From: Bill Rush <>

Subject: Rotary Valves

My 73 Canyonlands leaks down in the hold position over a week or so. The problem is in the rotary valve. I have replaced the o-rings in the valve but put them in dry. I remember an article many moons ago about rebuilding the valve and using a Dow Corning product on the o-rings.

I have called Dow and they don't know what I'm talking about. Surely someone has gone this route. The leak is irritating but not worth $100 plus per valve.





Date: Sat, 8 Nov 1997 22:07:05 -0500 (EST)


Subject: Re: GMC: [Fwd: H*lp with air cleaner]


Been there doing that. Your body mounts have seen better days. There are 4, one on each corner of the coach. They are big rubber mounts that isolate the coach from the frame (only motorhome that does that) there are also pads that run along the frame. If yours is a 73 it will be one long strip. Later models had separate pads. If you have any airline problems it could be the same problem. They get pinched when the old girl begins to sag. Put in new pads and mounts. It will be a uplifting experience.

Take Care



Second, the airbag on one side appears to be leaking. That side loses its pressure and the vehicle sits on an incline as a result. It seems to inflate sufficiently for driving and maintains its compression during travel, but loses it when parked. I worry that it does not raise enough on that side and may be wearing the tires when driving. I haven't noticed anything like this yet, but I'm a bit paranoid! Any suggestions about how to test and/or troubleshoot this problem?



Can't deal with all of your problems. I can talk about air system. I too am new to this game. Just bought a 76 Glennbrook. Don't bet on the airbag leaking. So far I have found that the leaks are everywhere else. Since yours is a 74 I will bet the leak is in the rotary valves on the dash. I chased mine for a long time before I found it was the valve. Also check plastic fittings on airlines had 2 that were leaking. I hope you get better info from the pros in here because I too have just arrived. If you don't just holler I will tell you what I know.

Take Care




Good chance it is not the airbag, probably the pump or lines. I have always

had minor problems with the airbags, even on my new coach in 1978! The colder

the weather, the worse the problem. My solution (there are probably others) I put a "shut off valve" ($50 in parts) just in front of the bag with a pressure guage. I also bought a system ($100) that raises the bag and reduces pressure by 25%. Less wear and tear. Now I inflate the bags to 60lbs (90-100lbs w/o lift kit) and shut off the bag. Set center switch to "HOLD" and the others to "CENTER". They

Never loose a pound and there is much less work on the compressors.



Put a liguid leak detector on the outside of all fittings.

The best leak liquid I have found, is called SNOOP it's available from Air Conditioning supply houses, its stays around longer than soap & water and shows smaller leaks than soap. Use the liquid on ALL fittings on ALL coach lines. the liquid will bubble with the slightest air leak. Go over the fittings several times. One fitting you should not overlook is the T-fitting on the main frame, beneath the drivers side near the brake diff. valve, it tends to leak more often because of engine heat. Since yours is a 74, it should have the manual rotary level switches under the dash, these can be rebuilt, clean them and replace the internal O-rings, there are kits available. Then ADD a 5 micron airline filter to the OUT-line of the air tank, this will keep any dirt particles from the inside of the tank from damaging any seals and valves. When we purchased our 73, it leaked down overnight, since reworking, it stays up for months. Most fittings that leak only need a slight tighting, don't crank down on them, it is possible to collapse the tubing by over-tightening. When you park your rig, put the rotary valves in the OFF position, do not leave them in TRAVEL position, when parked.


The suspension is air controlled only - no hydraulics. Most of the components are reliable and fairly inexpensive (although that's very relative). However, if you don't do the work yourself, labor to isolate leaks and replace parts can get expensive.

The air springs themselves last a very long time and don't need to be replaced until you can see exposed fabric (the rubber skin will develop cracks by virtue of all the flexing) although there is a failure mode called "hotdogging". Consensus seems to be that this type of failure is best prevented by storing the coach in the "squat" position.


There is lots of valuable information in the GMC International newsletter, GMC Motorhome News and GMC Motorhome Marketplace to help you maintain your air suspension. This is probably the best researched area in GMC maintenance.


Hi GMCers:

I'm in the process of doing some more things to the "new toy" and I need some info about the rear air suspension system. In particular, I'm going to solve the slow air leak problem and would like to put "Prestolock" air fittings on all places where connections are made. Hope that will solve the problem!

I found a source for the fittings here in NJ and wondered if anyone could provide a list of the number and type of fittings used in a typical setup before I dig around finding and counting all the air fittings? Looking at the air tank, it appears that those fittings are 1/4" male on one end and the 1/4" O.D. plastic tubing on the other. Is that correct? I've already gotten the shut-off valves for the air bags and will install them at the same time as I fix the leaks.

Any suggestions or hints will be appreciated.

Happy motoring. Ralph Edelbach


>Sunday, you mentioned that "The smaller pins affected '73 and some '74 models, but most of them have been upgraded and there is still an active recall on those that haven't."

> Can you shed more light on this, specifically what pins are we talking about? How do I tell if mine are okay? I have a 1973 Canyon Lands 230 model. Are you aware of what weak points Bob Brewer is talking about in the early suspension? Are we only talking about the air supply system here or something more serious like ball joints, etc.?

The recall was mentioned in Cinnabar's newsletter of March '97. Call Cinnabar's GMC Motorhome Assistance at 415/948-8664 and mention GMC dealer Product Campaign 74-C-07. The recall affects all models manufactured prior to May 1st, 1974. The parts to be replaced include everything from the control arm out on the four rear axle assemblies.

You can inspect to see if your coach qualifies by measuring the diameter of the axle spindle where it goes thru the backing plate. If the axle spindle or the hole where the spindle goes thru the backing plate is 1.886 (1 7/8) inches +/- then the coach has not been services. If this dimension is 2.256 in (2 1/4) +/_ then your coach has been serviced. The newsletter recommends all four axles be inspected.


