Home » Public Forums » GMCnet » vacuum assist - again
| vacuum assist - again [message #75652] |
Thu, 04 March 2010 13:26  |
jayrabe
Messages: 509
Registered: June 2009
Location: Portland, OR
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The flow of information and opinion is just a bit overwhelming at times to this relative newbie with only marginal auto mechanical experience. Thanks in advance to all for your patience.
I'd earlier been persuaded by the horror stories that I wanted to add an aux vacuum pump as a backup in case engine dies. So I'm sitting here waiting for time and budget to allow the mod, and along comes highly respected Jim Bounds saying it's a bad idea. Near as I understand, Jim is basically saying that the system is good enough as it is, and adding any new components/wiring/plumbing adds additional failure points, and THAT is a problem, since a failure to any point of this critical safety system can be disastrous, and more failure points means higher risk/possibility of failure. Jim please correct me if I'm misstating your position.
OK so far?
So now to the reservoir. I'm persuaded by GeneF that the reservoir by itself does not give you enough reserve in case of engine quitting, but Rob's recent post about adding a reservoir AND an aux vacuum pump seems pretty robust. Is this overkill?
Anyway, I'm trying to understand how all this works. I've redrawn Robs schematic,
http://www.gmcmhphotos.com/photos/showphoto.php?photo=32555&title=p3010029b&cat=5408
So first off, in normal operation, the engine manifold draws what? 15-20"? And with the check valve between the reservoir and the manifold, the reservoir will basically always be at that highest vacuum level, other than being drawn down by using the brakes. So then the aux vacuum pump only comes on when it's internal pressure switch reads below what? 5"? 10"?
OK, but what's the advantage/disadvantage of plumbing it this way rather than having the aux pump sucking down the reservoir basically in parallel with the engine manifold (still isolated with check valves, of course)? This is apparently the way GeneD has done it (though I agree with other posters that it seems a bad idea to have the pump require a switch rather than coming on automatically when low vacuum is sensed.)
http://www.gmcmhphotos.com/photos/showphoto.php?photo=32556&title=p3010030a&cat=5408
And the option LarC described, with the aux pump in between (in series) with engine manifold and booster, seems like a bad way to go IMO...
Anyway, just trying to get a better understanding of these things. Thanks for all the input.
J Rabe
76 Palm Beach
Portland, OR
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| Re: [GMCnet] vacuum assist - again [message #75653 is a reply to message #75652] |
Thu, 04 March 2010 13:41  |
emerystora
Messages: 4442
Registered: January 2004
Karma: 13
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On Mar 4, 2010, at 2:26 PM, Jay Rabe <jayrabe@hotmail.com> wrote:
> And the option LarC described, with the aux pump in between (in
> series) with engine manifold and booster, seems like a bad way to go
> IMO...
>
>
>
> J Rabe
> 76 Palm Beach
> Portland, OR
>
> _
What is your basis for saying that is a bad idea?
That is exactly the way most of us have it hooked up.
Mine has been that way for probably 10 years now.
The only problem is that if one had a cracked diaphram. Of course you
would get a warning long in advance if that happens because your pump
would run constantly.
And, as to a part breaking, that can happen with any system you put in.
Whether it's a pump, a tank, or combination, a hose or a fitting or
whatever can fail.
Emery Stora
78 Kingsley
Santa Fe, NM
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| Re: [GMCnet] vacuum assist - again [message #75654 is a reply to message #75652] |
Thu, 04 March 2010 13:46 |
zhagrieb
Messages: 676
Registered: August 2009
Location: Portland Oregon
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Jay, I'm in North Portland. If you'd like to see my setup and talk systems,
give me a call 283-9752. Glenn Giere
On Thu, Mar 4, 2010 at 11:26 AM, Jay Rabe <jayrabe@hotmail.com> wrote:
>
>
> The flow of information and opinion is just a bit overwhelming at times to
> this relative newbie with only marginal auto mechanical experience. Thanks
> in advance to all for your patience.
>
> I'd earlier been persuaded by the horror stories that I wanted to add an
> aux vacuum pump as a backup in case engine dies. So I'm sitting here waiting
> for time and budget to allow the mod, and along comes highly respected Jim
> Bounds saying it's a bad idea. Near as I understand, Jim is basically saying
> that the system is good enough as it is, and adding any new
> components/wiring/plumbing adds additional failure points, and THAT is a
> problem, since a failure to any point of this critical safety system can be
> disastrous, and more failure points means higher risk/possibility of
> failure. Jim please correct me if I'm misstating your position.
>
> OK so far?
>
> So now to the reservoir. I'm persuaded by GeneF that the reservoir by
> itself does not give you enough reserve in case of engine quitting, but
> Rob's recent post about adding a reservoir AND an aux vacuum pump seems
> pretty robust. Is this overkill?
>
> Anyway, I'm trying to understand how all this works. I've redrawn Robs
> schematic,
>
>
> http://www.gmcmhphotos.com/photos/showphoto.php?photo=32555&title=p3010029b&cat=5408
>
> So first off, in normal operation, the engine manifold draws what? 15-20"?
