OK, so for a while now, we'd been keeping the air system pressurized using an add-on air compressor connected to the air system. It's worked quite fine at keeping the bags full and a decent job of maintaining a minimal amount of level (assuming the spot is fairly level).
That pressurization is also what gave that air-hose the opportunity to leak while we're standing still here rather than on the road (definitely a good thing).
My question is this, should I continue to do that?
Is it better for the bags to stay full and the suspension be operating as it's designed when we're stopped? Or is it better to let the system depressurize and let the bags deflate and just sit on the stops?
We're going to be living in this full-time and constantly getting in and out and moving around in there. I'd like to do what is best for the health of the bags, and keeping them full seems to be a good idea; as that is how they'd be in the real world running nonstop all day everyday. I'm also not sure if it's good for them to deflate and just sit there empty.
In addition, I feel that if the air system actually has air in it, then condensation/water can't get in and stay there; assuming I drain the tanks of course.
So what are your thought? Is it better to keep them full or empty? I really don't mind running the additional compressor and it does a fine job keeping the system pressurized, only running a couple of times a day to keep things at about 100 psi; and is the reason I bought it in the first place.
Thanks
George
My air bags stay up for months, now that they are all new. I'm far happier keeping them inflated and the bus off the bump stops. Letting the bus down onto the bump stops can put a lot of torque into the chassis, I've heard tales of windshields cracking etc.
Brian
The P.O. of our bus defeated/unhooked the stock leveling valves. The airbag system was then replumbed to the dash with 1 valve for each corner. I have only had to add air twice in 10 years now. Even thn it was only 2 or 3 LBS. Hard to believe but that's the truth. I've read that many times that the deflating air bag "syndrome" can be traced to the stock leveling valves. One bonus of what the P.O. did is the ability to use the bags as a poor man's leveling system. Our system was done with 1/8" line and I got tired of how long it takes to air back up. I just use "lego" style blocks. Fast and easy. Another advantage is the ability to "fine tune" your ride. With the 6V92/auto change the rear ride height is very critical due to a shorter driveline. Through trial and error I keep 80# in the rear and 60# in the front.
Don & Sheila
Our Prevost came with the levlow system. When we park, I use the control valves to level up the bus and then place wood blocks under the rear engine cradle and frame (4 points) because the rear will leak down in a few days while the front stays up and level for eternity. This keeps us level and solid when parked for longer than a few days (usually by the month or longer) and the bags aren't crushed from being deflated. We also have a portable compressor built into the area behind the front bumper that I can turn on to pre-air everything before firing up the diesel so we can get moving faster. I originally installed it to keep the bus leveled while parked, but I couldn't adjust to the sound of it coming on in the middle of the night. It usually only comes on once a day when parked like that though.
Will
George we leave ours aired up all the time 70 lbs in front and 80 in back while driving unless a long tipped road then I adjust to the tilt and so on. When parked we adjust to level at a campspot each corner. I have it plumbed to each corner through paddle valves. When we are parked at the ranch I leave it on one side full and the other side at 20 front and 30 in the back because where I park the bus has a tilt to it to drain water away from it. Never had a problem leaving air in it. Some drop it down because they don't care for the floating feeling while walking around in their coach when parked. Our's is pretty stable either way.
We also have a compressor that when we get ready to leave and need to adjust air before we get on the road from campground then I just turn a 1/4" ball valve and start the extra compressor we have in the bay and let it fill the brake system and then adjust the bags if needed to travel without running the engine.
You should be fine as long as you drain your tanks because shop compressors develop a lot of water and slug that will push through the system if you don't.
Dave5Cs
Same as Tom. I replaced the leveling valves, airbags and installed new lines. They never deflate now, but the longest the bus has sat is maybe three months or so.
Well, as the temps have continued to drop over the last few weeks, I find myself asking this question again, under a different context.
Should I be keeping my bags full when it's freezing and below outside?
The compressor I use does develop some moisture in its tank, that it eventually pushes to the main wet-tank side and occasionally to the dry-tank side.
I try to drain the tanks about once a week. When I do, I get a small burst of water mist from the (external) compressor tank, a second or two burst of fine white mist from the wet-tank side purge, and sometimes a burst of white mist on the dry-side tank.
I hardly get anything out of the aux tank (under driver's seat) or back tank unless I neglect to empty the other tanks for a while.
My question is two fold:
1) Am I harming by bags by using them (with us moving around inside) when it's below freezing outside? My initial inclination is no, since these things would've been installed on a commercial vehicle operating at well below freezing, but I want to make sure.
