From: Al Falfa on

"C. E. White" <cewhite3(a)mindspring.com> wrote in message
news:hcui2i$94p$1(a)news.eternal-september.org...
>
> "ransley" <Mark_Ransley(a)Yahoo.com> wrote in message
> news:0b6605b2-aac9-44d2-8710-5ddd3f4f2b27(a)j24g2000yqa.googlegroups.com...
>
>> > The guy was supposedly a highway patrol officer....I just find it hard
>> > to believe they had time to make a 911 call and not time to put the
>> > car in neutral. I can understand the confusion with the start/stop
>> > button if it was a rental, but not the shift level.
>> >
>> > Ed
>
>>Or turn off the key and put on the parking brake
>
> Supposedly the car was a Lexus with the Start/Stop button. With the car in
> gear just pushing this button does nothing - you have to press and hold it
> for three seconds for it to kill the engine if the car is in gear. Since
> it was reportedly a rental, I can understand the driver not knowing this
> fact. However, I still cannot imagine him not putting the car into
> neutral.
>
> And why call 911? Did they figure Scotty was going to beam them out of the
> car?
>
> Ed
Under the circumstances, panic was very likely a factor. Putting one's car
in neutral under such unusual circumstances is not a conditioned response.
The 911 call from the back seat was a futile attempt to clear traffic.

From: C. E. White on

"dsi1" <dsi1(a)spamnet.com> wrote in message
news:P6CIm.3404$gg6.892(a)newsfe25.iad...

> Supposedly these cars use hydraulic pressure supplied by the power
> steering pump for braking assist not engine vacuum. Well, that's
> what I hear anyway.

For sure some cars use hydraulic brake assit instead of vacuum assit
for the brakes (my 2001 Mustang GT did for instance). However, the
reports I read indicated that the Lexus in the California wreck used a
vaccum booster (and the Lexus parts catalog supports this).

Hydralic type boosters depend on the engine running to provide
hydraulic pressure. You can include an accumulator in the circuit to
provide back up boost for sutuations where the engine dies, but this
is still limited.

I am not sure what the hybrid vehicles use. A hybrid you can't depend
on either engine vacuum or an engine driven hydualic pump to provide
brake boost, so I assume they have an electrically driven hydraulic
pump to provide the boost but I don't know for sure. Maybe they use
the ABS pump....

>> However, I still say if the guy had moved the shifter into neutral,
>> he could have stopped the car. But that is jsut my opinion.
>
> Odd, ain't it?

Yes. I guess even trained professionals can panic.

Ed


From: dsi1 on
C. E. White wrote:
> "dsi1" <dsi1(a)spamnet.com> wrote in message
> news:P6CIm.3404$gg6.892(a)newsfe25.iad...
>
>> Supposedly these cars use hydraulic pressure supplied by the power
>> steering pump for braking assist not engine vacuum. Well, that's
>> what I hear anyway.
>
> For sure some cars use hydraulic brake assit instead of vacuum assit
> for the brakes (my 2001 Mustang GT did for instance). However, the
> reports I read indicated that the Lexus in the California wreck used a
> vaccum booster (and the Lexus parts catalog supports this).

Thanks for that info.

>
> Hydralic type boosters depend on the engine running to provide
> hydraulic pressure. You can include an accumulator in the circuit to
> provide back up boost for sutuations where the engine dies, but this
> is still limited.
>
> I am not sure what the hybrid vehicles use. A hybrid you can't depend
> on either engine vacuum or an engine driven hydualic pump to provide
> brake boost, so I assume they have an electrically driven hydraulic
> pump to provide the boost but I don't know for sure. Maybe they use
> the ABS pump....

That's a good question. I would suppose you could even use the drive
motors to slow the car down. Hybrid cars are such a complicated animal.

>
>>> However, I still say if the guy had moved the shifter into neutral,
>>> he could have stopped the car. But that is jsut my opinion.
>> Odd, ain't it?
>
> Yes. I guess even trained professionals can panic.

My guess is that you don't really know how you'd act in such a situation
until it happens. Good thing this is such a rare event.


>
> Ed
>
>
From: Ray O on

"C. E. White" <cewhite3(a)mindspring.com> wrote in message
news:hcutqj$ijj$1(a)news.eternal-september.org...
>
> "dsi1" <dsi1(a)spamnet.com> wrote in message
> news:P6CIm.3404$gg6.892(a)newsfe25.iad...
>
>> Supposedly these cars use hydraulic pressure supplied by the power
>> steering pump for braking assist not engine vacuum. Well, that's what I
>> hear anyway.
>
> For sure some cars use hydraulic brake assit instead of vacuum assit for
> the brakes (my 2001 Mustang GT did for instance). However, the reports I
> read indicated that the Lexus in the California wreck used a vaccum
> booster (and the Lexus parts catalog supports this).
>
> Hydralic type boosters depend on the engine running to provide hydraulic
> pressure. You can include an accumulator in the circuit to provide back up
> boost for sutuations where the engine dies, but this is still limited.
>
> I am not sure what the hybrid vehicles use. A hybrid you can't depend on
> either engine vacuum or an engine driven hydualic pump to provide brake
> boost, so I assume they have an electrically driven hydraulic pump to
> provide the boost but I don't know for sure. Maybe they use the ABS
> pump....
>
>>> However, I still say if the guy had moved the shifter into neutral, he
>>> could have stopped the car. But that is jsut my opinion.
>>
>> Odd, ain't it?
>
> Yes. I guess even trained professionals can panic.
>
> Ed

Good question on hybrid brake assist. The power steering system uses an
electric motor to provide assist, and so there is no electrically driven
hydraulic pump for the power steering system. I would imagine that hybrids
use some kind of electric assist for the brakes. The ABS system on a Toyota
does not have a pump, just valves that open and close rapidly to modulate
brake force to individual wheels.
--

Ray O
(correct punctuation to reply)


From: Jules on
On Thu, 05 Nov 2009 08:11:51 -0600, hls wrote:
> The brakes dont stop working if the
> vacuum is lost...you just have to depend upon your leg muscles. You may
> THINK you have lost all brakes, but they are still there.

Yes - only had it happen to me once (coil lost power and so the engine
died) but I was running at around 80 at the time and it was something of a
surreal experience. I think the split second before I realised what was
going on was perhaps stranger, as the car began to slow due to the rear
wheels turning the dead engine.

Our truck's old enough to have no engine assist for the brakes at all, so
the leg gets a good work-out :-)

cheers

Jules