Just another word about finding leaks in the air system. When I couldn't find a local source for SNOOP, I found a product in the Sears hardware department called LDR Gas Leak Detector that's made to help find leaks in gas plumbing connections. Seems to be very sensitive- maybe better than the kids bubble making fluid, which is quite thick and much easier to use than soap and water. It comes in a small spray bottle for about $3. Even a small leak shows up in a short time as a ball of fine bubbles.


Date: Mon, 12 Jan 1998 18:55:19 EST

From: Sergeetc <>

Subject: GMC: About the air bags

I recently purchased a 1975 GMC motorhome and completely gutted it out. I

made it into a mobile video production studio. I love this vehicle but I have a leak in my air bag system. I installed some on/off valves to keep my bags inflated when I stop somewhere for more than two hours. I wonder, has anyone ever replaced those bags with springs? How, with what effect and at what cost? Any other suggestions as to improving my situation? I look forward to any constructive inputs on the subject, Thanks, Serge

MVP Studios, Redding, CA


Date: Mon, 12 Jan 1998 20:28:45 EST

From: (david l greenberg)

Subject: Re: GMC: About the air bags

Serge, I haven't heard of anyone replacing their air bags with springs and don't know if it is even feasible. I do know I would never try it. One of our club members has given up on his leakage and compressor problems and has simply installed shut off valves as you are considering. He carries a small air tank to top off the leveling system when needed. If you obviously aren't camping in less than level places this approach may very well work for you. The leaks can be fixed if you are willing to spend from a little to a lot depending on the cause. I have a 1977 with 563k miles on the chassis and have almost no air loss during period of several weeks.


Date: Mon, 12 Jan 1998 21:17:56 -0500

From: (Clark Searle)

Subject: Re: GMC: About the air bags

If the bags hold pressure by shutting off the valves you installed, you know your bags are OK. That tells you there's a leak or leaks in the connections of the supply lines, back at the compressor and valves, or if you have the

pre-Electro Level system, apparently the air valves on the dash are a frequent trouble source. The leaks can be hard to find, but usually can be fixed pretty easily. Get some "Snoop" from a parts store or "Gas Line Leak Detector" from Sears and spray it on all the connections (I've used only the Sears product). In a short time there'll be a bulging bunch of bubbles where ever there's a leak. Then either tighten the fitting, replace o-rings or whatever is necessary to fix it and you should be very happy with your air suspension system.

Clark Searle


Date: Thu, 22 Jan 1998 12:45:59 -0500

From: Patrick Flowers <>

Subject: Re: GMC: Air bags vs. springs

Sergeetc wrote:

I have a 1975 GMC that I completely gutted out and converted into a Video Production Studio. My air bag system has a slow leak so I installed shut off valves at the bags. I am very concerned about the risk of an air bag failing while traveling and wonder if anyone has ever added and/or replaced the bags with springs and to what effects? I am looking for added safety and peace of mind.

As long as the air spring is not showing any fabric, it should be safe to use. Since the cutoff valves stop the leak down, your problem is most likely either leaking lines or control valves. The lines are fairly inexpensive to replace and the valves are a little pricey. Also, if you haven't already done so, you need the Cinnabar air tank check valve and filter upgrade.

I don't think I would want to replace the bags with springs. The ride would definitely be worse and you would lose the ability to control ride height (very useful for speed bumps, bad driveways, etc.) and compensate for uneven loading.


Date: Thu, 26 Feb 1998 08:21:05 -0500

From: Patrick Flowers <>

Subject: GMC: Sources for air bags -Reply

Alena MacDonald wrote:


> I was wondering if anyone has a list of suppliers for the air bags.

> We own a 1976 Eleganza and need to replace both air bags. We would

> like a Canadian supplier if possible. Thanx for all the great

> information we've just started getting.

Several suppliers stateside(Cinnabar, Sirium, Gateway, etal) stock them,

but I don't know of any north of the border.


- --

Patrick Flowers


Date: Thu, 26 Feb 1998 08:38:53 -0811

From: Scott Woodworth <>

Subject: Re: GMC: Sources for air bags -Reply


You might try this dealership. They are Canadian and would probably

be able to help you.

- -Scott Woodworth



Date: Fri, 13 Mar 1998 16:28:54 -0500

From: Thom Hole <>

Subject: GMC: Ride height specs

Hello, I have '78 Transmode that's been converted to RV Use. While jacking up the Left rear of the vehicle (to replace a broken Shock Absorber) the linkage that operates the Ride height valve Pulled the valve off of the vehicle. I have reattached it but now I do not believe I have it set correctly. After AUTO leveling finishes, The left side is higher! What is the proper height? It also tore off the air line to the air bag. I have fabricated a makeshift connection but will see about getting the proper fitting from somewhere on Monday. Any Advice would be appreciated as I have owned this vehicle for 8 days!!! Thx............TH in North Carolina


Date: Sat, 14 Mar 1998 18:00:58 EST

From: CHill113 <>

Subject: Re: GMC: Ride height specs


I had a similar experience while replacing a shock. I used a fiberglass kit to repair the inside of the wheel well and reattached the device. I have manuals that show pictures and instructions for setting the proper level. Unfortunately I don't have a scanner but if you want to give me your snail mail address, I'll be glad to Xerox the pictures and instructions and send to you. It really isn't very complicated.

My wife and I are going out to dinner in a few minutes. When we get back I'll check the instructions and if I think they are sufficient without the pictures, I'll type them up and send by e-mail. If you don't hear from me over the weekend, you will know that I think they need to be mailed.

