[GMCnet] Ford A426C brake vacuum pump, your opinion please?

[Mike]

Hello, a fellow GMC'er has listed a Ford A426C pump for sale which I have expressed interest in purchasing.

Is this a good back up choice or is there something better out there, I seem to recall reading a short time ago about a newer system but can not find
the post right now?

Your opinion on this is important, it will help me make a more informed decision on this system for back-up braking in an emergency situation.

I have a 1975 Coachmen built Royale, 26' with a 455.

Regards,
Mike

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[Les Burt]

The A426C pump is a good pump, made with a cast zinc/aluminum alloy body.

There is a revised version now being made with a composite body.

The only reason I mention this is because Ford was having severe corrosion issues with the metal body pumps when exposed to road salt in northern climates. The solution was the composite body.

Does any of this make one pump better than another when the pump is used on a TZE? I rather doubt it.

Rockauto sells the a new composite pump for approx $200usd, so keep that in mind with regards to putting a price on the pump you found.

RobM recently provided comparison details on both pumps, so look up his recent posts if you need more data.

Les Burt
Montreal
'75 Eleganza 26'

[Mike]

Thanks for your input Les, I forgot who posted the thread but seemed to remember reading about this, thanks for that lead.

[John Wright]

Mike,
I have us the Ford Vacuum pump for a little over 2 years and it has been great. I also use the Lenzi brake booster and have gone back to the stock master cylinder giving up the p30 unit. Best brakes that I have had in the last 18 years. Other setups were good but this is the best.

http://www.gmcmhphotos.com/photos/general-pictures/p59295-dl-brake-layout.html
http://www.gmcmhphotos.com/photos/general-pictures/p59296-dl-brake-layout.html
http://www.gmcmhphotos.com/photos/general-pictures/p59297-dl-brake-layout.html
http://www.gmcmhphotos.com/photos/general-pictures/p59294-dl-brake-layout.html

For those of you with sharp eyes will have noticed the brake fluid from the master cylinder and that was a new unit too!

J.R. Wright
GMC GreatLakerTech Editor
78 Buskirk 30' Stretch
75 Avion Under Reconstruction
Michigan

[David Shafer]

powwerjon,

That is a nice looking setup up top. What is your choice at the wheels? ...six disks or less? If you are running disk brakes at the rear, what size
rotors?
Thanks,
Dave
--
1977 26 foot 403

[John Wright]

Dave,
I have run many combo of brakes over the years. I did have 6 wheel disk which was 80MM on the front and a Harrison setup on the middle bogie which has a 12.5 in Ford disk with the 80MM caliper and a Cad set up with the stock Cad cal with emergency brake option. See these pictures.d I also show the comparison between the Harrison and Cad rotor.

http://www.gmcmhphotos.com/photos/g5661-disk-brake-upgrade-leigh-harrison-brakes.html

The combo I run now is still the 80MM on the front, Harrison on the middle with 80MM and standard drum brake on the rear with a 15/16 inch slave cylinder and carbon metallic shoes. I will probably go to a 7/8 inch slave on the rear the next time I do a complete service on the brakes.

The majority of the braking is provided by the middle bogie with the rear not locking up. The real difference is that I have gotten the brake pressure back up to about 1200 psi compared to about 900 psi with the p30 master. Pressure means power to stop. The more pressure that you have at the brakes is king. If you have more questions I may answer ask.

J.R. Wright
GMC GreatLakerTech Editor
78 Buskirk 30' Stretch
75 Avion Under Reconstruction
Michigan

[Rob Mueller]

Dave,

Here's a link on how to install Cadillac disk brakes on the rear of a GMC:

http://www.gmcgreatlakers.org/gmcing/tech_docs/6-WheelDiskBrakes.pdf

Double Trouble has OEM disks on the front with 80 mm calipers, Caddy disks on the middle wheels with 80 mm calipers; and OEM drums
on the rear. I did that because I needed to have an emergency brake to pass NJ inspection which is where I registered it when I
bought it.

Regards,
Rob M.
The Pedantic Mechanic
Sydney, Australia
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426
USA '77 Kingsley - TZE 267V100808

[Jim Kanomata]

For those that want a ready to install kit, we have them .
You can see them on our web site.

On Thu, Dec 28, 2017 at 9:19 PM, Rob Mueller <robmu...@iinet.net.au>
wrote:

--
Jim Kanomata
Applied/GMC, Newark,CA
ji...@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502

[D C _Mac_ Macdonald]

Hi, Jim.

Is that a kit to install the Ford A426C vacuum pump or Caddy brakes?

