Home » Public Forums » GMCnet » Another Revcon Question- Brakes
| Another Revcon Question- Brakes [message #80909] |
Sun, 18 April 2010 13:31  |
hertfordnc
Messages: 1164
Registered: September 2009
Location: East NC
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OK, except that the master Cylinder is sideways and was probably made by Ford, the brake system is the same as a GMC
Unlike my last question, this time i went to gmcmotorhome.info and tried to figure it out first.
The brakes are really bad- like two feet on the pedal and to hands raised in prayer.
But they do not change at all with pumping.
i don't get any fluid to the rear brakes. i read how the system is supposed to work and it appears there is a catastrophic leak to the rears and the seconday is taking up the slack.
The wire to the indicator light has been cut.
Does the idiot light work by providing a ground? That would make it easy to figure ut what's going on in the maser cylinder.
I could just start cutting lines and guessing but i figure there is a process ot follow?
thanks
Dave
Dave & Ellen Silva
Hertford, NC
76 Birchaven, 1-ton and other stuff
Currently planning the Great american Road Trip Summer 2021
It's gonna take a lot of Adderall to get this thing right.
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| Re: Another Revcon Question- Brakes [message #80962 is a reply to message #80909] |
Sun, 18 April 2010 19:41  |
Keith V
Messages: 2337
Registered: March 2008
Location: Mounds View,MN
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I would bet that your isolator brake warning valve is stuck. That would turn on the brake light (as it should since there is a problem!)
And I think you are on the right track, you probably have a leak in the rear circuit that caused the problem
Keith Vasilakes
Mounds View. MN
75 ex Royale GMC
ask me about MicroLevel
Cell, 763-732-3419
My427v8@hotmail.com
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| Re: [GMCnet] Another Revcon Question- Brakes [message #80991 is a reply to message #80909] |
Sun, 18 April 2010 21:51 |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Dave,
This might help.
http://www.gmcmhphotos.com/photos/showgallery.php?cat=3510
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 dave silva
Sent: Monday, 19 April 2010 4:32 AM
To: gmclist@temp.gmcnet.org
Subject: [GMCnet] Another Revcon Question- Brakes
OK, except that the master Cylinder is sideways and was probably made by
Ford, the brake system is the same as a GMC
Unlike my last question, this time i went to gmcmotorhome.info and tried to
figure it out first.
The brakes are really bad- like two feet on the pedal and to hands raised in
prayer.
But they do not change at all with pumping.
i don't get any fluid to the rear brakes. i read how the system is supposed
to work and it appears there is a catastrophic leak to the rears and the
seconday is taking up the slack.
The wire to the indicator light has been cut.
Does the idiot light work by providing a ground? That would make it easy to
figure ut what's going on in the maser cylinder.
I could just start cutting lines and guessing but i figure there is a
process ot follow?
thanks
Dave
--
Free to good home- the rest of a 1974 GMC. good for extension, or trailer.
But you gotta' take the whole thing -zip 27944- rear wheels, glass, etc.
_______________________________________________
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GMCnet mailing list
List Information and Subscription Options:
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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] Another Revcon Question- Brakes [message #81040 is a reply to message #80991] |
Mon, 19 April 2010 08:41 |
hertfordnc
Messages: 1164
Registered: September 2009
Location: East NC
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That was very enlightening-
I have a lot more time to research answers than i do to actually work on the brakes so the more i understand the better.
Am i correct in my thinking- if it was the master cyl. I would feel it in the pedal, right? the pedal feels normal- normal resistance, does not "pump up" does not sink further with pressure.
The lines i can see look pretty good. I don't think there is a catastrophic break in the line leading aft.
There is NO fluid coming form the bleeder and very little fluid coming out when i ope the rear brake line at the proportioning valve.
Would and adjustable proportioning valve be a good idea? Or is that just for race cars?
Hanks
Dave & Ellen Silva
Hertford, NC
76 Birchaven, 1-ton and other stuff
Currently planning the Great american Road Trip Summer 2021
It's gonna take a lot of Adderall to get this thing right.