Justin Hill


Date: Fri, 24 Apr 1998 00:46:11 -0400 (EDT)

From: "Thomas G. Warner" <>

Subject: GMC: Air suspension system and other nightmares

As I previously posted bought a 1976 palmbeach In March 1998 and have been

working on it every since to make it roadworthy. I would be generous in

calling it a white elephant. Although it looks beautiful, mechanically it

was a nightmare!!! Would not stop in a 40 acre lot, wallowed like a ship,

40 MPH top speed, and never shifted out of 2nd gear.

I am a retired engineer and have over 40 years experience with cars as my main hobby(many Olds Toronados). The coach did not have much maintenance by previous owners. Engine for the most part is done (now sounds and feels like an olds 455)and I have been troubleshooting the air suspension system (it leaked like a sieve and the compressor never shut off). Replaced the connectors and some of the air lines (all available at my local truck dealer), check valve(excellent solid brass one from Gateway)and made several additions to make it work better. System now shows no pressure change overnight and seems to work fine. If anyone is interested in knowing how to troubleshoot the compressor and wet tank system to quickly find the problems let me know and I would be glad to help.


I hope you also changed out the oil cooler lines before going on a road trip.

As to the conversion to an Electro Level. Contact Ray Rhodes, 9837 Chiswell

Rd, Dallas, TX Phone 214 348-0616. The area code may not be valid since Dallas has recently gone to several new ones. Ray has put together and installed several Electro Level systems. He is considered the "guru" on air suspension systems in the GMC Classics


Date: Sun, 03 May 1998 14:45:23 -0400

From: Marcus McGee <>

Subject: GMC: Air Bags - Finally graduated from crash course - I hope

This list is a savior for me. I get to tell some one of my accomplishments on my beast (affectionately called "The Twinkie"). My wife listens, but in no way understands or comprehends my triumphs over the peverse gods of GMC. And they say men don't know how to really communicate.

Ok, here goes. For the last 3 weekends the project has been to leak proof air system and repair auto level. Got all leaks taken care of and thought that was the end of it. It would go up and down very slowly manually and hold where I put it, but the auto level system would not work. Tore down all solenoids and cleaned entire system of rust, debris and corrosion. Solenoids worked perfect after cleaning and I learned alot. Put everything back together, up, down ok but slow.

Checked switches and power. AOK. Then started at each solenoid to make sure each had power. Both sides operated exactly the same. There in lies the rub. After tracing each wire in the harness two wires were bad and they operated the same solenoid on each side so not having a wiring diagram I was fooled because both sides worked alike. Ripped out side panel on drivers side to check connector, all good to there. Had to remove top of drivers side wheel well cover to get to cable at that point. Turns out someone had previously cut the cable and patched in a replacement using crimp on butt connectors and then taped up the splice. Two wires were broken at the crimp on connectors. Both operated the last solenoid in the series of 3.

Tore apart all old crimp splices, soldered and heat shrunk all connections and retaped. It went up like toast out of a toaster, and down like my bank account when I work on this thing. Success. Now attacked the height control valve assembly. Full of rust, corrosion and crap. The rod that moves the acuator lever was frozen on each. WD 40 and some gentle persuasion fixed this and they are now back on the coach. I raised it all the way and put in auto. Low and behold it went down to level. I lowered to the ground and put it in auto - IT WENT UP.

Now all I have to do is put the entire inside back together. Some fun!!!

Well, I'll get up off the couch now and pay all you pyschiatrists for listening to my problems.


Date: Tue, 30 Jun 1998 22:51:59 -0700

From: Jim Bounds <>

Subject: Re: GMC: Rotary Valves


A loss of even 5 psi makes a big difference in our air suspension. The original valves seem to be weak in design in that the seal is dependant on the spring pressure on each piston. A small movement of the piston will affect the seal and thus leak. Being soft aluminum, moisture from the compressor even with a water separator will damage the cylinder wall in time. Thus, I do not like the design of that valve.

I have found a new style rotory valve assy. (spec. sheet available if necessary) that uses a much better route and seal design which I feel is much more reliable. Every coach I have installed this system on has lost its sorry leak down characteristics!

I am currently working on an install sheet and kit package and will have the kit for general sale soon. If you would like, I would be happy to send you a set and you could be a part of the field testing.

The kit pricing is not finalised yet, but I feel it will run $175-195 for the complete kit with valves for both sides.

Because of its simplicity, I would prefer a power level system if the dash valves were better and these are!

Jim Bounds


Thomas G. Warner wrote:

I thought cinnabar had already solved that problem. I talked with Wes Caughlan some weeks ago when I was working on my system and he told me that

they had a rebuild kit for the valves that resolved the leaking problem.


Jim, what does your system consist of and how much does it cost?


> At 01:23 AM 6/30/98 -0700, you wrote:

> >Bill,

> >Small leaks in the power level rotory valves has always been the weak link of the system. Actually, I think I would prefer the power level system over eather electro level systems in that it is much simpler and easier to trace problems if the dash valves would not leak. I have been working with a vendor from the cape and have come up with dash valves that do not leak. I have several on the road now the reports are good. I don't know many people with power level systems that say they are happy with the dash valve performance and all have had work onn their system more than once

If you are interested in going to an upgraded valve assy., give me a call. (1-877-275-4462)

> >Jim Bounds

> >Bill Rush wrote:

> >>

> >> My 73 Canyonlands leaks down in the hold position over a week or so. The problem is in the rotary valve. I have replaced the o-rings in the valve but put them in dry. I remember an article many moons ago about rebuilding the valve and using a Dow Corning product on the o-rings. I have called Dow and they don't know what I'm talking about. Surely someone has gone this route. The leak is irritating but not worth $100 plus per valves. Bill


From: "Mark Grady" <>

Subject: GMC: Air line check valves (reply)

I have a valve, water separator and cooling coil per the Cinnabar instructions. As we often have 4-6 people moving about in the coach ('77 Kinsley - ElectroLevel I), make frequent stops along the way which requires

re-leveling, the compressor runs frequently.

I am surprised at the amount of water in the separator bowl. I don't know if you put your leveling system under as much of a test as we do, but this setup does a great job for us, and is very trouble free.

Getting the water out of the air from the compressor made my (internal) valve leaks a thing of the past due to crud under the valve seats.

I'd recommend the upgrade.


