Home » Public Forums » GMCnet » Required air pressure for quad bag rear suspension
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Re: [GMCnet] Required air pressure for quad bag rear suspension [message #328929 is a reply to message #328927] |
Wed, 07 February 2018 13:08 |
Ken Burton
Messages: 10030 Registered: January 2004 Location: Hebron, Indiana
Karma: 10
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You guys are going through a lot of unnecessary scenarios. Do what Jim K. suggested. Air it up 2 or 3 in inches and turn off the valve. Let it set overnight and see if it goes down. If it does leak, fix the air leak somewhere at the bags. It should hold air for months. Mine has been holding air since last September WITHOUT shut off valves.
You are trying too get it to hold air for a day. All of this other stuff you are suggesting is totally unnecessary. Fix the leak somewhere between the shutoff valve and the bags or the bags themselves if necessary.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
[Updated on: Wed, 07 February 2018 15:23] Report message to a moderator
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Re: Required air pressure for quad bag rear suspension [message #329184 is a reply to message #328867] |
Thu, 15 February 2018 19:28 |
gibsongo
Messages: 116 Registered: October 2012 Location: Montreal West, Quebec, Ca...
Karma: 0
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Hello all,
Thanks for all the answers - but it turned out that we went the flatbed route rather than "the hook". I pumped the rear end up as high as possible then shut off the quad bags using the valves incorporated into the system. Luckily it was a bit warmer (-18) and the rear end was only down a but 12 hours later upon arriving at Borrmann's garage. Had it been the -25 we'd had in early January the rear would have been most if not all the way down and we might have had some difficulty getting yhe coach off the flatbed without damaging the tail pipe.
But I guess I still don't understand why (if we'd gone the hook route) 100 psi supplied to the air reservoir by a tow truck would be any different from 100 psi coming from my Viair pump....
Gordon Gibson
1976 23" Norris Upfit
Montreal West, Quebec, Canada
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Re: Required air pressure for quad bag rear suspension [message #329194 is a reply to message #329184] |
Thu, 15 February 2018 23:02 |
Ken Burton
Messages: 10030 Registered: January 2004 Location: Hebron, Indiana
Karma: 10
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Senior Member |
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I guess that I do not understand your concern with air pressure vs. temperature change. The rule has always been a 10 degree F. temperature change = 1 PSI. In your example -18c to -25c is 7c degree temp change. Or around 12F or 13F.
So even if the temperature changed you should not have seen more than 1 or 2 PSI difference in the bags. I did all of the numbers in my head so they are not accurate to .1 degree but they are close enough for academic discussion.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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Re: Required air pressure for quad bag rear suspension [message #329220 is a reply to message #328867] |
Fri, 16 February 2018 20:48 |
gibsongo
Messages: 116 Registered: October 2012 Location: Montreal West, Quebec, Ca...
Karma: 0
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No misinformation intended...and none conveyed if you take the time to read all the string carefully. New quad bag system, new Viair pump, all new tubing and fittings, new JR Slayton control valves - all installed 12 months ago by an experienced GMC mechanic. The system will hold air for weeks most of the year, but in very cold weather (-20C and colder), it just doesn't. Your experience may differ, but I am relating what happened out in the driveway 5 or 6 times in a cold by historic records late December and January when I would start the engine and get the rear end up to the proper travel level. Now of course, the air could be leaking from any number of fittings, but the "spray soapy water" diagnostic just won't work - the water would freeze long before any bubbles appeared. My bet is on the bags. The fact that the coach lost air over the 12 hours it spent on the flatbed with the shutoff valves closed at the rear suspension manifold (as recommended by several on this forum) tends to substantiate this conclusion.
Gordon Gibson
1976 23" Norris Upfit
Montreal West, Quebec, Canada
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Re: Required air pressure for quad bag rear suspension [message #329225 is a reply to message #329220] |
Sat, 17 February 2018 05:02 |
Ken Burton
Messages: 10030 Registered: January 2004 Location: Hebron, Indiana
Karma: 10
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Senior Member |
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OK Gordon. I was not picking on you. I just did not understand why all the concern over a 7 C temperature change.
You have an interesting problem there. It only leaks when cold below freezing. I have no ideas on the cause for that. I agree that if it leaked when the valves are shut off, that it is probably a bag leak but I also have never worked on a 4 bag system so I do not understand the plumbing involved.
On the soapy water idea, How about using some windshield solvent and soap mixed together? I have never tried that. Maybe that mix will not bubble.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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Re: [GMCnet] Required air pressure for quad bag rear suspension [message #329234 is a reply to message #329230] |
Sat, 17 February 2018 11:00 |
jimk
Messages: 6734 Registered: July 2006 Location: Belmont, CA
Karma: 9
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WE supply on ours and Coop units the DOT fittings that are used on the Big
rigs, so if installed carefully they will hold the air long enough.
