My brakes..............yet again!!!

Take the head Toyota mechanic for a ride down your road and duplicate the problem.

 

how fast were you driving down this bumpy dirt road?

 

I had some brake problems, too, but don't sound exactly like yours, but I'll describe them just in case. Mine lost brakes on startup, wouldn't recover (I infer that yours did), lit up the dashboard ABS and brake lights (you didn't say) and took 3 trips to the dealer before being diagnosed as a pedal sensor (they had to believe me since the brakes obviously didn't work). I could supply the details, including codes, etc if you like.

If this seems a little cavalier, remember it only ever happened on start-up while backing up at about 5 mph and I wasn't really worried about careening out of control on the freeway.

A thought occurred to me which I didn't see mentioned. Since its a rough dirt road, maybe your traction control or ABS is working overtime. Perhaps some aggressive driving and braking with the mechanic in the passenger seat on your dirt road might be illuminating.

 

I have yet to experience the "lack of brakes", but I do have an issue immediately after starting my Prius where the brakes are extremely sensitive. At the mere thought of applying the brakes, they toss you through the front windsheild. After about 1/4 mile, the brakes return to normal. Has the dealership given you any hints as to the source of this problem? I only have 2000 miles on mine, so I have yet to take it back for service.
Regards,

 

Most of the brake discussions center around either grabby reverse braking or a brief, half a second or less, transition between regen and friction braking. A complete loss of brakes is a very different problem and may not be related. The Dealer has to take your issue seriously!

 

Like Cyclistbob I have less than 2000 miles and have had the brake problem when backing out of my garage--they work OK after that.

 

Thanks,
I will be visiting the dealership very soon to have them take a look.

 

Can you document "my road" with Google Map or Google Earth?

• Altitude change
• Distance
• Lanes or private drive

How frequently has this happened since July?

Weather conditions each time?

Are you able to add instrumentation?

Proposed experiment:
If your drive slopes down, see if you can replicate the symptom by:

1. Start car in "Accessory" mode - press the Power button twice without holding the foot brake. The dash indicators should come on but not "READY"
2. Shift in either "D" or "N" - try to roll down the road
3. See if the brakes are or become unresponsive at bottom of road

Bob Wilson

 

The grabby brakes happens to me all the time. It happens after I drive the car, let it sit for 5 minutes or so then start the car and back up. If the car sits for less than 5 minutes or more than 10 minutes it usually doesn't happen.

 

Is this happening each and every day backing out of your garage? Or only on occasion?

When you get it, and apply the brake and start to "Ready" how long before you put it in reverse?

 

I'm guessing this is due to the "pre-pressurization" which the Prius does when you first get in the car - must be too much.

 

I have a similar problem with my 2010 Prius which I bought in Aug 2009. Whenever I apply my brakes to slow down and the car hits a depression on the road, the car surges forward as if the brakes are not working at all.

I came across this report the following report and wrote to Toyota Canada to find out what is going on. Waiting on their reply ......

*****************************************************
Toyota's Prius brake problem deepens, faces US probe

by Paul Eisenstein

DETROIT, Michigan 2009 (AFP) - Toyota is facing a potential safety issue with its highest profile vehicle, the Prius, the latest in a plague of quality problems that forced it to recall four million vehicles in 2009.

A growing number of owners allege that the brakes on the third-generation, 2010 Toyota Prius can malfunction unexpectedly, with at least 20 complaints filed so far with the National Highway Traffic Safety Administration.

The Japanese automaker said it has launched its own investigation. Robert Becker, 39, is one of those filing among at least 20 who have already submitted their concerns to the National Highway Traffic Safety Administration's Office of Defects Investigation.

He says he was heading to work on the west side of Manhattan, coming up to an intersection and squeezing the brakes of his 2010 Prius to slow down.

But when the car hit a pothole, Becker suddenly had the 'sensation of losing control,' as the brakes released, forcing him to slam down on the pedal.

'It scared the hell out of me. I wasn't sure I could stop in time,' he said, adding the problem has repeated itself a number of times since then. Becker is not alone, as NHTSA's defects office reveals.

One complaint on file quotes an owner: 'Initially, I convinced myself I must have been letting up on the brake when I hit the bump, but when this same thing happened three days ago on slippery, icy roads, I knew for 100 percent certain I had not let up on the brake.'

The Prius brake problem has become a hot topic on numerous websites, but federal investigators are so far declining to comment, although the file is open to the public.

Toyota admits it is aware of what a spokesman called 'the behavior people are reporting.'

'We're investigating those complaints as quickly as possible,' spokesman Mike Michels added.

Exactly what is happening is unclear. Like the vehicle's gasoline-electric powertrain, the brakes are also a hybrid technology.

During light to moderate braking, the car is slowed by a regenerative system that turns the vehicle's kinetic energy into electricity, which is then stored in a battery. For more aggressive stops, the Prius also has a conventional hydraulic brake system.

