Gen 1 Prius (2000) – Weak Brakes & High-Pitched Warning Noise – Advice Needed

Discussion in 'Generation 1 Prius Discussion' started by Diamond545, Dec 20, 2025.

  1. Diamond545

    Diamond545 New Member

    Joined:
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    Vehicle:
    2000 Prius
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    N/A
    Hi guys! I bought a 1st gen prius today, for $2000nzd, knowing it had a breaking issue.

    just want to get more info on this to try help me do some repairs and further diagnostics.

    basically, when the car turns on, there is a constant humming/warning noises, the breaks are very soft and weak, you need to press very hard to get them on.

    my understanding is that the brake actuator may be broken? And only one of the two brake systems are working currently, would anyone else have any information to add? The prius is 2000, 1st gen.

    apparently the issue occurred after jump starting it.
     
    #1 Diamond545, Dec 20, 2025
  2. Diamond545

    Diamond545 New Member

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    Location:
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    Vehicle:
    2000 Prius
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    Hi everyone,

    I recently bought a 2000 Prius (NHW11) knowing it had brake issues, and I’m trying to diagnose before replacing parts. Symptoms:

    • Brakes feel weak and spongy.

    • Constant high-pitched humming warning sound when the car is in READY mode. And ABS light on.

    • No obvious leaks, but the pump seems to run frequently.

    I suspect the brake actuator/ABS pump assembly might be failing, but I’d like to confirm before spending big on parts.

    Questions:

    1. Does this sound like a failing actuator/accumulator?

    2. Is there a way to visually inspect or test the actuator without removing it?

    3. Any tips for sourcing a replacement (OEM vs used vs aftermarket)?

    4. Will a scanner like Autel AP200 read the relevant ABS codes on Gen 1?

    Any advice or experience would be hugely appreciated! Thanks in advance.
     
    #2 Diamond545, Dec 21, 2025 at 12:10 AM
  3. Tombukt2

    Tombukt2 Senior Member

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    Vehicle:
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    I think even car scanner app and elm 327 will get ya codes like abs. Ap 200 will bled brakes if ya do them.
     
    #3 Tombukt2, Dec 21, 2025 at 7:31 AM
  4. ronlewis

    ronlewis Active Member

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    Location:
    texas
    Vehicle:
    2001 Prius
    Model:
    One
    Pretty much sounds like your booster pump is shot. It comes on when you turn the key on and pumps up the brake fluid pressure, then shuts off after a few seconds. Sounds like yours continues to run, which likely means it's unable to build pressure because of a leak. The leak is usually in the pump, unless you've had an accident that damaged brake lines/cylinders under the car. Check your brake fluid level. If it's full, it's an internal leak, i.e. the pump. If it's low, you have an external leak and your pump might still be good (don't keep driving it empty of fluid).

    Lotta these cars discarded when the actuator goes out because the new parts cost more than the car is worth. One solution is to buy the pump used from a dismantler - here's one with some old Prii in NZ - Current Stock at Avondale Yard (Auckland)
     
    #4 ronlewis, Dec 27, 2025 at 7:18 AM
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