Date: Mon, 13 Jul 1998 13:18:54 -0400

From: "Samuel Pickens" <>

Subject: Re: GMC: Air line check valves (reply)

And of course SS ball valves at the air bags maintains level.

- ----------

> From: Bartz, Paul <>

> To: ''

> Subject: RE: GMC: Air line check valves (reply)

> Date: Monday, July 13, 1998 11:24 AM

> Mark: Why do you find it necessary to re-level your coach so frequently??? I have the Electro-level II and keep the switches in the hold position other than when leveling. We routinely travel with seven people in the coach and never find it necessary to level, other than to check the level every month or so.

> Paul Bartz


Date: Mon, 13 Jul 1998 13:23:40 -0400

From: "Bartz, Paul" <>

Subject: RE: GMC: Air line check valves (reply)


You're right on that.

I should have mentioned them, as I have them, primarily because the tubing running to the dual needle air gauge on my McNeal instrument panel leaks somewhere. I haven't yet taken the time to trace down the leak(s).


Date: Tue, 14 Jul 1998 07:33:35 -0500

From: "Mark Grady" <>

Subject: RE: GMC: Air line check valves (reply)

Sam, Paul --

No valves at the air bags, and all tubing and electric valves have been replaced, and to the best of my knowledge, leak free. Perhaps that's one difference.


> -----Original Message-----

> []On Behalf Of Bartz, Paul

> Sent: Monday, July 13, 1998 12:24 PM

> Subject: RE: GMC: Air line check valves (reply)

> Sam:

> You're right on that.

> I should have mentioned them, as I have them, primarily because the

> tubing running to the dual needle air gauge on my McNeal instrument

> panel leaks somewhere. I haven't yet taken the time to trace down the

> leak(s).


Date: Fri, 17 Jul 1998 22:53:59 -0400 (EDT)

From: "Thomas G. Warner" <>

Subject: Re: GMC: Compressor Pressure and Microwave

I am sure that all of you know that the new rebuild kit for the Dana compressor contains a new valve and stainless steel spring to replace the flapper valve. At the last rally Ed Daniels had modified one of the old heads to do the same thing. I found the correct valve and springs at Home Depot for less than $1.00. With this modification it will pump up the small tank from a cold start in about 32 seconds. Anybody think that this would be a good project for the tech page?


Date: Fri, 07 Aug 1998 13:24:43 -0400

From: Patrick Flowers <>

Subject: Re: GMC: Help and advice to new owners

jtkthatcher wrote:


> We would greatly appreciate any advice/information on the following.

> 3. We have our new coach in a secure covered storage location. We do not plan to use it for the next 2 months. Is there anything special that we should or should not do? Specifically, how should the rear air bag suspension be set?

Some people recommend "squatting" the rear end when parked to increase the life of the air bags. I'm not sure it makes that much of a difference. Two months is not a very long storage period. You might want to set some rat bait stations around the wheels to prevent furry neighbors from moving in.


Date: Tue, 25 Aug 1998 00:43:46 -0400

From: Ritch Hwang <>

Subject: GMC: gmc:withdrawl symptoms

>Date: Mon, 24 Aug 1998 18:59:05 EDT

>From: <>

>Subject: GMC: gmc:withdrawl symptoms


>It's starting, itchy rash around my neck, watery eyes, sore joints, hair


Larry: Me too!!

Just when I thought the coach was roadworthy...

Keeping in mind that the previous owner's meager log indicate less than 4000 miles useage in the last 5 years & I bought it mid June......

Went camping with a few friends as a "shakedown run" and used the leveling feature to level the coach. Maybe 3" differential overall. This is the first time I'd used it for that purpose, and the compressor worked it's little pistons off. I let it run for about 5 minutes at a time. Came home Saturday very late.

Awoke Sunday to find the coach with right rear almost collapsed. I have the Electro Level 1, and have always just put it on Hold when parked with no noticeable leakdown over weeks at a time. While I did promised Betty I would not work on anything Sunday, I re=leveled it & blocked up the right rear. Cleaned the genset ground & reinstalled using stainless hardware while I was outside anyway (at least it was shady under the coach), and voila, the genset now starts remotely again. Then Betty came home from shopping.

Today I brought it up to level, put it in Hold, checked the rear ride height, was 11 5/8" on both sides. Checked for physical damage, soap tested all the outside connections I could see, including the ride height controller, & also soap checked the air bag using a mirror. Went back in for lunch, came back out and rate of leakage seemed to be getting worse.

Soap tested connections at the compressor. Installed a shrader at the tank, leveled 'er up again. Periodic checks with a tire gauge revealed the air tank was also leaking down. The air tank leak shouldn't affect just one side. Could it be a leaky or clogged 2 way or 3 way solenoid due a some debris being blown in because of sustained compressor useage and the lack of a good filter? If so, I am leaning towards the 2 way as it is the last one in the chain.

Comments solicited.

As always, best regards.

~ Ritch & Betty Hwang ~


Date: Fri, 4 Sep 1998 09:44:50 -0400

From: "Les & Des" <>

Subject: GMC: Air Bag System

Hi Guys,

For the first time in three years, we have our air bag suspension system working. Really it is the first time we have been on the Dana Compressor. For several years, we have been filling the air tank when we travel from an external compressor. Now we have something else we need help with.

Our compressor is working well. It takes about two minutes to fill the tank. The tank fills to about 112 lbs and holds at 110 lbs. It seems to have no air leaks at that pressure. Neither does our air bags themselves (while on hold). But.....Even with the Power Levels on hold (or not) the Compressor cycles on once every minute. What do we check next?


Les & Des

Living Praise Ministries

Visit us at:


Date: Fri, 4 Sep 1998 11:01:55 -0400 (EDT)

From: "Thomas G. Warner" <>

Subject: Re: GMC: Air Bag System

First the compressor should be set to go on at 100 PSI and off at 120PSI.