2) Am I doing harm to my air system (valves, lines, etc) doing so?
I also assume that I can't possibly be getting all the water out of the system entirely; and even if I do, the first time the compressor kicks on, it just puts more in. So now freezing water is a possible issue.
I've seen posts (here and elsewhere) about using air-brake line antifreeze. My concern with using this stuff is that a lot of people warn about it being bad on valves and especially on air-bags. Is there a recommended brand that doesn't cause these problems?
Another thing that I've noticed is that when the temps are relatively warm out (+50) I can hold air in those bags for hours at a time and the compressor only kicks in about 2 or 3 times a day. When the temps drop as low as they have been (<30), that seems to drop off precipitously and I notice the compressor running more and more frequently, sometimes as often as every hour! I suspect a valve is sticking, or maybe air is somehow escaping around the bags as they get cold and we move around, but I'm not sure. Any thoughts on that?
My suspicion of a valve sticking is due to hearing one of the (what I believe to be) leveling valves stuck open with a slight hiss. Tapping the metal bar next to it (what I believe is the leveling mechanism) both increased and then eventually stopped the sound. I have not, however, heard any hissing when listening to it now, even though it's requiring a top-off once an hour.
As always, thanks for all the help and advice.
George
I use a small inline air filter for my on-board electric air compressor: http://www.harborfreight.com/mini-air-line-filter-68225.html (http://www.harborfreight.com/mini-air-line-filter-68225.html) It works well, and self-drains when the pressure drops. I also ran a drain line and valve from the electric compressor so I can easily drain it along with the bus's four reservoirs. If you do this, you won't introduce any extra moisture into the bus's accessories air system. (Just don't use rubber air hose - it eventually leaks! Now it's all DOT 1/4" nylon air line and DOT fittings: no more leaks.)
John
First a disclaimer: I know about Prevost systems and that is it. So take the following comments with a grain of salt if they do not apply to your coach or how you use your coach.
In general the continuous use of an auxiliary compressor has proven on a lot of coaches to be a very poor way to compensate for a needed repair. It is like taking an aspirin for a brain tumor. The real need is to fix the leaks that cause the suspensions to lose air. That may sound to be an expensive answer to deal with a problem can can be managed for free using campground electric to run the aux compressor. But it is not free. First, the leak is going to get worse to the point the compressor will burn up or not keep up. Actually if the compressor would quit running you might be better off because rarely does an aux compressor installation include a means of drying the air. Rarer still is the owner that routinely drains the water trap even if one is installed, or the aux air tank.
Once water starts migrating through the system, and especially complex systems like the Prevost has the Norgren valves, leveling valves, protection valves and check valves really start getting internal corrosion and damage.
If you are sitting on a level site, just dump the air in the suspension and turn off the compressor. Internal to the air bags are bump stops and it does no harm to allow the coach to sit all the way down. For 25 years I have done that. Cut an air bag open and you will see doing that is OK.
If you own a Prevost with the level low suspension depending on the vintage the loss of aux air pressure may on early coaches cause the valve that retains an open path between the tag axle air bags and the drive axle air bags to close, and the air in the tag axle air bags to vent to atmosphere. Later model coaches (around late 95 or 96) used a different system logic and when the key was off the three five port Norgren valves went to the normal position and locked air in all the air bags. So if you coach is leaning or settling down it could be a loss of aux air pressure, or it could be a leak in the suspension system from the 5 port Norgren valves all the way to the air bags and their associated fittings. It is not a big deal to have a leak free suspension, but it is a serious big deal if you allow water into the system, especially if temps go below freezing.
George
"Heet" is a good one but you only need that if you are frozen up and need to move the coach or drive somewhere. If your bags don't fill because of ice and you need to fill them. Sounds to me if your compressor is always coming on there is a leak somewhere or a check valve that is not closing or needs replacing. Truckers have been using that stuff for many years without any problems from it. Other than with "Heet", don't ever spill any on your hands or pants.( Don't ask me how I know that). Old timer told me they would just use rubbing alcohol, but I would think that would mess with any rubber seals or parts and dry them out. Not good. If you put the Filter in that Iceni John was talking about that should keep the water out as long as you drain it or get the one with the automatic one.
Agree with Jon if you think you are getting any water or oil through that system you really need to drain the tanks more or even pick a day when your away and leave the drains open so it can run out. If you are getting spray out of them , you are not really draining them. The air is pushing some out but really going over whats in there and just letting wet air escape.
Dave
Heet is methanol. Aka methyl alcohol or wood alcohol. It is, according to its MSDS, incompatible with rubber.
