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Brake pedal hard

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by PriusDadNoob, Mar 5, 2022.

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  1. ChapmanF

    ChapmanF Senior Member

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    This PriusChat wiki page lists a variety of options for access to the repair manual.
     
    #21 ChapmanF, Mar 9, 2022
  2. PriusDadNoob

    PriusDadNoob Junior Member

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    I finally got time to work on my 2010 Prius and wanted to post a follow up.
    I ordered a USED replacement ABS module (the part the pedal connects to) and pressure accumulator (the cylindrical tanks). Paid around $200 each for these. I think the price has gone up with the cost of used cars skyrocketing. I replaced them and put a new gasket in between the ABS module and the firewall. I was faced with taking it to the dealer for the brake bleed or doing it myself and I like to do things myself. I had a ABS scanner that worked great to bleed my brakes on my 2007 but it did not work on this 2010. So I bought an old Windows laptop on eBay (that was a pain, so many junk laptops out there...) and a Tech Stream cable and software. After a lot of trial and error I did get the bleed procedure to work and my car is now stopping great again!

    One point, I did have to adjust the brake light switch to keep it from coming on when parked. I just twisted the green part of it and pushed it in and out until it was off when the pedal was fully up.

    Thanks again for all the help everyone.
     
    #22 PriusDadNoob, Apr 3, 2022
  3. ChapmanF

    ChapmanF Senior Member

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    Are you certain you got the replacement actuator completely seated down flat on the firewall? The adjustment you needed for the brake light switch makes me think the pedal might not be coming back when released quite as far as it used to.
     
    #23 ChapmanF, Apr 3, 2022
  4. PriusDadNoob

    PriusDadNoob Junior Member

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    It seemed to seat down pretty well. I think the difference in the old and the new (used) module was that the new one was adjusted differently at the yolk or whatever you call that u-shaped piece the pedal connects to. The threaded shaft that is adjustable may have been just a little off.

    I'll double check that it's totally against the firewall. Thanks for the insight.
     
    #24 PriusDadNoob, Apr 3, 2022
  5. Mr. F

    Mr. F Active Member

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    Going through Toyota's response (a critical portion of which is redacted) it would seem the nitrogen leak in the accumulator is an entirely separate issue from SLA valves in the actuator assembly developing surface wear and leaking slightly open. If the high pressure valve can no longer hold the accumulator pressure, the accumulator pressure will eventually drop and the pump will need to run to restore it.

    I've read in a few threads here that a failed accumulator assembly leaking nitrogen will/can eventually knock out the actuator assembly. How would that occur? What would be the failure mechanism? I ask because I had a failed accumulator (I heard it whistling between successive pump runs) which I replaced, but my actuator assembly is still whistling continuously in a different pitch. There are no external leaks, so would I be correct in assuming it is an internal leak in one of the SLA valves?
     
    #25 Mr. F, Apr 4, 2022
  6. ChapmanF

    ChapmanF Senior Member

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    The technical instructions for the D0H recall (nitrogen-leak-prone accumulator) did say to replace only the accumulator/pump assembly if it did not seem to have leaked yet, but both assemblies if it already had.

    I don't know what happens to the actuator if nitrogen leaks in, beyond needing to be carefully bled out again.

    I notice that, while they include bleed-the-actuator procedures in Techstream, they don't seem to be super confident in them. If I'm not mistaken, when they sell a new actuator, it's pre-filled and pre-bled, and they warn against messing it up while installing. You would still need to do some bleeding for air that came in at the connections you made, but they seem to want to keep that to a minimum.
     
    #26 ChapmanF, Apr 4, 2022
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