> And with the check valve between the reservoir and the manifold, the
> reservoir will basically always be at that highest vacuum level, other than
> being drawn down by using the brakes. So then the aux vacuum pump only comes
> on when it's internal pressure switch reads below what? 5"? 10"?
>
> OK, but what's the advantage/disadvantage of plumbing it this way rather
> than having the aux pump sucking down the reservoir basically in parallel
> with the engine manifold (still isolated with check valves, of course)? This
> is apparently the way GeneD has done it (though I agree with other posters
> that it seems a bad idea to have the pump require a switch rather than
> coming on automatically when low vacuum is sensed.)
>
>
> http://www.gmcmhphotos.com/photos/showphoto.php?photo=32556&title=p3010030a&cat=5408
>
> And the option LarC described, with the aux pump in between (in series)
> with engine manifold and booster, seems like a bad way to go IMO...
>
> Anyway, just trying to get a better understanding of these things. Thanks
> for all the input.
>
> J Rabe
> 76 Palm Beach
> Portland, OR
>
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
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Glenn Giere, Portland OR, K7GAG
'73 "Moby the Motorhome" 26'
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| Re: [GMCnet] vacuum assist - again [message #75663 is a reply to message #75653] |
Thu, 04 March 2010 16:02 |
jayrabe
Messages: 509
Registered: June 2009
Location: Portland, OR
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For one thing, didn't LarC report a suspicion that the engine manifold may have had a problem sucking through the pump? I guess my only uncertainty has to do with not knowing details of the innards of the pump. Is it designed so that this kind of configuration would not be a problem in any operation or failure mode? And the advantage of putting the pump in series is fewer new connections to fail I presume?
Emery you say yours has been in service this way for 10 years - have you had any engine failures that put the system to test? Did LarC or have you tested this config with the pump disabled, per Lar's concern? That is, does the engine manifold have any problem or restriction sucking through a pump that's shut off?
J
76 Palm Beach
Portland, OR
> From: emerystora@mac.com
> On Mar 4, 2010, at 2:26 PM, Jay Rabe <jayrabe@hotmail.com> wrote:
> > And the option LarC described, with the aux pump in between (in
> > series) with engine manifold and booster, seems like a bad way to go
> > IMO...
> What is your basis for saying that is a bad idea?
> That is exactly the way most of us have it hooked up.
> Mine has been that way for probably 10 years now.
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| Re: [GMCnet] vacuum assist - again [message #75665 is a reply to message #75663] |
Thu, 04 March 2010 16:16 |
emerystora
Messages: 4442
Registered: January 2004
Karma: 13
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There is no problem with the engine drawing a vacuum through a shut
off pump. Yes, this has been tested years ago.
Emery Storz
On Mar 4, 2010, at 5:02 PM, Jay Rabe <jayrabe@hotmail.com> wrote:
>
> For one thing, didn't LarC report a suspicion that the engine
> manifold may have had a problem sucking through the pump? I guess my
> only uncertainty has to do with not knowing details of the innards
> of the pump. Is it designed so that this kind of configuration would
> not be a problem in any operation or failure mode? And the advantage
> of putting the pump in series is fewer new connections to fail I
> presume?
>
> Emery you say yours has been in service this way for 10 years - have
> you had any engine failures that put the system to test? Did LarC or
> have you tested this config with the pump disabled, per Lar's
> concern? That is, does the engine manifold have any problem or
> restriction sucking through a pump that's shut off?
>
> J
> 76 Palm Beach
> Portland, OR
>
>
>> From: emerystora@mac.com
>> On Mar 4, 2010, at 2:26 PM, Jay Rabe <jayrabe@hotmail.com> wrote:
>>> And the option LarC described, with the aux pump in between (in
>>> series) with engine manifold and booster, seems like a bad way to go
>>> IMO...
>
>> What is your basis for saying that is a bad idea?
>> That is exactly the way most of us have it hooked up.
>> Mine has been that way for probably 10 years now.
>
>
>
> _________________________________________________________________
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| Re: [GMCnet] vacuum assist - again [message #75671 is a reply to message #75665] |
Thu, 04 March 2010 16:55 |
jayrabe
Messages: 509
Registered: June 2009
Location: Portland, OR
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OK. Thanks, Emory.
J
> From: emerystora@mac.com
> To: gmclist@temp.gmcnet.org
> Date: Thu, 4 Mar 2010 17:16:38 -0500
> Subject: Re: [GMCnet] vacuum assist - again
>
> There is no problem with the engine drawing a vacuum through a shut
> off pump. Yes, this has been tested years ago.
>
>
>
> Emery Storz
>
> On Mar 4, 2010, at 5:02 PM, Jay Rabe <jayrabe@hotmail.com> wrote:
>
> >
> > For one thing, didn't LarC report a suspicion that the engine
> > manifold may have had a problem sucking through the pump? I guess my
> > only uncertainty has to do with not knowing details of the innards
> > of the pump. Is it designed so that this kind of configuration would
> > not be a problem in any operation or failure mode? And the advantage
> > of putting the pump in series is fewer new connections to fail I
> > presume?
