Heard a hissing coming from the passenger-side front tire well after shutting down the engine last week. Here's what I saw/heard:
https://www.youtube.com/watch?v=oMrQyfryTiY (https://www.youtube.com/watch?v=oMrQyfryTiY)
Bus takes about 10 minutes for the low-air buzzer/light to disengage, and that's only if I increase RPMs a tad for a few minutes. Is this something that can be repaired? Is a replacement required?
Thanks,
Ron
Time for a dish-soap/warm water spray to see exactly where the air is coming from.
....and yes, it is not normal.
Mark
Thanks Mark. Not sure if you could see it in the video (last bit), but it appears that the bottom lip of the top half of the airbag is dislodged, and I believe the bottom lip on the bottom half also appears to be unseated. But I don't know enough about these to really know what to look for or how to fix it once I find it.
Does it inflate properly when coach is aired up? If so, may just look that way when down. Has it ever inflated properly? Use soapy water spray or mechanic's stethoscope with the metal tip removed to verify it is leaking around air bag and not the air beam it is attached to or leveling valve or air lines to it. Air beam is the coach structure that top part of air bag is attached to. They have been known, pretty common actually, to develop pin holes from salt corrosion over the years and leak. The fix is to install block off plate on top air bag mount to correct it. Luke carries or can get the parts you will need if the bag is the culprit. It is not recommended to install block off plate on one side only, as the air beam provides added air volume and better expansion/compression characteristics to the system. By doing one side only, the coach will act like a car with one firm and one soft shock absorber.
Not enough info here. We need to know this:
1. Does that airbag ever inflate? If it doesn't then it might be unseated but that's somewhat rare
2. Have you physically gotten under there to move your hand around and actually find the source of the air leak?
3. When you're airing up, do you use fast idle? If not, then it's normal for it to take a long time to air up. Most old coaches need fast idle turned on or you manually holding the throttle to raise RPM's to get it it air up at a decent rate.
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Are those plated ? it looks out of place big time
Thanks everyone! Great questions. I'll try to get under there today to inspect further and answer some of the questions you've asked.
Very common to hear air sounds for a few minutes after shutting down - it can be as simple as the suspension was a little high and is being exhausted down to it's set point. As far as time to turn off the low air alarm, 10 minutes from a cold start can be quite normal. The test is called compressor recovery. To do the test, follow these steps.
Air the bus up to full pressure - 120 psi, the air dryer purge valve will exhaust. Let it set at full pressure until the suspension is completely full and the pressure gauge is not moving.
Engine off
Time test - observe the pressure gauge with brakes off for 1 minute - should be no observable pressure loss.
Time test - apply the brakes and hold them. Observe the pressure gauge for 1 minute - should be less than 3 psi loss after the initial loss from applying the brakes.
Engine on again, fan the brakes until the pressure reaches 80 psi on the gauge. Measure the time taken for the pressure to build from 85 psi to 100 psi. Should take less than 30 seconds or so.
Brian
I ran bevans6's suggested tests and made a video showing the 4 airbags up front when the bus is at 120psi. It took around 14 minutes from 60psi (where it was at when I fired up the engine) to 110psi with fast idle turned on. 5 more minutes to 120psi with fast idle off and revs up via the accelerator pedal. 9 more minutes running and pressure drops by 5psi. You can watch the video here:
https://www.youtube.com/watch?v=K_jmrJsXOoU (https://www.youtube.com/watch?v=K_jmrJsXOoU)
I didn't have a chance to definitively isolate the source of the leak today (i.e. soapy water solution), but it seemed the sound of the hissing was easily augmented when I prodded the misshapen top airbag on the passenger side front set. I figured I'd upload the video I captured today to see what I could check off the list. I'll tackle whatever the next most practical steps are next, per your suggestions.
Thanks!
Ron
Oops. Link was incorrect. Updated with the correct link. Sorry!!
Ron, it doesn't look like your air bags are even inflating. They should have much more air in them than that. They should look like this:
(https://uploads.tapatalk-cdn.com/20180207/f157fdd083d20922fb00354c08bc51a9.jpg)
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Passenger front back is seriously wonky too. Where are you located Ron?
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Quote from: Scott & Heather on February 06, 2018, 07:19:41 PM
Ron, it doesn't look like your air bags are even inflating. They should have much more air in them than that. They should look like this:
(https://uploads.tapatalk-cdn.com/20180207/f157fdd083d20922fb00354c08bc51a9.jpg)
Passenger front back is seriously wonky too. Where are you located Ron?
