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'Whooshing' sound when brake pedal is held down

posted by  rstarkie on  Fri Dec 20 16:39 CST 2024
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last visit: Fri Oct 24 10:14 CST 2014
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1992 745 319K

I got a call from my son. He describes a whooshing sound when pressing the brake pedal that continues while the pedal is pressed, and then stops when he removes his foot from the pedal. I haven't encountered this before and the only thing I can think of is perhaps the check valve on the brake valve has failed.

Does that seem reasonable or does anyone have other ideas? I am not going to have access to the car for another three days. Should I have any safety related concerns about him continuing to drive the car?
--
Any twenty minute job is just a broken bolt away from a three day ordeal








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    'Whooshing' sound when brake pedal is held down

    posted by  Will740turbo on  Fri Dec 27 01:53 CST 2024
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    last visit: Wed Oct 22 16:09 CST 2014
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    I had this once. It's likely that the brake booster diaphragm is leaking internally and pulling air through the booster diaphragm. I had this happen once and it was bizarre. Nobody mentioned it as a possibility.

    For me, it sounded like water flowing through a showerhead.

    The brake booster check valve is to keep vacuum from flowing from the booster to the engine and tampering with vacuum readings. It doesn't really do anything to help the brake booster work better, so it failing wouldn't be noticeable.

    It could be a failed seal on the brake booster where the line goes into it, but I would bet on it being the booster diaphragm.

    Good luck!
    Will








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      'Whooshing' sound when brake pedal is held down

      posted by  someone claiming to be rstarkie on  Thu Jan 16 14:19 CST 2025 [RELATED]

      Thank you for your response and sorry for my late reply. I have not been able to access the Brickboard since seeing your response (I have been trying three different browsers). Today I got lucky.

      I finally was able to get a look and more importantly a listen to the car. I believe you are probably correct. It does seem to be a leak around the rod running into the booster from the pedal arm. If the weather breaks I will try to get the booster off of the parts car.
      --
      Any twenty minute job is just a broken bolt away from a three day ordeal








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      'Whooshing' sound when brake pedal is held down

      posted by  rstarkie on  Thu Jan 16 14:17 CST 2025
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      last visit: Fri Oct 24 10:14 CST 2014
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      Thank you for your response and sorry for my late reply. I have not been able to access the Brickboard since seeing your response (I have been trying three different browsers). Today I got lucky.

      I finally was able to get a look and more importantly a listen to the car. I believe you are probably correct. It does seem to be a leak around the rod running into the booster from the pedal arm. If the weather breaks I will try to get the booster off of the parts car.
      --
      Any twenty minute job is just a broken bolt away from a three day ordeal








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    'Whooshing' sound when brake pedal is held down

    posted by  Dave Stevens on  Sat Dec 21 03:12 CST 2024
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    last visit: Sun Jan 1 02:36 CST 2012
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    Consider the cruise control switch at the brake pedal. It's got a vacuum line on it. If it's leaking, it could hiss while the brake pedal is depressed. Pull the vacuum line off the switch and stick a screw or golf tee in it to see if the problem now goes away. Second would be a vacuum leak at the brake booster.
    --
    Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now








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    'Whooshing' sound when brake pedal is held down

    posted by  jwalker on  Fri Dec 20 16:55 CST 2024
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    last visit: Fri Jun 6 08:39 CST 2014
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    I assume you mean the the check valve for the brake booster? They can make a hissing sound. Not sure about a whooshing sound. Maybe a bad vacuum hose?

    Are there any other symptoms when braking?

    --
    Will I buy another Volvo??? We'll see....








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      'Whooshing' sound when brake pedal is held down

      posted by  rstarkie on  Fri Dec 20 17:23 CST 2024
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      last visit: Fri Oct 24 10:14 CST 2014
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      Yes, I meant the brake booster and some type of whoosing, hissing, rushing air sound.

      He said he hasn't noticed any change in the braking action on the car.
      --
      Any twenty minute job is just a broken bolt away from a three day ordeal








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        'Whooshing' sound when brake pedal is held down

        posted by  jwalker on  Fri Dec 20 19:00 CST 2024
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        last visit: Fri Jun 6 08:39 CST 2014
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        Disclaimer: I’m no brake expert…:)
        If it’s just hissing it’s probably ok to drive until he or you can fix it. Don’t let it slid, however…

        --
        Will I buy another Volvo??? We'll see....








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          'Whooshing' sound when brake pedal is held down

          posted by  Chris Mullet on  Fri Dec 20 22:46 CST 2024
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          last visit: Fri Oct 24 09:08 CST 2014
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          If it’s a constant hissing as long as the pedal is depressed then it could be the seal where the pedal rod goes into the back end of the booster. If it was an internal diaphragm leak I would think it might be affecting the braking efficiency.







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