Air suspension woes...

S

shawn bennear

New member
May 25, 2007
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I had the Palm Beach out for a ride and all was well... I am not sure what happened to it after I parked it, but now all of a sudden it will not build
air to either bag, and in fact, it will actually dump the air even when it is set to raise on either bag. The compressor is running and apparently
filling the air tank, but not sure why it isn't going where it needs to go. If you hit the switches to lower, you can hear the air hissing... Just no
raise. I have looked in the compressor spot in the cabinet, but I don't see or hear any hissing in there. I have no idea where the air tank is on the
Palm Beach, gonna have to hunt the service manual... I did notice that the round part on one solenoid spins, and it is the middle one for the blue
hose. Don't know if that has anything to do with it or not.

My friend Dave has a 78 coach, and he has 2 compressors and I didn't see any solenoids on his...Unless I'm blind...lol

Anyone have any thoughts on where to begin? I'd appreciate it.

I may just have to figure out the measurements for a couple 4x4 posts to sit under the bogies for the winter until I figure out the mystery...

Shawn
--
http://www.gmcmotorhomeworld.com

1977 Palm Beach, 403 V8 w headers.
 
Do you have a pressure gauge anywere on your setup? Do you have schrader valves? What kind of compressor do you have?
--
Rich Mondor,

Brockville, ON

77 Hughes 2600
 
> Do you have a pressure gauge anywere on your setup? Do you have schrader valves? What kind of compressor do you have?

No pressure gauge yet, It does have schrader valves, and the compressor is a Viair.
--
http://www.gmcmotorhomeworld.com

1977 Palm Beach, 403 V8 w headers.
 
Well you have leak somewhere or a compressor that failed.

The air tank is mounted in the same cabinet as the compressor and is usually mounted vertical on the right hand side as you look into the cabinet. It
is small. Probably not more than 1 quart.

Does the compressor pump up and shut off even though the bags are not inflating? If it does, then the compressor and tank are OK.

If you are not able to get it up to pressure and the bags are low then the leak could be anywhere. It does not take much of a leak to prevent the
whole system from coming up to pressure. I doubt you would hear it leak over the noise of the compressor running. That compressor does not pump much
volume of air.

There are several ways to approach this. I guess that I would first disconnect the line from the manifold that goes to the tank and compressor. Then
screw in a pressure gauge. The gauge is cheap. You can get one at TSC for around $6.00. With the gauge screwed in to the hose that you disconnected
from the manifold, turn on the system. The compressor should fill the tank and shut off at around 1 minute or so with the gauge reading somewhere
around 120 PSI. If that happens, let it sit or a few minutes to make sure that it does not leak down quickly.

If it passes the above tests then you can rule out everything to do with the tank, compressor, pressure switch, drain valve on the bottom of the tank,
and all of the associated plumbing associated with those items.

I guess the next thing to do would be to reinstall the removed line to the manifold. Then disconnect the lines to the left and right suspension and
plug the ports that feed the individual sides. Then try connecting the sides, one at a time, to determine which side is leaking. You will need to
use those shutoff valves to prevent the bags from deflating while you are doing this. Or you might put some blocks under both sides prior to
disconnecting the lines.

There are several other ways to approach this problem. This is just one that I dreamed up.

Ken B.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
 
Your 1977 has ElectroLevel, but my 1978 has ElectroLevel II. The EL II has one compressor and one electronic leveling switch per side. All of the valves are in the compressor itself. All of the valves are in the compressor itself. EL I is much different.

Do you have isolation valves at the bags? Something with a Schrader valve to blow it up that way?

-Dave
1978 Transmode near Pittsburgh

>
> Well you have leak somewhere or a compressor that failed.
>
> The air tank is mounted in the same cabinet as the compressor and is usually mounted vertical on the right hand side as you look into the cabinet. It
> is small. Probably not more than 1 quart.
>
> Does the compressor pump up and shut off even though the bags are not inflating? If it does, then the compressor and tank are OK.
>
> If you are not able to get it up to pressure and the bags are low then the leak could be anywhere. It does not take much of a leak to prevent the
> whole system from coming up to pressure. I doubt you would hear it leak over the noise of the compressor running. That compressor does not pump much
> volume of air.
>
> There are several ways to approach this. I guess that I would first disconnect the line from the manifold that goes to the tank and compressor. Then
> screw in a pressure gauge. The gauge is cheap. You can get one at TSC for around $6.00. With the gauge screwed in to the hose that you disconnected
> from the manifold, turn on the system. The compressor should fill the tank and shut off at around 1 minute or so with the gauge reading somewhere
> around 120 PSI. If that happens, let it sit or a few minutes to make sure that it does not leak down quickly.
>
> If it passes the above tests then you can rule out everything to do with the tank, compressor, pressure switch, drain valve on the bottom of the tank,
> and all of the associated plumbing associated with those items.
>
> I guess the next thing to do would be to reinstall the removed line to the manifold. Then disconnect the lines to the left and right suspension and
> plug the ports that feed the individual sides. Then try connecting the sides, one at a time, to determine which side is leaking. You will need to
> use those shutoff valves to prevent the bags from deflating while you are doing this. Or you might put some blocks under both sides prior to
> disconnecting the lines.
>
> There are several other ways to approach this problem. This is just one that I dreamed up.
>
> Ken B.
> --
> Ken Burton - N9KB
> 76 Palm Beach
> Hebron, Indiana
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
 
Start in compressor cabinet and check pressure at tank drain on bottom of tank. The tanks rust from inside out and get perforated pin hole leaks. If
leaks exceed compressor output you are not going to raise. Simple inspection and listen test. JimK has nice stainless replacement tanks.
--
John Lebetski
Woodstock, IL
77 Eleganza II
 
> Start in compressor cabinet and check pressure at tank drain on bottom of tank. The tanks rust from inside out and get perforated pin hole leaks.
> If leaks exceed compressor output you are not going to raise. Simple inspection and listen test. Jim K has nice stainless replacement tanks.

