Auxiliary vacuum system

S

sgilbert

New member
Dec 19, 1998
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Could someone explain to a new owner (and in simple terms please!) what=20
the aux vacuum pump does for the stock system. I have heard that=20
engine not running equals no vacuum which means no breaks, and can=B9t=20
figure out what another pump will do!
Thanks=20
Steve Gilbert
76 Eleganza
 
>Could someone explain to a new owner (and in simple terms please!) what=20
>the aux vacuum pump does for the stock system. I have heard that=20
>engine not running equals no vacuum which means no breaks, and can=B9t=20
>figure out what another pump will do!

Steve,

The auxilary vacuum pump ensures that there is vacuum to operate the brakes
in case the engine quits. The aux pump includes a pressure differential
switch that causes it to run when the vacuum drops below a setpoint. In
normal circumstances the pump just sits there. When the engine vacuum drops
below the setpoint the pump turns on and draws a vacuum. It's one of the
next add-ons for me.

Henry=20
Henry Davis Consulting, Inc / new product consulting=20
PO Box 1270 / product readiness reviews=20
Soquel, Ca 95073 / IP reviews=20
ph: (408) 462-5199 / full service marketing=20
fax: (408) 462-5198=20
http://www.henry-davis.com/ http://www.henry-davis.com
 
The vacuum pump provides boost vacuum to the brakes. If you lose your
engine on a hill, you have one time for brakes and no more. That is what
happened to me. I was on a hill, my engine stopped and I applies the
brakes. It slowed me down, and I quickly put it into park. If I had not
been able to do that I would have a runnaway backwards. With the pump, it
provedes an electric operated pump to help you use your brakes to stop.

Regards
Al Chernoff
77 Eleganza II

> Could someone explain to a new owner (and in simple terms please!) what
> the aux vacuum pump does for the stock system. I have heard that
> engine not running equals no vacuum which means no breaks, and can1t
> figure out what another pump will do!
> Thanks
> Steve Gilbert
> 76 Eleganza
 
With all the talk about the "Auxiliary vacuum system", I'd like to ask some
other "dumb" questions. When a GMC loses power, do they lose all braking, or
do they just lose the boost? I know in my SUV when the engine quits there is
still braking left. You just have to press harder on the pedal.

>From following this thread it sounds like you can be seriously screwed when a
GMC engine stops while you're driving down a steep hill. Is the "Auxiliary
vacuum system" another "must have" like an auxiliary fuel pump, replacing all
oil, gas, brake and transmission lines etc. etc.?

Richard Waters, '76 Palm Beach, Troy, MI

> The vacuum pump provides boost vacuum to the brakes. If you lose your
> engine on a hill, you have one time for brakes and no more. That is what
> happened to me. I was on a hill, my engine stopped and I applies the
> brakes. It slowed me down, and I quickly put it into park. If I had not
> been able to do that I would have a runnaway backwards. With the pump, it
> provedes an electric operated pump to help you use your brakes to stop.
>
> Regards
> Al Chernoff
> 77 Eleganza II
>

>
> > Could someone explain to a new owner (and in simple terms please!) what
> > the aux vacuum pump does for the stock system. I have heard that
> > engine not running equals no vacuum which means no breaks, and can1t
> > figure out what another pump will do!
> > Thanks
> > Steve Gilbert
> > 76 Eleganza
 
Steve, the diff is the aux pump is electric, running off the battery and
it provides vacuum while your engine isn't.

Others will provide more of the gory details but my competence is limited
to what I know.

David Lee Greenberg
Boston Homes, Inc
1220 US Highway 1, Suite B
North Palm Beach, FL 33408
T:561-776-1414 F:561-776-1788
 
>With all the talk about the "Auxiliary vacuum system", I'd like to ask some
>other "dumb" questions. When a GMC loses power, do they lose all braking,
or
>do they just lose the boost? I know in my SUV when the engine quits there
is
>still braking left. You just have to press harder on the pedal.
>



I'll jump in with a pennies worth.

It is indeed only the boost but without the boost you have to press VERY,
VERY HARD on the brake pedal. I've had occasion over the years to experience
unboosted braking on hills as well as coasting into gas stations on empty.
The hills were never big and even the coming to a stop coasting required
quite a bit of foot power. You do have one pedal push in reserve when the
engine quits, but unfortunately it's to easy to apply and release and then
when applying for real it's gone ;-)

Now this is/was with the stock Booster/MC setup.

I just added the Electric Vac Pump as another step towards peace of mind and
to adjust for possible lack of equivilant foot power being available as time
goes on :-)

With 20/20 hindsight this would now be a priority mod for me. I was just too
stupid, or rather not sufficiently knowledgable, to know that 1) the problem
is a problem and 2) that there's an easy fix. As folks have said, 25 bucks
at 'pick a part'. Patricks site has an excellent description of installation
options.

I choose to go the kit route. Got it from Leigh at $250, which included a
new GM pump, base and connector. Went in in a couple of hours.

