Brake system failure after changing front pads

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by sclieu, May 25, 2011.

  1. Bikeman

    Bikeman Junior Member

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    Ahhhh, the stories of mechanics mishaps. There's the time I caught the cords of my timing light in the fan of my Boss 429. Whoopa! Sucked that thing right out of my hand and wound it around the water pump, spewing light parts in every direction!
     
  2. sclieu

    sclieu Junior Member

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    Holy crap! After driving my car in it's bad braking condition for a few weeks now, I finally decided to try the "Clear DTC" trick, and low and behold the lights went off, and the car is braking a lot better now. I'm still a bit worried because just like the check engine light, if the system detects a problem after a period of usage, the lights would go back on and my problem would be back.

    I drive to work 45 miles each way, so tomorrow we'll see if the lights come back on! Crossing my fingers.

    Thx, Seilerts for your suggestion.
     
  3. Agape

    Agape Member

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    Hi Guys,

    Started to think about my front brake pads, pads may need replacement (possibly discs /rotors too). I wan't to avoid sclieu's bad experience, so:

    Could any member confirm if the following procedure written in this article does actually works (see link below):

    Brake Job: Toyota Prius

    ?
    PS: I have few reasons why I think pads may need replacement, reasons which I need to confirm. At the moment i'm just gathering data and knowledge.
     

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  4. sclieu

    sclieu Junior Member

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    Well, I can tell you that I changed my brakes like it was a normal car, and even then, was able to get rid of the warning lights using the reset trick (which is mentioned in that article). Other than not bleeding the brakes, everything else was pretty much expected. I did not even pull the fuse. From what others say, just make sure not to bleed your brakes, if you just need to change the pads.

    Regarding whether you need to replace or not...why don't you just take off the tires and see your wear on the pads and see if it needs to be replaced?
     
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  5. Patrick Wong

    Patrick Wong DIY Enthusiast

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    I suggest that you disconnect the 12V battery before you start brake work, so that you don't have to worry about the brake pressure accumulator pump turning on at an inconvenient moment or DTC being logged by the skid control ECU. Other than that, the article cited in post 23 is a good overview of the work that needs to be done.

    I also agree that visual inspection of the brake pads (don't forget to look at the inner pads as well) is the best way to determine their condition. For North American cars, new front pad thickness is 11 mm; while 1 mm is the minimum thickness required.
     
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  6. babybird

    babybird Member

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    I have a question about this. I've seen elsewhere that the Prius (not sure if it's only 3rd generation or if the 2nd or even 1st generations also have this) has a bank of capacitors designed to power the brake system as a backup in the event of a 12 volt battery failure. I think having the system activate on you on its own would probably be pretty unlikely, but if you're playing it safe, wouldn't the capacitor system need to be discharged as well? Or is that what the 2+ minute wait after powering the Prius off that I read about is for?

    Perhaps the capacitors aren't able to maintain their charge for over 2 minutes of powered down current drain with the 12 volt battery disconnected. I'm not sure what their capacity is.
     
  7. Patrick Wong

    Patrick Wong DIY Enthusiast

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    If you think it is unlikely that the brake system will activate, all you have to do is open the driver's door while the car remains IG-OFF. You will probably hear the brake pressure accumulator pump run, as the skid control ECU builds up pressure so that the car can be ready to be driven.

    Suppose this pump runs while you have removed the front disc caliper in preparation for replacing the pads. The piston might shoot out of the caliper.

    After you disconnect the 12V battery, you could press on the brake pedal a couple of times to discharge the brake power supply capacitors, if you like.
     
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  8. Agape

    Agape Member

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    Big thank you to Patrick's advise.
    Today I managed to look (perform a visual inspection) at my front brake pads.
    Followed Patrick's advise and disconnected the 12V battery (negative wire). In addition I have removed two ABS Relays (under the hood, dark blue ones) and pressed brake pedal couple of times,to discharge the brake power supply capacitors, I did like to do this.

