Home » Public Forums » GMCnet » The Proportioning Valve - AGAIN!
| The Proportioning Valve - AGAIN! [message #79593] |
Wed, 07 April 2010 16:22  |
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JShot
Messages: 485
Registered: October 2006
Location: NW Ohio
Karma: 0
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OK, let's go over this one more time. Our valve is a solid block of brass. I don't know if it's original, but from the '78 GM' stickers I found on the rubber brake lines, it probably is. On the 'front' end of the valve body is a little rubber cap with a tab. If you pull this cap off. there is a hex headed thingy with a hole in its center. If there's a pin in the hole, it's not sticking out.
Now, the front chamber of the MC (with the larger brake line) is for the rear brakes, right? So if I disconnect this line at the MC, I can flush the line out to both sides of the rear brakes, yes?
I've rebuilt the entire rear brake system to date. I will do the front system after Bean. But now I just want to get the rears going.
So, do I have to do anything with the proportioning valve for this exercise?
Thanks for the astute answers I'm going to receive from the greatest collective GMC minds on the planet!
John Shotwell
Ridgeville Corners, OH
78 Royale Center Kitchen
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| Re: The Proportioning Valve - AGAIN! [message #79598 is a reply to message #79593] |
Wed, 07 April 2010 16:40  |
midlf
Messages: 2212
Registered: July 2007
Location: SE Wisc. (Palmyra)
Karma: 1
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Senior Member |
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| JShot wrote on Wed, 07 April 2010 16:22 |
OK, let's go over this one more time. Our valve is a solid block of brass. I don't know if it's original, but from the '78 GM' stickers I found on the rubber brake lines, it probably is.
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If your rubber brake lines are original they should be changed out ASAP or sooner.
Steve Southworth
1974 Glacier TZE064V100150 (for workin on)
1975 Transmode TZE365V100394 (parts & spares)
Palmyra WI
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| Re: [GMCnet] The Proportioning Valve - AGAIN! [message #79600 is a reply to message #79593] |
Wed, 07 April 2010 16:59 |
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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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John,
Here is a picture of the OEM Steel proportioning valve posted by Ken
Henderson:
http://www.gmcmhphotos.com/photos/showphoto.php?photo=5314
Here is a picture of the aftermarket brass proportioning valve from Jim K's
website:
http://www.appliedgmc.com/prod.itml/icOid/770
As far as the brake hoses go if they have the OEM stickers on them IMHO it
would be a good idea to change them.
When I went through the brake system on Double Trouble I installed braided
stainless steel lines:
Fronts @ $64.00 each: http://www.appliedgmc.com/prod.itml/icOid/609
Rears @ $79.00 each: http://www.appliedgmc.com/prod.itml/icOid/785
Here's rubber ones:
Fronts @ $30.90 each: http://www.appliedgmc.com/prod.itml/icOid/831
Rears @ $48.95 each: http://www.appliedgmc.com/prod.itml/icOid/786
Cost comparison:
SS = $286.00
Rubber = $159.70
SS cost $126.30 more.
I also installed a stainless steel brake line kit from Classic Tube BUT
would not recommend it. When it arrived it was missing a long section that
went down the side of the coach and the angles the tubing was bent left a
lot to be desired. I had to do a lot of "coaxing" to make it fit. If I were
to do it again I would buy a set from Tom Hampton. They are more expensive I
have been advised by people that installed them THEY FIT PERFECTLY!
Regards,
Rob Mueller
Sydney, Australia
AUS '75 Avion-The Blue Streak TZE365V100428
USA '75 Avion-Double Trouble TZE365V100426
-----Original Message-----
From: gmclist-bounces@temp.gmcnet.org
[mailto:gmclist-bounces@temp.gmcnet.org] On Behalf Of John Shotwell
Sent: Thursday, 8 April 2010 7:23 AM
To: gmclist@temp.gmcnet.org
Subject: [GMCnet] The Proportioning Valve - AGAIN!
OK, let's go over this one more time. Our valve is a solid block of brass. I
don't know if it's original, but from the '78 GM' stickers I found on the
rubber brake lines, it probably is. On the 'front' end of the valve body is
a little rubber cap with a tab. If you pull this cap off. there is a hex
headed thingy with a hole in its center. If there's a pin in the hole, it's
not sticking out.
Now, the front chamber of the MC (with the larger brake line) is for the
rear brakes, right? So if I disconnect this line at the MC, I can flush the
line out to both sides of the rear brakes, yes?
I've rebuilt the entire rear brake system to date. I will do the front
system after Bean. But now I just want to get the rears going.
So, do I have to do anything with the proportioning valve for this exercise?
Thanks for the astute answers I'm going to receive from the greatest
collective GMC minds on the planet!
--
John Shotwell
Archbold, OH
78 Royale Center Kitchen
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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] The Proportioning Valve - AGAIN! [message #79650 is a reply to message #79600] |
Wed, 07 April 2010 21:20 |
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JShot
Messages: 485
Registered: October 2006
Location: NW Ohio
Karma: 0
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Senior Member |
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Thanks Steve and Rob,
As mentioned, I have completely replaced everything in the rear system, except the hard lines feeding that system, but including the rubber lines. My quandry was did I have to do anything with the proportioning valve to allow the flushing of the lines that go to the rear. When I replaced the passenger forward wheel cylinder, a lot of brown liquid came out of the old one and I wanted to alcohol flush the hard lines to the rear before installing the new MC and new brake fluid.
