buzzing sound during braking (sometimes)

This is the brake pressure accumulator pump. If you repeatedly pump the brake pedal, you will force the pump to run.

The sound is normal.

"Normal" cars do not have this pump, as they depend upon engine vacuum to create brake power assist. Since the Prius gasoline engine frequently is not running, engine vacuum cannot be counted upon to always be available. Hence Prius has an electric motor that intermittently runs this pump to build up hydraulic pressure so that when you depress the brake pedal, the car will stop.

 

you should have that inspected by your toyota dealer there are tsbs for abs actuator noise its a very expensive repair if your vehicle is out of warranty..yes there are some normal operational sounds but your dealer technicial will let you know

 

If it's just a little buzzing sound there is no need for a trip to the dealer - completely normal.

Tom

 

Mine does that as well. Don't worry. Perfectly normal.

 

They all do it. Some people can hear it, some not, but they all make that sound.

Tom

 

Hello Patrick,

Could this sound like a faint telephone ring? If not, I may be losing my mind!

I greatly appreciate your time.

 

"Faint telephone ring." Yeah, I could imagine describing it that way....

I'll have to remember the next time somebody posts a " new Prius owner!" thread here. It's really worth describing what this pump does and what it's for, and just having the new owner go out and listen to it. You can turn the ignition ON (just ON, not starting anything) so it's easiest to hear the pump. You might hear it right away, but after a few seconds it shuts off with a click. Then you can make sure that was what you were hearing, by pumping the brake pedal a few times until you hear it click back on and run again, and click off again.

Once you know it's there and you know what it sounds like when it works, it won't interfere with your peace of mind later.

A usual run is for several seconds ... instead of a telephone ring, I'd say more like a cell phone somebody left on 'vibrate' and laid on the table. If you listen very closely, over the several seconds while it runs, it can sound like it's working a bit harder toward the end just before it shuts off ... because it is, as the accumulator pressure builds up.

I guess people with Gen 2 and later can hear it even without turning the car ON, maybe as soon as the driver's door is opened to get in. On my Gen 1, it only runs if the ignition is ON.

-Chap

 

So is this normal everytime you push on the brake or slow to a stop you'll hear that or is there something wrong with it I drive a 2008 Toyota Prius just rolled 100,000

Posted via the PriusChat mobile app.

 

not every time, but quite often. it has to stay topped up.

 

I began to notice that mine progressively became louder as my mileage went from 97,000 miles up to 310,000 miles. I took my car to Toyota and they said yes, the brake actuator is on its way towards dying on me and that should make some noise but not THAT much noise. And they told me that the car was still under the extended warranty with unlimited miles until December 2017. The repair was listed as $2,500 but Toyota told me that if I had to pay them to fix it out of my own pocket, it would have costed me around $3,000.00

Posted via the PriusChat mobile app.

 

Note that there's two sounds. One is a buzzing or creaking sound from the pump restoring pressure to the brake system, and the other is a high pitched whine from charging occurring from the electric motors during regenerative braking at >5-10mph. Both of these are normal. If your brake pads are worn, you could get a high pitched or other sound during braking from this as well, which would indicate you need new pads/rotors.

Does the sound only occur while moving, or if you pump the brakes while stopped (try in P with the car in Ready), does it also occur?

To me it sounds like the brake pressure accumulator pump, which is normal to make some noise, but should not be a loud noise.

 

Bro, so your point is the abs pump sound will produce the sound quite often? my 2005 Prius produces that sound quite often when the car in the slow traffic speed and when i step on the break pad.

 

yes, you should hear it when you first open the drivers door. the randomly when you step on the brake, as it needs topping up.
if the sound changes and/or becomes more frequent, that's when you know you have an issue developing

 

I see, thanks bro.

 

pleasure

 

Bro, I forget to clarify. The sound I hear while my car in the slow traffic was not the continuous sound, it was start & stop, start & stop sound like when we open the driver door while my foot is not on the break pedal so it could be the sign of problem as well?

 

There is a pump, and a pressure accumulator. When the pressure in the accumulator gets low enough, the pump starts and pumps it back up. When it's high enough again, the pump stops. Every time you use the brakes, some pressure is used up (more or less, depending on the way you brake each time). When you've used up enough, the pump runs again.

Every Prius does this.

 

completely normal. if it becomes continuous, time for repair.