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Strange noise when braking??

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Bikeman, Apr 15, 2008.

  1. Bikeman

    Bikeman Junior Member

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    My 06 Prius just turned 40k miles and suddenly a new sound has appeared during braking. Right when you depress the pedal, a squeal sounds from the engine compartment area, almost like a pump or something starting up and squeaking. It goes away immediately, but occurs every time the pedal is depressed. Anybody have ideas? Thanks in advance!

    Bikeman
     
    #1 Bikeman, Apr 15, 2008
  2. morpheusx

    morpheusx Professor Chaos

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    A squeak? Are you sure it doesn't sound sort of like a muted Horn or chirp? If so if may be the Brake Actuator and I guess there is a TSB about it needing the fluid bled.
     
    #2 morpheusx, Apr 15, 2008
  3. Bikeman

    Bikeman Junior Member

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    It's hard to describe. I suppose you could describe it as a horn or chirp. It's a high-pitched noise, makes me think of a pump starting up dry before it gets water to it. So this requires a brake bleed? If not a pressure bleed I can handle that myself.
     
    #3 Bikeman, Apr 15, 2008
  4. legendx

    legendx New Member

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    Maybe need the rotors cleaned?
     
    #4 legendx, Apr 15, 2008
  5. morpheusx

    morpheusx Professor Chaos

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    Does it do it when you are stopped waiting at a traffic light with your foot on the brake also.
     
    #5 morpheusx, Apr 15, 2008
  6. Patrick Wong

    Patrick Wong DIY Enthusiast

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    See attached file.

    The Prius brake system is quite unusual. The repair manual requires use of the Toyota diagnostic laptop or hand held tester to properly exercise the various solenoids in the brake actuator when bleeding the brakes.

    Should you decide to try flushing the brake fluid yourself anyway, I strongly suggest that you not allow any air to enter the system; if you do so then it will be impossible to purge that air without having the Toyota diagnostic tool available.

    Note that if the brake bleed does not work, then the TSB suggests replacing the brake actuator which is an extremely expensive part. Unless your car is covered under extended warranty you may decide to live with the sound since the TSB says that braking performance is unaffected.
     

    Attached Files:

    #6 Patrick Wong, Apr 15, 2008
  7. Bikeman

    Bikeman Junior Member

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    This noise just appeared and I am trying to figure out under what conditions it occurs. It seems like it happens only when driving normally, not while stopped. I am out of warantee and do not have extended, so if this needs to be addressed will be out of my pocket.
     
    #7 Bikeman, Apr 16, 2008
  8. qbee42

    qbee42 My other car is a boat

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    Here are some tests that will help us with the diagnosis:

    1) Does the noise occur only above 8 mph, or only below 7 mph?

    2) Do you get the noise if you shift into N before braking?

    3) Does it occur every time you brake, every third time or so, or randomly?

    4) Sit in Park. Press and release the brake pedal repeatedly (at least a dozen times). Does this cause the noise?

    Tom
     
    #8 qbee42, Apr 16, 2008
  9. Bikeman

    Bikeman Junior Member

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    Ok, that'll take awhile, but I'll check this out and get back ASAP.
     
    #9 Bikeman, Apr 16, 2008
  10. Bikeman

    Bikeman Junior Member

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    No Noise

    Drove the car today, not a sound. Much braking in town, never heard a thing??? Weird.
     
    #10 Bikeman, Apr 16, 2008
  11. qbee42

    qbee42 My other car is a boat

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    Maybe you had a pedestrian stuck under the front bumper.

    Tom
     
    #11 qbee42, Apr 16, 2008
  12. Bikeman

    Bikeman Junior Member

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    I knew I heard a thump-thump!:)
     
    #12 Bikeman, Apr 16, 2008
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