by S85FI View Post
    DC voltage
    Couldn't reversing the polarity make it blow?

  19. #13
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    Can you get an absolute gauge on there to measure the actual pressure?
    xw Falcon 393 Full race cam. NGK plugs.

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  21. #14
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    i asked my mate, he said he just got an ebay jobbie and he is fifo so wont know what brand exactly for 11 more days.

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  23. #15
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    Definitely put a gauge on it to check what the pumps actually doing
    Check booster is operating correctly

    If that fails remove the rubbish and fit hydraboost or alternator with vac pump fitted

  24. #16
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    I went through all this years ago by checking manifold vacuum on engine with gauge. Was pretty good 24"
    Then fitted tank and check valves but still rock hard pedal.
    Ended up being a faulty reconditioned booster, they swapped it over and had a sweet pedal.
    xw Falcon 393 Full race cam. NGK plugs.

  25. #17
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    Quote Originally Posted by -Luke- View Post
    ^?
    Modern cars are DC voltage (direct current) basically one way eletrical circuit plugged in wrong either don't work or typically short out.

    Modern cars negative earth. Some older cars positive earth.

    AC is alternating current. Pending on set up motor can run both ways.

    Cars don't use AC voltage. Except for the Alternator which is AC but has a rectifier to convert to DC to charge the battery. Therefore the circuits are DC.

    In its simplest form.

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  27. #18
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    Umm...yeah. But a dc motor (assuming permanent magnet) will operate in either the direction if the polarity is swapped. The vac pump will have a dc motor in it.
    I drive a Prius cause I'm dead inside.

  28. #19
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    Checked vacuum on gauge today - at idle, motor is pulling 5"Hg.

    Vacuum pump pulls 20", and restarts dead on 15"Hg.

    Not sure just how much of a difference the rather large calipers make to vacuum usage makes?? Could account for some of the issue?

    Made 3 litre accumulator tank out of 100mm storm water pipe as a test unit - definately better, but at crawling speed, it still drains fast.

    Looked at https://www.youtube.com/watch?v=94ajut6OEek and my pump is no where near this quick to suck to 20"

    Pump in first test is mine.

    Either mine is a dud, or this is crap.

    Second pump looks faster - it is a vane pump where as the first is a diaphram pump.

    Shits wearing thin atm!

  29. #20
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    Vane style pump will be more efficient than your diaphragm style. If you plug the inlet with your finger does it pull down enough to shut off?

    Starting to sound like the pump is faulty and drawing air past the seal between the head and diaphragm or the internal check valves are stuffed ( assuming no external leaks)
    I drive a Prius cause I'm dead inside.

  30. #21
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    yes - it cycles properly - just not fast enough for what I need by the look of it.

    Quick way to waste $550.00.

    Grrr.

    Will look at VP-655 the vane pump tomorrow and see what $$$ it is.

  31. #22
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    How much vacuum does your motor make at 2000rpm no load?
    xw Falcon 393 Full race cam. NGK plugs.

  32. #23
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    Will check in the morning - at idle, its 5"Hg .

  33. #24
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    Quote Originally Posted by -Luke- View Post
    Umm...yeah. But a dc motor (assuming permanent magnet) will operate in either the direction if the polarity is swapped. The vac pump will have a dc motor in it.
    Not when every other circuit is negatively earthed. Motor will short out or blow a fuse. DC engines dont do that. AC do.

    Try and swap any wire in your car that is DC and see what happens when you turn on the Key?

  34. #25
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    Quote Originally Posted by heavyduty1340 View Post
    yes - it cycles properly - just not fast enough for what I need by the look of it.

    Quick way to waste $550.00.

    Grrr.

    Will look at VP-655 the vane pump tomorrow and see what $$$ it is.
    With out gauges and a big fuck off tank, I don't think 655 will be quick enough - not based on that clip.
    At 5 hg thats fuck all...typical of a camed car... actually camed car not that bad normally. So your solid cam must have some serious valve overlap.

    That pump might work for a burn out car.... but they don't normally need big demand. Burnout car you typically feather throttle on and off, creating fast and big vacuum - track car - big demand, throttle typically WOT and little to no vacumme. Untill you hit a corner, then big vacumme In that video set up, one brake application on a decent booster will empty the chamber before the guy even flicked the switch.

    A stock cam will do about 20hg and will suck the booster instantly. Under braking (track work) it will hit about 30.

    I think you will need a tank about a 6.0lt capacity and really close to the booster for no delay.

    Your stock booster is probably around 2lt. You can go a smaller booster to overcome the electric pump problem but then you need to change the bore size in the master cylinder to get the hydraulic leverage. This also means caliper piston size change

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