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jagcb750 · 08-15-2007, 02:26 PM

I've got a quick question or two and, probably dumb ones, but I need to know.
When I come to a stop in my 86 345, I hear a hissing sound coming out from the back of the coach. I am assuming air pressure being released from the air bag leveling system. Is that normal. I noticed that when I start up the Moho the low air pressure light is on, but it eventually goes out.. I read somewhere that you are supposed to purge the moisture out of the tank on occasion. How do you do that and is the air pressure released when you come to a stop and shut off the Moho?

Eddy · 08-15-2007, 02:40 PM

The only time that I have heard air being released is when using blocks or the jack system to level the coach. I checked my service manual and it says there is a "30 second time delay from the time of the leveling valve link moving and air being released from the valve. If air is passing through immediately than the valve is defective." Do you hear air leaking when parked?

jagcb750 · 08-15-2007, 02:47 PM

I will check it when I get home from work. I will start it up and see how long it takes for the low air pressure light to go off and see how long it takes to bleed out the air after I shut it off.

Thanks!

str8strm · 08-15-2007, 03:26 PM

usually runs for 2-3 minutes after start up. Our coach has a bad habit of slipping off the jacks unless you chock the tires immediately. ( Of course it will not do it for the mechanics!). The last time it happened the air bags deflated after leveling the coach, it rolled forward off the jacks and we had a heck of a time getting the jacks down afterward because the bags would not reinflate, actually had to dig a hole to get the jacks down! But it was better than pulling out and circling the campground!! Our airbags will also deflate if we sit on a sloped driveway for too long (dealing with traffic) You actually only have to turn the ignition key on to get the compressor working when it gets up to 100 psi it shuts off.

Chaplain Kent · 08-15-2007, 04:15 PM

Quote:

Originally Posted by jagcb750

I read somewhere that you are supposed to purge the moisture out of the tank on occasion. How do you do that and is the air pressure released when you come to a stop and shut off the Moho?

You think you are asking a dumb question? I'm an old timer around here and don't know the answer, other than my compressor will turn on to inflate the bags each time I turn on the ignition. However; if my air bags totally deflate the rear end droops so far down Chummy looks like a low rider. After my rewire this year they put in a new relay for the compressor taking the power direct from the battery and not the ignition giving the compressor a steady source and shorter run for power. The result is that the compressor now runs about 30 to 45 seconds on start up to fill the bags and not several minutes.
Now to bleed the system. Open up the rear door where the compressor is located and you will see a small valve on the bottom of the front side of the compressor. Simply open this valve and let the water flow. If you don't know where your compressor is have someone turn on the ignition while you are standing in the back, you will hear it.

jagcb750 · 08-15-2007, 07:03 PM

Here is an update of my situation. I started up "Ol' Nancy" and this time the low air light did not light up. The guage showed that there was 55 psi on it. I made the mistake of not disengaging the leveling jacks and I believe that is one of the reasons that the pressure did not build up any more. (Well, maybe up to 60 psi or so).
After I shut Nancy down I heard the hissing noise coming from her rear. I found some documentation from a PO that stated that in 1988 Airstream had sent out a bulletin to upgrade certain components in the leveling system. I found the hissing noise under the rear bedroom and it turned out, according to the bulletin, to be some kind of a pressure relief valve. I am going to check tomorrow if it isn't 100 degrees again with the leveling jacks disengaged this time to see if the compressor will pump the tank up to a higher psi. What struck me is odd is when I tried to bleed out the moisture in the tank nothing happened. no pressure. but after a little while it would blow about three little wet bubbles. What's up with that?

swebster · 08-15-2007, 09:16 PM

I would bet you have a leak. There is a check valve between the compressor and tank which allows air in but not back. This helps the compressor get started without a "head" on it. Also, you should find a schrader (car tire) valve mounted in the curbside wheelwell between the drive and tag wheels. You can take a manual reading from there. You should have more than 55 psi in the rears.

Also, the jacks will typically raise the rears enough to open the leveling valves. These are normally meant to release excess air or level a side to side situation, but with the jacks up they will just dump air. They are little valves connected to your tag axles with an adjustable rod.

I chased a number of gremlins out of my rear air syste, (most recently a replacement compressor). Some soapy water in a spray bottle will be your friend as you try and find leaks.

Good luck and keep everyone posted.

Howard Lefkowitz · 08-16-2007, 12:32 PM

Quote:

Originally Posted by jagcb750

I've got a quick question or two and, probably dumb ones, but I need to know.
When I come to a stop in my 86 345, I hear a hissing sound coming out from the back of the coach. I am assuming air pressure being released from the air bag leveling system. Is that normal. I noticed that when I start up the Moho the low air pressure light is on, but it eventually goes out.. I read somewhere that you are supposed to purge the moisture out of the tank on occasion. How do you do that and is the air pressure released when you come to a stop and shut off the Moho?

Check the bottom of the air tank. There is a bicycle valve which should be used to drain the tank at least every several months. Water builds up and will rust out the tank if you don't keep it drained.

jagcb750 · 08-16-2007, 02:44 PM

The bottom of the tank has the valve that I was referring to earlier that did not have any pressure on it when I tried to bleed out the moisture. I took the cap off of the valve and pushed in the middle and no pressure. after 20 seconds or so it would blow a small bubble. It did it 2 or 3 times. I thought maybe since I tried all of this with the moho still on the leveling jacks that that might have been the reason for no pressure. Otherwise, I think that valve may be stopped up.

