I took my Gen III in to the dealer yesterday. I have experienced what I call "hopping" sometimes while driving in reverse. It most often happens when backing out of a parking space. The brakes feel like they are "grabbing," not just once, but multiple times. Trying to brake harder makes no difference. The only fix I've found is to put the car in "Park" and then try reverse again. The dealer told me this is not a known issue and they couldn't recreate the problem while they had my car.
I think you'd have to leave the car with the dealer overnight. You need a degree of dampness to produce the phenomenon and even then it's very hard to replicate on demand.
This has to be a known issue at this point. It isn't like it only happens in one or two cars. The issue must have happened in pre-production vehicles during testing and they ignored it. They can't really be that clueless. Not everyone brakes right after hitting a pothole and experiences the other publicized brake issue, but everyone backs up and at some point will have this brake grabbing issue.
Yes and no. We experience it with our Gen III here, where dampness isn't an issue. I do think a cold engine is a part of it, so leaving the car overnight is probably necessary. While I can't reproduce it reliably 100% of the time, it happens more than half the time for me under these conditions: car parked in the garage overnight, back out of the garage (about 20 feet), turn off the car, wait about a minute, restart the car, and back down an incline out of the driveway. Of course, if it doesn't happen on the first try, it's probably not going to happen that day, so you have to wait over another night to try again. Given that it's a fairly minor problem, I'm not sure many people would find it worthwhile to spend a few days with the dealer if necessary to reproduce it. Maybe if someone lives next door to a dealer, or is a dealer, they can try this.
I had this happen 3 times the other day- twice on an incline and once pulling out of a parking lot. I put the car in drive then reverse again to correct it...but I think I'll try putting it in park instead. The finance guy at my dealership, who drives a Prius as well, said he has this problem, too. I thought it was a hybrid thing (I used to drive a compact SUV) and that I needed to get used it..or maybe I was doing something wrong. I've had my car a little over a month now and this still keeps happening. Every time I reverse I have to brace myself...it's very annoying and I hope there's a fix for it.
Until Toyota elects to find a fix, you can correct it yourself on the spot by releasing your foot completely off the brake and re-applying it and it'll return to normal.
Obviously, it is not quite that easy. People do release their foot from the brake when they notice it was extra sensitive. It usually takes several brake reapplications, restarting and/or fiddling with the gear selector position before the issue temporarily resolves. Maybe just waiting another 30 seconds might "fix" it also, but just lifting your foot off the brake once doesn't fix it.
Some people have stated that the brake pedal seems much firmer than normal when grabbing occurs, which indicates a build up of pressure in the hydraulic system. Any increase in pressure over the normal would cause the brakes to be applied more rapidly and more severely. For the hydraulic pressure to build up beyond normal would indicate: 1. a sticking valve, 2. a faulty sensor, or 3. a computer error. If those cars that have the grabbing problem, if the cause is 1. or 2. I would expect it to happen relatively frequently, but it doesn't so I suspect it is 3. The error could be caused by faulty data input.
I've never had the brake problem that the recall is going to address, but I have had the brake problem that occurs when backing up. Does anyone know if the recall software update will address both problems? No one seems to be asking that question, or I have missed the discussion.
I don't think Toyota wants to believe there is yet another problem at this time. So, either they will refuse to believe it, so it won't ever be fixed or they will fix it very quietly with the other brake problem so it doesn't hit the news. Either way, I don't expect to hear them say they are fixing this problem.
My understanding is that the brakes are activated when you enter the car. I am not a mechanic so my description is poor. Basically, the brake pressures are over compensating. If you don't start going in reverse within five minutes, the brakes become very sticky. It only happens to me when I start the car from a cold start and wait for more than five minutes before going into reverse. I have had it happen to me about 4-5 times in the last three months. Mostly, on my driveway in reverse. I found that it goes away if you put the car in park and then proceed going back into reverse. I think there needs to be a recall/software update on this issue as well.
Eddy, your explanation is OK. However, the sticky bit concerns me, perhaps grabby would be more appropriate. If putting the car in park cures the problem then there is no sticking of the brakes. As I said in an earlier post, it appears that the brake fluid pressure builds up to a higher level than normal brake pressure. This build up indicates an intermittent fault somewhere in the system (relief valve, sensor, ECU error). Yes, it needs fixing because the surprise effect on the driver could lead to an accident.
I have this issue and have had it occur mostly in reverse but at least one time going forward, leaving a parking spot. Releasing the brakes fully and reapplying always "fixes" it for me. I have heard no indication it is related to the brake let up that is part of the recall, and I doubt it will be fixed. I have not found a way to recreate it but it sounds like some of you can come close to recreating it or at least it occurs frequently for you. I'm around 7500 miles and have not had it occur in at least a few thousand miles now.
We have also felt the "hair trigger - grabby" brakes in reverse & also in forward, when we've just started the car. I complained to my dealer at the 5k oil change & the service manager told me that it happens to most Priuses & "it's normal." It worries us, though -- especially with the recall.
It's interesting that depending on the dealer you talk to, the response varies between: "They all do that. It's normal." to "I've never heard of that. No one else is complaining." I don't think this parking lot speed braking issue is a safety hazard unless you get whiplash, but it is a warning sign that something is wrong with the brakes and that is not normal! Whatever is causing this annoyance may evolve into a serious issue later.
There is hard acceleration instead of ths normal "creeping" of the car as one starts to gently ease off on the brakes. This unexpexted acceleration is the danger. The abrupt braking has nothing to do with soiled or "sticky" braking surfaces.
I never put it in reverse without my foot on the brake. And sometimes, when I first start the car and back out of my garage the brakes are so super sensitive that I cannot back up without jerking. The brakes seem to have a mind of their own, grabbing at the slightest touch. Most of the time it's fine, but those times when it's not make me wonder what's going on.