What else would you suggest then because when you talking to trucker that's what they talk about using and say no problems. ???
He was asking what to use and most including myself said ideally to drain his tanks regularly and either have an airdryer or a filter before air entered the system to begin with. Deicers Heet and CRC has been used for years and yes it is not the best for rubber but take a long time and should not be used more than a few times before fixing what ever is causing the problem.
Isopropyl alcohol is a major ingredient in "gas dryer" fuel additives. In significant quantities, water is a problem in fuel tanks, as it separates from the gasoline, and can freeze in the supply lines at cold temperatures. Alcohol does not remove water from gasoline; rather, the alcohol solubilizes water in gasoline. Once soluble, water does not pose the same risk as insoluble water, as it will no longer accumulate in the supply lines and freeze. Isopropyl alcohol is often sold in aerosol cans as a windshield de-icer. Isopropyl alcohol is also used to remove brake fluid traces from hydraulic braking systems, so that the brake fluid (usually DOT 3, DOT 4, or mineral oil) does not contaminate the brake pads, which would result in poor braking.
PS. Air lines are not rubber....they are synthetic material.
PSS. I would also fix the leaks...as a priority.
Once I replaced the leveling valves and bags and air lines the bags stay up for at least 4 months. I've never not ran it longer than that but I'd bet money they would stay up for years now.
They used to deflate 30-60 min after shut down. Apparently for many years like that. The old bags showed a lot of wear from being deflated over and over and over. Creases were worn through the cords from where they folded down each time. I don't think they are made to ever deflate. If you left your tires go flat every time you parked your bus for an hour or more you would expect them not to last as long. Just my opinion but I'd fix the leaks. They should stay up without an air compressor. From my personal observation the repeated deflation did cause harmful extra wear on the airbags.
I do not disagree with Scott's observation relative to his coach, but all coaches are not alike. An older Prevost with an air tight suspension system will still sag in the rear if the aux air pressure drops below about 30 / 35 PSI because the 3 port Norgren valve between the tag and drive air bags will dump tag axle air. A simple solution instead of using wood blocks is to put a pipe plug in the exhaust port on the Norgren valves that are on the frame between the tag and drive axles. That will prevent the loss of air pressure so if the rest of the suspension in the rear is leak free the coach will not settle.
However, that change will not allow the lifting of the tag axle.
As to harm to air bags, some may get damaged by allowing the coach to be lowered all the way down. The ones used on all my 3 coaches never suffered any ill effects from having the coach fully lowered. Due to the configuration of my driveway in fact I actually have to drive for 50 feet or so on fully deflated air bags when entering my garage. Obviously I drive very slow but there has not been any consequences from doing that. As a preventive maintenance I change all my air bags every ten years. Regardless of condition. I throw away perfectly good air bags because over the last 25 years of Prevost ownership I have determined from that age on I could begin to have issues and I am not willing to risk any while on a trip.
Thanks all for the great replies! Very useful info indeed.
Well I finally lost the battle last night to try and keep the bags full. The compressor was coming on more and more frequently (to where it eventually was coming on every 45 minutes). So I decided to cut my loses and let her settle on the stops. I shutoff the compressor, and within a few hours, we dropped the 5 or so inches down. Plus with what Dave has said about how I empty my tanks, I'm concerned if I'm emptying them correctly. I've always thought that I should blow some air through the drains until the watery mist is just air. I do that two or three times (on/off/on etc), until there's no mist. From the sounds of what Dave was saying, however, I need to occasionally completely empty the tanks of air and let gravity empty them out. That will be an occasional nuisance, so I have to figure out how to deal with it, long term.
As far as the leak, I have no doubt there's some sort of leak. But it's not a constant one (i.e. I don't think anything is necessarily broken), it's a highly variable one that only manifests when it gets this cold. When it climbs back up to the 40s+, I have little doubt she'll hold air in those bags for hours. I also have no... aspirations that I'll ever be able to hold air in there for days, weeks, or months at a time. I realize every coach is different, but in looking at what I saw underneath this coach, a few months ago, I can not imagine any way that system was ever designed to be that air tight. Heck, I wouldn't be able to get a Mylar balloon to hold air for that long, I wouldn't expect a complex series of lines, valves, switches, pumps, drains, manifolds, bags, etc to do so. That being said, I'm perfectly content if I have to fire up the compressor once or twice a day for a top off. Where things go south (or is that north because it's cold :D) is when it gets really cold. Something is changing and more air is somehow escaping. I cannot hear it while I'm outside and I really don't want to go crawling around under there in 20 degree weather ;D So I suppose it'll remain a mystery for now. I do intend on replacing whatever looks worn or old with new(er) at her next annual :) (within reason of course). I also strongly suspect the leak is in the suspension system, because when I had that brake line leak a few months ago, the system had completely depressurized, but the bags stayed fairly full for a couple of days (it was warmer then), but last night it took less than 5 hours to be sitting on the stops. I strongly suspect that the "leveling" valves are the problem. I presume that as we move around in the coach, they're struggling to maintain "level" and purging too much air out and not closing correctly or quickly enough, and thus draining the bags. Does that sound feasible?
