Brake noise on depression and release, with audio

not getting the video

 

If I remember right, not so very long ago, the PriusChat media gallery wouldn't even let a video be uploaded.

So I'm thinking, the ability to upload a video, even if it doesn't quite exactly play yet, could be a sign of progress?

 

Without watching your video at the moment, from your description of the sounds I suspect bubbles in the system. In a conventional car, you would feel a spongy low brake pedal, because you're squeezing the bubbles. You don't feel that in a Prius, because the computer just shoots more pressurized fluid into the brake lines until the bubbles are squeezed and the pressure is right, but you hear an extra little whoosh from it doing that. Then when you release the brakes, the bubbles expand again and drive that extra fluid back to the reservoir, and you hear that little whoosh too.

The Prius brake system has a magical way for bubbles to slowly appear in it over time even when no one ever did any work that let air in. You can read about it here.

The long-form "there might be bubbles in the head end" brake bleed procedure can get those out. You may eventually have to do it again, and you may eventually have to replace the actuator. But if the only bubbles so far have come from a very slow leak, then there may be quite a while before you have to repeat the process.

If it doesn't take quite a while, then the time to replace the actuator may have come.

I definitely would try to bleed the bubbles out, the sooner the better. There are rare but occasional reports here of people experiencing floored-pedal-no-stoppie brake failures (much more rare than the usual "I had to stomp really hard but it stopped" kind, which aren't as awful). My unproven theory for those is that there were bubbles in the line, probably there for a while, normally not very noticeable except for the whoosh sounds, but then something else happened that triggered the brakes to the fail-safe pedal-powered mode, and then the bubbles were too big for the pedal to squeeze the brakes. (In other words, with big enough bubbles, the "fail-safe" mode may not really be safe.)

 

You are right about that.

It is highly unlikely you need another new master cylinder/brake booster. Without Techstream or an XTool D8, you don't bleed everything in the current brake booster. Let Toyota do it for an hours labor especially since you are in for $1300 already.