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Toyota Prius Brake Problems

85 messages,  Last post on Dec 05, 2009 at 4:34 AM

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What is this discussion about? Toyota Prius, Brakes, Hatchback, Sedan

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#76 of 85 Re: Prius slides on wet roads [gghol] by whitey9 Oct 02, 2009 (8:33 am)
Replying to: gghol (Oct 02, 2009 6:41 am) Slides? Or drifts ( sideways )? Steering sharply while braking? Tire pressures OKay? Tires not worn? Too much speed? Braking too late? Any function/malfunction lights illuminating on the dashboard?
#77 of 85 Re: Prius slides on wet roads [gghol] by vspin1 Oct 04, 2009 (8:38 am)
Replying to: gghol (Oct 02, 2009 6:41 am) I have had this happen on more than one occassion on my 2007 Prius. I had to brake hard when a vehicle cut in front of me to make an unexpected turn, but it felt like the brakes never engaged. I hit the vehicle that cut me off, which caused no damage to his pickup truck, but about two thousand dollars worth to my Prius. I have contacted my dealer, the main Toyota company, and have spoken with a rep. Basically they sy that it needs to be documented by my dealer in a road test, but trying to simulate this is nearly impossible. I have new tires on the car, and it happened to me again about a week ago. I feel its a combination of ABS sensitivity, and the lack of weight of the car which causes this problem. . . but I can't prove anything at this point. Replies to this message: oxyman (Nov 26, 2009 10:44 am) hal_cat (Nov 27, 2009 5:15 am) jacquesc (Nov 27, 2009 7:42 am) oxyman (Nov 29, 2009 11:57 am)
#78 of 85 Re: Prius slides on wet roads [vspin1] by oxyman Nov 26, 2009 (10:44 am)
Replying to: vspin1 (Oct 04, 2009 8:38 am) Success!!! Got it to happen without causing an accident. After reading all of these messages I decided to try this with our 2007 Prius. I've never put the car through its paces until I heard news of a recall. I didn't need wet conditions like reported on this site, just going down a hill over a speed bump at about 22-24 mph I slammed the brake and the car did not stop normally on first try. I'll need to videotape this to figure out how long before the brakes acted normally, but I experienced about 1 to 2 seconds of weak braking before I felt normal brake action with the car finally coming to a halt.   I was also able to replicate in an empy parking lot in a spirited turn at about 20 mph. Every panic (stomp the brake like your life depends on it) brake application results in extremely weak braking action. When I hit the brake less violently the car stops normally under control also.   I did not feel the ABS pulse in any of these tests until the last few milliseconds before the final stop. The anti-skid light came on in many of these tests so I suspect that the system is overriding my panic stop. In my mind this is clearly caused by a system (software & hardware) malfunction, or design flaw, not mats, hitting the wrong pedal etc.   While my tests were certainly not standard I you should know that I have experience autocrossing with the Porsche Club of America and know how to test a car and see how it should react to driver inputs. In my mind there is no question that the Gen II Prius could be deadly in a panic stop. While I would be comfortable in my ability to handle a panic stop in this car I would gauge it as being dangerous for general public use until Toyota reprograms or redesigns the braking systems.   My next step is to contact Toyota and find out if they have a solution. Otherwise I will have to video tape my tests as evidence should it be needed. Replies to this message: hal_cat (Nov 27, 2009 5:15 am) jacquesc (Nov 27, 2009 7:42 am) oxyman (Nov 29, 2009 11:57 am)
#79 of 85 Re: Prius slides on wet roads [oxyman] by hal_cat Nov 27, 2009 (5:15 am)
Replying to: oxyman (Nov 26, 2009 10:44 am) Please forward your comments and test results to the National Highway Traffic Safety Board. There needs to be corrective action and a recall before someone is killed by malfunctioning software. (I don't believe the problem is mechanical).
#80 of 85 Re: Prius slides on wet roads [oxyman] by jacquesc Nov 27, 2009 (7:42 am)
Replying to: oxyman (Nov 26, 2009 10:44 am) Fantastic job on the testing. I have performed similar tests which resulted with the same conclusion. I was appauled with the attempt to create a campaign to pitch the problem being the floor mats. Almost as if they had planned it from before the vehicle release. I have attempted to contact Toyota and the National Highway Traffic Safety Board -- but, have not yet recieved a repsonse.   Please continue your exposure of this plight with aggression...