Assuming that the tank is not losing air and the compressor is turning on above 100 PSI, than the limit switch is either misadjusted or bad. I would adjust the pressure switch on the tank to the above limits first and see if it than works OK. If not, replace the pressure switch. It is the only thing that controls the compressor.



Date: Fri, 4 Sep 1998 11:03:37 -0400

From: "Balcom, Robin S" <>

Subject: GMC: PowerLevel Valves, Exhaust Manifold, Rear Suspension

Hi there - some questions...

1. Inside the Power Level valves are some o-rings - are they regular o-rings, with a round cross-section, or are they some kind of special, with something other than a round cross-section? I found some regular o-rings, size 007 & made of viton, which I'm going to try, but I wanted to know if they're correct.

2. To those who are resurfacing both the head and the exhaust manifolds to

fix the exhaust leaks - what are you doing about the oil dipstick tube on the left side? It's quite a close fit already.

3. Has anyone ever seen anything other than air bags fitted to the rear suspension? Perhaps coil springs, rubber springs, or ??? I built a utility trailer a few years ago with swing axles like the GMC, but with a leaf spring, rather than air bags. I initially thought about using some kind of air suspension so I could lower the back of the trailer down (by letting the air out of the air bags) for loading motorcycles, but I went with the leaf springs to keep things simple. So it got me thinking about designing something different for the rear of the GMC - simpler, with the sacrifice of adjustabiltiy.

Inputs, anyone?


Date: Fri, 4 Sep 1998 14:06:39 -0400 (EDT)

From: "Thomas G. Warner" <>

Subject: Re: GMC: PowerLevel Valves, Exhaust Manifold, Rear Suspension

Since the power level control uses standard o-rings, does anyone have the dimensions and o-ring size? O-rings are readily available at Home depot and it would be nice to try the repair.


Date: Fri, 4 Sep 1998 14:55:38 -0400

From: "Balcom, Robin S" <>

Subject: GMC: O-rings


The o-rings I got are size 007, and the dimensions are 1/16" wide x 5/32" i.d. x 9/32" o.d. The ones I used are made of Viton: I see other materials are available (Buna-N, polyurethane, silicone, etc.), but I have no idea if one material is better than the other. They're pretty cheap, too if you get them from the right place - McMaster-Carr Supply Company of New Brunswick, NJ sells a package of 100 for $8.34.



Date: Sat, 5 Sep 1998 19:14:36 -0400

From: "Les & Des" <>

Subject: Re: GMC: Air Bag System


Thanks so much for your help. We adjusted the pressure switch, but really to no avail. We did get the pressure to raise to 120lbs, but could not get it quit cutting-on ever minute or two. We are going on a trip Tuesday, so we installed a manual switch inside so we can fill the tank, but then we are able to cut the compressor off.

After three years of using an external compressor, we feel we are

really "up-town" with an indoor switch. When we get back in October, we will start looking at replacing the pressure switch. In fact, with the work we have done on the air system, we discovered an Construction Equipment Store, so we will now know what to buy and where to buy it. Thanks for the lead.

Les and Des

> Les: Check your pressure switch. It may be out of adjustment or defective. I couldn't adjust mine to the correct pressure and finally replaced it. The switch I purchased from a vendor had the unloading mechanism and external "Off & Auto" manual lever. (The unloading mechanism is not used.It is designed to unload the compressor's pressure side when the compressor shuts off so the motor would not labor when it starts

> Any store or company that sells construction equipment should have one.


> Switch nomenclature is:

> "Square D"

> ` Pumptrol Pressure Switch

> Class 9013 Type FHG12


> I think I paid $28.00 for it.


> Now I can turn the compressor off at the unit in lieu of the switch panel that is when needed.


> This switch doesn't fit in the same location. Slightly larger, so I > purchased the fittings and air line from a truck/car parts store. The > fitting and air line are used on 18 wheelers and GMC's. The switch then is mounted on the top left side of the compressor compartment. Makes it easy to work on the unit without the switch in the way.


> My $.02 worth

> Bob 77PB

Les & Des

Living Praise Ministries



Date: Sat, 5 Sep 1998 23:37:49 -0400 (EDT)

From: "Thomas G. Warner" <>

Subject: Re: GMC: Air Bag System

If my memory serves me correctly there is a pressure differential setting on the control also, a small set screw on the left of the control after you remove the cover. I do not have my books here I keep them in the coach. Try adjusting it for greater pressure differential. The control can be bought new from W.W. Grainger., square D model 9013, grainger part # 5B419 for $13.65.

To check the tank for leaks make a liquid soap and water solution and spray it on all of the connections on the air tank and see if any of them are leaking. Be sure and spray the tank also as it may have started to rust through.

At 07:14 PM 9/5/98 -0400, you wrote:



>Thanks so much for your help. We adjusted the pressure switch, but really to no avail. We did get the pressure to raise to 120lbs, but could not get it quit cutting-on ever minute or two. We are going on a trip Tuesday, so we installed a manual switch inside so we can fill the tank, but then we are able to cut the compressor off.

> After three years of using an external compressor, we feel we are really "up-town" with an indoor switch. When we get back in October, we will start looking at replacing the pressure switch.

>In fact, with the work we have done on the air system, we discovered an Construction Equipment Store, so we will now know what to buy and where to buy it. Thanks for the lead.


>Les and Des


Date: Sun, 6 Sep 1998 03:18:54 -0400

From: "Les & Des" <>

Subject: Re: GMC: Air Bag System


Thanks! We did find the "set screw." Actually, ours was missing, and we replaced it with one like the other three screws that are there, but there was no change. We will replace it when we get back.

Les and Des


Date: Sun, 06 Sep 1998 16:39:07 -0600

From: Robert Shimanek <>

Subject: Re: GMC: Air Bag System

The Square D model 9013, Grainger part No. 5B419 for $13.65 does not have

the "on/off auto unloader" feature like the one I bought. The stock number

in the Granger book lists mine at $25.55. I guess I didn't get ripped off

if I would included shipping charges.

