The brake barking noise

I believe your brake actuator wishes to be a saxophone. So maybe you could buy it sax lessons.

Only I guess it's easier to find lessons on playing a saxophone than on being one.

Going through the post-actuator-replacement brake bleed procedure may help. I believe there are likely some nitrogen bubbles in there that you might be able to chase out, and those would be what's making the fluid shoot through the valves as through saxophone reeds.

 

I would not recommend bleeding the brakes, unless you’re prepared to buy a new actuator when the brake system can’t calibrate itself afterwards

 

The only difficulty I've had with bleed procedure (caveat: I have a Gen 3) was when I was using a cheap-nice-person Mini VCI and it would repeatedly "lose communication" usually during the very last step of the procedure. That was annoying, and I got to "go back to start" about five times before getting lucky and finishing.

Since getting a better dongle to use with Techstream, I've never had that problem again.

We have a thread compiled with some effort by mr_guy_mann reviewing a bunch of non-Techstream alternatives and which of those can also bleed brakes:

Gen2 OBD2 app review | PriusChat

If my brake system was showing symptoms of fluid bubbles, the possible risk of something not going right in the bleeding would not, to me, outweigh the risk of not bleeding it.

Having bubbles in the fluid isn't just a matter of some annoying bark sounds. It also makes the pump and accumulator work harder: each time you use the brakes, more fluid has to be valved into the lines to take up the space the bubbles occupy, and each time you release the brakes, that much more fluid gets spouted back to the reservoir as the bubbles re-expand, and that hastens the use of fluid from the accumulator and the need for the pump to run again.

That situation puts even more wear on the accumulator for as long as you continue putting up with it. That makes it the sort of condition that spirals: a tiny leak in a worn accumulator can be what starts it, but then the condition itself accelerates the wear that makes it worse.

When the bubbles in the fluid get big enough, you can be at risk for the floored-pedal-no-stoppie kind of brake failure (that's the kind that nobody likes).

Ordinarily, the way Prius brakes work, bubbles in the fluid don't make the pedal feel any different: you're just pushing on a stroke simulator, and the brake system meters whatever amount of fluid into the lines that it takes to get the braking effect. At most, you might notice an extra whoosh sound when you apply the brakes, or a bit of a bark when you release. The feel of the pedal doesn't tell you anything is wrong.

But there can be some other conditions that cause the system to switch into "fail-safe mode" (maybe better called fail-usually-safe?) where it really is just your foot on the pedal pushing fluid, and if that happens when you've got bubbles in the fluid, suddenly you're going to notice. And if it turns out at that moment that the bubbles are big enough for the pedal to touch the floor without slowing the car, you're not going to like it.

 

Prius ABS modules are around $500. That's not too bad considering the one on the SUVs are around $1000 for essentially the same part.

 

Don't overlook the obvious.
It could be a costly mistake.

First check the pads and rotors (visual inspection).
Pads sometimes start "barking" when they get real thin.

The brakes in my C tend to bark when it's been sitting in the rain for a while
and then is driven at low speeds. I assume that is partly due to scrubbing
off the surface "rust" on the rotors.

 

I am new here, and I have a long post up that I posted last night, but no one has answered yet. I am about half way in on purchasing a 2007 Prius with about 87,000 miles. I drove it with the owner, but we were talking and the radio was going, so nothing sounded odd. However, after I dropped her off and took the car home, on the way, when I was stopped at lights, I heard some odd sounds. One was a random bark (more like a yip than woof type sound), that I had at first brushed off to be the pedestrian traffic signals or something. I wasn't paying close attention, and the windows were up, but as I drove, and then sat stopped, I would hear a bark or two before the light changed.

This 2007 appears to not have had any work on the ABS system, which is the problem I suspect may be starting up, so missed any initial warranty type repairs. The only codes on the dash are the ones for the tire pressure sensor not working, so not a big issue there, and then 'air' which I think is because I had my water bottle in the passenger seat?

Another sound I heard related to the brakes was very faint, and coming from somewhere near the steering wheel. It, too, was random, and seemed to start when I was stopped at a light as well. I am trying to remember how it sounded, and I almost think I thought it was an antenna trying to automatically extend or something, but the location of the sound was wrong. Sorta a tiny ding ding or beep beep? I read somewhere that sound may be related to needing a new brake booster, but does fixing the ABS fix the brake booster? I apologize, I know nothing about this sort of stuff, but am trying to learn - and fast so i can make the right decision about this car. Thank you!