I recently purchased a 2014 Prius with the package 5 trim. I'm completely loving the car, but noticed when stepping on the brake pedal I hear a soft "swoosh" noise from under the dash. Almost like a short vacuum or sucking sound. The car has 500 miles, and I don't recall hearing that noise initially. Is this normal, or something I should have the dealer look at?
I hear that when I suddenly press the pedal hard. None of that with the usual brake modulation. No idea what that is as the brakes should be hydraulic and not air assisted. There is a compressed nitrogen compartment, but it shouldn't be near the brake pedal IMHO.
No, we are not talking about the usual hydraulic pump action, but rather compressed air release like sound.
Yes the sound seems to happen every time I step on the brake. It's kind of annoying every time I step on the brake to hear "pssssst". It's coming from somewhere under the dash in the center of the car. The first few hundred miles driving the car it never made that noise, so I'll probably take it in to the dealer.
The noise is normal ... I drove another new Prius that does it too. I'm not sure of the exact explanation why, but they said all Toyota's will eventually make the noise with the new braking systems.
I too have recently noticed that same sort of hissing sound and mine is new also. It's not noticeable till I've almost come to a complete stop and it's not generated by the pads.
Sounds like the rubber boot that protects the brake plunger is being compressed, and air is escaping from the inside. I suppose someone could try to open a wider vent-hole if it's really a problem.
I have had my 2013 prius for almost a year now and I notice that sound once in a while. One time a soccer ball rolled across the street and I slammed on the brakes and I heard a fart noise coming from probably the master cylinder. Felt it on the foot pedal too. The GF swears it wasn't her farting so must be the car! Get this - in the winter when it is near freezing, the master cylinder makes even a louder fart noise a few minutes after I power off the car. Even my best buddy who is the master tech at a Toyota dealership can't give me a direct answer.
That swoosh sound is indicator of a good working accumulator , an accumulator its spherical ball that has a bladder split horizontally, one side has Nitrogen gas the other side has brake fluid, its function is to act like a brake booster to reduce brake pedal effort so you can stop your car without pumping your brakes several time, since our engine cuts off its is not applicable to have a conventional vacuum brake booster, so in place it has an electric pump and an accumulator, the electric pump takes the brake fluid and stores into the accumulator as more brake fluid enters the accumulator the nitrogen side of the accumulator begins to compress until a specific pressure is reached then the pump cuts off and its now ready for the next brake application, when you hit your brakes the pressure that was build up in the accumulator by the electric pump is released into the brake master cylinder to decrease brake pedal effort and when it dose that it makes a swoosh releasing the pressure that was stored up and sending it into the brake master cylinder then to the abs module and to the brakes. That's about it folks!
Good story, but like I said in my above post that air sound should be audible in engine compartment and not brake pedal well.
