Abs pump fail, brake booster intermittent

If you do go to the dealership, be aware that others have just reported that Toyota has just issued a goodwill TSB and warranty extension on the v's ABS system. It may apply to yours. We also have a 20012 v Five, but have not received any Toyota notice (or had a problem with the ABS system, thankfully).

See this link: Brake Booster & Brake Booster Pump Assembly Support | PriusChat

 

Is the check engine light on? Or other lights?

 

I don't know that anyone has seen the complete procedural detail of the Toyota TSB that may apply to your VIN.

 

It pays to be super careful about the names of the parts, because in a Gen 3 Prius there are two different parts here, and their names are only one word different:



The problem you're reporting, frustratingly enough, could be in either one. The beep you are hearing is an alarm that the fluid pressure is too low to assist you. That's why the brake pedal feels hard at those times. As the pressure gets pumped back up, the beeping stops, and there is pressure to assist you again.

When the pressure falls behind like that, it could mean the booster pump is old and worn out and unable to keep up. Or, it could mean there is excessive internal leakage in the system, and that's why the pump isn't keeping up. (Internal leakage doesn't mean brake fluid is leaking out of the system—you won't find puddles anywhere—but only leaking through the system, finding its way back to the reservoir, making more work for the pump to do.) The leakage could be in either part, but the booster (check the picture again, when we say "booster" without the word "pump", that's the part without the pump) is where the majority of the valves are.

Both parts are kind of expensive and they're both a job to replace, so there's money to be saved if you can pin down which one you need. Also, we haven't ruled out simple and inexpensive issues yet, like flaky electrical supply to the pump. If you got your hands on (a) a way to read the trouble codes, and (b) the repair manual (more info), there would be more information on next steps.

 

I think they replace both items if the dealer gets in there.
I replaced both units and they came out of a Lexus..... it's not easy and actually took all day to tear it apart and reassemble everything. Bled the brakes the next day.... I'm sure I could do one faster now but don't want to.

 

Don't want to start a new thread - so reviving this older thread.
How to determine WHICH unit is faulty?

 

No totally sure-fire way. If the internal leak is substantial (making the pump run quite often), you might be able to hear a hissing sound with a mechanics' stethoscope, more loudly in one unit than the other (between those noisy pump runs, of course).

If you don't mind playing odds a little, the unit on top has a bunch more valves inside to go possibly leaky than the unit on the bottom.

It's also easier to get to....

 

Gotcha.. My only symptoms now are constant pumping like slight noise when I depress the pedal, even with the vehicle off, and the pump kicking on every 15-30 seconds regardless if I use the brakes or not.. sometimes when I ride the brakes softly to stop the car sort of slightly "pumps" to stop.

 

Failure is Imenent. Just don't know how long.

 

Symptoms of an internal brake master/ABS pressure accumulator leak.

 

Yup, symptoms of an internal leak, which can be in either of those two units. The relative odds are discussed a little in #9.