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  1. #1
    Dani_B19's Avatar
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    Question Brakes causing vacuum/boost issues.........

    Right.

    Pulled up from work today, parked the car up the drive and let it idle for a minute or 2, but for some reason i pressed the brake to which i noticed the boost gauge move.
    The car idles bang on 20 inhg without any movement on idle now but, when i started to press the brakes, the vacuum was creeping up to 17/18 inhg, if i kept pressing the brake the needle would just keep flicking up and down between 20 and 17 inhg.

    Now to me this isn't normal and shouldn't happen, it should sit bang on 20 inhg regardless of the brakes!

    I do remember Andrew having to replace the brake pipe behind the heat shielding next to the bulk head, cant remember what the proper name for it is, could this be at fault?
    Driving the most secretive S3 on ASN

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  3. #2
    jay1601's Avatar
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    its normal. the brake booster runs off the vacuum system (normally pipe coming off the intake manfiold)
    Audi A3 8L 1.8T breaking.
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  4. #3
    Dani_B19's Avatar
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    So does yours do this jay?
    Driving the most secretive S3 on ASN

  5. #4
    jay1601's Avatar
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    mine will go between 18-21depending on throttle load, gear, braking, ect.
    Audi A3 8L 1.8T breaking.
    front bumper, impact bar, slam panel, full engine and loom sold.
    everything else for sale.

  6. #5
    Dani_B19's Avatar
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    What on idle? Surely if the cars sat idling then the idle shouldn't move.
    Driving the most secretive S3 on ASN

  7. #6
    jay1601's Avatar
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    when on idle (no brakes or clutch/gears) will sit bang on 20
    Audi A3 8L 1.8T breaking.
    front bumper, impact bar, slam panel, full engine and loom sold.
    everything else for sale.

  8. #7
    Dani_B19's Avatar
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    yeah thats what i mean mate. I was sat on the drive earlier in neutral and then the above as post 1# started happening which to me doesnt seem right.
    Driving the most secretive S3 on ASN

  9. #8
    S3featesV9's Avatar
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    Mine never sits bang on 20? Always about 16inhg. What would this indicate. Also it fluctuates when steering wheel is moved, even at idle :s
    MODS - Custom Code phase 1, 007p DV, various powerflex bushes, EBC grooved and drilled - red stuff pads, N249 deletion. Badger5 V2 80mm TIP. Scorpion backbox + custom centre section, LCR front splitter, Jetex Fr-08001, R32 rear ARB, Forged IE rifle drilled rods, 20mm rear & 15mm front spacers.

    TO DO - Coilovers, adjustable tie arms, DP/mani/decat, FMIC and new remap


  10. #9
    Dani_B19's Avatar
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    MAY JUST BE YOUR GAUGE MATE, BUT YOU WANT IT TO SIT AROUND 18 TO 20 INHG, IF LOWER THEN NORMALY MEANS A VACUUM LEAK ETC.
    MINE DOESNT DO THAT WITH THE STEERING WHEEL.
    Driving the most secretive S3 on ASN

  11. #10
    Dani_B19's Avatar
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    So anyone else any thoughts?
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  12. #11
    Alais DJA's Avatar
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    Quote Originally Posted by Dani_B19 View Post
    So anyone else any thoughts?
    Turn on your heaters

    Open your electirc windows

    Turn on full beams....... it always drops a tad

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  13. #12
    Westy's Avatar
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    Quote Originally Posted by S3featesV9 View Post
    Mine never sits bang on 20? Always about 16inhg. What would this indicate. Also it fluctuates when steering wheel is moved, even at idle :s
    Nothing to worry about mine is exactly the same.
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  14. #13
    S3featesV9's Avatar
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    Yeah. All good and bill said it should fluctuate when steering wheel is moved as it putting load on the engine.

    One less thing to worry about
    MODS - Custom Code phase 1, 007p DV, various powerflex bushes, EBC grooved and drilled - red stuff pads, N249 deletion. Badger5 V2 80mm TIP. Scorpion backbox + custom centre section, LCR front splitter, Jetex Fr-08001, R32 rear ARB, Forged IE rifle drilled rods, 20mm rear & 15mm front spacers.

    TO DO - Coilovers, adjustable tie arms, DP/mani/decat, FMIC and new remap


  15. #14
    Dani_B19's Avatar
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    Thanks lads.
    Driving the most secretive S3 on ASN

 

 

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