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Brake concern

Discussion in 'Gen 3 Prius Main Forum' started by badbob47, Oct 10, 2011.

  1. badbob47

    badbob47 New Member

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    Hi folks,
    I purchased a 2011 Prius 2 (Sandy Beach Metallic)in August and just love it. Besides the unbeatable gas mileage, It really is a quiet, nice driving car. This coming from someone who really is a Jeep and truck person. I just got tired or paying a high monthly gas bill running my two gas hogs around. I'm located in Hawaii and gas here is right at $4.50/gallon now so the Prius really makes a lot of sense.

    Anyway, since I've had my Prius, I've noticed that every now and then, the brake pedal doesn't feel right. It happens intemittently when I first start the car. The pressure on the brake pedal doesn't feel normal. I can best describe it as being similar to a vehicle with power prakes that has loss vacuum. The brake pedal goes down and stops suddenly with the result that the braking action is jerky. Once underway, things are fine. I have an appointment with the Toyota dealer on Tuesday. Hopefully, we can get the peculiarity to show up while there. If not, I am hoping the the car's computer has logged the action as an error although no indication has showed on the display when it has happened. Has anyone else experienced this oddity?
     
    #1 badbob47, Oct 10, 2011
  2. The Critic

    The Critic Resident Critic

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    I have had the same issue on mine. The conclusion that I have come to is that because of the infrequent use of the friction brakes, rust/debris may buildup on the rotor which may cause the brakes to feel "different" or be less effective during the first or second stop. However this does not always occur for me, and cannot always be reproduced, so I've chalked it up as normal behavior unless there's a TSB that addresses it.
     
    #2 The Critic, Oct 10, 2011
  3. Teakwood

    Teakwood Member

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    First off, the brakes are electronically controlled, just like the accelerator and the steering. The "feel" of the brake pedal is totally artificial.
    When you press the brake pedal down hard, you go into a function called "Hill Start Assist." This means that when you let up on the pedal, it will keep the brake engaged for a few seconds. This is to provide an Assist when Starting after a stop on a Hill.
     
    #3 Teakwood, Oct 10, 2011
  4. jdenenberg

    jdenenberg EE Professor

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    As far as the rotors developing rust. This is a common issue with a Prius in humid environments as the friction brakes are normally only used under 7 MPH or in panic stops. You can easily clean the rotors by periodically getting your Prius up to about 25 MPH, put it in neutral so that regenerative braking becomes unavailable and lightly apply the friction brakes. Repeat this a couple of times and the rotors will be cleaned up and the rubbing noise will be reduced.

    JeffD
     
    #4 jdenenberg, Oct 10, 2011
  5. badbob47

    badbob47 New Member

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    Thanks for your inputs. I don't think rusty rotors is a problem. I can see that they are very nice and shiny. The peculiarity has shown up after driving several miles under various braking conditions. It always seems to happen immediately after starting the vehicle up. For example, one day I was driving and had a cell phone call so I stopped on the shoulder of the road. The call was lengthy so I turned the car's power off. On restarting, I noticed that the peculiarity happened on the first brake applcation then went away. Another day, it happened after a brief stop at Mcdonalds. Same thing, shut the car down, then it happened after applying the brakes after starting up and backing out of the parking area. The most significant incident happened after having the car for about a 10 days. I went to my friends house to pick he and his wife up. Thier driveway is on a uphill grade. I shut the car down as I was waiting in the drive way for them. When they got in and under way, I restarted the car and reversed down the driveway. What caught me by surprise is that the brake pedal didn't have the normal steady, normal progressive feel, It went down and stopped the car, I had to relaese the pedal to reverse further, and brake again. Repeated this about 3 times. It's happened when backing out of my garage also. I think another way of describing it (after further reading on how the brake system works) is that it feels as though the system has not been brought up to normal pressure thus affecting the feel on the brake pedal and the braking action. Anyway, I have an appointment with the Toyota dealer tommorrow and we'll see what they have to say.
     
    #5 badbob47, Oct 10, 2011
  6. spiderman

    spiderman wretched

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    It is good to get it reported, however as I mentioned in your other post, many of us have had it happen. There is a good thread on the issue somewhere. It happened twice to me early on (< 5,000miles) and has not happened since.
     
    #6 spiderman, Oct 10, 2011
  7. Mendel Leisk

    Mendel Leisk Senior Member

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    I've noticed a very intermittent behaviour with ours: just after startup, in reverse, it's near impossible to modulate brake pressure. It's either off or near-locked. Once I get going it's ok, it's just that initial back up, and it's infrequent.

    And it's not always when the car is cold started either: once I was reversing to get out of a parallel parking spot, and honestly thought I'd hit the car behind, but it was just the touchy brake.

    I'd call it a minor design flaw, since it's quite infrequent, and has minor impact, but it should be addressed.
     
    #7 Mendel Leisk, Oct 10, 2011
  8. Tideland Prius

    Tideland Prius Moderator of the North
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    I think I know what you're talking about. Are you talking about a really sensitive brake pedal? One where it seems like the application is on or off? And that it ONLY happens after you start the car and slowly inch out of the parking spot (unless you completely release the brake pedal)?

    If so, yeah I've had that happen. I can't remember the exact conditions that will trigger it but it freaked me out the first time it happened as it was a very hard stop when I meant to only back out of the spot. And yes it feels like there's no vacuum boost. It's hard and feels like you're stepping on a block of wood.
     
    #8 Tideland Prius, Oct 10, 2011
  9. badbob47

    badbob47 New Member

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    It's happened to me about 8 times in 1500 miles.

    Well, if it's a design flaw, it's still an area that they can improve on.

    That pretty much describes it. Right now, I am a little reluctant to let others drive the car because of it.
     
    #9 badbob47, Oct 10, 2011
  10. TheSpoils

    TheSpoils Member

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    Open and close the door and the brake will prime again and should fix the problem.
     
    #10 TheSpoils, Oct 10, 2011
  11. badbob47

    badbob47 New Member

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    The problem is that it's intermittent. Once it happens, it seems a couple more applications of the brake pedal clears it up.
     
    #11 badbob47, Oct 10, 2011
  12. TheSpoils

    TheSpoils Member

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    Open and close the door and it wont happen at all. Another option is to just leave the car in the "ON" position while you make your calls, unless you plan on being on the phone for a very long time, (longer than 30 or 40 minutes) it should be fine in the on position, the gas engine will be off.

    good luck
     
    #12 TheSpoils, Oct 10, 2011
  13. badbob47

    badbob47 New Member

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    #13 badbob47, Oct 11, 2011
  14. spiderman

    spiderman wretched

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    #14 spiderman, Oct 11, 2011
  15. kithmo

    kithmo Couch Potato

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    Mine actually primes twice, once when I approach the car with the smart key and again when I touch the brake pedal before pressing the start button.
    I have had no problems when I reverse out of my driveway every morning, although it is flat I still have to brake to stop the car going too fast and the brakes work fine and progressive, no different to any other car I've owned.
     
    #15 kithmo, Oct 12, 2011
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