Mac in OKC

"The Money Pit"


________________________________
From: Gmclist <gmclist...@list.gmcnet.org> on behalf of Jim Kanomata <jimka...@gmail.com>
Sent: Thursday, December 28, 2017 23:27
To: gmc...@list.gmcnet.org
Subject: Re: [GMCnet] Ford A426C brake vacuum pump, your opinion please?

For those that want a ready to install kit, we have them .
You can see them on our web site.

On Thu, Dec 28, 2017 at 9:19 PM, Rob Mueller <robmu...@iinet.net.au>
wrote:

> Dave,
>
> Here's a link on how to install Cadillac disk brakes on the rear of a GMC:
>

> https://eur01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.gmcgreatlakers.org%2Fgmcing%2Ftech_docs%2F6-WheelDiskBrakes.pdf&data=02%7C01%7C%7C7b2ee6a45732450159f408d54e7cf301%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C636501220909006303&sdata=V7vAIY1dlZ7QV6WDSQdgUB4PccAhl%2Fl22tbbFF5L5oo%3D&reserved=0

[Gary Kosier]

John,

What is the purpose of the piece of angle iron attached to the rear of the
caliper bracket?

Gary Kosier
77PB w/500Cad
Newark, Ohio

--------------------------------------------------
From: "John Wright" <poww...@gmail.com>
Sent: Thursday, December 28, 2017 11:53 PM

To: <gmc...@list.gmcnet.org>
Subject: Re: [GMCnet] Ford A426C brake vacuum pump, your opinion please?

[Johnny Bridges via Gmclist]

I put a GM pump from a midsize late 80s Buick from Pick n Pay on the 23', along with a reservoir made from 3 feet of four inch PVC which worked fine.
Current 26' has the Ford pump fitted, but no reservoir. Given the cam in it, it needs the pump.

--johnny
--
76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
"I forgive them all, save those who hurt the dogs. They must answer to me in hell" - ol Andy, paraphrased

[John Wright]

Gary,
It is use to route and attach the brake line and hose to the caliper.

John

> On Dec 29, 2017, at 9:47 AM, Gary Kosier <gko...@roadrunner.com> wrote:
>
> John,
>
> What is the purpose of the piece of angle iron attached to the rear of the caliper bracket?
>
> Gary Kosier
> 77PB w/500Cad
> Newark, Ohio

[Mike]

Looks like I missed out on the pump advertised on the GMC Swap Meet forum, I responded pretty quick but someone else beat me to it.

If you have one you would like to sell please let me know?

There are approximately 13 options available from the GMC motorhome page (http://www.gmcmotorhome.com/tech/vacuum_pump/index.html) as well as the GM
offered pump, are these antiquated or have they been surpassed by newer technology?

If there is a newer / better alternative (subjective I know) available, I'm still open to options as I would like to fit my coach with some back-up
system?

Thanks again,
Mike

[Rob Mueller]

Mike,

Below you will find a couple of emails I sent in earlier this month.

Regards,
Rob M.
The Pedantic Mechanic
Sydney, Australia
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426 USA '77 Kingsley - TZE 267V100808

-----Original Message-----
From: Gmclist [mailto:gmclist...@list.gmcnet.org] On Behalf Of Rob Mueller
Sent: Saturday, December 9, 2017 11:43 PM
To: gmc...@list.gmcnet.org

Subject: Re: [GMCnet] Ford Azure / F-150 Eco Boost Vacuum Pumps

G'day,

Additional info on the F-150 Eco Boost Pump:

RockAuto P/N: MOTORCRAFT BRPV30

Link: https://www.rockauto.com/en/parts/motorcraft,BRPV30,vacuum+pump,5172

McMaster-Carr Rubber isolator mounts:

https://www.mcmaster.com/#rubber-isolators/=1alwgb6

I used a metric size for the metal Azure pump and don't remember the size, sorry.

You'll have to tap the plastic pump screw holes to install rubber isolators therefore you'll have figger out what size to use after
you tap them.

Regards,
Rob M.

-----Original Message-----
From: Gmclist [mailto:gmclist...@list.gmcnet.org] On Behalf Of Rob Mueller
Sent: Friday, December 8, 2017 9:58 PM
To: gmc...@list.gmcnet.org
Subject: [GMCnet] Ford Azure / F-150 Eco Boost Vacuum Pumps

G'day,

As promised here's a revised album showing both the Ford Azure and F-150 Eco Boost Vacuum pumps.

http://www.gmcmhphotos.com/photos/g7124-ford-azure-2f-f-150-eco-boost-vacuum-pump.html

Feel free to ask questions.

