We just purchased a 2009 Prius this past week-end and are so far liking it very much. I notice though that often as I am braking (city) that there seems to be a subtle "rattling" noise, not too loud but noticeable from the front, that is hit and miss. Is this normal, perhaps due to the regenerative braking, or could it be a problem. TIA Paul
Hi Paul. I'm not sure about a "rattling" noise, but many of us definitely notice a kind of electrical "humming" noise under regenerative braking. If you've worked around electric motors/generators under load then you'll recognize the sound. Could that be what you're hearing, or is it really more like a mechanical rattle?
Thx for the reply. I guess it sounds more electrical than mechanical, though hard for me to accurately describe. Perhaps like a vibrating whistle. I will check with my dealer as we have only driven it casually for barely three days, including today. I am hoping it is normal.
I would describe the normal regen braking sound as a fairly soft hum (or lower pitched whine) from the motors and, depending on how good is your hearing, a little bit of quite high pitched whine (you could probably call it whistle) from the inverter.
My 2008 does that too. Does it always happen when you first get in the car and press on the brake (before even turning on the car)? If so, that is normal.
Thx, actually I have not noticed it like that rather more while driving and braking. Oddly though it did not do it much, if at all, yesterday. I saw an earlier post (2011?) about shifting to N while driving at moderate speed, then braking to clear rust buildup I believe. Thx again
Well it has been almost a week now and that noise I heard while driving and braking has seem to disappeared. Perhaps because we just bought it used it was just somewhat idle for so long that driving it for the first time caused those sounds? Thx all for the replies.
Thanks for the update. BTW. Can you clarify, was it the brake accumulator noise that Freydnot mentioned? This is like a clicking or even a "purring" noise from the engine bay area. This is due to the Prius' use of an electric pump to provide hydraulic pressure for the brakes. (Obviously it can't rely on engine vacuum like a normal car, because the brake boost must work even when the engine is off). BTW. I misunderstood you previously and thought you were referring to some more subtle electric machine noises that you hear under regenerative braking.
If it sounds like a rattlesnake its the pump like Uart says. It can be forced on so you can listen to it and identify it by stepping on the brake a few times with the car in READY and the engine off.
does anyone know a "fix for this rattlesnake sounding noise" that is intermittent, under the hoos and under the dash?
If your referring to my post above yours the sound of the vacuum pump is normal. You will hear it quite often. Just about every time you step on the brakes it runs for a few seconds. Sounds like its under the dash right in front of you but its under the hood tucked under the Inverter. You must be new to the Gen II. Many new owners come to this forum chasing all of the various weird sounds the car makes. Most are normal. There's alot to learn about this car. Keep reading here.
In reply yes I do get a similar sound that Freydnot mentioned. I also get the rattlesnake noise that I see from here is normal. The original rattling like noise I heard while braking during driving is generally less frequent, or perhaps I am just getting used to it. Thanks to all.
I have only had my Prius C for 12 days. It has less than 500 miles on it. Tonight on the way home it started making a loud distinct single click when I first hit the brake pedal, and then a loud squeak/ pumping (compressing) air sound when I press it down to break. It's not coming from the tires or wheels. It seems to be the pedal itself. The same loud single click would happen after I take my foot off the brake. It's very loud, not subtle at all. Is this normal? I am guessing it is not considering it did not happen until today. I will be disappointed if it is because it is quite annoying. I couldn't turn my music up loud enough to cover it. I checked to make sure it wasn't rubbing against anything on the floor when I got out. I also noticed that my battery is not charging over 50%. I drove 20 miles from work to home, braking frequently in the charge zone, so I assumed this should not be the case. This could be coincidence and I am looking for problems because of the noise. I'd take it straight to the dealer if they weren't 2 hours away. Could it be the electric pump to provide hydraulic pressure mentioned above? I get the impression if it was, it would be a more subtle noise.
