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swebster · 09-02-2007, 02:32 PM

I replaced mine in a parking lot in December (this type of thing seems to be a theme with me) so I've blocked out a lot of it for mental health purposes.

If I remember correctly, there is a hard line that runs down from the compressor (below the floor) behind the tank and connects to the roadside fitting on the tank. The check valve is somewhere along this hardline.

Mine developed a crack and allowed all of the air to dump out (over an hour or so). Simple to replace it and I think it cost about $20. Don't forget teflon tape on the threads.

jagcb750 · 09-03-2007, 07:15 PM

I think you guys are right about the check valve. No pressure at all on the compressor even when I fill it up manually at the tank with a plugged in air compressor. It just leaks out the pressure release valve under the bed. I believe that as long as the key is on, the compressor kicks on and gives the system the 90+ pounds needed, but the compressor I figure is over worked and must run most of the time. When I turn the key off, the compressor kicks off and all the pressure is released through the pressure release valve located under the bed. Now I looked for this in-line check valve to no avail. I followed the air line down through the coach under the rear curbside of Nancy. From the bottom it went into a 1 inch black corriageted looking tube. This tube ran down the frame of Nancy until it was between the tags and dual wheels and then it went into the compressor tank. I could not see anything obvious where there might have been a check valve located. The guage mounted on the dash when key is on shows that it is getting adequate air pressure. I wonder if the pressure is in the air bags or whether the pressure is between the compressor and the check valve. What I'm trying to figure out is, if I can't locate this elusive check valve, whether I can just add one under the bed before it goes down through the floor????

Robfike · 09-04-2007, 12:33 PM

You should be able to just add one in the compressor outlet line. Just make sure that it is after the pressure relese that dumps pressure at compressor shut-down. My 345 did not have a check valve, and had some other missing parts of this system. I figure a PO got in over his head and screwed is up.
Rob

jagcb750 · 09-04-2007, 07:11 PM

Appreciate it Robfike. that is what I was hoping. I will get the check valve and maybe this will resolve my problem. Thanks to all I will post with an update soon.

jagcb750 · 09-04-2007, 08:04 PM

o.k. what size check valve do I need? Part # or product Id? I looked on Andy's site and couldn't find it. also looked on grainger's site and found several. Since I don't have one to match up, what does this thing look like and what size. Help.....

Robfike · 09-06-2007, 07:59 AM

I will try to get you a picture or some info this evening.
Rob

Robfike · 09-17-2007, 05:33 PM

Sorry for the long time getting the picture out.
In the photo, the aluminum cylinder in the center/right is the check valve. There are no part numbers on it. It just has the flow direction arrow stamped in it. It can be taken apart and cleaned.
If you follow the black plastic line from the compressor, it goes first to a "T", and then to the check valve. The other line from the "T" goes to the pressure relief valve (lower left) that dumps the compressor head pressure when the compressor shuts down. It is an electric solenoid valve. This way the check valve holds system pressure while the pressure between it and the compressor is dumped.
Hope this helps, Rob

jagcb750 · 09-18-2007, 11:44 AM

Thanks Robfike for the pic. I put in a small hospital in line check valve this past Sunday. It isn't nearly as elaborate as yours, but It may do the trick. I am going to test it in a bit to see if it is still holding pressure. After I installed it Sunday, it was the 1st time that the tank has held any pressure since I've owned my coach. I forgot to take her off of the leveler jacks and it wasn't pumping up, but after I released the hydraulic jacks it started filling up like it was supposed to. It seemed like it took quite a long time to fill up the tank. The tank probably didn't get filled over 70 psi before the compressor finally shut itself down. I will look into it soon and will post a pick when I can get it resolved if it works. Thanks to all.

bkahler · 09-18-2007, 05:12 PM

Quote:

Originally Posted by jagcb750

The tank probably didn't get filled over 70 psi before the compressor finally shut itself down. I will look into it soon and will post a pick when I can get it resolved if it works. Thanks to all.

If the orifice in your check valve is to small your pump will have to work harder to pump the air into the tank. Do you know if your pump shutdown due to the pressure switch setting or from a blown fuse?

70 psi is definitely not enough, Airstream says something like 90 - 110 psi. I think my 310 manual says 100 psi.

Brad

jagcb750 · 09-18-2007, 07:43 PM

I placed a metal insert into each of the ends of tubing in which I spliced in this check valve. It was some I had bought for another check valve that I was going to install initially. These inserts keep the tubing from being pinched together. I hope it doesn't restrict the air flow too badly. The air compressor wasn't running hot. I will check it soon after I get my master cylinder back on and can disengage my hydraulic jacks. I'm afraid to screw something up right now with nancy's brake components laying about. I ended up buying several check valves. This option seemed to be the most likely fix. I plan on getting some pics together soon. Oh, also I think my pressure guage on the dash may be off a little. I used a tire pressure guage on the tank the other day and the pressure was closer to 100 psi. I will check again later.

