| Auxiliary Vacum Booster [message #158696] |
Tue, 31 January 2012 09:06  |
docsdad
Messages: 32
Registered: May 2008
Karma: 0
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In reviewing my GMC brake system, I have discovered that my GMC includes an additional vacum booster unit mounted on the front line of the master cylinder going down to the equalizer valve. It gets its vacum from the normal vacum to the other booster on the master cylinder and from a reservoir built into the square frame system that was built under the front end for helping in the lifting and jacking of the front end. As I am seeing some loss of fluid from the front MC reservoir I may need some new parts for this unit. Has any one seen one of these and know where one could find parts. Picture of unit is located at: http://www.gmcmhphotos.com/photos/data/500/medium/P10100037.JPG
Jim Thompson
[Updated on: Tue, 31 January 2012 10:13] Report message to a moderator |
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| Re: [GMCnet] Auxiliary Vacum Booster [message #158715 is a reply to message #158710] |
Tue, 31 January 2012 10:37  |
emerystora
Messages: 4442
Registered: January 2004
Karma: 13
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Gene
Did you look at his picture?
http://www.gmcmhphotos.com/photos/showphoto.php?photo=42566&title=brake-auxillary-booster&cat=500
Have you seen one of these before?
Emery
On Jan 31, 2012, at 9:11 AM, gene Fisher wrote:
> everyone should have one
>
> here is the new version
> http://goo.gl/4WuYn
>
> gene
>
>
>
> On Tue, Jan 31, 2012 at 7:06 AM, James Thompson
> <tjamessherry@bellsouth.net>wrote:
>
>>
>>
>> In reviewing my GMC brake system, I have discovered that my GMC includes
>> an additional vacum booster unit mounted on the front line of the master
>> cylinder going down to the equalizer valve. It gets its vacum from the
>> normal vacum to the other booster on the master cylinder and from a
>> reservoir built into the square frame system that was built under the front
>> end for helping in the lifting and jacking of the front end. As I am
>> seeing some loss of fluid from the front MC reservoir I may need some new
>> parts for this unit. Has any one seen one of these and know where one
>> could find parts.
>> Jim Thompson
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>>
>
>
>
> --
> Gene Fisher -- 74-23,77PB/ore/ca
> “Give a man a fish; you have fed him for today --- give him a URL and
> -------
> http://gmcmotorhome.info/
> Alternator Protection Cable
> http://gmcmotorhome.info/APC.html
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Emery Stora
77 Kingsley
Santa Fe, NM
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| Re: [GMCnet] Auxiliary Vacum Booster [message #158718 is a reply to message #158715] |
Tue, 31 January 2012 10:59 |
Dave Mumert
Messages: 272
Registered: February 2004
Location: Olds, AB, Canada
Karma: 0
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Hi All
That appears to be a Hydrovac (or similar) booster. They are most commonly
seen hanging under the mid frame of medium duty trucks with hydraulic
brakes. I found one like this tucked up inside the driver's side fender of
a '74 Cadillac Eldorado.
See here
http://www.bendixvrc.com/itemDisplay.asp?documentID=3246
Is the control line teed into the front MC line? That is the line that runs
under the vacuum hose.
Do you have rear disk brakes?
Where does the output line connect?
The use of one of these was discussed some time ago to deal with the
additional brake fluid volume/pressure requirements for rear disks.
Good Luck
Dave Mumert
> >> In reviewing my GMC brake system, I have discovered that my GMC
> >> includes an additional vacum booster unit mounted on the front line
> >> of the master cylinder going down to the equalizer valve. It gets
> >> its vacum from the normal vacum to the other booster on the master
> >> cylinder and from a reservoir built into the square frame system that
> >> was built under the front end for helping in the lifting and jacking
> >> of the front end. As I am seeing some loss of fluid from the front
> >> MC reservoir I may need some new parts for this unit. Has any one
> >> seen one of these and know where one could find parts.
> >> Jim Thompson
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| Re: Auxiliary Vacum Booster [message #158720 is a reply to message #158696] |
Tue, 31 January 2012 11:14 |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
Karma: 6
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interesting my '55 ford had a remote power brake unit that looked somwhat similar. It looks like one of the brake lines is missing?
