So I've got this 2013 PiP 2 month ago. I always hear these 2 sounds from this suppose to be very quiet car. I tends to think they're just normal sounds but... First, humming electric motor sound. Especially under low speed and gentle brakes, I can hear this bee humming sound relatively loud. If you have an old style not well lubricated electric fan in summer time, that's the sound. And then, every time, about 1 minute after I shut the car off, there's always a clunk sound from front of the car, maybe from under hood, or maybe from brakes which is really hard to tell. As if two metal pieces get engaged or disengaged. Are they normal Prius sounds? thanks for any input.
The first is probably the Vehicle Pedestrian Notification System. It cuts out over 10mph or so. Not sure about the second.
Self-test of brake system, couple minutes after power off, every time. If you listen carefully, it's more than just "clunk", but more like "clunk ... clickity squish ... squish clunk". Utterly normal. Sometimes, it will need to repressurize during the test, so you'll hear the brake pump too ("whirrrrRRPclunk"). Not every time. Depends on what the accumulator pressure happens to be when the test starts. Don't be concerned because you do or don't hear it every time. If the car detects any problem, it'll tell you. That's why it self-tests. No news is good news.
I’ve had my Prius 18 months now. I’ve heard just about every noise the car can make. However, some of my family members are still surprised when it starts itself or pressurizes the brakes jaut sitting in the driveway. They think it’s haunted. I tell them the car is just smarter then all of us and is getting ready to leave.
... except that there is no use of vacuum anywhere in the braking system. There is a pump that puts brake fluid into a high-pressure accumulator though.
Thanks, I found a video on YouTube, exactly this sound. Link of the video: What a relief. Thanks again.