Sienna brake failur

In article ,
Hachiroku ÉnÉ`ÉçÉN wrote:

> On Sat, 30 Jan 2010 04:01:16 -0800, Salmon Egg wrote:
>
> >
> > My daughter reported a ONE TIME brake failure on a first model year
> > Sienna. The brake pedal went down to the floor once, and that never
> > happened again.
> >
> > I would dismiss this report as mistaken if it were not for possible
> > serious consequences if it is correct. I have difficulty working up a
> > scenario of how this can happen. She did not notice any indication of a
> > brake failure on the dashboard. How can such a thing happen? The vehicle
> > uses ABS and a dual master cylinder.
> >
> > Bill
>
>
> When you say "first model". are you referring to like a '99 or 2001?

I believe tp be 1999.

Bill

--
An old man would be better off never having been born.
 >> Stay informed about: Sienna brake failur 

If there was a pulsating -- very rapid, by the way, with a sound like a
machine gun -- in her foot, then the car was detecting a wheel lock and
activating the ABS system. The symptom you report is normal in this
condition, and the proper action for the driver is to hold the pedal on the
floor and let the ABS computer do its thing.

ABS detects that some wheels are rotating and some are not, and activates a
a system that removes brakeing pressure from the locked wheel(s) momentarily
then reapplies that pressure via a pump, and repeats until the vehicle
either stops or the locked wheel ceases to exist. If the locked wheel(s)
was(were) allowed to exist, a skid would be the likely result and this could
be problematic from the perspective of the objective of maintaining
directional stability of the vehicle. When the wheels are prevented from
locking -- especially the front wheels -- then the driver can continue to
steer the vehicle around approaching obsiticles. Of course, the ABS has no
idea that there are obsitcles or not, so the lack of an obsiticle does not
mean the system will not work.

If the vehicle is operated in a climate where there can be snow or ice on
the roadway, or water for that matter, then your daughter may have just
experienced the ABS system in action. Her keeping her foot in the pedal and
holding it there was the right thing to do. And the pedal would be on the
floor ...





"Salmon Egg" wrote in message

>
> My daughter reported a ONE TIME brake failure on a first model year
> Sienna. The brake pedal went down to the floor once, and that never
> happened again.
>
> I would dismiss this report as mistaken if it were not for possible
> serious consequences if it is correct. I have difficulty working up a
> scenario of how this can happen. She did not notice any indication of a
> brake failure on the dashboard. How can such a thing happen? The vehicle
> uses ABS and a dual master cylinder.
>
> Bill
>
> --
> An old man would be better off never having been born.
 >> Stay informed about: Sienna brake failur 

On Sat, 30 Jan 2010 19:04:47 -0800, Salmon Egg wrote:

> In article ,
> Hachiroku ÉnÉ`ÉçÉN wrote:
>
>> On Sat, 30 Jan 2010 04:01:16 -0800, Salmon Egg wrote:
>>
>> >
>> > My daughter reported a ONE TIME brake failure on a first model year
>> > Sienna. The brake pedal went down to the floor once, and that never
>> > happened again.
>> >
>> > I would dismiss this report as mistaken if it were not for possible
>> > serious consequences if it is correct. I have difficulty working up a
>> > scenario of how this can happen. She did not notice any indication of a
>> > brake failure on the dashboard. How can such a thing happen? The vehicle
>> > uses ABS and a dual master cylinder.
>> >
>> > Bill
>>
>>
>> When you say "first model". are you referring to like a '99 or 2001?
>
> I believe tp be 1999.
>
> Bill


I had this happen with a '92 Grand Voyager. Went to the floor once, and
never did it again! We looked at all the fittings, seals, plungers, etc
and never found it.

That said, I would look at the lines, fittings at the wheels, calipers,
brake cylinders, master cylinder, etc for signs of leakage. Maybe
something came loose and then lodged itself in such a way to mask the
problem....for now...

And, like Jeff said, it could be a hiccup in the ABS.
 >> Stay informed about: Sienna brake failur 

"Salmon Egg" wrote in message

>
> My daughter reported a ONE TIME brake failure on a first model year
> Sienna. The brake pedal went down to the floor once, and that never
> happened again.
>
> I would dismiss this report as mistaken if it were not for possible
> serious consequences if it is correct. I have difficulty working up a
> scenario of how this can happen. She did not notice any indication of a
> brake failure on the dashboard. How can such a thing happen? The vehicle
> uses ABS and a dual master cylinder.
>
> Bill
>
> --
> An old man would be better off never having been born.

Did the pedal go to the floor without any braking action?

Does the van have disc or drum rear brakes?

A pulsating sensation would indicate that the ABS system was activated, but
the brakes would still work.

Start by checking the fluid level in the master cylinder. If the fluid
level is low, the brakes may be worn or there may be a fluid leak.

Check the bake pads and/or shores for wear; replace if less than 2 mm thick.

If the van has drum brakes, check the read wheel cylinders for weeping brake
fluid.

Check the disc brake calipers to make sure that the slide pins are not
frozen or sticking and that the sleeves move freely.

If the brake fluid has never been flushed, consider flushing the fluid with
fresh fluid as the fluid may have absorbed moisture, especially in humid and
cold climates.
--

Ray O
(correct punctuation to reply)
 >> Stay informed about: Sienna brake failur 

On Jan 31, 3:28 pm, "Ray O"
wrote:
> "Salmon Egg" wrote in message
>
>
>
>
>
> > My daughter reported a ONE TIME brake failure on a first model year
> > Sienna. The brake pedal went down to the floor once, and that never
> > happened again.
>
snip
>
> If the van has drum brakes, check the read wheel cylinders for weeping brake
> fluid.
>

I had a 1998 which was the first year for the Sienna. Yup, it had rear
drum brakes (all grades).

> Check the disc brake calipers to make sure that the slide pins are not
> frozen or sticking and that the sleeves move freely.
>
> If the brake fluid has never been flushed, consider flushing the fluid with
> fresh fluid as the fluid may have absorbed moisture, especially in humid and
> cold climates.
> --
>
> Ray O
> (correct punctuation to reply)

I'd strictly follow Ray O's advice. My old Sienna was a little
sensitive to brake system maintenance in that the ABS system would
activate more readily, especially over an irregular road surface, as
the pads/shoes wore. It could feel like the pedal was sinking if the
car was skidding and the ABS was engaged. The need for a set of tires
with more grip might also be indicated.
 >> Stay informed about: Sienna brake failur