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| Re: [GMCnet] Another Revcon Question- Brakes [message #81056 is a reply to message #81040] |
Mon, 19 April 2010 11:25 |
GMCWiperMan
Messages: 1248
Registered: December 2007
Karma: 1
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Dave,
If your Revcon valve is like the GMC valve, it is NOT a proportioning valve.
It's a Combination Valve: A metering valve to delay application of the
front disc brakes until the rear drum brakes have begun to be effective + a
differential pressure switch to notify the operator if either the front or
rear brakes alone fail.
A proportioning valve is intended to prevent one set of brakes from
receiving as much maximum pressure as the other.
Ken H.
On Mon, Apr 19, 2010 at 9:41 AM, dave silva <gmc@davesilva.com> wrote:
>
>
> That was very enlightening-
>
>
> I have a lot more time to research answers than i do to actually work on
> the brakes so the more i understand the better.
>
> Am i correct in my thinking- if it was the master cyl. I would feel it in
> the pedal, right? the pedal feels normal- normal resistance, does not "pump
> up" does not sink further with pressure.
>
> The lines i can see look pretty good. I don't think there is a
> catastrophic break in the line leading aft.
>
> There is NO fluid coming form the bleeder and very little fluid coming out
> when i ope the rear brake line at the proportioning valve.
>
> Would and adjustable proportioning valve be a good idea? Or is that just
> for race cars?
>
> Hanks
>
>
>
>
>
> --
> Free to good home- the rest of a 1974 GMC. good for extension, or trailer.
> But you gotta' take the whole thing -zip 27944- rear wheels, glass, etc.
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
_______________________________________________
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| Re: [GMCnet] Another Revcon Question- Brakes [message #81075 is a reply to message #81056] |
Mon, 19 April 2010 14:04 |
hertfordnc
Messages: 1164
Registered: September 2009
Location: East NC
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| GMCWiperMan wrote on Mon, 19 April 2010 11:25 |
Dave,
If your Revcon valve is like the GMC valve, it is NOT a proportioning valve.
It's a Combination Valve
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So how might it look different? The master cyl. and the valve have the same lines, same elctrical connection and the same distribution as the GMC.
It looks slightly different with lines coming out in different places, but otherwise the same.
Thanks
Dave
Dave & Ellen Silva
Hertford, NC
76 Birchaven, 1-ton and other stuff
Currently planning the Great american Road Trip Summer 2021
It's gonna take a lot of Adderall to get this thing right.
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| Re: [GMCnet] Another Revcon Question- Brakes [message #81087 is a reply to message #81075] |
Mon, 19 April 2010 17:06 |
GMCWiperMan
Messages: 1248
Registered: December 2007
Karma: 1
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The one in the album is the only one I've ever seen inside, so I'm no expert
on them. You should be able to tell if you disassemble it and study the
functions of the parts. If it has a part number on it, you may be able to
learn about it on the internet.
Ken H.
On Mon, Apr 19, 2010 at 3:04 PM, dave silva <gmc@davesilva.com> wrote:
>
>
> GMCWiperMan wrote on Mon, 19 April 2010 11:25
> > Dave,
> >
> > If your Revcon valve is like the GMC valve, it is NOT a proportioning
> valve.
> > It's a Combination Valve
>
>
> So how might it look different? The master cyl. and the valve have the same
> lines, same elctrical connection and the same distribution as the GMC.
>
> It looks slightly different with lines coming out in different places, but
> otherwise the same.
>
> Thanks
>
> Dave
>
>
> --
> Free to good home- the rest of a 1974 GMC. good for extension, or trailer.
> But you gotta' take the whole thing -zip 27944- rear wheels, glass, etc.
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
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| Re: [GMCnet] Another Revcon Question- Brakes [message #81090 is a reply to message #81075] |
Mon, 19 April 2010 17:24 |
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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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Dave,
Not to be cheeky but this question doesn't make any sense!
How would anyone that doesn't have a Revcon or seen a combination valve out
of a Revcon be able to tell you how it looked different?
Here's the link to the first picture in Ken's album on the combination
valve; it shows where all the lines go.
http://www.gmcmhphotos.com/photos/showphoto.php?photo=5314
Here's a link to the brass one that Jim K sells:
http://www.appliedgmc.com/prod.itml/icOid/770
I reckon if you follow the steps below you'll be able to isolate your
problem.