    Brakes(generally) and brake pads (condition):
    as you may see it it's not necessary to explain too much.


    Prius has 135,231kms, I presume pads too, can't verify this 100%, however I have kept all service history invoices (9 services at Toyota Main Dealer) and non of them mentioned front Brake Pads, it will let me assume that these are the original set of brake pads.

    Ps: nothing exploded, everything nearly like every other car, just followed strictly Patrick's procedure. So far no strange lights on the dash, no problems. Test drive done and also no problems reported.

    Tools needed:
    -spanner 17mm
    -spanner 14mm
    -spanner 10mm
    -Medium/small flat screwdriver to slightly lift Relays
    Time: relaxing includes photographs 1h 30 minutes.
    Pros: Satisfaction and updated info on brake pads, rotors condition
    Cons: None

    - No Brake system failures after removing rotor and performing visual inspection of the front pads (none reported so far) -

    Note: I have NOT touched any hydraulics, pipes, did not bleed, did not open any valves and not touched brake fluid. As s result No air was introduced to the system.

    Agape
     

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  9. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Thanks for posting your experience and the photos. Looks like the two old pads that were measured show 5 mm remaining lining thickness, so they had ~40% life remaining, if the new pads are like those installed in North American cars: 11 mm when new, 1 mm minimum thickness spec.

    Did you notice that the pads were worn evenly or were the inner pads worn differently compared to the outer?

    I assume that you worked on the front axle...how did the rear brake pads look?
     
  10. seilerts

    seilerts Battery Curmudgeon

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    Any grease added to the caliper slide pins?
     
  11. Agape

    Agape Member

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    I would need to check with Toyota Dealer as not sure what is the thickness of European pads


    By looking at inner and outer pads it appear that in with tolerance of ~4~5% both pads were worn evenly, I would say inner pads had just a bit more dust accumulated on the pads element

    I didn't look at rear pads as yet.

    Currently not, however I noticed that someone added Copper Grease on the outer Metal pad element (it's shown on the photo number dsc_0046 where, Toyota brand is written on the pad). I didn't have any copper grease so I didn't apply any.

    Overall, I would need to arm myself with a small wire brush (to remove rust from the any brakes elements and with some brake cleaner plus some copper grease and of course 3/4 of day to clean all wheels around and apply grease on slide pins.

    Currently I have mechanically removed rust (using a flat screwdriver) and dust from slide pins and from pads to allow more movement.
     
  12. LinusNLucy

    LinusNLucy New Member

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    Very nice post!. Many Thanks
    How did you push the piston back? Did you use a c-clamp and the old pad? Did you remove any brake fluid from the reservoir before pushing the piston in?

    Thanks
     
  13. Mendel Leisk

    Mendel Leisk Lapsed Cargo Cultist

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    Wait for the originator for definitive answer, but my hunch is he did not push the piston in. That's never really necessary, unless you intend to replace the pads: to accomodate the increased thickness of new pads.

    When you're opening up the caliper per his pics, and then reassemble everything and rotate the caliper back down, there's no problem. And I suspect the car's computers are not aware anything's happened.

    OTOH, if you push in a piston: at some point you're going to turn the car on, step on the brake pedal, and have to push the pedal through an abnormal amount of travel, and that's when the car's computer is very likely to freak.
     
  14. seilerts

    seilerts Battery Curmudgeon

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    Disconnect the battery if you are pushing the piston in, otherwise there is a pressure sensor in the actuator that becomes unhappy. It should not be necessary to turkey baste any fluid from the reservoir unless it has been topped off in the past.
     
  15. ChapmanF

    ChapmanF Senior Member

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    Paid $169 at Tactrix's online store and it works like a charm with Techstream on my Gen 3. Still made in USA by the people who designed it, unlike all the cheaper clone VCIs. (However, beware, it can be counterfeited too, something to suspect if "it" seems to show up with a fabulous price somewhere else than their store.)

    -Chap
     
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