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  1. #1
    Non-member car.crash's Avatar
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    Hissing brakes

    My rear bias valve hisses when I depress the brake pedal when driving. It doesn't do it when I'm stationary with the engine running. Any ideas on what's going on?

  2. #2
    Non-member J$£5GTT's Avatar
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    Re: Hissing brakes

    not sure what that could be,bias not leaking at all?,your brakes are fine otherwise?
    how do you know its the bias?

  3. #3
    Non-member car.crash's Avatar
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    Re: Hissing brakes

    No fluid loss, no air in system and brakes work fine. You can hear the valve hissing and I have no interior.

  4. #4
    Non-member Brigsy's Avatar
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    Re: Hissing brakes

    Are you sure its not the servo hissing?

  5. #5
    Non-member Gttnutter's Avatar
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    Re: Hissing brakes

    Weird why it only does slowing down at greater speeds. It does sound from the rear. It's as if the pad is taking of the surface rust..that's the kind of sound I was hearing.

  6. #6
    Non-member car.crash's Avatar
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    Re: Hissing brakes

    Quote Originally Posted by Brigsy View Post
    Are you sure its not the servo hissing?
    100% from the rear of the car. I've read the valves can hiss as fluid exchanges but never heard it on a Gtt before.

  7. #7
    Non-member car.crash's Avatar
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    Re: Hissing brakes

    I've also swapped the bias valve and it's off my old car and never did it on that. Also if I'm above 3.5k revs and left foot brake the pedal is high and stiff but below that the pedal is low and soft. I've pretty much swapped every component but non of it was for new parts so can't guarantee fully working.

  8. #8
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    Re: Hissing brakes

    Quote Originally Posted by car.crash View Post
    I've also swapped the bias valve and it's off my old car and never did it on that. Also if I'm above 3.5k revs and left foot brake the pedal is high and stiff but below that the pedal is low and soft. I've pretty much swapped every component but non of it was for new parts so can't guarantee fully working.

    if theres not a lot of vacuum in the manifold there will be not a lot of help from the servo

  9. #9
    Non-member car.crash's Avatar
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    Re: Hissing brakes

    that would make sense on the pedal issue, any ideas on the hissing tony?

  10. #10
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    Re: Hissing brakes

    no mate not really, are you 100% its the bias ?

    could try unspringing the lever an tieing it back so no brake effort to the rear, does it still do it.

    could try removing rubber boot, does it still do it

    how have you bled the brakes ? ive had all sorts of trouble with rears on a couple of cars. trapped air thats jus being pushed sucked about an not actually going anywhere ?

  11. #11
    Non-member car.crash's Avatar
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    Re: Hissing brakes

    new discs and pads are on all round and all bedded in, brakes have been bleed countless times and the car stops very well and pretty well balanced after much adjusting. at high revs when i touch the pedal even slightly i can hear it hiss and the pedal is also higher, at low revs its quiet and the pedal is softer. the rear discs are drilled but surely it wouldnt be that and it deffo souns like its coming from middle of boot floor.

  12. #12
    Non-member modfather's Avatar
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    Re: Hissing brakes

    could it be the brake compensator

  13. #13
    South West Regional Rep jesus in the seat of a 5's Avatar
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    Re: Hissing brakes

    despite laughing at logs post id say it may be the servo.....

  14. #14
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    Re: Hissing brakes

    how did you bleed them, leg power, sucker bleeder, pressure bleed ?
    are the rear pads new fandango fancy things made of noisy stuff ?

    by the looks of it rich has heard it ? best thing i recon get him round again, tie him to a skate board, bunjee him to the floor pan an drive around untill he is 100% where its coming from.
    prob best to keep it below a ton as ive seen some proper tank slapping speed wobbles on skate boards, be funny as **** seeing a human [term used loosly as we talking about richy] torpedo lauch out the side of an r5 on a roundabout

  15. #15
    Non-member car.crash's Avatar
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    Re: Hissing brakes

    I did swap the servo a few years back but it was a used part. It holds vacum and the one way valve on the engine and servo is also new.

  16. #16
    Non-member rs250nut's Avatar
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    Re: Hissing brakes

    Quote Originally Posted by fishead View Post
    how did you bleed them, leg power, sucker bleeder, pressure bleed ?
    are the rear pads new fandango fancy things made of noisy stuff ?

    by the looks of it rich has heard it ? best thing i recon get him round again, tie him to a skate board, bunjee him to the floor pan an drive around untill he is 100% where its coming from.
    prob best to keep it below a ton as ive seen some proper tank slapping speed wobbles on skate boards, be funny as **** seeing a human [term used loosly as we talking about richy] torpedo lauch out the side of an r5 on a roundabout

    Nutter, im going to start calling you danger mouse

  17. #17
    Non-member car.crash's Avatar
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    Re: Hissing brakes

    I bled them with a pressure bleeder. Lost count of how many times but they are sharp. Front pads are ds2500 and rears are Renault ones. It was front heavy on the brakes but a quick tweak and it feels very balanced but the noise remains the same. No interior is in the car so im fairly sure it's the bias valve.

  18. #18
    Non-member modfather's Avatar
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    Re: Hissing brakes

    Quote Originally Posted by car.crash View Post
    I bled them with a pressure bleeder. Lost count of how many times but they are sharp. Front pads are ds2500 and rears are Renault ones. It was front heavy on the brakes but a quick tweak and it feels very balanced but the noise remains the same. No interior is in the car so im fairly sure it's the bias valve.

    im sure i got 1 round here if you need 1

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