Some speculation focuses on the regenerative system, and whether a sharp jolt to the vehicle could inadvertently trick vehicle sensors and controls into releasing the brakes.

But Michels cautioned Toyota will have to look at a variety of things. 'Rather than throwing out theories, the important thing is to do a scientific analysis. When we have an answer, we will provide it to owners as soon as possible,' he said.

The Prius problem is one of the last things Toyota needs right now. Just 12 months ago the automaker was basking in headlines reporting that it had finally beaten arch-rival General Motors to become the world's best-selling automaker.

But by March, things didn't look so good. Battered by the recession in the US, its key market, the maker reported its first annual loss in a half century.

In August, a California Highway Patrol officer and three members of his family were killed in a fiery crash when their Lexus went out of control.

Two months later, Toyota announced it would recall 3.8 million vehicles, blaming the problem on floor mats that could come loose and jam the accelerator pedal.

Another recall impacted 110,000 Tundra pickups which, according to NHTSA, are prone to 'excessive corrosion' so severe their brakes could fail.

In all, Toyota will have recalled around four million cars, trucks and crossovers, in the United States, during 2009. That's about four times more than in previous years.

And it means Toyota will have recalled more vehicles than any other auto manufacturer for the first time ever.

It is looking like 2010 could also be a difficult year. Another probe was recently opened by the government into complaints that 2006 versions of Toyota's Corolla and Matrix models may be prone to unexpected stalling, sometimes at highway speeds.

Although Prius sales will only account for about 100,000 units this year, less than seven percent of Toyota's US total, it has been positioned as the company's halo vehicle due to its environmentally-friendly hybrid technology.

But analyst Stephanie Brinley, of AutoPacific, Inc., warned that if it is suddenly seen as dangerous, the damage to Toyota could be huge.

Early customers may be more willing to accept problems with new technology, she added, but for 'late adopters, who care more about mileage and less about technology, this could be a red flag.'

 

Gasitman,

Your explanation of your issue seemed much more intense than the occasional "brake issue" over a bump, manhole etc.

It sounded like you had a different issue that appeared when on the gravel roadway...I would definitely DOCUMENT at least this with the dealer at this time.

I had a GEN 1 Prius and noticed sometime on bumps it would happen and it's the same "type" of feeling that happened on my 2007 Honda Civic Hybrid.

I can produce this on occasion in the Gen III on a road seperation or drop in road level (say at a bridge to road level). But it will NOT always happen...so that's what's baffling....

We need to document the issue with Toyota and see what they come up with from an engineering perspective I guess whether a recall or modification is in order....

 

Thanks for all of your responses to this concern about brakes that are extremely sensitive immediately after I start up in the morning. Has anyone learned if Toyota find anything that would cause such a condition? I will update what I learn from Toyota once they look at my vehicle.
Regards,

 

My guess is that you car was left in the cold and not in the garage. It was very cold? Cars have a tendency to lose all braking when they are very cold. I think this could be fixed with more expensive parts. Toyota and others have this problem so it is not Toyota specific. Just guessing.

This is just an example, not Prius specific and not related to you. As I said, all manufacturers have this problem come up from time to time. I understand, of course, a hybrid does not rely on vacuum for braking either. But these sorts of problems always happens due to one reason or another. So see the example below just as a pure example.

By the way, this is a quote, not my spelling.

"Toyota has announced a voluntary recall of approximately 95,700 Toyota and Scion cars to correct a problem with the braking system. In extremely cold temperatures, the problem could result in less assistance from the brake booster and more difficulty in stopping the car.

The cars in question are 2009 and 2010 Toyota Corollas and Toyota Matrixs and 2008 and 2009 Scion xDs equipped with the 1.8L four-cylinder engine. No other engines or Toyota or Scion models are affected. Toyota has discovered that in extremely low temperatures, moistures from the Positive Crankcase Ventilation (PCV) system can leak into the brake vacuum port and freeze, closing off the port. With the brake vacuum port partially or totally blocked by ice, the brake system will loose vacuum pressure and will therefore lose its power-assist, making the brake pedal much harder to apply and increasing the effort needed to apply the brakes and stop the vehicle, which could lead to longer stopping distances and possible accidents.

Because the problem only occurs at very low temperatures, the recall is only being put into effect in 19 states where temperatures typically get low enough to cause a problem. Those states include Alaska, Colorado, Idaho, Illinois, Kansas, Iowa, Maine, Michigan, Minnesota, Montana, Nebraska, Nevada, New Hampshire, New York, North Dakota, South Dakota, Vermont, Wisconsin, and Wyoming.

Read more: Toyota Recalls 95,700 Corollas, Matrixs and xDs for Brake Problems in Cold Temps - Wide Open Throttle - Motor Trend Magazine"

 

Ok, the problem he is presenting sounds scary. It sounds like he had something wrong with his friction brake system. However, from some of the posts I'm seeing this thread is quickly decaying into the non-existent problem people have who aren't experienced in regenerative braking technology.