Brake Booster Replacement

So, your best bet.. I went through this, first replace both booster and master cylinder with new don't try used...

goto
Toyota Parts and Accessories - Official Online Store
and enter your VIN and search for booster.

youll need the brake master cylinder and the pump assembly, brake booster.

 

For starters, in a Gen 3 you have to be really careful with the names of what did or didn't bite the dust. The brake booster is the thing on top here, and the brake booster pump is the thing on the bottom, and people mix them up all the time.



The top thing (booster) is also the master cylinder, actuator, and ECU.

The bottom thing (booster pump) is also the accumulator.

So now, knowing that, when you read something like this:

you see that if you were to replace "both booster and master cylinder", you'd only have replaced one thing.

If you replace the booster pump and the master cylinder, that's replacing two things.

In the online parts catalog, that thing on top (which is the booster, master cylinder, actuator, and ECU) is called "brake master cylinder".

The thing on the bottom (which is the booster pump and accumulator) shows up as "brake booster pump assembly" in the catalog. (Ok, it really shows up comma-inverted as "pump assembly, brake booster" the way people used to do in big typewritten alphabetized lists, but we don't have to sound like Yoda when we talk about it.) It's tucked away where you might not look, in the "brake tube and clamp" drawing.

Replacing both items is always an option, but sometimes people prefer to do a little more diagnosis and pin down which one bit the dust really.

 

There's a skirmish of wit between them.
Shakespeare's "Much Ado About Nothing"

Good advice.

I am not sure who is confused about the nomenclature. There is a Master Cylinder with lots of extras and a separate hydraulic pump that includes an accumulator.

 

What you slide over as "lots of extras" is the fact that the ("master cylinder", "booster", "actuator", and "skid ECU") are all the same thing, and even in Toyota literature, you will find that one thing referred to by all of those names. You see the illustration in #3 calling it the booster assembly, and that's pasted straight from a Toyota publication.

Meanwhile, the ("booster pump" and "accumulator") are also one thing, and it also gets referred to by both names, even by Toyota. And people here on PriusChat mix up the "booster" (one thing) and the "booster pump" (other thing) all the time.

None of this has to be confusing, but it definitely can confuse new members when we who know better aren't careful about it, and telling someone to replace "both booster and master cylinder" counts as not being careful, because those are the same thing. That doesn't help new readers who come here needing to understand their brakes.

The other reason to be careful is that the details I've just given in this thread are right for Gen 3 (and Gen 1 plug-in), but those of us who also visit forums for other Prius generations have to remember there are big differences in which parts are combined and separate and what they are called. There's an old post with the needed detail to keep that straight for gens 1 through 4.

 

i'm assuming you're back up and running?

congrats on 300k!

 

I get your point and only used those words to accompany what will be found on the Toyota Parts site. Sooner or later they would've got it as we all have.

There is no accumulators the parts site, so it would've confused them when all they wanted was the part number.

I personally though if my instructions were followed their end game would be there... no?

 

True, they wouldn't have found "accumulator" on the parts site, but they wouldn't have found "booster" either.

They'd have found "booster pump assembly" on the mothership parts site, or just "pump assembly" on the different parts site that rjparker screenshotted.

So if you had written booster pump and master cylinder, that would have nailed it. It would clearly have covered both assemblies, using one of the several correct names for each one, and it would have avoided giving the wrong idea about which part the "booster" is.

The fact that the "booster" and the "booster pump" are two different things in different assemblies, that's one of the most surprising things about this system. Newcomers don't automatically figure it out, and it's kind of on us to help them out—if not by explicitly explaining it, then at least by not confusing the two parts ourselves.