1) Get wife in driver seat.
2) Crack front fitting on master cylinder.
3) Instruct wife to press on brake pedal lightly.
4) If fluid oozes out front piston is working properly.
5) If no fluid oozes out master cylinder is suspect.
6) Tighten fitting.
7) Crack rear fitting on master cylinder.
8) Instruct wife to press on brake pedal lightly.
9) If fluid oozes out rear piston is working properly.
10) If no fluid oozes out master cylinder is suspect.
11) Tighten fitting.
12) Crack fitting that goes to rear brakes on combination valve.
13) Instruct wife to press on brake pedal lightly.
14) If fluid oozes out combination valve is working properly.
15) If no fluid oozes out the combination valve is suspect.
16) Tighten fitting.
17) Crack fitting at junction of hard line and rubber line in drivers side
brake lines.
18) Instruct wife to press on brake pedal lightly.
19) If fluid oozes out hard line from combination valve is clear.
20) If no fluid oozes out hard line from combination valve is suspect.
21) Tighten fitting.
22) Crack bleed fitting in driver side middle wheel cylinder.
23) Instruct wife to press on brake pedal lightly.
24) If fluid oozes out rubber line and wheel cylinder are OK.
25) If no fluid oozes out rubber line and wheel cylinder are suspect.
26) Tighten bleed fitting.
27) Repeat steps 22-26 for rear wheel on driver side.
28) Repeat steps 17-21 on passenger side.
29) Repeat steps 22-26 for both wheels on passenger side.
Let us know what you find.
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 dave silva
Sent: Tuesday, 20 April 2010 5:05 AM
To: gmclist@temp.gmcnet.org
Subject: Re: [GMCnet] Another Revcon Question- Brakes
So how might it look different? The master cyl. and the valve have the same
lines, same elctrical connection and the same distribution as the GMC.
It looks slightly different with lines coming out in different places, but
otherwise the same.
Thanks
Dave
_______________________________________________
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] Another Revcon Question- Brakes [message #81100 is a reply to message #81090] |
Mon, 19 April 2010 18:43 |
hertfordnc
Messages: 1164
Registered: September 2009
Location: East NC
Karma: 0
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Senior Member |
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| Robert Mueller wrote on Mon, 19 April 2010 17:24 |
Dave,
Not to be cheeky but this question doesn't make any sense!
|
So that's Australian for 'dave, you're an idiot' ? 
OK, let me start over; when i began this question i didn't know there was a difference between a proportion valve and a combination valve.
I've also learned that the Revcon valve is identical to the GMC.
Now I'll go back and try Robs 29 steps and come back with a more intelligent question.
Forgive me for wasting your time.
Dave
Dave & Ellen Silva
Hertford, NC
76 Birchaven, 1-ton and other stuff
Currently planning the Great american Road Trip Summer 2021
It's gonna take a lot of Adderall to get this thing right.
[Updated on: Mon, 19 April 2010 18:44] Report message to a moderator |
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| Re: [GMCnet] Another Revcon Question- Brakes [message #81106 is a reply to message #81100] |
Mon, 19 April 2010 19:03 |
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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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Dave,
Nah, if an Aussie that doesn't know or like you thinks you're an idiot he'd
say "you're a bloody f'n idiot!"
If he knows you but is undecided as to your status he'd say "you're a bloody
idiot!"
If he's a friend he'd say "you're a bloody idiot, Mate!"
I would have used the third term if it thought that! ;-)
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 dave silva
Sent: Tuesday, 20 April 2010 9:44 AM
To: gmclist@temp.gmcnet.org
Subject: Re: [GMCnet] Another Revcon Question- Brakes
So that's Australian for 'dave, you're an idiot' :)
OK, let me start over; when i began this question i didn't know there was a
difference between a proportion valve and a combination valve.
I've also learned that the Revcon valve is identical to the GMC.
Now I'll go back and try Robs 29 steps and come back with a more intelligent
question.
Forgive me for wasting your time.
Dave
--
Free to good home- the rest of a 1974 GMC. good for extension, or trailer.
But you gotta' take the whole thing -zip 27944- rear wheels, glass, etc.
_______________________________________________
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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