Brakes went out!!! 2010 Owners beware!!!

That thread was a classic. Prius busts through a fence and careens down a hill, but the poster was watching his wife's feet and swore that he saw her foot on the brake, not the gas.

I heard that the court gave them a Ford Pinto and a lighter.

 

Michael Mann...I would get some real legal advise on this one before you do or say anything else.

 

Based on both other reports here, and on personal experience of two incidents in the 2010 that I had for three years, I don't discount the possibility of at least a transient partial brake failure (firmware problem?) in that Prius. But both of mine happened at startup on sloped parking lots, and were resolved very quickly by some combination of reflexive hard pressure / pumping / cycling ignition power before I could think enough to collect more information. I was never clear whether it was a real but transient brake failure or just pilot error. I did experience a few other pilot errors that prevented proper startup, those have disappeared with experience.

My 2012 has not experienced such an incident.

 

Sure, software gremlins existing and disabling all power brakes is a very real possibility. But if those gremlins disabled the manual brakes (which it sounds like didn't happen to you either), that is a completely different story. And the reason those manual overrides exist!

 

One of the investigations after the Toyota Sudden Unintended Acceleration found poor firmware design in the brake controllers, raising the very real possibility of transient malfunctions from bad real-time fault-tolerant software. I can't discount the possibility of that happening to me or others, but mine were resolved by reflexive actions before I had time to think to about them.

Unlike other reports here, I also lack the confidence about mine not being pilot errors, self inflicted. But that personal experience raises unanswered questions about most of those other reports.

Since reading up on SUA investigation results, and on NHTSA braking requirements, I haven't had a repeat to consciously test and collect evidence to really verify that the manual brake path still works during my incidents. But at least I do have enough continuing experience with manual braking in farm equipment to have very hard pedal force built into my reflexes.

 

The override is a real thing; if all the electronic jazz gives up, the brake pedal in a Gen 3 still pushes on a master cylinder piston, which still pushes on fluid, which still pushes on the brakes.

Unless ... the fluid badly needs to be bled, and you didn't know it, because as long as the electronic jazz was working, you didn't feel any excess pedal travel because of it, but the moment the jazz clicks off, your pedal is pushing a piston that pushes a bubble.

As I've said before, this is speculative on my part. I've had no access to a car where such an incident was claimed. But it is consistent with things we know about the Prius brake system, such as the ability for the accumulator sometimes to leak nitrogen, and the way the electronic pressure control could mask the effects from you, as long as it's working. And it would not require suspecting deliberate sabotage.

I've never had such a problem in my 2010. But I did go out this summer and run a complete (as if actuator replaced) bleed, just because I had been hearing what seemed like an increase in squirty noises when using the brakes. I did not get a lot of gas out, and maybe I will never know whether I made a possible failure less likely, but it had a positive effect on my peace of mind.

 

Which wonderful Bay Area dealer is providing you with this service?

They think it’s power steering fluid?

Good luck .

 

Has this been the sole or primary service shop for some significant time? If so, these sort of documents should help your case if the contamination was a servicing error.

 

Looks like the other invoice is from Antioch Toyota, so a different dealer in the area.

Might be another nail in the coffin for Antioch Toyota.

Hard to believe a tech would think the brake fluid reservoir would be a power steering one.

Unemployment rates are historically low, so maybe not.

 

what's the date on the fluid top up invoice?

 

had same Experience with same lights on dash back n april. they didnt want to honor the warranty work because i changed the engine. They also gave me stupidest reason " the car is missing a botton engine cover". At that point we knew we are being thrown around. Then my wife spoke to manager couple of times over the phone and he just said to bring it in and will get it done but wont give back our $129.99 Diagnostic fee. We picked up the car few days later and been working fine ever since then. Just talk to the manager and have toyota customer service rep involved if the manager doesnt resolve it. Also post your DTC codes here.

 

See this is what bothers me about this situation. The electric pump is what puts pressure for the rear disk brakes. With out that pump energized, you can’t bleed or use the rear brakes.

Several Toyota techs as well as other independent shops have told me the same thing. So if the pump fails you have no rear brakes.

So while there is failsafes, I can see where the op is comming from

 

fly by wire makes the company so much money, the few lawsuits are worth it

 

Drive (and fly) by wire is MUCH safer than direct input. How many people do you know who drove pre-by-wire vehicles that had to at some point emergency stop the vehicle when the throttle cable broke and jammed the throttle open? There is a reason why planes are fly-by-wire with mechanical hydraulic backup today too, it's the best of both worlds with redundancy and backups.

 

The electric pump stores fluid under pressure in the accumulator. The accumulator holds enough fluid and pressurized gas that should the pump fail right now, you have about two dozen uses of the brake, front and rear, with power assist. And you will have plenty of lights and a buzzer telling you that you are drawing down the reserve.

The situation of having only foot-generated pressure and only in front is an additional, final level of failsafe beyond that.

The brake system is described quite well, with diagrams and fluid flows, in the New Car Features manual, for anybody who wants to understand how it works. There are certainly some issues with the system that are worth discussing on PriusChat, but the discussions stay most useful when we keep the details straight.

The manual and the diagrams are available to them too.

 

Even so, you have to admit that it can come to only having foot pressure and front brakes working, which means you have one circuit working properly. I am not trying to argue with you, but when several Toyota techs who are professionals, tell me this, I would tend to believe them.

I don’t doubt that you will get warning lights and buzzers before or during that situation, but it can happen suddenly.

Even if you have a dozen or so pumps of the brakes, if the pump is leaking there is a possibility there would be no pressure. Am I correct?

Also every instructional video on the Prius says in order to bleed the back brakes, you need to put it into invalid mode. Basically the pump pushes the fluid out as you open the bleeder.

My friend who happens to be a Toyota tech showed me the procedures they go through because of this setup. If it fails the only way to operate the rear brakes is to use the parking brakes.

Unless you have been in this situation, you don’t know how it would operate under these extreme conditions.

 

I've met a surprising (maybe) number of professional techs who would not be harmed by a gentle introduction to some material that's in their own service literature.

The pressure in the accumulator is what pushes the fluid out as you open the bleeder. The pump runs as the pressure drop is detected, and refills the accumulator. If you've ever lived in a house with a well pump, remember how that worked.

Why single out the pump? If leaks concern you, there are other places in the system they're more likely to develop.

I don't want to discourage you from having questions about how the braking system works. I only want to encourage you to spend enough time with the available information and diagrams so your questions and answers reflect the system as it is built.

There does seem, by a small but non-ignorable number of reports, to be a rare possibility of a sudden and severe loss of braking. It's been discussed on PriusChat in a number of threads. Those events are a legitimate matter of interest, concern, and explanatory effort. Pump failure, though, isn't in the running as an explanation for them.

It's also helpful to remember that a key engineering question is always "compared to what?". It would be easy to make a rather obsessive list of all the failure modes the Prius braking system could exhibit. But there would be a large overlap of that list with the brakes in other modern cars.