If anyone wants to access the Grainger Web Site for products and service

information the Web Site is:

They have 78,000 brand name items. They are a main source for Industrial

and Commercial & Supplies. Their catalog is 4100 plus pages.



Date: Sun, 06 Sep 1998 07:54:36 -0400

From: Dick Kennedy <>

Subject: Re: GMC: Air Bag System

I've been following this thread and from the description I can't tell if the tank is bleeding down or if the pressure switch is just arbitrarily recycling. I've also got bleed down and occasionally have to wiggle the switch to get it to make contact. I'm going to need to work in this area in the not too distant future so keep the info flowing.

Also at one time mine developed a leak around the base of the switch. I believe the bottom is held on with screws and it would lose it's seal only as the system reached high pressure. It's been a while so I'm a little fuzzy on the details. Just remember to check up under the switch too.



Date: Sat, 5 Sep 1998 23:19:00 -0400

From: "Les & Des" <>

Subject: Re: GMC: Air Bag System

Thanks, Dick, for the info. We are fairly certain that the tank is not 'bleeding down.' We have checked the tank and all connections with soapy water. Also, we have an air gauge on the tank itself. It holds fairly well, dropping maybe 10 lbs overnight. However, the nights here have been below 50 and, according to Wes, that can cause the pressure in the tank to drop. At any rate, it certainly shouldn't cause recyling of the compressor every minute or so. We tried adjusting the set screw. It does make a difference, but not sufficiently. At the low end it cycles every 5 or 10 seconds. At the high end it cycles every minute or so.

Thomas: Thanks for the tip about the WW Grainger part. We are going to be in Winston Salem this next week and there is a WW Grainger store there. If there is a leak around the switch itself, as Dick suggested, it is worth the $13.00 to replace the switch. Cuts out a lot of guess work!!!

Thanks to everyone for all the info.


Sorry to be so late in adding to this note. Gone for 3 weeks and going through over 500 messages. Went to Grainger to buy the air compressor control. They would not sell it to me. Said that they were "business" only. So much for retirement.


Date: Sat, 12 Sep 1998 20:20:58 EDT


Subject: Re: GMC: Air bag "system"

In a message dated 98-09-12 17:45:18 EDT, you write:


Thanx to all for the info on insurance and original prices. This list is

important to me because I'm about to buy a '75 Avion model GMC. The only

problem with the unit is a deflated left rear air bag. I'm told their is

a leaking fitting at the bag. It's to be repaired tomorrow. I've also

been told to get 1/4 turn ball type isolator valve(s) fron Jim Bounds

before I try to drive the coach home. I don't understand the system.

could somebody on the list explain it to me. Thanx, Skip



I bought a set of Jims Valves. I did it because I know I have problems left in my air system. Heck when I touch my control valves they hiss at me. I could not keep my lady up for more than 4 days before I got the valves. She has now been up for 4 months. I would not drive with them closed but that is my problem. If your compressor will get the lady up and running ------go for it.

If it runs all of the time-------think about. When I first started this

Project I drove mine with an air charge from the junk yard air compressor------set the controls to hold and ran for it. Made it the 14 miles home. She was down the next morning. But we made it. My compressor was dead. Did that first. With Jims valves you can isolate the bags from all of the rest of the system. So if you can get her up and check the fittings between the valve and the bag you should be able to fix her enough to get her home.

Take Care



Date: Tue, 6 Oct 1998 13:43:19 EDT


Subject: Re: GMC: Air Bag System


The trick is to find a friend with a small business (or a friendly business!). Doesn't matter what kind of business, computer consultant to seamstress, so long as they have a business license and sales tax number.

(Those fortunate folk in the Granite State can skip the sales tax!) Have them order for you, and collect the tax. Many small businesses would be glad to for a small percentage/fee. Good luck.

Rick Staples


Date: Tue, 6 Oct 1998 13:57:15, -0500


Subject: Re: GMC: Air Bag System

- -- [ From: Eugene Fisher * EMC.Ver #2.5.3 ] --

Have you contaced Cinnabar?? They have done a lot of work on upgrade of these systems and their prices seem ------ ok. See the articles for the numbers etc.


Date: Fri, 4 Sep 1998 12:49:06 EDT


Subject: Re: GMC: Air Bag System

Just my opinion, of course, but when I had the same problem, and replaced the valve assembly with a Slaten unit, NO MORE LEAK DOWN!

Larry nelson, PB 75



Date: Fri, 4 Sep 1998 10:09:07 -0700

From: "Tipton, Eric" <>

Subject: RE: GMC: Air Bag System

I am not familiar with the Slaten Unit. - What is it? Price?


Eric Tipton


Date: Tue, 06 Oct 1998 21:35:39 -0600

From: Robert Shimanek <>

Subject: Re: GMC: Air Bag System

Rick: You can go to a Sears Store that sells air compressors to get the same switch. They have a service department that can help you out if Grainger doesn't sell it to you or check the parts catalog on the compressor in the store. They'll order for you.




Date: Thu, 22 Oct 1998 09:13:52 -0400

From: "Bartz, Paul" <>

Subject: RE: GMC: Still looking for air leak (1974 Eleganza SE)

Go to GMCer Byron Maxwell in Boerne TX, 210-816-3004 for your Schraeder valves. He has a kit which also includes compact ball valves for the air bags.

Paul Bartz

From: []

Sent: Thursday, October 22, 1998 8:54 AM


Subject: Re: GMC: Still looking for air leak (1974 Eleganza SE)

As a temporary fix, you can disconnect the air lines into the air bags

and put in schraeder valves and air them up. If you have trouble finding them locally, I bet Camping World where your wife wants to shop will have them.


A few Questions:

(1) I am tracking an air leak (1974 Eleganza SE) without success. The coach leaks down on one side (usually over night). I have pulled out the controls at the front of the coach by removing the four (4) screws. Using soapy water, I could see no leaks. I have traced the air lines to the compressor and the tanks, and still I have not found the leak. I have checked around the air bags and the connections at the rear of the coach. I realize that I am looking for air bubbles or the sound of leaking air but so far, nothing. I did notice that there was an open line at the rear wheels and, depending on the position of the front valves, there would be some air escaping from the open tube. I do not know if this is a problem or normal.