You also need to understand that there is no such thing as a Perfict work
on anything.
On Sat, Feb 17, 2018 at 8:38 AM, Gary Mills wrote:
> On 2/17/2018 6:02 AM, Ken Burton wrote:
>
>> OK Gordon. I was not picking on you. I just did not understand why all
>> the concern over a 7 C temperature change.
>>
>> You have an interesting problem there. It only leaks when cold below
>> freezing. I have no ideas on the cause for that. I agree that if it leaked
>> when the valves are shut off, that it is probably a bag leak but I also
>> have never worked on a 4 bag system so I do not understand the plumbing
>> involved.
>>
>> On the soapy water idea, How about using some windshield solvent and soap
>> mixed together? I have never tried that. Maybe that mix will not bubble.
>>
>>
>
> My left front tire will hold air all year. Except during the very cold
> days of winter. Then it will go flat. Have never found leaks with water and
> bubbles.
>
> --
> Gary W. Mills
> Livonia, MI
> . ___________
> ./_][__][] []| 1974 GMC M/H
> .*O-------OO-* Painted Desert
>
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
Jim Kanomata
Applied/GMC, Newark,CA
jimk@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502
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Jim Kanomata
Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
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Re: Required air pressure for quad bag rear suspension [message #329242 is a reply to message #329225] |
Sat, 17 February 2018 12:51 |
NextGenGMC
Messages: 146 Registered: December 2017 Location: Washington State
Karma: -1
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Ken Burton wrote on Sat, 17 February 2018 03:02OK Gordon. I was not picking on you. I just did not understand why all the concern over a 7 C temperature change.
You have an interesting problem there. It only leaks when cold below freezing. I have no ideas on the cause for that. I agree that if it leaked when the valves are shut off, that it is probably a bag leak but I also have never worked on a 4 bag system so I do not understand the plumbing involved.
On the soapy water idea, How about using some windshield solvent and soap mixed together? I have never tried that. Maybe that mix will not bubble.
What about using RV antifreeze with dish soap mixed into it?
Vadim Jitkov
'76 Glenbrook 26'
Pullman, WA
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Re: [GMCnet] Required air pressure for quad bag rear suspension [message #329261 is a reply to message #329245] |
Sun, 18 February 2018 09:35 |
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Tangerine
Messages: 192 Registered: February 2004 Location: Livonia, MI
Karma: 0
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Senior Member |
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On 2/17/2018 3:54 PM, D C _Mac_ Macdonald wrote:
> Might be a bit of rust or dirt on the rim or even the tire! Low temps cause one or both to shrink a very small bit? Demount tire and hit both the rim and the tire bead with some fine grit sandpaper?
>
>
> D C "Mac" Macdonald
> Amateur Radio K2GKK
> Since 30 November '53
> USAF and FAA, Retired
> Member GMCMI & Classics
> Oklahoma City, OK
> "The Money Pit"
> TZE166V101966
> '76 ex-Palm Beach
> k2gkk + hotmail dot com
>
>
>
> ________________________________
> From: Gmclist on behalf of Gary Mills
> Sent: Saturday, February 17, 2018 10:38
> To: gmclist@list.gmcnet.org
> Subject: Re: [GMCnet] Required air pressure for quad bag rear suspension
>
> On 2/17/2018 6:02 AM, Ken Burton wrote:
>> OK Gordon. I was not picking on you. I just did not understand why all the concern over a 7 C temperature change.
>>
>> You have an interesting problem there. It only leaks when cold below freezing. I have no ideas on the cause for that. I agree that if it leaked
>> when the valves are shut off, that it is probably a bag leak but I also have never worked on a 4 bag system so I do not understand the plumbing
>> involved.
>>
>> On the soapy water idea, How about using some windshield solvent and soap mixed together? I have never tried that. Maybe that mix will not bubble.
>>
> My left front tire will hold air all year. Except during the very cold
> days of winter. Then it will go flat. Have never found leaks with water
> and bubbles.
>
THX Mac The last time I put a new tire on that rim. I wire wheeled and
painted the rim. Next time I will replace the valve stem. Should work
unless there is a hair line crack in the rim somewhere.
--
Gary W. Mills
Livonia, MI
. ___________
./_][__][] []| 1974 GMC M/H
.*O-------OO-* Painted Desert
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1974 GMC 260
Tangerine Dream
Livonia Michigan
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Re: [GMCnet] Required air pressure for quad bag rear suspension [message #329264 is a reply to message #329261] |
Sun, 18 February 2018 12:42 |
jimk
Messages: 6734 Registered: July 2006 Location: Belmont, CA
Karma: 9
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Senior Member |
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Make sure the rim has a R stamped on it as the old rims were not rated for
Radial tire , also the 5year rule. Sounds redicules, but based on our
customers and my experiance, it is vey valid.
