Home » Public Forums » GMCnet » Air bag/Piping Leak (Need to know maximum allowable pressure)
| Air bag/Piping Leak [message #311107] |
Wed, 30 November 2016 09:56  |
SCFire1
Messages: 19
Registered: April 2016
Location: Cross Anchor, SC
Karma: 0
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Junior Member |
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I've got a '78 Royale (owned about six months) and have had an air leak for the past couple of weeks. Start up and bags air up but the right side leaks down over a period of several days. I've checked for audible leaks (no luck, but with my poor hearing, it was a long shot at best).
I'm going the "soapy water" route and would like to know the maximum pressure allowed on the bags. Any help is much appreciated.
P. S. As an aside, what's the normal operating pressure when travelling down the road. Thanks again....
John Mitchell Cross Anchor, SC (upstate SC)
1978 Royale
Owned by my cousin in California for 30 years....purchased by a gentleman in the Atlanta area 7 years ago...finding my cousin's GMC by accident....Priceless!
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| Re: Air bag/Piping Leak [message #311109 is a reply to message #311107] |
Wed, 30 November 2016 10:08  |
lqqkatjon
Messages: 2324
Registered: October 2010
Location: St. Cloud, MN
Karma: 5
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Senior Member |
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OEM air bags run between 90-105 psi. You can pump a bit more air into them.
Check if you have any plastic fittings, and go to a good truck part supply place and replace them with good brass DOT one's.
Leak down overnight, I think you will find easily. Leaking down after a few days, I think you may be better installing shut off valves right at the Bags, and save your time trying to hunt down that leak. Especially on your newer Royale that I don't think has much air capacity, and you need to find that leak with the pump running full tilt.
My coach drops in a bout a weeks time, not fully, but noticeably. When I leave it parked, I just flip the valve closed on the bags and it stays level. When I go to leave, I flip the valve open and the air system is operational. Also forces me to do a walk around the coach once in a while to look for other oddities. I could not find my leak.
Jon Roche
75 palm beach
EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
St. Cloud, MN
http://lqqkatjon.blogspot.com/
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| Re: Air bag/Piping Leak [message #311110 is a reply to message #311107] |
Wed, 30 November 2016 10:32 |
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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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SCFire1 wrote on Wed, 30 November 2016 10:56I've got a '78 Royale (owned about six months) and have had an air leak for the past couple of weeks. Start up and bags air up but the right side leaks down over a period of several days. I've checked for audible leaks (no luck, but with my poor hearing, it was a long shot at best).
I'm going the "soapy water" route and would like to know the maximum pressure allowed on the bags. Any help is much appreciated.
P. S. As an aside, what's the normal operating pressure when travelling down the road. Thanks again....
John,
You have been here since April, but never officially welcomed.
Welcome to the group, family, cult, asylum....
Leaks of the airbag itself are rare, but do happen. Along that line, be vary careful when you are around the airbags (airsprings) as they are known to burst with no warning at all. This is also why you always block the coach when you go under it. If you are wondering, if you have a 2X4 under the coach and dump the air, you will not be able to get the board out.
Please do both us and you a favor, go to <Control Panel/Account Settings> and scroll down to where you can put in a sigfile. This should have your real name (so others will know you when you meet), a short bit about the coach (year, model and major mods)because there can be big differences and a geographic reference (because the e-mail readers don't get the header) because someone in striking distance may want to offer assistance. Then remember to scroll down more to <update> .
If you don't have the valve and schrader set on the rear springs, order up a pair of 1/4 pipe-schrader adapters to carry in the case that the air system takes a hit. You should also consider carrying a little 12V compressor.
If you have not figured it out already, you are now a part of an amazing community. It is full of helpful and supporting people that want you to enjoy your coach as much as we all enjoy both our coaches and the community. I have a special way of welcoming new people (that I missed in April) because the only other community that I know of that is this solid is that of the watermen that are my world. I like to welcome a new owner here much as a new owner or vessel is welcomed there. So,
May the Good Lord Bless this coach and all those that set forth within her.
