Prius brake (squawk/bark/honk/grunt type noise from brake accumulator/booster/actuator) severity

Hello Folks,

I have a 2011 Prius with 129k miles on the clock. I am experiencing the brake clunk/thump noise when exercising brake pedal to stop followed with typical energizing sound (bit of non coasting/regenerative type of stop). I am certain that this from brake booster/accumulator assembly( below the fuse box in engine bay)
I vaguely remember this noise being present super occasioanlly, but lately it seems to be getting more pronounced.

My brakes (disks and pads) are good, tires, suspension components are good and the Toyota technician itself confirmed about the noises being abnormal themselves and easy to replicate during test drive. But, so far functionality is not affected.

I am trying to understand/gauge the brake clink/clunk noise to see if any part(brake booster/accumulator) is about to fail, unfortunately Toyota wouldn't cover it as there is no error codes or lights.

Toyota tech did apply newer s/w for brake accumulator/assembly to see if the noises would away, but it didn't.

CSB: ZJB

I am looking to see if this being expericienced y others as well and for how long, if this noise is to be taken as tell-tale sign.

I also hear this noise when the car is in parked mode but turned on after pressing the brakes, just enough till the hill assist does not engage and when depress the brakes too.

Also found this read out: Toyota Prius buzz, squish or honk noise when using the brakes

Video capture of the noise/sound:

 

My brake pad and the disc rotors are brand newish, they were installed around 18 months back. The calipers appear to be rust free along with disc rotors.
The brake pedal feels is almost consistent and travel appears normal, the brake fluid is topped off from recent service around 4 weeks back, the dealer during service performed basic checks and no issues absolutely, not even the noise, this is just been recent development.

I have had a caliper pin seizing issue in past my Acura tax in past, where the tire would become super hot.

 

Once the car is turned off, after pressing in the brakes, I don't hear the noises from engine bay (clunk from brake accumulator), after few iterations, the pedal stiffens up. Once disc bulge subsides, let me check that out too.

If you see the video, it doesn't appear like grinding video, it appears more like what I found online of Prius brake noises but very discussions around them. There are some videos in YouTube with same exact issue but no follow up comments :-(

 

The reason why I am sure that it's not from rotors is, because the same noise occurs even when the vehicle is parked, just slam in the brakes while vehicle is stationary, and the noise is super audible, inline of thump/clunk

 

I see this noise when the car is actually parked but turned on, and pressing the brakes seems to generate this noise.

 

The dealership today during diagnosing did check that too as well (now looking at the work order).

My Acura TSX had seized pin issue a while back, where the pads wouldn't retract all the way. I found out by the abnormal heat that particular tire emitted, but currently, they are running normal hot.

Even, when the brakes are pressed, this thump noise is not continuous, it happens once only while the brake pedal is still engaged.

 

Yup, that's my next step once my disc bulge subsides,.

If you see the YouTube video I posted, you can hear brake regenaration and then followed with this clunk/clink/thump noise once the brake pedal is pressed.

 

Aah, sorry, no worries,

I found this : Toyota Prius buzz, squish or honk noise when using the brakes

This exactly explains my observation currently.

Sorry, I keep getting confused between brake actuator/accumulator/booster, I am sure that initial whine/whistling noise and this honk type noise is from the same location, I had my wife start and pedal a few times, followed the noise beneath the fuse box, sort of inward between hybrid motor and fuse box

 

Thanks for the noise names , I just updated the title to reflect this part.

Ahh, my Prius verbiage has gotten out of date

Toyota dealer did update both the MG recall and brake system updated s/w and still the issues persist.

 

Oh, that they didn't tell me the rev version, all they said is they plugged in my vin, and it automatically updated, but they kept existing Caliberation because my Prius was upgraded to 17 inch wheels but factory spec is 15 wheels, this is the same dealership who had originally sold the car with this change, I knew this would be critical so we t to the same dealership.

Anything, further they kept arguing that this is the best :-(