When should you hear the brake booster usually on a Prius 3rd gen?(can you check on your car?)

I hear it when I first open the driver's door and each time as I come to a stop. That's all.

 

i hear mine sporadically. mostly when i hit the brake, and sometimes in between. although it is almost 8 years old, i don't think it has changed much

 

Mine sounds like @bisco. Most times that I open the driver's door it whirs, and just one in a while when drivng; definitely not every time the brakes are used.

 

yes, seems more than normal. probably what mine was like when newer

 

You should hear the brake booster when you open the driver side door with the key fob or when you step on the brake pedal with the key fob. that should be the only time you hear it, that’s why when you do brake pads replacement, they tell you not do any of those things or else the brake caliper piston will engage.

 

Mine is probably leaking a bit then

 

I think it has to repressurize (or whatever's making that noise) periodically, as the car's running. Not that often, once in a while. Ours has always been like that.

 

That's what it does exactly. Like the pressure tank and well pump at your house (if you have those), it runs every time enough fluid has been used to drop below the pump-on threshold, and then stops when the pressure is back to the pump-off threshold.

And how often that happens just depends on a bunch of things. How many applications of the brake. How hard they were. How far the pads and pistons move to contact the disc, and how far the pistons return when you release. Whether a disc has a bit of wobble. Etc. Leakage will also contribute, if there is any, but it's hardly the only factor.

Ultimately, it's the kind of thing that is too easy to obsess over without having nearly the instrumentation to follow all the factors feeding into it. Unless it is really running near-constantly or the ECU is giving you warnings about it, well, it runs when it runs, and you hear it when you hear it, and the times it runs that you don't hear it, you don't.

The pressure pump itself is not really the reason people take precautions working on the brakes, because all it does is store fluid under pressure in a bottle. Whether any of that fluid gets sent to the brakes is under the control of valves in the actuator, not the pump.

The ECU does, though, have a little self-test dance it does a couple minutes into snoozing, and that dance does involving twiddling the valves open and verifying pressures, and that indeed will complicate your workflow if you have a caliper out of position when it happens.

 

Mine is doing it now more frequently than previously, also I have the accompanying barking/squawking noises, do you ahve the same noises too ?

Captured here:
Prius brake (squawk/bark/honk/grunt type noise from brake accumulator/booster/actuator) severity | PriusChat

 

I assume you've already searched this forum, found the posts about the firmware version that was for quieting the honk/grunt noises, and checked whether your brake ECU is running that version or higher?

 

Yes,.

 

And the version is

 

Ah, dang the dealer they didn't it to me, but they mentioned it was upgraded to version that would supposedly quiet it, but in my case it didn't work out, I have an oil change and brake bleed this week scheduled, let me try and get this s/w version.

 

Just in case you have problems with it. There is a FREE FIX from TOYOTA if your brake booster is defective. Check if you may subject of Voluntary fix by Toyota https://static.nhtsa.gov/odi/tsbs/2019/MC-10164922-9999.pdf . 31 August 2021/unlimited mileage.

 

H᠎i, welcome to PriusChat, where a lot of people come looking for accurate information about their Prius cars.

The 'campaign ZJB' document linked above applies only to 3rd generation Prius liftback and Prius Plug-in (PHV) cars, not to the v or the c. The end dates vary by model year:



So it's already over for 2010s (unless anybody's got one that hasn't rolled 150k by now).

For 2011s through 15s, it is still in force through August 2021 and then to your tenth year or 150k miles, whichever comes first.

It is a replacement conditioned on specific failures ("certain internal malfunctions of the brake booster and brake booster pump assemblies"). It is good to remember that in the 3rd generation Prius, those are two different assemblies:



There is a list of trouble codes that may mean the covered failure has occurred. They are codes that can also be set for other reasons. Sometimes a few simple steps of diagnosis will reveal that something else has caused the codes you have, and that replacement of one or even both these assemblies would not be the necessary solution.