On Sun, Feb 18, 2018 at 7:35 AM, Gary Mills wrote:
> On 2/17/2018 3:54 PM, D C _Mac_ Macdonald wrote:
>
>> Might be a bit of rust or dirt on the rim or even the tire! Low temps
>> cause one or both to shrink a very small bit? Demount tire and hit both
>> the rim and the tire bead with some fine grit sandpaper?
>>
>>
>> D C "Mac" Macdonald
>> Amateur Radio K2GKK
>> Since 30 November '53
>> USAF and FAA, Retired
>> Member GMCMI & Classics
>> Oklahoma City, OK
>> "The Money Pit"
>> TZE166V101966
>> '76 ex-Palm Beach
>> k2gkk + hotmail dot com
>>
>>
>>
>> ________________________________
>> From: Gmclist on behalf of Gary Mills > daveel@ix.netcom.com>
>> Sent: Saturday, February 17, 2018 10:38
>> To: gmclist@list.gmcnet.org
>> Subject: Re: [GMCnet] Required air pressure for quad bag rear suspension
>>
>> On 2/17/2018 6:02 AM, Ken Burton wrote:
>>
>>> OK Gordon. I was not picking on you. I just did not understand why all
>>> the concern over a 7 C temperature change.
>>>
>>> You have an interesting problem there. It only leaks when cold below
>>> freezing. I have no ideas on the cause for that. I agree that if it leaked
>>> when the valves are shut off, that it is probably a bag leak but I also
>>> have never worked on a 4 bag system so I do not understand the plumbing
>>> involved.
>>>
>>> On the soapy water idea, How about using some windshield solvent and
>>> soap mixed together? I have never tried that. Maybe that mix will not
>>> bubble.
>>>
>>> My left front tire will hold air all year. Except during the very cold
>> days of winter. Then it will go flat. Have never found leaks with water
>> and bubbles.
>>
>> THX Mac The last time I put a new tire on that rim. I wire wheeled and
> painted the rim. Next time I will replace the valve stem. Should work
> unless there is a hair line crack in the rim somewhere.
>
>
> --
> Gary W. Mills
> Livonia, MI
> . ___________
> ./_][__][] []| 1974 GMC M/H
> .*O-------OO-* Painted Desert
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
Jim Kanomata
Applied/GMC, Newark,CA
jimk@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
Jim Kanomata
Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
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Re: [GMCnet] Required air pressure for quad bag rear suspension [message #329265 is a reply to message #329264] |
Sun, 18 February 2018 12:56 |
James Hupy
Messages: 6806 Registered: May 2010
Karma: -62
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Senior Member |
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If you are still running 16.5" steel rims, you more than likely have a
welded spot seeping air. CURE? find the leak and grind it and weld it, or,
replace the wheel, or replace all 7 wheels with eagle or Alcoa hub centered
alloy wheels.
Jim Hupy
Salem, Or
78 GMC ROYALE 403
On Feb 18, 2018 10:43 AM, "Jim Kanomata" wrote:
> Make sure the rim has a R stamped on it as the old rims were not rated for
> Radial tire , also the 5year rule. Sounds redicules, but based on our
> customers and my experiance, it is vey valid.
>
> On Sun, Feb 18, 2018 at 7:35 AM, Gary Mills wrote:
>
>> On 2/17/2018 3:54 PM, D C _Mac_ Macdonald wrote:
>>
>>> Might be a bit of rust or dirt on the rim or even the tire! Low temps
>>> cause one or both to shrink a very small bit? Demount tire and hit both
>>> the rim and the tire bead with some fine grit sandpaper?
>>>
>>>
>>> D C "Mac" Macdonald
>>> Amateur Radio K2GKK
>>> Since 30 November '53
>>> USAF and FAA, Retired
>>> Member GMCMI & Classics
>>> Oklahoma City, OK
>>> "The Money Pit"
>>> TZE166V101966
>>> '76 ex-Palm Beach
>>> k2gkk + hotmail dot com
>>>
>>>
>>>
>>> ________________________________
>>> From: Gmclist on behalf of Gary
> Mills >> daveel@ix.netcom.com>
>>> Sent: Saturday, February 17, 2018 10:38
>>> To: gmclist@list.gmcnet.org
>>> Subject: Re: [GMCnet] Required air pressure for quad bag rear suspension
>>>
>>> On 2/17/2018 6:02 AM, Ken Burton wrote:
>>>
>>>> OK Gordon. I was not picking on you. I just did not understand why
> all
>>>> the concern over a 7 C temperature change.
