Air bag information from the horse's mouth

Vegasdan · 03-09-2010, 02:32 PM

My 01 Tradewinds does not have an air bag dump control. I should say it had one but the former owner had removed it. I have been concerned about this as my air bags are always inflated. I called Freightliner of Las Vegas today to ask when I could bring in my coach to get the control put back in. The RV service tech told me that it was a good thing that I did not have one!! He said that air bags were never meant to be cycled, inflated and dumped. He said that is the number one reason for air bag failures. The constant flexing during the process of inflation and deflation results in crimping of the material and eventual failure.

madrone · 03-09-2010, 04:39 PM

I made the mistake of storing my Luxor for several months without dumping the airbags and putting it on the jacks on my Oshkosh chassis (later became Freightliner). When I returned and started it up as the air reinflated the airbags it
blew the leveling valve and arm completely off! Repair about $550, I will not be making that mistake again. You might consider getting a second opinion, I think truck
and RV service are two different animals for airbags.

Jim Stewart · 03-09-2010, 04:45 PM

I think the serviceman is shining you on or stupid!

azloafer · 03-09-2010, 05:39 PM

Quote:

Originally Posted by Vegasdan

My 01 Tradewinds does not have an air bag dump control. I should say it had one but the former owner had removed it. I have been concerned about this as my air bags are always inflated. I called Freightliner of Las Vegas today to ask when I could bring in my coach to get the control put back in. The RV service tech told me that it was a good thing that I did not have one!! He said that air bags were never meant to be cycled, inflated and dumped. He said that is the number one reason for air bag failures. The constant flexing during the process of inflation and deflation results in crimping of the material and eventual failure.

There is no actual switch marked "air Dump" in my
coach, BUT there is a way to do it. This is from
Freightliner:

You have no air dump switch, but your suspension
has an auto dump that works in conjunction with your
jack system. It is not imperative to dump the air bags
for storage or parking because the coach will settle
on its own. On the other hand, If you feel that you
want to dump it you can always manually lower the
jacks “just enough” to activate the bags to dump. Joe

EngineerMike · 03-09-2010, 05:43 PM

Jim- its hard to tell what you really mean by that

Dan- Madrone & Jim have a point. Air bags are intended to be used. That's why we have a dump valve setup. Air bags have a finite life; they are built like tires w/cord reinforcement, but the rubber will wear out over time. I'm figuring maybe 8 years is a good time to replace them for reasonable safety factor, tho I'm sure there are lots of bags out there w/much more time on them than that. They have a rubber bumper inside made for setting coach on; most truck bags don't have that bumper (you can order the same bag w/or w/out the bumper per the end use req'mt and most truck applications don't use it). If you have never changed the bags, yours would be about 10 years old now; they are not too tough to change for a well heeled DIY'er, and shouldn't cost too much if you have the shop do it. While they are in the neighborhood monkeying w/blow-off valve assemblies might be a good time to do both.

Vegasdan · 03-09-2010, 05:50 PM

Well, first of all I didn't talk to the "truck service" I talked to the guy at Freightliner who is in charge of their motorcoach service. I knew this would get alot of comments about pros and cons of dumping, but mine was removed for a reason, obviously. I'll call Gafney and see what they say.

majfrizz · 03-09-2010, 06:01 PM

When I was at Gaffney earlier this year for the Boot Camp class this subject came up. it was suggested when you store them for the winter, get a couple of 6X6s under each jack, drop the jacks on the wood blocks. they said this relives the pressure on the bags just enough so they can breathe.

Vegasdan · 03-09-2010, 06:34 PM

Quote:

Originally Posted by Jim Stewart

I think the serviceman is shining you on or stupid!

I would think if it was the other way round and he tried to talk me into spending a thousand bucks on something that didn't make sense to me, I'd consider he'd be "shining me on" but to turn away work? Doesn't make sense, especially in Vegas where auto and truck service people will tell you anything to make a buck.

tboss619 · 03-09-2010, 06:34 PM

whn you go back to the service man who fed you this bunch of bulls,,t ask him then why do the third axles on dump trucks have a way to lift the xl from the ground. ,,for 15 years I not only repaired air bags on xls but I designed several systems using dump vlvs to deflate the lift xl...The leveling vlv you are speaking off is located on the xl where the air bags are and they are very easily changed and they arent very expensive. dont go to the dealer to purchase it google velvac and they will tell what you need ,,there is only 2 small bolts that hold the on and there is an adjusting arm to attain the rite ride height..if you have any questions pls feel free to post it here..it takes longer to get under the rig than it does to change the vlv..Im just saying,,,,air bags are made to withstand the punishment of the load ,,our trucks hauled abt 20 tons and they were inflated and deflated several times a day,,,Inside the air bag is a rubber dome for the weight to sit on while deflated so they are made for this purpose...the vlv will come with complete instructions as how to change it ,,,so put your money in the fuel tank and go on a trip some where...the vlv is very easy to find just trace the air lines from top of the air bag and it will lead you to the vlv.it has two air lines ( with compression or push pull connectors holding the air lines )) attached to it with a long arm ( abt 10 inchs lond ) attached to it..if I remember correctly with my old 68 yr old brain it takes a 7/16 inch wrench to change it out.. If your not familuar with a push pull connector I can walk you thru iy its very simple to do ..so go for it my friend and I will be glad to help...

Jim Stewart · 03-09-2010, 06:35 PM

Sorry Mike at times I confuse myself!. I meant as if the serviceman's answer came from a politician. "The American Public is in favor of the Heath Care Plan, they just don't know it". The serviceman was giving an answer that he did not know to be true or he was just lying because he thought no one would know the difference, like a politician. (Moderators, please no warning about politics, just using it as an excellent example).

How many times have you heard "I've never seen that before and I have been doing this for 20 years" when you know it is a common problem and he has had to have seen it before. I do not know why service people feel they have to do these types of things. My Brother said he used to work with a Guy who lied to stay in practice, can't believe he wasn't a serviceman!

Vegasdan · 03-09-2010, 08:38 PM

Like I said, I'll call Gafney and talk to them. They should throw some light on this and then I can take action.

Wayne M · 03-10-2010, 09:27 AM

Please let us know what Gafney has to say.
Thanks.

Vegasdan · 03-10-2010, 12:43 PM

OK, this horse was wrong! (The guy at Gaffney said something about bulls**t). Gaffney says my coach has an auto dump that dumps when the jacks come down. The hole that is there was for a toad brake control probably. Mystery solved.