Alumatube · 08-16-2007, 02:47 PM

What's really funny is when your bags get pumped up while driving, you park the coach and walk back through the rear bedroom to get stuff out before you exit and the coach noticeably sinks with each step! Poor Brad had a bunch of work to do to fix our system, but he eventually conquered it!

Susan

Eddy · 08-16-2007, 03:03 PM

Could the presure gauge be connected to the front air bags? Some have a compressor that air up the fronts only and 55 PSI would be the correct setting at the front end.

jagcb750 · 08-19-2007, 12:19 PM

Here is an update: I believe the air suspension system is working like it is supposed to. The compressor seems to fill up with air when I start up the engine. And when I stop it releases the pressure. I noticed that the guage is going up higher around 90 psi when I am on the road. I am going to check to see if I can bleed the water out of the tank.. Last time I tried I had no pressure just three wet bubbles. If there is supposed to be some pressure in the tank then I suspect that the bleeder valve is defective.
I will post back with the results soon. Thanks to all who have helped on this issue.

choctawmel · 08-19-2007, 05:30 PM

For the longest time, after I bought 'The Silver Bullet' the air would bleed off the air ride and the spring ends would rest on the frame. Then one day I stopped by (to talk to the own of) another 345 that had been setting for months and the air bags were up. I went home and started leak checking and found a cracked fitting on the air compressor. Now 'The Silver Bullet' air system stays up all the time. I don't think the compressor comes on just because I start the coach. I can raise it up on the jacks and the air don't breed off either.
As for the air tank drain valve, mine was stopped up too. I took the hose off, unscrewed the 'schrader' valve and cleaned it out with a wire (with no pressure in the tank).
mel

Inland RV Center, In · 08-19-2007, 05:49 PM

Quote:

Originally Posted by jagcb750

Here is an update: I believe the air suspension system is working like it is supposed to. The compressor seems to fill up with air when I start up the engine. And when I stop it releases the pressure. I noticed that the guage is going up higher around 90 psi when I am on the road. I am going to check to see if I can bleed the water out of the tank.. Last time I tried I had no pressure just three wet bubbles. If there is supposed to be some pressure in the tank then I suspect that the bleeder valve is defective.
I will post back with the results soon. Thanks to all who have helped on this issue.

There is also a very small "in-line" check valve, that easily corrodes on the inside.

When that happens, the air pressure simply bleeds back thru the air compressor when it's not running.

We have that check valve.

Andy.

Geophilist · 08-20-2007, 12:03 PM

JaG

You probably have two pounds of rusted crud in the bottom of your tank. When you go to let the air out, it keeps the schrader valve gummed up. Get a tool to take the schrader valve insert out as well as a few of the inserts(any auto parts store should have them). Take the valve out and see what comes out with it. If you try and re-use the old valve, it will probable leak forever, as will the one that you have already disturbed. Make sure the cap is on tight when you are finished. Be careful as there may be some pressure behind it and could blow crud everywhere, especially your eyes if you are looking into the hole. Ask me how I know.

As mentioned before, the check valve is probably gone and a new one would be in order.

Steve

jagcb750 · 08-21-2007, 08:28 AM

@Geophilist:
That is what I plan on trying next. I have been working on my generator, which is another issue, until 10:00pm last night and haven't had time to try that yet. I will pick up a few inserts first from the local auto parts store first though. Thanks!

jagcb750 · 08-21-2007, 08:12 PM

o.k. I unscrewed the bleeder valve and poked a nail up in there to see if it is stopped up and it was not. No water either. so I started up nancy and I heard air coming out the valve. So I put in a new valve core in it and It seems to be fine. It was kinda weird that it didn't have any moisture in it or that no pressure was on it when I took out the old valve core.

Geophilist · 08-26-2007, 04:58 AM

JaG,

So much for that theory. Perhaps the air has been leaking out of your system for so long that no water has accumulated in the tank. You must have some pressure to that point because air leaks out when you started it up with the core out. At least you don't have a tank full of rust!

As others have pointed out, the check valve between the compressor and the system might be bad. Good luck and happy hunting.

Steve

swebster · 09-01-2007, 06:41 PM

JaG.
There is a leak somewhere. You tank should have pressure in it (90 - 100 psi or so). The check valve can be purchased from Grainger. The fact that you removed the drain valve and there was not pressure in the tank means your system is not working correctly. A note on this, you should not drive you coach over 20 - 30 mph without the rear air system working. It places too much of the rear suspension load on the tag axle suspension.

You mentioned in a previous post that the compressor comes on with the igition and you hear a "release" of air when you turn it off. This is normal. The compressor has a release in it to remove any pressure between the check valve and the compressor so the next time you start the compressor it doesn't already have a 90 psi head of pressure on it.

I suspect your check valve is not allowing air into the tank. Or you have a leak between the valve and the tank.

jagcb750 · 09-01-2007, 07:24 PM

@swebster: Hey bud! Where exactly is this in-line check valve between the compressor and tank? I hope to get to the bottom of this, because I don't want to damage anything when I take her out soon.