That is exactly what I was thinking but did not want to say it until he did some more diagnosis. There are just too many other things that it could
be. In my case it was a 20 year old fitting that decided to crack it's own.

I wanted to see if his problem is on the supply side (before the valves) or in the valves and hoses beyond there. After that is determined we can
diagnose it farther from there.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
 
What Air bags are on the coach?
Some of the bags will not allow air to enter is it is down all the way, so
you need to raise it a little to overcome the restriction.

On Tue, Nov 26, 2019 at 8:56 AM Ken Burton via Gmclist <

> > Start in compressor cabinet and check pressure at tank drain on bottom
> of tank. The tanks rust from inside out and get perforated pin hole leaks.
> > If leaks exceed compressor output you are not going to raise. Simple
> inspection and listen test. Jim K has nice stainless replacement tanks.
>
>
> That is exactly what I was thinking but did not want to say it until he
> did some more diagnosis. There are just too many other things that it could
> be. In my case it was a 20 year old fitting that decided to crack it's
> own.
>
> I wanted to see if his problem is on the supply side (before the valves)
> or in the valves and hoses beyond there. After that is determined we can
> diagnose it farther from there.
> --
> Ken Burton - N9KB
> 76 Palm Beach
> Hebron, Indiana
>
> _______________________________________________
> 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
http://www.appliedgmcrvparts.com
1-800-752-7502
 
> What Air bags are on the coach?
> Some of the bags will not allow air to enter is it is down all the way, so
> you need to raise it a little to overcome the restriction.
>
>
>
> --
> Jim Kanomata
> Applied/GMC, Newark,CA
> jimk
> http://www.appliedgmcrvparts.com
> 1-800-752-7502
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org

Jim, It has the factory bag setup on it. I was planning on something different down the road, but gotta find this gremlin first...
--
http://www.gmcmotorhomeworld.com

1977 Palm Beach, 403 V8 w headers.
 
Shawn, if you have the time and the facility to do this. You might
consider removing the manifold, valve assembly, compressor and reseal all
the connections. Replace the O-rings in the skinner valves and bench test
the operation of the pump, pressure valve, and check for leaks on all
connections with soapy water. .
Next in line would be replacing the O-ring in each bag. Once these items
are sealed use soapy water on the rest of the air line connections.

Ken Henderson did a small write up on the skinner valves in this posting
gmc.mybirdfeeder.net/GMCforum/index.php?t=msg&goto=254825&rid=2253&srch=skinner+valves

You can find the electrical schematics From the 1977 / 1978 Maintenance
Manual Suppliment

Chassis Area

1977 / 1978 with Electro Level I
http://www.bdub.net/wirediagrams/77-78-chassis-electrolevel-I.pdf (Models
ZEO6581, ZEO6584) (520kb)

http://www.bdub.net/wirediagrams/77-78-chassis-electrolevel-I.pdf

On Tue, Nov 26, 2019 at 6:41 PM Shawn Bennear via Gmclist <

> > What Air bags are on the coach?
> > Some of the bags will not allow air to enter is it is down all the way,
> so
> > you need to raise it a little to overcome the restriction.
> >
> >
> >
> > --
> > Jim Kanomata
> > Applied/GMC, Newark,CA
> > jimk
> > http://www.appliedgmcrvparts.com
> > 1-800-752-7502
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
>
> Jim, It has the factory bag setup on it. I was planning on something
> different down the road, but gotta find this gremlin first...
> --
> http://www.gmcmotorhomeworld.com
>
> 1977 Palm Beach, 403 V8 w headers.
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

--
Bruce Hart
1976 Palm Beach
Milliken, Co
GMC=Got More Class
 
What i did with mine to start with, as i had the same problem, was install a pressure gauge and a shrader valve....nothing fancy just a shrader valve
at the bottom of the tank were the drain would go.....then i grabbed one of those cheap tire pressure gauges that you can clip onto the valve stem and
fill your tire with the gauge installed.

I then filled the system with my portable compressor to 120psi and hit the raise switches for each side, one at a time while adding air through the
gauge till it lifted and held 120psi approx per side.

Then i shut it down to see what would happen....in my case everything seemed to hold for 4 or 5 days (well i have a tiny leak in the right somewere i
need to fix)

What this proved is the solenoids etc work but from the tank back i had a problem.....in fact i had 2 problems....one the one way check valve was
stuck open and the system was bleeding back through the compressor.....once fixed i redid the test and again it held but would pump up....turns out my
DANA was pooched.

In your case the compressor works so possibly the check valve etc but without someway of pressurising the system youll never know whats going on.
--
Rich Mondor,

Brockville, ON

77 Hughes 2600
 
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