Prius Prime makes a clicking noise when coming to a stop. Can anyone check theirs to see if normal?

Does it sound somewhat like a "vibraslap" (

That's what it sounds like on my Gen-2 at least.

If so, I was wondering whether the P.Prime would have that sound too...

I'll tell you what I *think* it is, but I'm not 100% sure: I think it's a vacuum pump pumping down a vacuum reservoir that powers the brakes.

Almost all cars use ICE intake vacuum to power brakes. Diesel cars always have a wide-open throttle, so their would-be intake vacuum becomes more of a vague suction. They therefore add a mechanical vacuum pump, so that, as long as the engine is turning, it generates a vacuum.

The Prius, of course often intentionally turns off the engine entirely. It appears that what it does is seal off the vacuum system when they turn off the engine, leaving a vacuum reservoir the brake system sucks against. When that vacuum amount bleeds down a bit, it sucks it down further with a vacuum pump, which I believe is what's making that sound.

That then is why, at least by my theory, on my Gen-2, I can sometimes, while the engine is off, seemingly lightly tap the brakes, but instead get almost a "banging" hard application of the brakes: the vacuum reservoir is ... full (meaning empty), so even a slight application of the brakes produces a sudden bang of brake force.


iPhone ? Pro

 

Mine does not make this clicking sound.

 

I have no clicking as well.

 

I have not discovered this..on my Prime or my wife....
I do have noise for couple second after car is seating for couple hours and you turn the ignition on in READY ....
What is normal what owners manual describes
In my opinion is best way to test with hood open and have someone else do this for you while you looking at the engine bay to see where is this noise coming from

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I hear it in my Gen 4 sometimes when braking. Sounds a lot like when the ABS pump would be working in a previous car, and I'd guess that's exactly what's going on - it's modulating fluid pressure in the braking system to ensure consistent braking performance at the same pedal pressure.

Remember, the Prius has a weird braking system, in which it simulates brake feel to try (emphasis on try) to make things consistent between regenerative and friction braking.

 

I'm hearing a clicking sound, which is almost certainly the solenoids in the braking system functioning to modulate fluid pressure. This is in addition to occasional pump sounds.

 

Did you ever find out what the noise was? My gen 4 prius is making it and there taking it into the shop next week. We think it might be the driver side axle

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