Is there any procedure documented for tracking down an air leak? It seems that, when I am on the road, the compressor starts every few minutes. If the air system is normal, how often should the compressor start? My wife wants me to take her to Myrtle Beach, SC next week (she wants to go to Camping World and fondle everything in the store). I really need to resolve the air problem first.

I hope that these questions are not too elementary. I visited the section on Frequently Asked Questions at Is here a place where the questions and answers from GMCnet are cataloged other than the Archives? Many answers are there but they are not always easy to dig out.

Thanks for any help or advice.


Thomas P. Winslow

1977 GMC Coca-Cola TZE167V101893

1974/75 GMC Eleganza SE TZE064V101146

189 Hicks Creek Road, Troutman, NC 28166

h704-528-5868 * f704-528-5868 * p704-878-1157

E-Mail: *

Web Page: <>


> (1) I am tracking an air leak (1974 Eleganza SE) without success. The

> coach leaks down on one side (usually over night).

Since it only leaks down on one side, the offending side is where your leak is. In addition to connection points trace the air lines where they run under the coach. Often they rub against the frame, resulting in leaks.

I believe GMC Motorhome news published a leak detection procedure in an early issue. I'll check when I get home if you don't get a more definitive answer.

> It seems that, when I am on the road, the compressor starts every few minutes.

> If the air system is normal, how often should the compressor start?

Once you get your leak fixed, the compressor should cycle less often.

How often is determined by the road surface and any shifting of weight inside the coach. Depends on how hard the system is working to keep the coach level.


Date: Thu, 24 Dec 1998 16:49:49 -0700

From: Darren Paget <>

Subject: Re: GMC: cold weather

My air system stayed up all summer with no leak down. Temp. hit 20 below zero and the system would only last one day. Finally got the rig in to work on it at a friend's shop and found that the plastic fittings loosened in the cold.

Retightened them and the system now holds air again. It seems the plastic fittings really don't like the cold air. I think I will replace the plastic fittings with brass. This should resolve the problem, I hope. I am also really thrilled to find out that both air bags need to be replaced. Now I have to decide whether or not to replace with OEM or go to the four bag system.



Date: Mon, 14 Dec 1998 00:36:33 EST


Subject: GMC: AIR system

We have a 1975 GMC motorhome that we have recently purchased. It has some problem with the air suspension system. It leaks down. The previous owner had installed shutoff valves at each of the bags. When you have these valves shut off the vehicle will take about 5 days to settle down even with the top of the tires. When the valves

are left open it only takes about one day. I have checked the connections and all the hoses that I can reach with soaapy water, fixed one leak but find no others. I took out the valve between the tank and the compressor and cleaned and freed it up but that didn't help. It doesn't seem to matter whether the are left in hold or travel.

Also the left bag will not inflate automatically. When the ignition is turned on and the compressor runs with the control in travel the right bag will inflate, but the left one won't. Looking at them it appears that the arms are connected differently. One goes toward the front a little and the other toward the rear. Is this right? Does anyone know?

I have rebuilt alternators and starters and done automotive electrical work for many years. If any of you have problems in those areas I might be able to help you.

Thanks and Happy Holidays,

Date: Mon, 14 Dec 1998 06:56:14 +0000

From: "Walter M. Drew" <>

Subject: Re: GMC: AIR system


I have experienced similar problems. You can isolate the components. First you could just remove everything from the air bag and install a tank valve (Schrader valve ) with a 1/4" to 1/8" reducer. I bought this same equipment on the road for $2.00. Now you can pump up each bag independently. 85 to 95 Lbs appears to do the job. No melt down, no leaky air bags. Next you can isolate the shut off valves. The collective wisdom is that you need ball valves not needle alves. A small brass block with a male 1/8" npt and two female 1/8" npt will allow you to reuse the tank valve and your air line from the compressor. I bought the parts at a local hydraulic hose shop. A brake wholesaler will also have them. Jim Bounds also has them in kit form at a reasonable price. His number is 877-275-4462. I have replaced the airlines and put new fittings on the lines coming from the compressor to the solenoid. No more leaks, but when I put my electro level two in auto both sides go down in a hurry . I am open to suggestions.


78 Royale



Date: Sun, 27 Dec 1998 12:13:19 -0500

From: John Wright <>

Subject: Re: GMC: air bags how much are stock ones / How much is a 4 bag system

The latest prices for the firestone air bags is 225 to 250 dollars each depended if you get the cone or not. Just priced a set.

J.R. Wright]

77 Eleganza II


Date: Sun, 27 Dec 1998 21:01:15 -0500

From: "Bob Morris, Cortland NY" <>

Subject: Re: GMC: Cabinets & Air Bags

I bought new airbags from Gateway in St Louis a year ago for about 200.00 each without cones plus freight. I have been told that some sources won't sell airbags without new cones. That they come as a set.

My understanding is that these are readily available from the normal parts sources.

Bob Morris

74 Elganza SE

Cortland NY

- -----Original Message-----

From: hemogoblin <>

To: <>

Date: Sunday, December 27, 1998 7:55 PM

Subject: GMC: Cabinets & Air Bags

>I'm still searching for Louvered front over couch cabinets for a '77 Palm

>Beach. Any out there?

>Does anybody have any info on the problem with manufacture of Replacement

>Air Bags? Dies from Firestone worn out?

>A number of years ago, when I owned my '77 Birchaven I seached in vain for

>other Air Bags as mentioned in GMCIntl. Newsletters. Has anybody in this

>group ever pursued this?

>Happy Holidays to All!

>Mark '77 Palm Beach LI NY




Subject: Re: GMC: Cabinets & Air Bags

Hi Mark!