I spoke to Dave Lenzi and he's still selling his kit; please contact him directly for info on the kit:

http://www.gmcmotorhomemarketplace.com/lenzi/index.html

Regards,
Rob M.

-----Original Message-----
From: Gmclist [mailto:gmclist...@list.gmcnet.org] On Behalf Of Mike
Sent: Saturday, December 30, 2017 6:00 AM
To: gmc...@list.gmcnet.org
Subject: Re: [GMCnet] Ford A426C brake vacuum pump, your opinion please?

[James Hupy]

A running GMC engine in good shape, at sea level, will make in excess of 25
inches of vacuum at 30 mph with your foot off the gas. Like when you might
be using the brakes. It will make 2 or 3 times more vacuum than your coach
brakes will ever need.
So, now we have established that a running coach really does not have
any need for an auxiliary vacuum pump, we can deal with "Yes, but, OMG,
what if the engine quits?" The booster has enough reserve vacuum for you
to bring the coach to a safe stop, ONCE. If the GMC needed an auxiliary
vacuum pump, why didn't GMC install one from the factory? Because it was
not needed? Don't know for sure if that is the real reason, but, it seems
likely to me. A hydro boost system is also reliant upon the engine running
to be able to multiply the pedal effort. No back up system there, either.
Seems to me that it would make good sense to insure that the fuel
tanks are not close to empty, and that the engine is in good enough shape
that it does not stop running except when the driver wants it to. But, it's
your money, spend it how you want.
Jim Hupy
Salem, Or
78 GMC ROYALE 403

[Emery Stora]

> On Dec 29, 2017, at 1:50 PM, James Hupy <james...@gmail.com> wrote:
>
> A running GMC engine in good shape, at sea level, will make in excess of 25
> inches of vacuum at 30 mph with your foot off the gas. Like when you might
> be using the brakes. It will make 2 or 3 times more vacuum than your coach
> brakes will ever need.

> So, now we have established that a running coach really does not have
> any need for an auxiliary vacuum pump,

NO we haven’t. How often is the average GMC er going to be driving at sea level at 30 mph with his foot off the gas???

More likely the need to apply the brakes is when some idiot cuts you off at highway speeds when you are at 3000 to 7000 feet elevation. Or if there is an accident in front of you.
What is the vacuum there? Probably closer to 10 inches than 25 inches. The vacuum pump at those conditions will be closer to 20 inches.
Ask Dave Lenzi how much more braking you’ll have with your booster at 20 instead of 10. Or watch one of his demonstration when he has a booster and vacuum pump hooked up to a master cylinder with pressure gauges at one of the GMCMI conventions.
If you are in a panic braking situation you’ll be very thanking that you have a vacuum pump attached to your booster instead of depending on engine vacuum alone.

Now, if your only concern is how many pumps you have for your brakes when rolling backwards on a hill you may be OK without a pump but a lot of people that have been in that situation will disagree with you.

Emery Stora
77 Kingsley
Frederick, CO

[Ken Henderson]

IMHO, the most reliable and economical backup for vacuum brakes is a large
reservoir, such as a 30" section of 4" pvc pipe mounted inside the GMC's
front cross member with wire ties. Properly constructed and installed,
such a device should hold enough vacuum for 2-3 fully assisted brake
applications at near the ambient atmospheric pressure. That assumption is
based on the likelihood that since the last previous brake application
(including the current stop) the engine will have been providing its full
vacuum capability several times. With the engine braking at closed
throttle the vacuum it generates should be nearly as good as a
purpose-designed vacuum pump. Installing a vacuum gauge and monitoring it
during normal driving will show that full vacuum occurs at almost every
significant deceleration event -- the reservoir will capture and retain
that vacuum.

Achieving that "proper construction and installation" may not be as easy as
it sounds. I've made quite a few of them and found that leak-proofing can
be difficult. There must be a check valve at the "entry" to the reservoir
(the connection to the engine). I found that many new off-the-shelf
booster check valves leak; my best source proved to be the junk yard. More
than one check valve removed from long-stored junkers released vacuum when
pulled from their boosters. The hose connections to the reservoir and to
the various components, including the check valve at the booster, and its
mounting grommet, MUST be snug & air tight. Vacuum is easily destroyed by
the smallest air leak.

This is not to denigrate the value of an electric boost pump, but absent
that more expensive improvement, the reservoir is a vast improvement over
just booster reserve. I always ran both.