Roy Keen
Minden,NV
76 X Glenbrook
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| Re: Auxiliary Vacum Booster [message #158731 is a reply to message #158696] |
Tue, 31 January 2012 12:32 |
docsdad
Messages: 32
Registered: May 2008
Karma: 0
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This unit has only the one hydraulic brake line coming from the front fitting of the MC down to this unit and then hydraulic one line coming back out of the unit running to the equalizer valve. The vacuum line is connected to the same vacuum line that feeds the master cylinder booster. All lines are run very neatly and almost appear to have been installed by someone who did excellent work. There is a "T" in the vacuum line and it goes to a fitting in the square tube frame, which appears to be a extra tank for additional vacuum supply when engine stops. There is no other connection that I can see and I have no idea how the thing can do anything as it appears to have vacuum applied to it at all times. Have front disk and rear drum brakes. However I have had excellent braking on my GMC and always wondered why people complained about braking.
Jim T
[Updated on: Tue, 31 January 2012 12:38] Report message to a moderator |
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| Re: [GMCnet] Auxiliary Vacum Booster [message #158732 is a reply to message #158714] |
Tue, 31 January 2012 12:42 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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It is, as originally reported, a vacuum booster -- hydraulically controlled
rather than by foot as is the OEM one. They were quite common in the 50's
& 60's, especially on trucks. IIRC, the '50 Ford had them as optional
equipment. I've seen them on several GMC's over the years.
As for repair parts, probably the only chance is to find a manufacturer's
ID on it; or, more likely, disassemble it and try to match soft parts at a
cooperative parts store.
Ken H.
On Tue, Jan 31, 2012 at 11:36 AM, Emery Stora wrote:
> Here is the lilnk to the picture rather tahn to the thumbnail.
>
> http://www.gmcmhphotos.com/photos/showphoto.php?photo=42566&title=brake-auxillary-booster&cat=500
>
> I am not sure just what that is.
> Anyone else know?
>
> Emery Stora
>
> On Jan 31, 2012, at 9:04 AM, James Thompson wrote:
> >
> > Here is picture
> > I added it to GmC photos.
> >
> > http://www.gmcmhphotos.com/photos/data/500/thumbs/P10100037.JPG
> > ___________________________________________
>
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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| Re: [GMCnet] Auxiliary Vacum Booster [message #158733 is a reply to message #158718] |
Tue, 31 January 2012 12:56 |
Carl S.
Messages: 4186
Registered: January 2009
Location: Tucson, AZ.
Karma: 13
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| Dave Mumert wrote on Tue, 31 January 2012 09:59 |
Hi All
That appears to be a Hydrovac (or similar) booster. They are most commonly
seen hanging under the mid frame of medium duty trucks with hydraulic
brakes. I found one like this tucked up inside the driver's side fender of
a '74 Cadillac Eldorado.
See here
http://www.bendixvrc.com/itemDisplay.asp?documentID=3246
Is the control line teed into the front MC line? That is the line that runs
under the vacuum hose.
Do you have rear disk brakes?
Where does the output line connect?
The use of one of these was discussed some time ago to deal with the
additional brake fluid volume/pressure requirements for rear disks.
Good Luck
Dave Mumert
> >> In reviewing my GMC brake system, I have discovered that my GMC
> >> includes an additional vacum booster unit mounted on the front line
> >> of the master cylinder going down to the equalizer valve. It gets
> >> its vacum from the normal vacum to the other booster on the master
> >> cylinder and from a reservoir built into the square frame system that
> >> was built under the front end for helping in the lifting and jacking
> >> of the front end. As I am seeing some loss of fluid from the front
> >> MC reservoir I may need some new parts for this unit. Has any one
> >> seen one of these and know where one could find parts.
> >> Jim Thompson
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I believe you are right about it being a hydrovac unit. I have an '82 Ford F-600 that has a similar set-up under the floor. No booster on the firewall. I had to replace it a few years ago and had no problem getting a rebuilt unit.
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.
Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles, Solar battery charging. GMCSJ and GMCMI member
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