Home » Public Forums » GMCnet » brake question
| brake question [message #171055] |
Mon, 28 May 2012 08:04  |
chasingsummer
Messages: 434
Registered: May 2011
Location: asheboro, nc
Karma: 0
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today while checking fluid i noticed my brake fluid looked more like mud than fluid. i topped it off for recent trip and besides warning light coming on on the way home no indication brakes were bad. this means 2 things,
everyone should go look at there fluid if they have not recently, and
i think it is time for a new master cylinder.
i see bolts that mount to booster are real rusty,
if i end up with a oh crap moment how hard is brake booster to replace?
also related,
i understand there is a book available to club members which help with part numbers. i appreciate the idea that there must be a benefit to being a club member, so before i ask what is proper mc part number, i wonder who thru paypal i should buy this book from
thanks bgk
brian
asheboro, nc
75 eleganza, 74 build
119k miles and counting,
DOG HOUSE
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| Re: brake question [message #171062 is a reply to message #171055] |
Mon, 28 May 2012 09:13  |
GeorgeRud
Messages: 1380
Registered: February 2007
Location: Chicago, IL
Karma: 0
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The parts interchange manual is sent as part of The membership in GMCMI. It seems to be updated yearly so it's quite current.
If you need the correct master cylinder or brake booster (since the originals are now at least 34 years old, they should be replaced), either of the Jim's should be able to supply the correct parts. I understand that the booster is a problem as the actuation rod usually supplied from the local FLAPS is not correct for our application. If the calipers have been changed or the rear brakes have been converted to discs, some folks recommend changing to a different master cylinder as well.
When it comes to brakes, you don't want to fool around with so-so parts.
George Rudawsky
Chicago, IL
75 Palm Beach
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| Re: [GMCnet] brake question [message #171064 is a reply to message #171055] |
Mon, 28 May 2012 09:08 |
mickeysss
Messages: 1476
Registered: January 2012
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you may have put transmission fluid in the brake fluid or the wrong fluid. I had a driver that did that with one of my vehicles and
the brake lines melted sort of. ? Just an idea. thank you mickey :-)
On May 28, 2012, at 6:04 AM, brian wrote:
>
>
> today while checking fluid i noticed my brake fluid looked more like mud than fluid. i topped it off for recent trip and besides warning light coming on on the way home no indication brakes were bad. this means 2 things,
> everyone should go look at there fluid if they have not recently, and
> i think it is time for a new master cylinder.
> i see bolts that mount to booster are real rusty,
> if i end up with a oh crap moment how hard is brake booster to replace?
>
> also related,
> i understand there is a book available to club members which help with part numbers. i appreciate the idea that there must be a benefit to being a club member, so before i ask what is proper mc part number, i wonder who thru paypal i should buy this book from
> thanks bgk
> --
> brian
> asheboro, nc
> 75 eleganza 2 74 build
> 118k miles and counting,
> DOG HOUSE
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
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| Re: [GMCnet] brake question [message #171066 is a reply to message #171055] |
Mon, 28 May 2012 09:33 |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Senior Member |
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Brian,
It sounds like your brake fluid in your master cylinder (M/C) has been
contaminated by water.
When you topped it off before your recent trip did it look like fluid then?
When you topped it off were you careful to make sure the rubber seal in the
M/C cover was in place?
Were both of the cover bales snapped into place properly?
It is a well documented fact that the hoods on the GMC do a lousy job of
preventing water ingress. In fact I seem to remember seeing a modification
(possibly factory installed) to keep water off the M/C.
If I were you I would:
1) suck all the "mud" out of the M/C
2) order one of these pressure bleeders from Jim Hupy:
http://bdub.net/jhupy/
3) buy a couple quarts of the cheapest Dot 3 or Dot 4 brake fluid
4) order one can of ATE Super Blue Racing brake fluid and one can of ATE
Type 200 brake fluid from the Tire Rack (it took me about 1 liter to fill a
completely empty brake system on Double Trouble that has a P-30 M/C, disks
on the front and middle wheels, and drums on the rear)
ATE Super Blue Racing: Dry boiling point: 536°F Wet boiling point: 392°F
http://www.tirerack.com/brakes/accessoryDetail.jsp?ID=21
ATE TYP 200: Dry boiling point: 536°F Wet boiling point: 392°F
http://www.tirerack.com/brakes/accessoryDetail.jsp?ID=22
5) fill the brake bleeder with the cheap brake fluid and flush the system in
the following sequence: passenger rear wheel, passenger middle wheel,
driver rear wheel, driver middle wheel, passenger front wheel, driver front
wheel until you get nothing but nice clean brake fluid out of each bleeder
6) wait a week or so and repeat step 5) and see what you get, if it's nice
clear fluid replace the cheap fluid in Jim's bleeder with the ATE Super Blue
Racing fluid
7) flush the system again as per step 5) until you get blue fluid out of
each bleeder
8) write the date you performed these steps and in several months fill Jim's
bleeder with ATE TYP 200 fluid and perform step 5) again.
One additional point; DOT 4 is hydroscopic (absorbs moisture) so don't leave
the brake fluid in Jim's bleeder empty it back into the can and tightly seal
the cap on the can. After you've drained the bulk of the fluid out of the
bleeder it wouldn't hurt to dry it out using clean paper towels.