About a month ago I spent about two weeks trying to find alternate suppliers for GMC parts. One contacted was Firestone, the maker of our air bags. I still have the documentation but not at hand to quote. The dies for

making these air bags are 30 years old. The Firestone representative told me

that the cost to retool was in the neighborhood of $60,000 and that it was unlikely that they would spend the money to make a new die when this one


In my opinion, I believe there is an air bag that is being made by Goodyear or Firestone that would/could be used as a replacement with modifications but haven't had the time to pursue this yet. I have not as yet

received the catalogues from Goodyear or Firestone. My thoughts are along the

line of using 1 standard air bag if manufactured large enough with minor modifications or using two smaller air bags, similar to the four bag system

size, however, leaving the engineering geometry's of the wheels as is. (Two

small air bags to make one larger one) Scott

Date: Mon, 8 Feb 1999 14:29:01 EST


Subject: Re: GMC: Air bag question (was: Gas or Water fill cover)

In a message dated 2/8/99 1:29:39 PM Eastern Standard Time,


> Maybe there's a way to get something done if we have the right mfg. part

> number. That's all I know. I'll look at home to see if I wrote anything else

> in my big book of GMC facts tonight.

Hi Mark!

I spent a considerable amount of time trying to wiggle my way into Firestone.

Talked to a distributor of Firestone Air bags in Cleveland also. The person I

talk to a Firestone was Jerry Klavon--sales. 1-800-airides. The part number

that I have written down is 2T2B. Napa also has them for sale but expensive

#4502 $$257. or with cones #4503 $318.00 each, wonder who they buy from?

Jerry Klavon is the person that told me that only Gateway and Buskirk have

distributorships. I mentioned in some Gmcnet response back in November I

believe -- Cinnabar has to buy them from either of them -- quite a surprise?

Firestones website for air springs -- has a nice picture of air bags. In my opinion between all the manufactures of airbags there has to be one manufactured that that can be retrofitted somehow--I just haven't had the time to research it.

As for Darren, I feel for you--I just got some used ones from Clarence Martin

(Cleveland, OH) -that are better than the ones that came with the motorhome--I

can't afford new ones right now. " That's all I have to say about that"--Forrest Gummp



Date: Mon, 08 Feb 1999 14:34:29 -0700

From: Darren Paget <>

Subject: Re: GMC: Air bag question (was: Gas or Water fill cover)

Mark, Original part #W013584503. That is a Firestone number. Give it a shot. Good luck, and I really really really mean that. Darren

Feb 1999 21:10:47 EST


Subject: Re: GMC: Air bag question (was: Gas or Water fill cover)

Hi Mark and Darren and others:

In a previous post I mentioned Air Bags available through Napa----the prices

were what I was quoted but the numbers I guess are the Firestone Numbers. I

looked through my old E=mails and found a copy of a letter received through



Subj: Air Springs for the GMC Motorhome

Date: 11/30/98 7:46:30 AM Eastern Standard Time

From: (Kevin Brown)



Dear Sir,

The air springs that were used in the GMC motorhome (front wheel drive dual

axle) were made by Firestone. The replacement parts are listed as a 2T2B

(order number 4502 is air spring only and order number 4503 is air spring

and pistons).

Please contact our sales manager Jerry Klavon @ 800-888-0650 ext 8623.

Kevin Brown

Sr. Sales Engineer



Date: Tue, 9 Feb 1999 20:24:26 -0500

From: "hemogoblin" <>

Subject: GMC: Air Bags--Vent--Overhead Cabinet

Hi All

A couple of years ago I heard about Peterbuilt using an Air Bag that would

work on the GMC. The Firestone # was 9901, with a molded in # of 100593 if

someone has the time to research on the net this might be a source. Some talk has been going on about the Fantastik Vent, round corners vs square. On my former GMC a '77 Birchaven the square corner Fantastik was an exact fit except I had to run a wire for power. On my present GMC '77 Palm Beach my new Fantastik Vent ($120 at Camper World with discounts etc.) will require me to Modify round openings to square. I guess Coachman models (Royal and Birchaven) used a different OEM Fan than GMC Finished Models. I believe all Fantastik are Square designs. Still looking for Louvered Door over couch Cabinet. Any out there?

Mark '77 Palm Beach LINY



Date: Wed, 10 Feb 1999 16:39:13 -0600

From: "Neely Butler" <>

Subject: Re: GMC: Leveling Probs


Had some time to do some more checking today. It seems the right airbag functions correctly, inflates and deflates but the left bag appears to be fully inflated and will not deflate, or lower that side when switch is placed in "lower" position. Is there a relief valve somewhere to let pressure off of that side??


Neely B. Tenn

- -----Original Message-----

From: <>

To: <>

Date: Wednesday, February 10, 1999 2:21 PM

Subject: GMC: Leveling Probs

>Neely, check to see if you might have shut off valves on your air bags.

> David Lee Greenberg

>Boston Homes, Inc & GMC Registry

> 1220 US Highway 1, Suite B

> North Palm Beach, FL 33408

> T:561-776-1414 F:561-776-1788

Date: Wed, 10 Feb 1999 21:28:04 -0500

From: "Les & Des" <>

Subject: Re: GMC: Leveling Probs


We are going to butt in on this for just a second. We had our GMC for a little over a year before we found out that our left side air bag had not been deflating or inflating. It was just there. Being that we did not know squat (and that is still questionable) about the GMC, we just thought that was the way it worked. We developed a leak in the height control assembly on the left side. While we were working on it, we discovered that it would not deflate, and the

problem was that the air lines were installed wrong on the control valve itself for that side only. If we remember correctly, the raise and lower hoses were swapped. So really, the control was not doing anything. We made the correction, and since then it has worked great!

Date: Thu, 11 Feb 1999 17:16:20 -0500

From: "Bartz, Paul" <>

Subject: RE: GMC: bags of air


Leigh currently sells them (Firestone) for $110 each.

Paul Bartz