On my next visit to the local friendly mechanic, I plan on asking him how they might be defeated (hopefully temporarily) so as to not bleed air.
Thank you John for the tip on the water separator. I had no idea they there this reasonably priced. I'd looked at "air line driers" but they ran in the hundreds of dollars. While they probably would work better in a professional type setup, these little water separators might just be perfect for my "once in a while" needs.
I'm really hesitant to use things in the air system that could further deteriorate the bags. After looking into these dryer products, all use some form of alcohol, which does deteriorate rubber. It seems that methanol (air brake line dryer) is more detrimental than iso, but neither is exactly good, at least in liquid form. I don't know what all in that air system is rubber, but I suspect at least the bags are. They're probably ok to use occasionally, and certainly a necessity if you're stuck somewhere with frozen valves; but for sitting around in a rv park, they may be overkill. I'll see how successful I am with the water separator mod, first. I'm also going to look into one of those iso based line dryer add-ons (for when we're driving the coach in freezing weather). In vapor form, I believe alcohol is much less damaging.
Anyway, thanks all again for the very useful info. I've got some additional things to think about, and I suppose some shopping to do, lol. I wish we were still back in KC, there was a harbor freight 5 minutes away from us. Amazon seems to have those separators, but they're more expensive and have so-so reviews. I suspect it'll be a bit of trial and error till I find one that works and doesn't itself introduce a leak :)
Thanks
George
George just get you some cable pull drains. One for each tank. Unscrew the drain that you have to open by hand and install the pull cable drain in it's place. Mine were 1/4 pipe thread. I would bet yours are also. Run the cable out to somewhere where you can reach it without have to go under the bus to use it. Have something to hold it open and let it drain good every so often after driving somewhere. If it is from the shop air then yep get that dryer in there. ;D
Dave5Cs
Hello George-- When i park my bus I prefere to keep it at the normal ride height or close to. I feel it is better for the bags. Also the rubber bushings inside the radius arms are tightened when the bus is at normal ride height, so anything out of that position and the rubber bushings are trying to move the body and axle back to that neutal position. I would think over long period of time this would have an effect on rubber bushings. ( I believe GM and MCI have same type radius rods for axle alignment) I accomplish this with blocks, short pieces of 8X8 with a few shims. The bus is parked in same spot so pile never changes. As far as drain points I added 12 volt air solinoids (6) at drain locations to switchs near driver seat. I knew I would not climb underneath as offen as I should to drain. It happens on a regular base with switches. Solinoids from Princess Auto $25.00 each --rated at 140psi
Larry B
Quote from: Larry B on December 31, 2014, 08:10:11 PM... As far as drain points I added 12 volt air solinoids (6) at drain locations to switchs near driver seat. I knew I would not climb underneath as offen as I should to drain. It happens on a regular base with switches. Solinoids from Princess Auto $25.00 each --rated at 140psi
Larry B
Or for simpler and cheaper (and maybe more reliable??), you could put in a plain 1/4" NPT thread coupling to 1/4" DOT nylon tube instead of the on-tank drain. Then put a plain 90 degree twist valve someplace easy to reach on the end of the DOT tube. The water/crud will settle to the low point in the tank and be pushed out the remote drain. All mechanical, no electrics - simple.
With freezing weather all metal shrinks and hot air pumped into a system the air turns cold all buses leak more in freezing weather and I am not a big fan of the cable pull drains
Like Bruce said just remote mount the drains in a easy spot and then use the little Propane tank bleeder valves 4 bucks each, you need to enlarge the bleeder hole on those but they work like a charm
:o If Jon can keep a Prevost leak free a GM should be a cake walk I remember when Prevost said they were changing from the Humphrey valve to the less trouble free Norgren valve boy did they miss that one
Quote from: luvrbus on January 01, 2015, 04:24:24 AM
... I am not a big fan of the cable pull drains
My issue is the they work like a charm when you pull the cable. The problem is that they often stick (I'm guessing on a bit of trash or sludge) when you're trying to get them to close. Sometimes it takes a couple of tries of pulling them and letting them "snap closed". IMO, just not a perfect system.
