Brakes fading, then failed

My grandmother had a bit of a scare yesterday. She doesn't drive her Fiat
Punto (8 years old, 12k km or so, bought new) very much (it is, in effect,
the Real Thing of the 'always driven by an elderly lady' car -- maintained
at a local garage on a yearly basis), but yesterday she went to take it
around a block or two, mainly to keep the battery from running down
(again), and as she described it, the brakes started working less than
stellar, and eventually failed completely -- no resistance to the pedal.

She got it home, carefully and with the handbrake. When I looked at it
this afternoon, all the fluid levels including the brakes appeared to be
in good shape, and starting it up revealed no immediate warning lights[1].
With the handbrake released, I could move the car back and forth by hand
easily, but with the brake pedal depressed (which does not now appear to
go down to the stops) it had at least enough braking to stop me from doing
that (this is not necessarily inconsistent with there not being enough
braking action to matter when acting on a ton of metal moving at speeds,
of course).

So, what the hell happened? My pet theory: She left the handbrake on a
notch or two and the drag caused the brakes to heat up enough to boil the
brake liquid. If the garage doesn't find anything wrong with the brakes in
the area of things that are actually broken, this'd be my best theory. Are
there any other options that cause the brakes to fade out to nothing
gradually (that tends to argue against, say, a piece of the caliper
breaking off), and possibly return after cooldown?



Jasper

[1] I don't have a license, plus I don't like brakeless cars, so I didn't
drive it.

Jasper Janssen > wrote in message
...
> My grandmother had a bit of a scare yesterday. She doesn't drive her Fiat
> Punto (8 years old, 12k km or so, bought new) very much (it is, in effect,
> the Real Thing of the 'always driven by an elderly lady' car -- maintained
> at a local garage on a yearly basis), but yesterday she went to take it
> around a block or two, mainly to keep the battery from running down
> (again), and as she described it, the brakes started working less than
> stellar, and eventually failed completely -- no resistance to the pedal.
>
> She got it home, carefully and with the handbrake. When I looked at it
> this afternoon, all the fluid levels including the brakes appeared to be
> in good shape, and starting it up revealed no immediate warning lights[1].
> With the handbrake released, I could move the car back and forth by hand
> easily, but with the brake pedal depressed (which does not now appear to
> go down to the stops) it had at least enough braking to stop me from doing
> that (this is not necessarily inconsistent with there not being enough
> braking action to matter when acting on a ton of metal moving at speeds,
> of course).
>
> So, what the hell happened? My pet theory: She left the handbrake on a
> notch or two and the drag caused the brakes to heat up enough to boil the
> brake liquid. If the garage doesn't find anything wrong with the brakes in
> the area of things that are actually broken, this'd be my best theory. Are
> there any other options that cause the brakes to fade out to nothing
> gradually (that tends to argue against, say, a piece of the caliper
> breaking off), and possibly return after cooldown?
>
>
>
> Jasper
>
> [1] I don't have a license, plus I don't like brakeless cars, so I didn't
> drive it.

The obvious thing to look at would be when the fluid was last changed and if
necessary replace it. Brake fluid absorbs water over time and boils very
easily when it gets old.
--
Dave Baker - Puma Race Engines (www.pumaracing.co.uk)

Dave Baker wrote:

> Jasper Janssen > wrote in message
> ...

>>[1] I don't have a license, plus I don't like brakeless cars, so I
>> didn't drive it.
>
>
> The obvious thing to look at would be when the fluid was last changed
> and if necessary replace it. Brake fluid absorbs water over time and
> boils very easily when it gets old.

Sure sounds like brake fluid vapor lock. I don't why that would
happen with just a "drive around the block". Might have been a
combination of "wet" brake fluid (i.e. high moisture content) along
with something creating a lot of heat.

Many automakers don't have any recommended period to flush the
brake fluid - at least for US service. General Motors and Toyota
come to mind.

On Thu, 09 Jun 2005 01:54:56 GMT, y_p_w > wrote:
>Dave Baker wrote:
>
>> Jasper Janssen > wrote in message
>> ...
>
>>>[1] I don't have a license, plus I don't like brakeless cars, so I
>>> didn't drive it.
>>
>>
>> The obvious thing to look at would be when the fluid was last changed
>> and if necessary replace it. Brake fluid absorbs water over time and
>> boils very easily when it gets old.
>
>Sure sounds like brake fluid vapor lock. I don't why that would
>happen with just a "drive around the block". Might have been a

Well, longish block. About half an hour or so. But all small roads, max
speed 80 km/h (50 mph), not highway driving.

>combination of "wet" brake fluid (i.e. high moisture content) along
>with something creating a lot of heat.
>
>Many automakers don't have any recommended period to flush the
>brake fluid - at least for US service. General Motors and Toyota
>come to mind.

I'll see if I can look at the service book next time I'm there. It's
(supposed to have) had all scheduled maintenance, but obviously on the
'time' schedule rather than the kilometer schedule, because at about 2000
km/1300 miles a year average the kilometer schedule would have it in for
its first service at 7.5 years old.


Jasper

Jasper Janssen wrote:

> My grandmother had a bit of a scare yesterday. She doesn't drive her
> Fiat Punto (8 years old, 12k km or so, bought new) very much (it is,
> in effect, the Real Thing of the 'always driven by an elderly lady'
> car -- maintained at a local garage on a yearly basis), but yesterday
> she went to take it around a block or two, mainly to keep the battery
> from running down (again), and as she described it, the brakes
> started working less than stellar, and eventually failed completely
> -- no resistance to the pedal.



Master cylinder is bad, I'll bet. That's the usual reason for this sort
of thing.

Early on, the leak is internal, so does not lower the reservoir level.
Leave it long enough and it will begin leaking into the booster,
wrecking that.

On Thu, 09 Jun 2005 22:38:06 -0500, "Hugo Schmeisser"
> wrote:

>Early on, the leak is internal, so does not lower the reservoir level.
>Leave it long enough and it will begin leaking into the booster,
>wrecking that.

Does 'leave it long enough' include sitting out on the street, or is it
just driving? If the former, I'll see if I can push my grandmother to get
it fixed quickly.

Jasper

Jasper Janssen wrote:

> On Thu, 09 Jun 2005 22:38:06 -0500, "Hugo Schmeisser"
> > wrote:
>
> > Early on, the leak is internal, so does not lower the reservoir
> > level. Leave it long enough and it will begin leaking into the
> > booster, wrecking that.
>
> Does 'leave it long enough' include sitting out on the street, or is
> it just driving? If the former, I'll see if I can push my grandmother
> to get it fixed quickly.
>



You'd have to keep driving it for a long time.

On Tue, 14 Jun 2005 08:43:36 -0500, "Hugo Schmeisser"
> wrote:
>Jasper Janssen wrote:
>> On Thu, 09 Jun 2005 22:38:06 -0500, "Hugo Schmeisser"
>> > wrote:
>>
>> > Early on, the leak is internal, so does not lower the reservoir
>> > level. Leave it long enough and it will begin leaking into the
>> > booster, wrecking that.
>>
>> Does 'leave it long enough' include sitting out on the street, or is
>> it just driving? If the former, I'll see if I can push my grandmother
>> to get it fixed quickly.
>
>You'd have to keep driving it for a long time.

Fair enough. Then it'll probably be better off with no more than a gentle
push now and then, especially as her license is currently expired and the
renewal is pending.

Jasper