| A very good day [message #64078] |
Thu, 12 November 2009 20:19  |
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Found the illusive air leak in my GMC air bag system!
<HAPPY DANCE> <HAPPY DANCE> <HAPPY DANCE>
John Ruff
Chandler, AZ
1975 Eleganza
WA3RIG
If I use ZDDP in a new car - will the tappets go flat?
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| Re: [GMCnet] A very good day [message #64122 is a reply to message #64103] |
Fri, 13 November 2009 09:01  |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Senior Member |
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| ALAN SIMS wrote on Fri, 13 November 2009 00:35 |
Hi John:
How did you do it:? We have a leak in ours and we are pretty sure it's not in the bag proper.
Alan & Janet
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Alan & Janet,
Finding air leaks can be a frustrating process, but it can be done.
I started out with a three-day squat and now rarely hear the compressor run unless I do some serious leveling.
Your notes don't contain any information as to geographic location or coach vintage, so I will go along with the Power-level system. You also don't describe how fast a leak you are looking to stop.
First do some checks. Set the the system to hold and let it sit as long as you can.
If it does not squat, but the compressor runs every time you turn on the ignition, the leak can be anywhere but the bags. Tank pressure air goes everywhere.
Does one side squat first? - Look at that sides parts first. Each bag only connects to the control valve for that side. That gives only two parts to check.
I suggest you invest in either a real bottle of leak finder (household detergents are not as good at this as they once were) or a squirt (not spray) bottle and some bubble stuff (like for kids to blow bubbles). This will be difficult to do in freezing weather, and remember that the metal temperature has to be warm enough for the bubble stuff to behave correctly.
Start with the simple and easy to access places. This will not be where the leak will be - that would be too easy - but it will give you a lot of progress to feel good about. This would be the compressor fittings, the air tank and all the stuff in the rear suspension. The check valve should keep the compressor from being the leak, but the switch that is below it can be. Air lines can leak mid-run, but this is fortunately rare.
You say that you don't think it is the bag leaking, but that is easy to check while the T-skirt is removed (if you have).
The level controlling valve has a vent (exhaust) port near the supply port. This is one the four places that air is supposed to leave the system (two on the level controls and two on the control valve - more about those later). If the valve is leaking, you can often detect this by using a detection fluid covered finder to draw a film across the port. If it blows a bubble . . .
Now you have to start take some things apart. Start with the PowerLevel panel. This is where the other vent ports are. These are drilled holes in the valve body. Use the same check as you did at the rear. Check the fittings. Then carefully check the body joint of this valve. All four of the valves in my collection leaked in this area. It only takes champagne bubbles to let the system down in a week or less.
To get more than this, you have to start disassembling the system and plugging things to isolate and pressure check individual components of the system. This will require a handful of DOT airfittings and caps (~25$) to do these pressure checks. If it gets to that come on back here and I will step you the rest of the process.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: [GMCnet] A very good day [message #64133 is a reply to message #64103] |
Fri, 13 November 2009 10:37 |
Mr ERFisher
Messages: 7117
Registered: August 2005
Karma: 2
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Senior Member |
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here are some hints on trouble shooting , both systems
http://gmcmotorhome.info/levelsch.htm#power
gene
On Thu, Nov 12, 2009 at 9:35 PM, ALAN SIMS <jasims@shaw.ca> wrote:
> Hi John:
> How did you do it:? We have a leak in ours and we are pretty sure it's not
> in the bag proper.
> Alan & Janet
>
> ----- Original Message -----
> From: John Ruff <j_r_ruff@yahoo.com>
> Date: Thursday, November 12, 2009 7:19 pm
> Subject: [GMCnet] A very good day
> To: gmclist@temp.gmcnet.org
>
> >
> >
> > Found the illusive air leak in my GMC air bag system!
> >
> > <HAPPY DANCE> <HAPPY DANCE> <HAPPY DANCE>
> > --
> > John Ruff
> > Noxen, PA
> > 1975 Eleganza
> > WA3RIG
> >
> >
> > If I use ZDDP in a new car - will the tappets go flat?
> > _______________________________________________
> > GMCnet mailing list
> > List Information and Subscription Options:
> > http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
> >
>
> Janet Sims
> 3715-117 Street NW
> Edmonton, AB T6J 1S5
> 780-437-3878 home 780-945-3878 cell
> www.simscityca.blogspot.com
>
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription 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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