Inflating sound

There are Brake Actuator Capacitors near the back, they charge up to run the brakes when there is no power. You could be hearing them.

about 2/3 down this page http://techno-fandom.org/~hobbit/pix/uyv3/i.html

 

i would have the dealer take a listen, when did this start? how long have you owned it?

 

It is coming from the front and almost certainly is the brake actuator booster pump pressurizing, I believe it's located by the master cylinder. Just open the driver's door when the car is cold and listen, you should hear it without even getting in. You can close the door and wait, it will eventually release the pressure. If the car is warm, you may not hear it if it's still pressurized.

 

is there anything in the owners manual about this gizmo?

 

Yes, page 36 says:
The brake system operation sound heard from the front of the vehicle when the driver's door is opened.

 

thanks! i would like to learn more about this. i am going deaf, so miss many sounds those more fortunate are able to hear.

 

maybe the 2012 doesn't have it.

 

It is definitely the brake gizmo up front, doing exactly what it is supposed to be doing.

If you would like to learn more about it (and other interesting stuff on your car), take a skim through the New Car Features Manual ... in a way, the most useful first thing to check out over at techinfo.toyota.com, because it's the one that tells you what all the gizmos in the car are and what they're there for, and how they work when they're working right.

-Chap

 

I would have thought you might be hearing the ICE cooling water being transferred from the Thermos bottle (front, driver's side) into the ICE cooling system - it is stored there after the car has been shut down so that any heat in the cooling system might be used to get the ICE up to its efficient operating temperature as quickly as possible when re-starting (…so there's also a similar pumping noise when the system is shut down)

 

While the Gen 2 has that system, Gen 3 does not.

 

Ah! I've learned something new today (always good to learn at least one new thing per day!) Thanks!!!

 

My 2012 PiP seems to make the same sound under the same conditions as the OP.

 

It's also meant for people with a $15 short-term subscription fee who are curious to learn about and take better care of their $$,$$$ cars.

I admit I didn't expect this thread to be showing how little-known and little-recognized the brake accumulator pump seems to be among Prius owners. There are a lot of parts of the car I might not be very curious about, but "how do the brakes work in this thing" was one of my earliest questions....

-Chap

 

Yes, all Prius have a hydraulic brake pressure pump. Because our engine may shut down at any time, we can't rely on vacuum from it. So we have an electrically powered hydraulic pump to produce the pressure in the system for "power brakes". This pressure may bleed off overnight. In my experience each Prius bleeds at different rates. Oh, and if this makes you nervous, I don't think it's indicative of the state of any component, unless it won't shut off, of course.

Anyway, so when you open the drivers door your car may start up the pump (to be ready to go when you are). When you depress the brake pedal multiple times it may also start up. All normal operation.

 

I have found that the prius is a much different car from the norm. Noises and sounds from it are not uncommon, but are usually for a reason (mostly good reasons). I quit freaking out about buzzing, humming, beeping, gurgling and hissing sounds my car makes because everytime I go to find out what the noise is, its just a part of the prius way. I'm fairly certain that if my car is in need of serious repair, it will tell me far before it becomes a real issue.

 

I went to pick up my granddaughter from school today and sat in the car reading with the windows open for a bit after I turned it off. After short time I heard a kind of hiss that seemed to be coming from the rear. I say "seemed" only because I wasn't really paying attention. I assume it was the actuator pressure being released. I believe the booster still had pressure though because when we got back in, I didn't hear anything. I wasn't really paying attention then either, so I could be all wet. I believe I've heard the booster release pressure too when I've shut the car off and then fiddled in the garage long enough.