New GenIII brake recall affects 87,000 cars

Hydraulic accumulator - Wikipedia, the free encyclopedia

Basicly, it's a way of storing hydraulic pressure. Essentially a battery for your power brakes. It could have many functions in the braking system. The obvious one with hybrids is in allowing the brakes to work normally while the ICE is off. Non hybrids rely on the vacuum produced by a running engine for providing the boost of power brakes.

 

A co-worker (and fellow Prius owner) sent this to me as well. Checked my VIN but I'm not in the group. It did make me aware of the Toyota Owner website where I registered and got access to my vehicle service history. Very nice.

 

More from Green Car Reports

Recall For Some 2010 Toyota Prius, Lexus HS 250h Models

 

Source: owner's page for my wife's 2010 Prius

So I don't see this as a 'set your hair on fire' problem . . . especially for those of us who drive as if we have no brakes. <GRINS>

Bob Wilson

 

Bob,

This brings up a possible conflict with Prius owner's desire for higher FE by using elevated tire pressure. Higher tire pressure generally leads to more vibration of the vehicle. What do you think?

 

I believe this may be true. I do have that theory on those stating they have rattles everyone (only rattle I've had has been the gate remote or my sunglasses in the sunglass holder) the added tire pressure is causing premature wear and tear.

 

Even when using 'driving without brakes' to save fuel 99% of the time, I still want full braking effectiveness for the other 1% when something unexpected happens. Whether one's driving skill puts that emergency need at 1%, or 0.1%, or 0.01%, a problem there still adds up to a lot of risk over a driving lifetime.

The earlier brake 'pause' over bumps didn't bother me much because it appeared with light and moderate braking, and didn't seem to arise during hard or panic braking.

 

From the recall web site:

Q1: What is the condition?
A1: The subject vehicles are equipped with brake pressure accumulators consisting of a metal plunger
containing brake fluid encased in a metal housing. The plunger is designed with metal pleated bellows to
allow for motion. Nitrogen gas is sealed between the plunger and housing. There is a possibility that a
fatigue crack could develop in the bellows due to the vertical vibration of the plunger while driving. If this
occurs, nitrogen gas could leak into the brake fluid and gradually cause the brake pedal stroke to become
longer, resulting in decreased hydraulic pressure. Under certain circumstances, this condition could
affect stopping distance and increase the risk of a crash.
Q1a: What is the Brake Pressure Accumulator?
A1a: Brake fluid is discharged by the Brake Booster Pump and passes through a check valve where it
is then stored in the accumulator. The brake fluid that is stored in the accumulator provides the
hydraulic pressure that is needed for brake operation.
Q1b: What is the cause of the condition?
A1b: The cause of this condition is insufficient strength of components inside the brake pressure
accumulator.
Q2: Are there any warnings that this condition exists?
A2: Yes. You may notice a squeak from the engine compartment during brake application. Additionally, the
brake pedal may have a longer stroke and/or spongy feeling. If this condition is present, the warning
lights listed in the table below may illuminate and the skid control buzzer may sound

 

Well, this is an interesting situation. My car is on the recall list for a new accumulator, but I just paid $3000 for a brake master cylinder. I originally suspected the pressure accumulator or pump. Plus after waiting for weeks, Burien Toyota still hasn't obtained any compensation for me.

I think I'll find another dealer to replace the accumulator when I get my letter.

 

Hm... I can't seem to get into mine. Put my VIN number in though and it said mine is not in the recall. Just checked mfr date and it's 10/09. Hope they're right that I'm not supposed to be in the recall...

But about a month or two ago I had to stop abruptly on the freeway and felt that the brakes weren't very responsive, that the pedal went so far down and I didn't feel it braked accordingly.

 

Sorry if my comment seemed a little flip. Brakes are important and I well remember the problems we had recreating the "brake pause" problem. It also came from user reports at PriusChat of a problem that we were able to eventually recreate.

As I read this problem description, it sounds as if the risk is nitrogen in the brake lines . . . in effect what happens with brakes are not properly bleed. Just it isn't clear that the typical, dual-hydraulic lines are at risk. I'm also curious about the failed part.

The description sounds as if the bellows was made from a metal that can work-harden:

The "vertical vibration" just doesn't make a lot of sense. From what I know of fatigue cracks, there needs to be some motion. Application of the brakes, yes, but vibration in this case does not make a lot of sense. On one side is incompressible brake fluid and the other high pressure nitrogen, a gas 'spring.' I don't see a way vehicle motion could induce the 'vertical vibration' but there is potential source, the pump.

There is a high pressure, hydraulic pump that pressurizes the accumulator. You can hear it when you first open the door, whining sound that soon stops. It reasonable that this pump is the source of any vibration since it is responsible the pressure in the accumulator and compressing the nitrogen, gas-spring.

Application of the brakes would increase the pump operation but in ordinary driving, the pump should be idle, waiting for a pressure change to trigger operation. So those who drive so as to minimize braking are likely to have fewer, pump activations, than those who have to touch their brakes more frequently. Fortunately, this is a testable hypothesis. Looking at the schematic, it should be possible to instrument the brake, accumulator pump circuit to measure how often it is applied and the current draw.

Bob Wilson

 

^^^
It'll be interesting to see what the associated documents say once they're finally posted on safercar.gov. I don't see them yet.

 

Yesterday I communicated with the local representation (CZ) of Toyota. Yes the brake accumulator recall applies for EU spec of the car. I bought the car in Sept 2009 and my VIN (163xx) will aplly for the recall sometimes in July/Aug. The service campaign includes dealership check and if they spot the problem, the replacement will be free of charge.

 

Yours may be a later October 2009 build date where evidently a change in the brake accumulator must have been made. According to the Toyota Owners' site all involved in the recall will be receiving a letter in the mail.

I would check with your dealer to be sure especially after your braking issue above.

 

Rang my dealer today and I was informed I will get a recall letter by the end of the month.

PS Our recall is for vehicles from October 2008 to October 2009.

 

<AHEM>The symptom, "fatigue cracks" in the accumulator bellows is not something that can be inspected. It reads like a materials problem and requires replacement of the at-risk part.

I suppose Toyota is looking at rebuilding the brake assembly in a service center versus the significantly more expensive, brake assembly swap. It also means having a source of dry nitrogen since the bellows is replaced.

The risk is rebuilding the assembly means manufacturing quality, torque and possibly bolt or fastener replacement. It is one step below rebuilding an engine or transmission in complexity. Fortunately, much smaller and lighter but on the down-side, a critical safety system.

Bob Wilson

 

My dealer's service manager was aware of the recall based on my phone call to him this morning. He expressed frustration that he's been talking to many Toyota corporate folks about getting me some compensation and no one told him about the forthcoming brake equipment recall.

RE xpcman's Q and A sequence: it's entirely likely that the bellows mentioned were copper, which in pure form does work-harden over time, with the work-hardening in this case due to vibration motion. If the bellows had multiple pleats and wasn't constrained from sideways motion, wiggling up and down would lead to work-hardening and cracking.

 

Thanks, I see I'll be visiting my dealer soon. I'll wait for the letter, and give them time to get used to installing this thing.

 

It is just a translation of what they wrote me in the email. We will see when the recall campaign documentation becomes available.