> >
> > Emery you say yours has been in service this way for 10 years - have
> > you had any engine failures that put the system to test? Did LarC or
> > have you tested this config with the pump disabled, per Lar's
> > concern? That is, does the engine manifold have any problem or
> > restriction sucking through a pump that's shut off?
> >
> > J
> > 76 Palm Beach
> > Portland, OR
> >
> >
> >> From: emerystora@mac.com
> >> On Mar 4, 2010, at 2:26 PM, Jay Rabe <jayrabe@hotmail.com> wrote:
> >>> And the option LarC described, with the aux pump in between (in
> >>> series) with engine manifold and booster, seems like a bad way to go
> >>> IMO...
> >
> >> What is your basis for saying that is a bad idea?
> >> That is exactly the way most of us have it hooked up.
> >> Mine has been that way for probably 10 years now.
> >
> >
> >
> > _________________________________________________________________
> > Hotmail: Powerful Free email with security by Microsoft.
> > http://clk.atdmt.com/GBL/go/201469230/direct/01/
> > _______________________________________________
> > GMCnet mailing list
> > List Information and Subscription Options:
> > http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
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| Re: [GMCnet] vacuum assist - again [message #75674 is a reply to message #75653] |
Thu, 04 March 2010 17:18 |
shawnee
Messages: 422
Registered: February 2004
Location: NC
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| emerystora wrote on Thu, 04 March 2010 14:41 |
On Mar 4, 2010, at 2:26 PM, Jay Rabe <jayrabe@hotmail.com> wrote:
> And the option LarC described, with the aux pump in between (in
> series) with engine manifold and booster, seems like a bad way to go
> IMO...
>
>
>
> J Rabe
> 76 Palm Beach
> Portland, OR
>
> _
What is your basis for saying that is a bad idea?
That is exactly the way most of us have it hooked up.
Mine has been that way for probably 10 years now.
The only problem is that if one had a cracked diaphram. Of course you
would get a warning long in advance if that happens because your pump
would run constantly.
And, as to a part breaking, that can happen with any system you put in.
Whether it's a pump, a tank, or combination, a hose or a fitting or
whatever can fail.
Emery Stora
78 Kingsley
Santa Fe, NM
|
Obviously I agree With Emery. The vacuum pumps off old cars are getting old becoming unreliable. Jim K does have one that is new and will do the job. I used 3 units from old cars and all of them failed over a period of time. I bought a heavy duty one from Stainless Steel Brakes that has a separate vacuum sensor from the pump. Two of those sensors broke and there is no indication of the failure so I decided to tie the pump in parallel with the auto vacuum line using a small tank with a built in check valve and operating it with a switch. The most critical time for engine dying is if you are going up a mountain. Without a vacuum pump you have one pump of the brakes and then you are on your own. Like the cars that have unintended acceleration, put the brake on hard and keep it there. I don't consider it a bad idea since I can test it at any time and it is a lot safer than not having a second vacuum source. The vacuum tank is just suspenders.
Gene Dotson
74 Canyonlands
www.bdub.net/Motorhome_Enhancements New Windows and Aluminum Radiators
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| Re: vacuum assist - again [message #75695 is a reply to message #75652] |
Thu, 04 March 2010 23:40 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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The GM pump that most of us use was designed by GM to go in series with the vacuum line between the MC and the engine. GM designed it that way and I see no reason to change it. Mine was an install it and forget it. If I want to check it I can step on the brakes twice before starting the GMC. I will hear it turn on when I turn the key on and it will run a few seconds until the booster tank is up to vacuum which is only a few seconds. Why second guess or re-engineer something that has worked fine for GM and Volvo on 1000's of vehicles since the 1980s?
I thought the reserve tank idea came about because some GMCers were having problems finding good pumps. I feel the reserve tank is a cheap but lesser alternative to a real pump. I would install one only if I could not find a real pump.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: vacuum assist - again [message #75702 is a reply to message #75699] |
Fri, 05 March 2010 00:39 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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| WD0AFQ wrote on Thu, 04 March 2010 23:57 |
Ken, after we replaced my booster, with the one Jim sent, mine is like your's. To test it I do same thing. Otherwise, it does not come on. I like it. Simple and fast install. Forget it.
Dan
change your mind and come on down. u cant be any poorer than I am now.
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The vacuum pump also told you when the old booster was bad / leaking. A reserve tank would not have done that.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: vacuum assist - again [message #75705 is a reply to message #75704] |
Fri, 05 March 2010 01:00 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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No I haven't. It is on the list to do. I just finished fixing my 4 wheel drive on the Blazer last night. I still have a few more things to fix on it like an ABS light and an occasional air bag light. Then maybe it will be warm enough to go to the hanger and work on the GMC.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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