#81 of 85 2009 Brake problem by phaters Nov 27, 2009 (10:44 am)
I had a problem with my 2009 Prius a few days ago, scared me to death. I was driving down a hill and the roads were wet. I was going about 30mph. The car in front of me hit the brakes due to the guy in front of her decided he wanted to turn right. Anyway, I hit the brakes and the car started jumping! It felt like it was in slow motion. I had 2 1/2 to 3 car lenghs in front of me yet the car kept stopping and then jumping. I had plenty of time to look around. I looked at the floor mat, it was fine. My foot was hard on the brake, I looked to make sure the car was in drive and it was, I then put both feet on the brake and still the car keep jumping until I hit the lady in front of me. I'm really scared to drive this car, living in Seattle there are a lot of hills and the roads are always wet! I must say when I test drove the Prius what sold me is the sales guy was bragging about the brakes and that they could save my life someday. We drove the car up to 50mph and slammed on the brakes and it stopped on a dime. Now with that said the roads were dry. I've called Toyota to complain, haven't heard back yet.
#82 of 85 How to evoke Prius brake delay problems by oxyman Nov 29, 2009 (11:57 am)
Replying to: oxyman (Nov 26, 2009 10:44 am) I have been able to carry out a couple more test with our car over the Thanksgiving holiday. I've found that the brake delay symptom is harder to evoke on a full fuel tank. Also we had rain recently and I took our 2007 out and easily provoked a 1-1/2 second brake delay going downhill on a wet road coming off a speed bump, and after passing over a storm drain. The ABS came on hard only after the delay and I was able to stop with no further problem (My wet road tests were with full fuel tank).   I'm presenting my findings in writing to Toyota and will document their response to the ODI office of the NHTSA if I judge it to be irresponsible in light of the public risk. In the meantime I've found someone with an accelerometer that I can borrow to get some hard facts on this, and remove subjectivity. I'll post the results of our g-force tests here when I get that done.   I hope that the Anti-skid system interference in Prius braking is easy to fix (without causing other problems).
#83 of 85 Prius Brake Failure/Delay - Dallas, TX by rickpoole Dec 04, 2009 (10:04 pm)
Has anyone who has experienced the Prius brake failure/delay reported it to one of the Toyota dealers in the Dallas, TX area? I called all the service managers in the Dallas area and all of them denied this problem exists and said they had never had anyone report it to them. A few of them claimed all of these were made up stories from people who didn't want the Prius to succeed. Even after pointing out all the reports on the NHTSA website these few still denied the problem exists and still thought people were making these up. Given that the 5 other cars we've considered have a sum total number of brake failure reports of zero and I counted 50 for the 2004-2009 Prius in just a few minutes there is obviously an issue with more than just a few cars. I even called the regional Toyota Service Manager and got the infamous "since we can't duplicate it there is no problem and it is user error" crap.   The one question I could not get answered by either the service managers or the regional manager was if the 2010 Prius brake system was redesigned to solve this problem. I was hoping to confirm this was the case since we're really interested in the 2010 Prius. Replies to this message: hal_cat (Dec 05, 2009 4:34 am)
#84 of 85 Re: Prius Brake Failure/Delay - Dallas, TX [rickpoole] by hal_cat Dec 05, 2009 (4:34 am)
Replying to: rickpoole (Dec 04, 2009 10:04 pm) Certainly the rear brakes have changed, but I don't know that this requires a software change, and it is the software that I believe is the problem. One change they did make to the software (it is noted in the owners manual somewhere) is to record (black box style) information which would help diagnose what happened just prior to a crash. While having this information is a very good idea, it makes me suspicious that they cannot figure out what the problem is, or how to duplicate it, and are looking for data.   When I took my car into the dealership in Michigan, I came in with the many page printout of customer complaints posted at http://www.hybridcars.com/forums/brake-failure-2007-t1013.html . I appreciate that they took me seriously.

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