Heinz
'76 Transmode

P.S. Had it not been for this list, I'd still be worried about it on
occasion. /Thanks Patrick.
 
Yes you still have brakes. Just minus the vacuum assist. Darren

> With all the talk about the "Auxiliary vacuum system", I'd like to ask some
> other "dumb" questions. When a GMC loses power, do they lose all braking, or
> do they just lose the boost? I know in my SUV when the engine quits there is
> still braking left. You just have to press harder on the pedal.
>
> >From following this thread it sounds like you can be seriously screwed when a
> GMC engine stops while you're driving down a steep hill. Is the "Auxiliary
> vacuum system" another "must have" like an auxiliary fuel pump, replacing all
> oil, gas, brake and transmission lines etc. etc.?
>
> Richard Waters, '76 Palm Beach, Troy, MI
>

>
> > The vacuum pump provides boost vacuum to the brakes. If you lose your
> > engine on a hill, you have one time for brakes and no more. That is what
> > happened to me. I was on a hill, my engine stopped and I applies the
> > brakes. It slowed me down, and I quickly put it into park. If I had not
> > been able to do that I would have a runnaway backwards. With the pump, it
> > provedes an electric operated pump to help you use your brakes to stop.
> >
> > Regards
> > Al Chernoff
> > 77 Eleganza II
> >

> >
> > > Could someone explain to a new owner (and in simple terms please!) what
> > > the aux vacuum pump does for the stock system. I have heard that
> > > engine not running equals no vacuum which means no breaks, and can1t
> > > figure out what another pump will do!
> > > Thanks
> > > Steve Gilbert
> > > 76 Eleganza
 
That settles it then! I will go with an aux vacuum system this Spring. I'll
buy new parts so I don't have to worry about anything wearing out.

Thanks for the insight for everyone that responded!
Richard Waters '76 Palm Beach
.......

> >With all the talk about the "Auxiliary vacuum system", I'd like to ask some
> >other "dumb" questions. When a GMC loses power, do they lose all braking,
> or
> >do they just lose the boost? I know in my SUV when the engine quits there
> is
> >still braking left. You just have to press harder on the pedal.
> >
>
>
>
> I'll jump in with a pennies worth.
>
> It is indeed only the boost but without the boost you have to press VERY,
> VERY HARD on the brake pedal. I've had occasion over the years to experience
> unboosted braking on hills as well as coasting into gas stations on empty.
> The hills were never big and even the coming to a stop coasting required
> quite a bit of foot power. You do have one pedal push in reserve when the
> engine quits, but unfortunately it's to easy to apply and release and then
> when applying for real it's gone ;-)
>
> Now this is/was with the stock Booster/MC setup.
>
> I just added the Electric Vac Pump as another step towards peace of mind and
> to adjust for possible lack of equivilant foot power being available as time
> goes on :-)
>
> With 20/20 hindsight this would now be a priority mod for me. I was just too
> stupid, or rather not sufficiently knowledgable, to know that 1) the problem
> is a problem and 2) that there's an easy fix. As folks have said, 25 bucks
> at 'pick a part'. Patricks site has an excellent description of installation
> options.
>
> I choose to go the kit route. Got it from Leigh at $250, which included a
> new GM pump, base and connector. Went in in a couple of hours.
>
> Heinz
> '76 Transmode
>
> P.S. Had it not been for this list, I'd still be worried about it on
> occasion. /Thanks Patrick.
 
If you lose the engine, you have one, I repeat, one brake pedal push with boost,
then its sayonara (sic). Anyway, you are screwed, as I was. So, please do think
about putting one in... it can save your coach, and even your life.
Al Chernoff
77 Eleganza II

> With all the talk about the "Auxiliary vacuum system", I'd like to ask some
> other "dumb" questions. When a GMC loses power, do they lose all braking, or
> do they just lose the boost? I know in my SUV when the engine quits there is
> still braking left. You just have to press harder on the pedal.
>
> >From following this thread it sounds like you can be seriously screwed when a
> GMC engine stops while you're driving down a steep hill. Is the "Auxiliary
> vacuum system" another "must have" like an auxiliary fuel pump, replacing all
> oil, gas, brake and transmission lines etc. etc.?
>
> Richard Waters, '76 Palm Beach, Troy, MI
>

>
> > The vacuum pump provides boost vacuum to the brakes. If you lose your
> > engine on a hill, you have one time for brakes and no more. That is what
> > happened to me. I was on a hill, my engine stopped and I applies the
> > brakes. It slowed me down, and I quickly put it into park. If I had not
> > been able to do that I would have a runnaway backwards. With the pump, it
> > provedes an electric operated pump to help you use your brakes to stop.
> >
> > Regards
> > Al Chernoff
> > 77 Eleganza II
> >

> >
> > > Could someone explain to a new owner (and in simple terms please!) what
> > > the aux vacuum pump does for the stock system. I have heard that
> > > engine not running equals no vacuum which means no breaks, and can1t
> > > figure out what another pump will do!
> > > Thanks
> > > Steve Gilbert
> > > 76 Eleganza
 
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