txraz · 09-27-2007, 08:31 PM

I had similar problems as those listed here. My tank needed filling every time I started it and at the end of everynight the rig sat on the frames. I put the back end on blocks this past winter and stripped the tag axle out and gutted the suspension system. I found several age related problems that all added up to a leaky old air system. First my original firestone airbags had simply outlasted thier lifetimes. I was able to find exact replacements from Forestone however the numbers are very different due to a numbering system change. Also removed the leveler values and found that one of them had a faulty o-ring and was leaking. They are hydrolic fluid based and will not open imedeately. A fluid flow pressue must equalize for valve action and it takes 5-10 seconds. I also found that several original air line fittings had started to leak. The new push on are much more reliable and easier to work with. Thankfully teenagers have discovered air systems and the parts are readily available. My air tank was rusted badly inside from years of not draining so I replaced it with one as close in tank capacity that I could find. The single heavy cross member that the airbags rest on was removed and the two end knuckle joints had become lose and sloppy. Not wanting to spend money or time on a replacement, I cleaned the member and rebuilt the bushings with the clever use of brass shims. Now it's tight as it ever was. The electric cut off valve and pressure indicator switch was also replaced (again thanks to teenagers and airparts). All in all probably spent $600 on the parts and spent five weeks under the frame but the results are a brand new suspension unit. I put air in the new system last March and don't think I've added a pound since.

If anyone needs part numbers or suppliers, let me know and I'll hunt down the reciepts.

TXraz.

str8strm · 09-28-2007, 05:50 PM

We have not had to do it yet but know the time is coming. If you could post part numbers and suppliers that would be great.

wpapke · 11-02-2007, 12:23 PM

Every time i pick up my 345 something else seems to go wrong. the alternator had to be replaced and now the levelers don't work and the air compressor runs when the ignition is on. The nags seem to stay full when it is off so I am baffled. Of course, that's not difficult. I am beginning to think my wrenching skills are not up to owning an RV, especially a 1988 airstream. Any ideas anyone? Oh yeah, the steps stopped working as well and there is an intermittent short to the instrument panels that blows periodically. I am about to give up on this unit. HAd it 10 months and still haven't been able to use it. Thinking about a complete rewire if I can find someone to do it.

klattu · 11-02-2007, 02:15 PM

I see now...
Mine drains down because the check valve leaks and when it is trying to release head pressure, it drains the tank backwards.
Must fix.

Inland RV Center, In · 11-02-2007, 02:19 PM

Quote:

Originally Posted by jagcb750

o.k. what size check valve do I need? Part # or product Id? I looked on Andy's site and couldn't find it. also looked on grainger's site and found several. Since I don't have one to match up, what does this thing look like and what size. Help.....

Our web site parts list, is a "sale list only."

We carry over 3300 different Airstream parts in stock, including that check valve.

Andy

buckwheat · 11-09-2007, 04:39 AM

Hey wpapke, I feel your pain. No one tells you when you buy one of these classic beauties that not only do you need to be a mechanic but also an electrician, plumber, and a carpenter with infinite patience and an obsession for tinkering. For your air bag woes, the owners manual is fairly good for the general system layout and electrical connections, but translating the diagrams to reality is usually quite the adventure. The air compressor is wired to the ignition "on" position by design, I think mostly to work in concert with the low air pressure warning indicator. If a check valve is your problem, a simple test is to fill the air tank to 90 psi using the external air fitting, located at the bottom of the tank (and if you're lucky, connected by hose to a curb side mounted tire style air stem valve). The check valve should keep the air in the tank with no more than a 10 psi drop in pressure over 24 hours unless you have leakage elsewhere (this drop is based on observation not technical specs). Mine has the check valve at the top of the tank connected to a 90 degree elbow pipe fitting that screws into the tank.

wpapke · 11-11-2007, 07:45 PM

Thanks Buckwheat,

the unit is now at an rv repair in ocala, fl. hoping they can figure out why i lost the levelers, stairs, gear vendor as well the exhaust fans. air bags now seem to be fine so who knows.

str8strm · 11-11-2007, 08:11 PM

are very sensitive to the fluid level. they take ATF and are a major pain to refill. Our tank is located at the back of the doghouse under a wiring loom. My husband says he will eventually cut a little access door. If you call gear vendors they can talk you thru some tests to eliminate problems---they were very helpful----we had to "bleed" our system 3 times with the drive shaft disconnect at 35 mph and got another 2000miles out of our set up but now are gonna go for a reman unit. But having a gear vendor unit is great -- we run about 600 rpm less saving wear and tear on the engine and decreasing the cabin noise. D

buckwheat · 11-11-2007, 08:56 PM

Levelers, and stairs, and fans, oh my! (Sorry, couldn't resist, Wizard of Oz was on tonight!) Wpapke, sounds like you got 12V DC fuse or relay problems. All of these systems come off the main auto battery (except for fans that come off the 12V coach distribution system, but that system can be cross connected to the auto battery). The short in your instrument panel may be causing/caused by problems in the stairs and levelers. Maybe it's time to pull the panel and start looking. Label every wire before you disconnect it, and be aware that the indicator housings were attached to the dash panel using some sort of hot glue. The original crimped connectors and star washered nuts come loose over time, tighten everything, especially ground connections. Good luck, wish you lived closer to Cullman, AL, I'd pop over to share some beers and splice some wires!

wpapke · 02-04-2008, 06:25 PM

Thanks to everyone for their input. Been in the hospital off and on for the last 2 months so the airstream wasn't my biggest concern. The bags won't stay up past 60 or 70 lbs when I'm driving but go up to around 85 stationary. They also bleed off when I stop over night. From what everyone says I suppose the check valve is shot. Also found everything electrical was connected to a short behind the service panel in the nose. The compressor lead had rubbed and made an intermittent short. I would have never found it but a wrench (dean) at American Pro found it and fixed it. Now he has to replace the check valve and give me a 6 gauge hotwire through a relay. Many thansk for all the suggestions.