From the pics of the valve on Jim's web site, some PO has replaced the valve with the newer brass one. If you look real close at the pic, you can see the rubber cap over the end 'pin'.
Thanks again,
John
John Shotwell
Ridgeville Corners, OH
78 Royale Center Kitchen
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| Re: [GMCnet] The Proportioning Valve - AGAIN! [message #79668 is a reply to message #79650] |
Wed, 07 April 2010 23:46 |
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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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John,
It is my understanding the proportioning valves stops fluid from going to
the front calipers until the pressure reaches 350 psi to the rear wheel
cylinders.
To bleed the front calipers you must depress the little "pin." Therefore to
flush the rear brake lines you don't need to depress it.
The line to the rear brakes tee's off on the drivers side over to the
passenger side. The passenger side wheel cylinders are the "furthest" from
the master cylinder. See Maintenance Manual X-7525 Page 5-14 Figure 1 -
Brake bleeding sequence.
I wonder if it wouldn't be better to flush the system with brake fluid
rather than alcohol?
If you use alcohol it will be important to get it ALL the alcohol out after
flushing and to do that you'll have to blow it out with compressed air. The
problem with that is you could introduce water into the system. If you
decide to do that it would be a good idea to drain the water out of your
compressors tank and do it on a day with low relative humidity.
If you use brake fluid you won't have to worry about that.
If I were you I would:
1) Suck all the fluid in the master cylinder out using a syringe and fill it
with cheap dot 3 fluid.
2) Pump the brake pedal and flush the brakes in the sequence noted in the
Maintenance Manual. Keep flushing until you get fresh clean brake fluid out
of each caliper or wheel cylinder.
3) Get ATE Type 200 and ATE Super Blue Racing Fluid as they are the best
I've been able to find. I will send you an article about brake fluids off
net. Below is a link to the ATE website.
http://tinyurl.com/q2xtm
http://www.ate-na.com/generator/www/us/en/ate/ate/themes/20_ate_brake_produc
ts/50_brake_fluid/bf_info_us.html
4) Fill the master cylinder with the ATE Super Blue Racing Fluid and start
pumping it through until you get blue fluid out of each caliper or wheel
cylinder.
5) Next time you change the brake fluid use the ATE Type 200 and stop
pumping when you get yellow fluid out each caliper of wheel cylinder.
Regards,
Rob Mueller
Sydney, Australia
AUS '75 Avion-The Blue Streak TZE365V100428
USA '75 Avion-Double Trouble TZE365V100426
-----Original Message-----
From: gmclist-bounces@temp.gmcnet.org
[mailto:gmclist-bounces@temp.gmcnet.org] On Behalf Of John Shotwell
Sent: Thursday, 8 April 2010 12:20 PM
To: gmclist@temp.gmcnet.org
Subject: Re: [GMCnet] The Proportioning Valve - AGAIN!
Thanks Steve and Rob,
As mentioned, I have completely replaced everything in the rear system,
except the hard lines feeding that system, but including the rubber lines.
My quandry was did I have to do anything with the proportioning valve to
allow the flushing of the lines that go to the rear. When I replaced the
passenger forward wheel cylinder, a lot of brown liquid came out of the old
one and I wanted to alcohol flush the hard lines to the rear before
installing the new MC and new brake fluid.
From the pics of the valve on Jim's web site, some PO has replaced the valve
with the newer brass one. If you look real close at the pic, you can see the
rubber cap over the end 'pin'.
Thanks again,
John
--
John Shotwell
Archbold, OH
78 Royale Center Kitchen
_______________________________________________
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
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] The Proportioning Valve - AGAIN! [message #79683 is a reply to message #79593] |
Thu, 08 April 2010 07:05 |
Steven Ferguson
Messages: 3447
Registered: May 2006
Karma: 0
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Senior Member |
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John,
When I change out the brake fluid in my system, I just open the
bleeders (starting with the rears) and let the fluid run out til the
clear,new stuff starts coming out. Same for the front. I have never
had to depress the shuttle on the comb valvle. I've done this every
three years with the GMC and never had to disconnect the lines from
the MC except for the time I changed out the MC.
On Wed, Apr 7, 2010 at 2:22 PM, John Shotwell <jshot@rtecexpress.net> wrote:
>
>
> OK, let's go over this one more time. Our valve is a solid block of brass. I don't know if it's original, but from the '78 GM' stickers I found on the rubber brake lines, it probably is. On the 'front' end of the valve body is a little rubber cap with a tab. If you pull this cap off. there is a hex headed thingy with a hole in its center. If there's a pin in the hole, it's not sticking out.
>
> Now, the front chamber of the MC (with the larger brake line) is for the rear brakes, right? So if I disconnect this line at the MC, I can flush the line out to both sides of the rear brakes, yes?
>
> I've rebuilt the entire rear brake system to date. I will do the front system after Bean. But now I just want to get the rears going.
>
> So, do I have to do anything with the proportioning valve for this exercise?
>
> Thanks for the astute answers I'm going to receive from the greatest collective GMC minds on the planet!
> --
> John Shotwell
> Archbold, OH
> 78 Royale Center Kitchen
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
--
Steve Ferguson
'76 EII
Sierra Vista, AZ
Urethane bushing source
www.bdub.net/ferguson/
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