>>>>
>>>> You have an interesting problem there. It only leaks when cold below
>>>> freezing. I have no ideas on the cause for that. I agree that if it
> leaked
>>>> when the valves are shut off, that it is probably a bag leak but I also
>>>> have never worked on a 4 bag system so I do not understand the plumbing
>>>> involved.
>>>>
>>>> On the soapy water idea, How about using some windshield solvent and
>>>> soap mixed together? I have never tried that. Maybe that mix will not
>>>> bubble.
>>>>
>>>> My left front tire will hold air all year. Except during the very cold
>>> days of winter. Then it will go flat. Have never found leaks with water
>>> and bubbles.
>>>
>>> THX Mac The last time I put a new tire on that rim. I wire wheeled and
>> painted the rim. Next time I will replace the valve stem. Should work
>> unless there is a hair line crack in the rim somewhere.
>>
>>
>> --
>> Gary W. Mills
>> Livonia, MI
>> . ___________
>> ./_][__][] []| 1974 GMC M/H
>> .*O-------OO-* Painted Desert
>>
>>
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>
>
>
>
> --
> Jim Kanomata
> Applied/GMC, Newark,CA
> jimk@appliedairfilters.com
> http://www.appliedgmc.com
> 1-800-752-7502
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
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Re: [GMCnet] Required air pressure for quad bag rear suspension [message #329276 is a reply to message #329265] |
Mon, 19 February 2018 05:37 |
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Tangerine
Messages: 192 Registered: February 2004 Location: Livonia, MI
Karma: 0
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Senior Member |
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THX Jim Hupy
I would like to get all 7 wheels replaced with eagle hub centered alloy
wheels. I am waiting for Jim K to have the Hot Shot wheel design
reproduced.
On 2/18/2018 1:56 PM, James Hupy wrote:
> If you are still running 16.5" steel rims, you more than likely have a
> welded spot seeping air. CURE? find the leak and grind it and weld it, or,
> replace the wheel, or replace all 7 wheels with eagle or Alcoa hub centered
> alloy wheels.
> Jim Hupy
> Salem, Or
> 78 GMC ROYALE 403
>
> On Feb 18, 2018 10:43 AM, "Jim Kanomata" wrote:
>
>
> My left front tire will hold air all year. Except during the very cold
> days of winter. Then it will go flat. Have never found leaks with water
> and bubbles.
>
> THX Mac The last time I put a new tire on that rim. I wire wheeled and
> painted the rim. Next time I will replace the valve stem. Should work
> unless there is a hair line crack in the rim somewhere.
>
>
> --
> Gary W. Mills
> Livonia, MI
> . ___________
> ./_][__][] []| 1974 GMC M/H
> .*O-------OO-* Painted Desert
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
1974 GMC 260
Tangerine Dream
Livonia Michigan
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Re: [GMCnet] Required air pressure for quad bag rear suspension [message #329344 is a reply to message #329276] |
Tue, 20 February 2018 19:31 |
Bullitthead
Messages: 1411 Registered: November 2013
Karma: 5
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Senior Member |
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The GMC right side used to fall down at 15 degrees F. This was when I winterized it and allowed it to get cold inside as well. It was 23 degrees inside when it was 15 outside. Before I put a block under the right rear, I learned valuable lesson about door not opening enough for me to get in and correct the situation Could not find leak after pumping system back up while running engine and compressor. Surmised it was the supply line to the right bag, and the control valve also leaking system air to the bag when there was enough pressure differential. Bags and system held up all the rest of the year. Found problems next temp drop(using leak check that doesn't freeze)...PLASTICS...did not warm up engine or interior, used external compressor for air in system. In addition to the internal valve leak, the plastic hose compression type connection for the right bag leaked when it got that cold. Fixed the hose with warmth followed with a little bit of disassembly and rework. Still haven't found the rebuild kit for the valves, but was informed of JR's replacements. I'm too cheap right now for new valves, and have further system mods being added on which may get incorporated into that system. There are some compression unions under the coach that didn't leak back then, but after they got blasted with exhaust leakage last summer (muffler explosion) they leaked to the point that the system only stayed up for about 15 minutes. Was able to stop leakage by tightening, but reworked 2 of the connections to be sure. Those connections are not supposed to be there, I can tell by the way the hoses ended up being routed. Muff explosion due to ignition cutoff from electrical spike must have happened to the P.O. also The temperature changes really affect the plastics...all of them...
Terry Kelpien
ASE Master Technician
73 Glacier 260
Smithfield, Va.
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