"Changed" brake fluid on an '03, now have to pump pedal sometimes to stop?

Discussion in 'Gen 2 Prius Main Forum' started by atikovi, Sep 10, 2010.

  1. atikovi

    atikovi Junior Member

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    I tried to change the brake fluid with a MityVac. I've done it to dozens of cars with no problem. With the Prius it didn't take it well as I have to pump the pedal sometimes to stop or the pedal goes way down. Only now I read about how a special Toyota scan tool is recommended to do it. Is there any other way? I only really did the front brakes since after trying one rear wheel cylinder and getting nothing out of it, I quit. The dealer wants $165 and I'm sure that doesn't include any extra shop fees and such they tack on. What other way can I try before taking it in?
     
  2. danix

    danix Junior Member

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    You probably need to bleed the ABS pump, that's what the dealer tool probably does.
    Go find a sandy lot and do some panic stops, making the ABS go off. See if the brake pedal improves. If it doesn't, follow the factory procedure for bleeding -it's that way for a reason.
     
  3. Patrick Wong

    Patrick Wong DIY Enthusiast

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    If you allowed the brake fluid to run dry in the brake fluid reservoir, then air has gotten into the brake actuator and you must follow the prescribed procedure per the Toyota repair manual to bleed the air out.

    I changed the brake fluid in my 2001, a few years ago. My procedure was to have my wife very gently depress the brake pedal while I opened up one wheel cylinder valve at a time with a vinyl tube connecting the valve to a glass jar, keeping an eye on the brake fluid reservoir so that it did not drop below 1/2 full. I closed the valve before she released the pedal. This worked amazingly well.

    However this procedure would not work on 2G.
     
  4. atikovi

    atikovi Junior Member

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    None of the dash lights are on if that helps.
     
  5. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Then, perhaps you can find a helper and see if the process I suggested above would help to get air out of the system. If the air is only in the lines near the brake wheel cylinders, you might be successful. However as mentioned previously, if you got air into the system via the brake fluid reservoir, forget it.
     
  6. vertex

    vertex Active Member

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    It is not possible to bleed the Gen II brakes without a scan tool or equivalent. There is a complicated procedure, and the tool tells you when to bleed each wheel. It also involves removing the ABS relays. Unless you have the tool, or can borrow one, you will need to go to a dealer or a mechanic that has the tool.
     
  7. vertex

    vertex Active Member

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    Oh, I see you gave a Gen I, My statement above does not apply. This is posted in the Gen II not the Gen I forum. Follow Patrick's instructions.
     
  8. brownsnoutuk

    brownsnoutuk Active Member

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    Why do people change their brake fluid?
     
  9. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Brake fluid is hydrophilic, so over time water vapor accumulates in the fluid and lowers the boiling point of the fluid. High performance European vehicles usually require a brake fluid change every year or every other year because the maintenance schedule anticipates that your daily driving may be at 100+ mph on the autobahn.
     
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