01 brake master cylinder help?

Discussion in 'Generation 1 Prius Discussion' started by Str8pile, Jul 21, 2025 at 10:19 PM.

  1. Str8pile

    Str8pile New Member

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    Okay first time posting but need to see if anyone has advice or a solution. 2001 prius 195k on it. No codes relating to abs. No brake line leaks nor leaks at the wheels. Car bleeds off brakes at stoplights. I have diagnosed it as a bad master cylinder is that a correct diagnosis? That being said master cylinders for Gen 1s are discontinued and I dont see any aftermarket solutions. Does anyone know of a retro fit or should I do the "rebuild kit" that has a new piston seal and retainer (my worry there is a possible worn cylinder) or is my best bet to find one at a junkyard or a full blown parts car. Thanks in advance.
     
  2. Tombukt2

    Tombukt2 Senior Member

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    You talking about the part that pedal connects to ? I believe that's a somewhat normal hydraulic 3/4 bore type master cylinder. If so very rebuild able.. but usually leak downs are in accumulator.
     
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  3. Str8pile

    Str8pile New Member

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    How would I go about checking and or verifying which component is the issue? Rather than throw parts at it that are expensive and discontinued?
     
  4. ChapmanF

    ChapmanF Senior Member

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    Can you give any more detail on exactly what happens at stoplights, and how you went about your diagnosis that it's the M/C?

    If you're right, you're in luck, in that gen 1 had an inexpensive M/C rebuild kit available, which later gens did not.
     
  5. Str8pile

    Str8pile New Member

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    Well considering normal vehicles and i see that these are more complex now i may be incorrect. But at a red light if I hold steady distance aka stop then hold my foot in that position the car will slowly start to release until it will just start rolling forward. I can push and hold constant firm pressure down and it will slowly go do the floor. Maybe 20-30 seconds. If it release all i do is pump it and i will have the pedal back at normal position and restart the process. Is that enough for you to go on? Thank you in advance.
     
  6. Trombone

    Trombone Active Member

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    If it is the accumulator, you're looking at 1K for the part. Labor cost is heavy, too, since a bunch of stuff has to be removed under the hood to get to the thing.
     
  7. ChapmanF

    ChapmanF Senior Member

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    The gen 1 accumulator is in a tricky place, over on the passenger side, but PriusChat member rlin78 years ago worked out a way of replacing it with a lot less removal of stuff.
     
  8. Str8pile

    Str8pile New Member

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    Does it sound like the accumulator then or the master cylinder?
     
  9. Tombukt2

    Tombukt2 Senior Member

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    So then when it bleeds down do you hear a pump pumping or you have to pup pedal to get pump to run n pump accumulator up?
     
  10. ChapmanF

    ChapmanF Senior Member

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    Well, nothing you have written here sounds like the accumulator to me. I was just responding to a drive-by post about the accumulator that happened to show up in your thread. :)