The book you mention is called the GMC Motorhomes International Parts
Interchange Index. AFAIK it is not for sale by itself, it's one of the
benefits of joining GMCMI.
To do that click here: http://www.gmcmi.com/app.html
Regards,
Rob M.
-----Original Message-----
From: brian
today while checking fluid i noticed my brake fluid looked more like mud
than fluid. i topped it off for recent trip and besides warning light coming
on on the way home no indication brakes were bad. this means 2 things,
everyone should go look at there fluid if they have not recently, and
i think it is time for a new master cylinder.
i see bolts that mount to booster are real rusty,
if i end up with a oh crap moment how hard is brake booster to replace?
also related,
i understand there is a book available to club members which help with part
numbers. i appreciate the idea that there must be a benefit to being a club
member, so before i ask what is proper mc part number, i wonder who thru
paypal i should buy this book from
thanks bgk
--
brian
asheboro, nc
75 eleganza 2 74 build
118k miles and counting,
DOG HOUSE
_______________________________________________
GMCnet mailing list
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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| Re: [GMCnet] brake question [message #171070 is a reply to message #171069] |
Mon, 28 May 2012 09:58 |
stick miller
Messages: 1036
Registered: March 2010
Location: Americus, Georgia
Karma: 0
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Although I don't deny that it happens, I had the same problem on "White Trash", I don't understand how water gets into a "closed" system. If the system will let in water, it seems like it would let in air.
Isn't that sort of a basic premise that makes brakes work?
Stick Miller
'78 Royale - "White Trash" - she left me for another man
'76 Eleganza - "Cousin Eddie" Sold
'84 Bluebird Wanderlodge - "Past Tents"
Americus, GA
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| Re: [GMCnet] brake question [message #171078 is a reply to message #171070] |
Mon, 28 May 2012 11:34 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Just a little thing called condensation, caused by temperature and humidity
changes. Doesn't seem to matter if the system is "open" or "closed" to the
environment. A drop here, a drop there, add in 2 or three years, and
shazaam, water in the system. Flush it every 2 years in high humidy
conditions, every three years or so as needed in very arid conditions.
Jim Hupy
Salem, OR
78 GMC Royale 403
On Mon, May 28, 2012 at 7:58 AM, Stick Miller <stickmiller@gmail.com> wrote:
>
>
> Although I don't deny that it happens, I had the same problem on "White
> Trash", I don't understand how water gets into a "closed" system. If the
> system will let in water, it seems like it would let in air.
>
> Isn't that sort of a basic premise that makes brakes work?
> --
> Stick Miller
> '78 Royale - she left me for another man
> Americus, Georgia
>
>
>
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| Re: brake question-follow up question [message #171087 is a reply to message #171055] |
Mon, 28 May 2012 13:29 |
chasingsummer
Messages: 434
Registered: May 2011
Location: asheboro, nc
Karma: 0
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Senior Member |
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my combination valve does not have the tool thing which mm mentions to push in on switch when bleeding brakes.
how important is it to push in on this switch ? is there another way to activate this switch?
thanks bgk
brian
asheboro, nc
75 eleganza, 74 build
119k miles and counting,
DOG HOUSE
|
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|
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| Re: [GMCnet] brake question-follow up question [message #171089 is a reply to message #171087] |
Mon, 28 May 2012 13:35 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Senior Member |
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When the spool valve is centered ( the brake warning light is not on) and
you are using a pressure bleeder that pressurizes both resevoirs in the MC
with the same pressure, it is not necessary to worry about the combo valve.
The pressure is equal on both sides of the valve, and it will stay
centered. If you are unable to get the warning light to go off after
bleeding the brakes, more than likely you have crud in the combo valve that
has wedged the spool valve. If that is the case, I personally would
recommend replacing the valve.
Jim Hupy
Salem, OR
78 GMC Royale 403
On Mon, May 28, 2012 at 11:29 AM, brian <chasingsummer@triad.rr.com> wrote:
>
>
> my combination valve does not have the tool thing which mm mentions to
> push in on switch when bleeding brakes.
> how important is it to push in on this switch ? is there another way to
> activate this switch?
> thanks bgk
> --
> brian
> asheboro, nc
> 75 eleganza 2 74 build
> 118k miles and counting,
> DOG HOUSE
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
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Unsubscribe or Change List Options:
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| Re: [GMCnet] brake question-follow up question [message #171107 is a reply to message #171089] |
Mon, 28 May 2012 15:58 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Senior Member |
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Brian,
You and Jim are talking about two different features of the combination
valve: You asked about disabling the metering valve portion. Jim replied
about the differential pressure switch.
It takes only a little pressure on the nipple at the front of the
combination valve to disable the 135 psi delay before engagement of the
front brakes. I usually use a small "squeeze clamp" -- the little bar
clamps with one fixed arm and one operated by squeezing a handle -- over
the length of the valve. Just a little pressure.
Ken H.
On Mon, May 28, 2012 at 2:35 PM, James Hupy wrote:
> When the spool valve is centered ( the brake warning light is not on) and
> you are using a pressure bleeder that pressurizes both resevoirs in the MC
> with the same pressure, it is not necessary to worry about the combo
> valve...
> On Mon, May 28, 2012 at 11:29 AM, brian wrote:
>
> > my combination valve does not have the tool thing which mm mentions to
> > push in on switch when bleeding brakes.
> > how important is it to push in on this switch ? is there another way to
> > activate this switch?
> >
>
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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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