Hello all! I have a 2008 Prius, and lately I've been noticing that when I go down hills, or when I start braking from above 60kph, the car sounds like a helicopter. When going downhill at speeds above 60kph, the sound stays until you start accelerating, but when braking, it is only there for a second or two and then is gone. I'm thus assuming that it has something to do with regen braking. I tried hard braking, and it helped for a couple minutes, but then it came back again. I've searched all over trying to find answers, but with no luck. Any ideas on what it could be?
Weird sounds and how people describe them on here are near impossible to diagnose. Even worse when they try to make a recording of it. Let's focus on way easier stuff: Is anything wrong with your Prius other than the noise? How many miles? How is the MPG? Is regen data on your screen different than usual? Are you using original battery? Are you using original brakes?
Hard braking uses your hydraulic brakes; normal braking uses regen to turn the transaxle's motor generator to slow you. Hydraulic braking takes over from regen when moving slower than ~6 mph. If your hybrid battery has low capacity it is conceivable that it maxs out quickly and the hybrid system goes to engine braking which is much louder. Watching the state of charge and amps into the hv battery would help diagnose.
Is all this available to the average driver on a 2008's interface? I wonder, and please excuse me for not having a 2008, but does it have a "B" setting like my Gen5? I think of "B for engine brake". If so, does it sound or act like that?
I've looked around a bit . 8 think everyone's trying to keep miles off he he .I'm fixing to be on Piaggio MP3 almost full time. If a 5 could fit a lot better than a gen2 . I might consider a unit without park assist and lane holding etc 17 instead of 19 wheels etc
That right there is a jigga mess. That has nothing to do with your regen that's all hydraulic you're probably stepping thru even for life of car . That's really sad looking rt there. Non car persons vehicle. Go round car w new brake shiet about 300 for bolt on parts. about anyone could do .
Fastest way to clean those up before further diagnosis is to put the car in neutral at freeway speed and do a hard breaking several times... Then once you've done that you'll better be able to investigate what else is wrong.
When there is light surface rust on the rotors, braking in neutral does rub it off. Doesn't even have to be hard braking, or freeway speed. I normally do it at the first 2 or 3 stop signs on the way out of my neighborhood, if I notice that rough sound. If I have a passenger and they're not watching my hand shifting to neutral, they don't notice I'm doing anything special. Once the rotor rust gets like that in the picture, though, it's a different story. The pads won't rub that off: it's too hard now, and will mill the pads into a matching shape. Needs a flat-surfaced rotor and flat-surfaced pads to go with it.
Yea... But before deciding on what to replace seeing how much rubs off seems wise. For example I'm willing to bet that if this a front rotor, the rear rotors might not be as urgent to replace. Also after thinking about it, I doubt this photos is even from a Prius because the caliper seems too small and is in the wrong location.
Since that car is almost as old as you are; when was the last time the traction battery cooling system been torn apart and cleaned out???
That picture is odd. Is it just me, or does that brake pad only wipe part of the rotor clean? It looks like the part of the pad closest to the axle isn't contacting the rotor, or at least, not as well as the part farthest from the axle. Does the disk on the other side look the same?
Yeah, I agree... It's just some random photo of a rusted out disk and caliper that doesn't look like a Prius and there's no explanation. Seems to me like @notspam3 is not thinking things through or participating in the actual discussion. Very much not appreciated!
When the rotor is flat as-new, and the pads are flat as-new, the pads can "sweep clean" rust that is quite fresh, say the flash rust after being parked in one night of wet weather. Rust that has not been swept clean, soon enough after it formed, eventually becomes grinding-wheel tough, and then it turns the tables, and reshapes the brake pads in its own image. This happens at both the central and outer rotor circumference. The ground-away pad edges no longer usefully brake against or clean the rotor, leaving just a progressively narrower and narrower band in the middle where the braking happens. I first observed this on my Gen 1 Prius in west-central Indiana. The photos above are from it. Especially in a place where road salt is used, this can be a fact of life. As much as anything can help, it will probably help to drive the car more frequently, or at least to make a point of driving it soon after rainfall or damp weather. You can hear rusted rotors when you brake; there will be a rough grinding sound as you slow to a stop (around 7 MPH or below, when the friction brakes are brought back in). A quick way to get the flash rust scrubbed off is to make several stops in neutral (which takes regen out of the picture so the brakes have to do all the work). The stops don't have to be intense or from high speeds. I'll usually just shift to neutral for my first two or three regular stop signs on the way out of my neighborhood. Just keep repeating until the brakes sound good again. Also, inspect frequently. You're supposed to do that anyway, per the Warranty and Maintenance Guide. Many drivers neglect that, but that probably works out best in sunny places with no salt. More on that in this post.