Quote from: luvrbus on January 01, 2015, 04:24:24 AM... just remote mount the drains in a easy spot and then use the little Propane tank bleeder valves 4 bucks each...
I like this thought because I don't want anyone to say "oh, my drains are too hard to get to, I have to kinda half-crawl under my bus and it's raining, I'll do it tomorrow .." And tomorrow turns into next week, and then it's been a month, and before long it's a couple of months. Not good - get a simple, reliable system to drain, we all need it and we need to drain those tanks.
Happy New Year everyone! ;D
I have several 12V solenoid type LP gas valves that should be rated for 300 PSI. I wonder if I can use them for drain valves instead of having to slide underneath all the time? Even setting on blocks, I don't like releasing air from anything while I'm 'down under'. Any opinions on this use of the valves?
Thanks, Will
I forgot to add-they have 1/4" female pipe thread fittings in and out.
Well then I aman army of one because I like the cable drains. Never had a problem with them sticking and like Bruce said just give it another tug. I like your idea Clifford but on my 5c the two tanks are in the front wheel well in the middle, so if I ran copper 1/4' line from the drain on the bottom of the tank with a drain on the end to get any slope on it 1/4 per foot it would have to be 6 inches off the ground by the time it got to where I could reach it so wouldn't work on mine. My luck I would catch it on a curb and rip out the tanks, lOL :o
Dave5Cs
A remote drain does not need to be lower than the tank. It just needs to leave from the bottom of the tank. I use this setup on my service truck and works great. I have elbows installed on the bottom of the tanks with a rubber hose run out to the edge of the box with a quarter turn ball valve with another elbow so it points at the ground. The one on my main air compressor actually is above the bottom of the tank by about 6". It is so easy to reach down about knee level, turn the valve, let it spray out the water and close it! Done! :-)
Also, you can leave it open to completely drain the tanks....
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Please use methyl hydrate in the air system for antifreeze purposes if you choose. Isopropyl isn't for the job.
Air systems leak worse in the cold.
The best defense is dry air 24/7/365. Catch the moisture before it gets in there
Bags up or down, environmental decay of the material is our problem.
Happy coaching!
buswarrior
So what it sounds like to me is ...if I were to eliminate my level valves my bus would stay inflated....as long as I installed manual valves to adjust coach... My lines are new and my airbags are new.... I can't hear air leaking ... Overnite coache is sitting on stops.....
Or renewed your leveling valves...
Happy coaching!
buswarrior
Quote from: Dave5Cs on January 01, 2015, 01:32:09 PM
Well then I aman army of one because I like the cable drains. Never had a problem with them sticking and like Bruce said just give it another tug.
Dave5Cs
Lol, sorry to break the news to you Dave, but you can't comment on this thread. You live in California, where it never snows, and rarely rains. So you don't have mud and slush to foul them up. Basically your cable drains are living in a natural museum. So yeah. They should work well. The rest of us that have (or had) buses, usually use them in less then ideal conditions. Hence why they sometimes have issues.
;D ;D ;D
And for those of you who don't know how Dave and I roll, I'm guessing he is chuckling just as much reading it, as I did writing it. That is a tongue in cheek explanation of why they might work for some and not others.
Happy New Year! May this next year be filled with cheap fuel and many happy times.
No, No,No my OK friend John, yours might have clogged up from torn up road tar if yas know what I mean, LOL,
Ok you got me there Dang-it. you were the only one to catch that!...But I still have a lot of old Camel Dung I haven't got out of the system as well as the Tailings from the Gold Bars that were hauled in the sand from Aramco.
Yep I almost lost my keyboard when I was reading it. Lemonade doesn't work well in it as you know.
Take care you Buslessnut, ;D
Dave5Cs
Earlier in this thread one mentioned the effects of letting a car sit on flat tires and what it would do to the tires. This is a relatively true state however the analogy is incorrect. If there are bump stops the bags will still have some air in them, and the weight of the bus is not on the bag but on the stops so there is no additional stress on the bag. A tire without air is no problem if there is no weight on it. Check the spare in a lot of cars. That's my thought anyway. Happy New Year all. Don
Don I was thinking the same, just makes sense
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After I removed the auto leveling system that is on the bus and changed to my manual 4 corner set up with new bags it never looses any air . Holds at what ever air pressure I set it at , no power required just push in to add air or pull out to decrease air
dave