I have a 2011 Prius w 51k that run great but has 2 intermittent problems that the dealer has not been able to identify or fix. 1) When braking on uneven road especially when raining of going downhill, the brake seems to lose power when switching over to the hydraulic braking Ang car doesn’t slow down but on hill it even seems to accelerate. I have to Floor the brake pedal to actually stop. Dealer says this is normal transfer from abs to hydraulic, but it’s not. My stopping distance on the same road is significantly increased and only stopped with a great deal of force of my foot depressing pedal all the way down. 2) not sure if related, intermittently, after normal braking the car give a gas release kind of sound like a fart. I’ve even gotten this after I park my car on my sloping driveway and shut off the car. Sometimes even when I then get out of the car that I hear this 1-2 seconds fart sound. Any ideas? I have extended platinum warranty but toyota and the dealer insist that everything is ok even though they seem to have recalled the 2010 for similar issue? Thx in advance
Full peddle to the metal and still unable to stop? I call that brake failure. When the car senses slip, the regenerative braking is switched to mechanical braking. I do feel there is a reduced in performance when that switch happens over uneven road and anything that will cause a transition. But not to a extent that you will loose stopping ability. The pop you hear might be from the master brake cylinder decompression. My also has a sound of pressure release after the car stops for a while but not too loud like yours.
The fart/quack noise when you release the brake was addressed by a firmware update. You can see this post for the firmware version that should be (or later) in your brake ECU, and if it isn't, go ask your dealer to update it, and if it still quacks after that, perhaps something more is going on, but make sure the firmware version is right first. The brief feeling of "whoopee!" when the car makes an unplanned switch from regen to friction is absolutely universal across every generation of Prius back to the Gen 1 sedan. Your description of it sounds more drastic than most, but whether you're expecting or not expecting something to happen can have a huge effect on how drastic it feels. When I bought my first Prius, people on this board advised me to go find an uneven road and make it happen a bunch of times and get used to it, before it ever had a chance to surprise me. Sometimes I do end up pushing the pedal a bit harder post-whoopee to get the car to stop where I had planned, but it's my muscle memory now and I don't really notice. It doesn't feel to me like I am "flooring" the pedal, but the same action might feel a lot different to me if I were blindsided by the event. Obviously I'm not in your car and it isn't my foot on the pedal. Though you describe "flooring" the pedal, the car does stop when you do, so we're not talking about a floored-pedal-no-stoppie event, a whole different kind of animal.
Something is definitely up with the brakes. Good luck putting that hefty chunk of paid extended warranty into use.