Welcome John
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: Air bag/Piping Leak [message #311114 is a reply to message #311107] |
Wed, 30 November 2016 11:15 |
pzerkel
Messages: 212
Registered: September 2007
Location: Salisbury, IL
Karma: 0
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Senior Member |
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SCFire,
You have a 78 so it is most likely an Electrolevel II system. They are a little different than the Power Level (which is what most 73-76) coaches have (and makes up the majority here); Some 77's had an ElectroLevel I which was an intermediate system that I do not know a lot about.
The ElectroLevel II on the '78s does not have an air tank. But it has two compressors (one for each side). You can force the compressor(s) to run though, by putting your middle switch in "hold" and then putting either or both switches in "raise". This would put enough pressure in the lines, that I would think you could do a bubble test.
I have a 1978 Eleganza, and the location of my compressors is in the passenger side cabinet under where the power converter is installed, but it is likely in a different location on your Royale. Maybe someone with a 78 Royale will chime in. They aren't hard to find though; put one in raise and then walk around the coach listening for compressor noise 
The Electrolevel II's have less tubing overall, but two compressors vs one, and some finicky electronic components. If your ride height sensors are working, count yourself among the lucky ones.
Paul Zerkel
'78 Eleganza II
Salisbury IL (near Springfield)
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| Re: Air bag/Piping Leak [message #311115 is a reply to message #311107] |
Wed, 30 November 2016 11:29 |
C Boyd
Messages: 2629
Registered: April 2006
Karma: 18
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Senior Member |
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Bags can leak down from other places. Usually there is a clump of oem inline connectors around the brake booster. Spray with soapy water and observe as helper changes valves. In travel leave it 30 sec or so to open. Check each connection. Inside the panel the connectors or valves themselves could leak. Again check each in every position. I use The DOT brass inline slip on connectors for replacement. Push on real hard to seat.
Operating pressure varies with load weight versus preset ride height. It varies but as long as ride height is adjusted correctly it's ok. Coach air systems are set ~ 125psi max. Most big trucks are regulated to 90psi out of the 125 psi in the tank. The air bags should take a whole lot more just from pot holes. I'm thinking 500 or better.
SCFire1 wrote on Wed, 30 November 2016 10:56I've got a '78 Royale (owned about six months) and have had an air leak for the past couple of weeks. Start up and bags air up but the right side leaks down over a period of several days. I've checked for audible leaks (no luck, but with my poor hearing, it was a long shot at best).
I'm going the "soapy water" route and would like to know the maximum pressure allowed on the bags. Any help is much appreciated.
P. S. As an aside, what's the normal operating pressure when travelling down the road. Thanks again....
C. Boyd
76 Crestmont
East Tennessee
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| Re: Air bag/Piping Leak [message #311154 is a reply to message #311110] |
Thu, 01 December 2016 09:16 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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You can also find 1/4" schrader valves at Ace hardware. I believe they are around $2.00 each. I have a pair somewhere in the coach but have never used them.
When I had air leaks that I could not easily find, I replaced ALL of the plastic air line fittings. I found the replacements locally at an independent Auto Parts store. NAPA also also has them at twice the price. Now my system sits all winter without going down.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: Air bag/Piping Leak [message #311221 is a reply to message #311154] |
Sat, 03 December 2016 17:49 |
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John Sharpe
Messages: 71
Registered: February 2006
Location: Porter, TX
Karma: 0
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John, Do you have Electro Level II? If you have a unit with 2 small compressors inside the coach near the left rear tire and electric level sensors in the wheelwells (no air hoses connected to the sensors), then it's Electro-Level II. In that case, with age the hold valves begin to leak causing the problem you describe.
One way to check the hold valves is to install a block off valve on the air bag. Pump the bag up to ride height and close the block off valve and use the panel switch to energize the down button for 20 seconds. If the bag stays up after a few days, you can surmise that the bag and lines to the block off valve are not leaking. Now the problem is the line to the hold valve solenoid or the hold valve solenoid itself. To check the hold valve, you need to: 1) disconnect the line from the compressor to the hold valve solenoid. 2) open the block off valve at the inflated air bag. 3) Use soap bubbles on the inlet of the hold valve solenoid to see if it's leaking. If it's not, you need to repeat the test because it's either the line or the hold valve solenoid.
John Sharpe
Porter, TX
78 Eleganza II, TBI
40 Ford Panel, TPI
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