​Ken H.​

[Johnny Bridges via Gmclist]

One comment on Ken's approach - please don't use Ty-Raps <tm> (Known as zip ties) to hold the canister. The white ones deteriorate in ozone and
sunshine, the black <UV proof> ones are quite brittle. Use stainless steel hose clamps to fasten the canister to the crossmember. If it manages to
fall off and pull the lines loose, you'll have zero boost to stop.

--johnny
--
76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
"I forgive them all, save those who hurt the dogs. They must answer to me in hell" - ol Andy, paraphrased

[Ken Henderson]

Good idea, Johnny, even though I've never had one of the black 3/8"x18"
tywraps fail. And I usually use 4 of them, two around the upper and two
around the lower web of the cross member.

Ken H.

On Sat, Dec 30, 2017 at 8:56 AM, Johnny Bridges via Gmclist <
gmc...@list.gmcnet.org> wrote:

> One comment on Ken's approach - please don't use Ty-Raps <tm> (Known as
> zip ties) to hold the canister. The white ones deteriorate in ozone and
> sunshine, the black <UV proof> ones are quite brittle. Use stainless
> steel hose clamps to fasten the canister to the crossmember. If it manages
> to
> fall off and pull the lines loose, you'll have zero boost to stop.
>

[Bruce Hislop]

Just my farm-boy mechanic thoughts on vacuum pumps and reservoirs.

In my opinion, both are a great idea. I do have an opinion (or idea) on how they should be plumbed and why. The engine has a huge capacity to draw
down vacuum (hoping that is proper terminology), as compared to an electric pump. I currently have a JC4 pump which is plumbed in series between the
vacuum booster and the engine, in other words the engine vacuum flows through the pump. My idea is the system should be plumbed in the following
order.

Vacuum booster ->check valve --> vacuum pump ---> vacuum reservoir ->check valve ---> engine.

My reasoning is the engine's vacuum capacity will draw down the reservoir and booster almost immediately and the check valves will keep the system at
maximum vacuum (or minimum depending on your point of view). If the engine quits, and say you were going down a hill which required multiple brake
applications, the vacuum reservoir would provide a source of vacuum for a short while. Once the reservoir vacuum went below the pump setting, then the
pump would start.

Now this is point where my configuration come into play. With the pump in-line right at the booster, there is only the booster reservoir to pump
down, so the pump should be able to do that fairly quickly to regain power in the brakes. If the pump had to draw down the reservoir as well, it
would take much longer to do so and in the meantime your booster brake assist would be very poor.

Does this make sense? I haven't seen where this has been written-up in the past. Or maybe my assumptions are all wrong here.

Comments or ideas?

Thanks


--
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.
Hubler 1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that

[Rob Mueller]

Bruce,

Dave L's configuration:

Booster port #1 - check valve #1 - Ford Azure / F-150 vacuum pump

Booster port #2 - check valve #2 - Engine

Regards,
Rob M.
The Pedantic Mechanic
Sydney, Australia
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426
USA '77 Kingsley - TZE 267V100808



-----Original Message-----
From: Gmclist [mailto:gmclist...@list.gmcnet.org] On Behalf Of Bruce Hislop
Sent: Sunday, December 31, 2017 1:21 AM
To: gmc...@list.gmcnet.org
Subject: Re: [GMCnet] Ford A426C brake vacuum pump, your opinion please?

Just my farm-boy mechanic thoughts on vacuum pumps and reservoirs.

In my opinion, both are a great idea. I do have an opinion (or idea) on how they should be plumbed and why. The engine has a huge
capacity to draw down vacuum (hoping that is proper terminology), as compared to an electric pump. I currently have a JC4 pump which
is plumbed in series between the vacuum booster and the engine, in other words the engine vacuum flows through the pump. My idea is
the system should be plumbed in the following order.

Vacuum booster ->check valve --> vacuum pump ---> vacuum reservoir ->check valve ---> engine.

My reasoning is the engine's vacuum capacity will draw down the reservoir and booster almost immediately and the check valves will
keep the system at maximum vacuum (or minimum depending on your point of view). If the engine quits, and say you were going down a
hill which required multiple brake applications, the vacuum reservoir would provide a source of vacuum for a short while. Once the
reservoir vacuum went below the pump setting, then the pump would start.

Now this is point where my configuration come into play. With the pump in-line right at the booster, there is only the booster
reservoir to pump down, so the pump should be able to do that fairly quickly to regain power in the brakes. If the pump had to draw
down the reservoir as well, it would take much longer to do so and in the meantime your booster brake assist would be very poor.

Does this make sense? I haven't seen where this has been written-up in the past. Or maybe my assumptions are all wrong here.

Comments or ideas?

Thanks
--
Bruce Hislop