Thanks Scott. That's what I was guessing. I don't know much about how these air systems work in specific detail, but it would seem that if one or more airbags are leaking large amounts of air, the rest of the system will suffer. I see lower than expected performance in the rear as well, though none of those airbags seem to be more or less completely un-inflated like the front passenger side airbag (last of 4 in the video). Perhaps it's a leak in the air beam as has been suggested, but based on the fact that that one airbag is so off-kilter and that's where a massive flow of air is coming from, I would assume that's the obvious place to begin troubleshooting.
Please let me know if that's off base. Again, I'm going off of gut since I know very little about the specific mechanics of how these systems operate. If there's something I should be attempting to get that airbag re-seated/re-inflating (assuming that's the logical next step), I'd be very grateful for any suggestions/guidance you can give.
Ron
P.S. I'm in Northern Utah
Find out where exactly that air is coming from. It's enough that you will be able to feel it if you get your hand in there. You should probably jack it up and block it. Remove the wheel if you have the means to do so. Ultimately, you're going to have to do that to fix the problem.
You either have a hole (crack) in the front passenger air bag, or the air beam has a hole in it.
As far as how they work: The front and rear bags on the front axle are tied together with the air beam. The two sides are separate (i.e. they have two separate air beams, with two bags on each, Left and Right). The drive axle is set up similarly. Main difference is the drive axle uses larger air bags, and has a leveling valve on each side, whereas the steer axle only has a single leveling valve which fill both side air beams.
You have a major hole somewhere. Either in the front passenger air bag, probably in the upper lobe, or in the passenger side air beam.
BTW, here's a page with a bit of detail on replacing the front airbags: http://www.gumpydog.com/Bus/MC9_WIP/Mechanical/Steer_Axle/steer_axle.htm (http://www.gumpydog.com/Bus/MC9_WIP/Mechanical/Steer_Axle/steer_axle.htm)
BTW, you might want to consider putting you location and bus model in your profile so the rest of us have a better idea what we're dealing with when you have a question.
On a stock mc-9, the front air beams are connected together, so a leak in either beam, any of the air bags, or the connecting piping and the central leveling valve will make the whole front suspension not inflate.
Quote from: bevans6 on February 07, 2018, 09:40:33 AM
On a stock mc-9, the front air beams are connected together, so a leak in either beam, any of the air bags, or the connecting piping and the central leveling valve will make the whole front suspension not inflate.
The only connection between the two is the 1/4" line that comes from the T off the leveling valve output. But, yes, a large hole in one of the bags might affect the other 3, as it appears to be in this case.
Quote from: gumpy on February 07, 2018, 09:11:39 AM
Find out where exactly that air is coming from. It's enough that you will be able to feel it if you get your hand in there. You should probably jack it up and block it. Remove the wheel if you have the means to do so. Ultimately, you're going to have to do that to fix the problem.
You either have a hole (crack) in the front passenger air bag, or the air beam has a hole in it.
As far as how they work: The front and rear bags on the front axle are tied together with the air beam. The two sides are separate (i.e. they have two separate air beams, with two bags on each, Left and Right). The drive axle is set up similarly. Main difference is the drive axle uses larger air bags, and has a leveling valve on each side, whereas the steer axle only has a single leveling valve which fill both side air beams.
You have a major hole somewhere. Either in the front passenger air bag, probably in the upper lobe, or in the passenger side air beam.
BTW, here's a page with a bit of detail on replacing the front airbags: http://www.gumpydog.com/Bus/MC9_WIP/Mechanical/Steer_Axle/steer_axle.htm (http://www.gumpydog.com/Bus/MC9_WIP/Mechanical/Steer_Axle/steer_axle.htm)
Thanks gumpy. It sounds like I'll have to get the bus jacked up as you suggest since I can't quite reach the airbags through the wheel well.
So question guys, if he's leaking air that bad, how on earth is he getting 120 psi to the dash gauge?
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My friend and previous owner of the bus (owner of a truck sales company) says he's pretty sure his guys put in a brand new air compressor when they rebuilt the engine. Would that explain the healthy performance despite the leak?
120? I dunno. Sounds like something may be frozen, unless he lives in the south. Also, how long has it been this way? Has it set for a looong time and he just obtained it?
After watching your video again, I'm kind of wondering it it's not coming from the air dryer moisture ejector valve. That's a lot of air noise coming out of there. Can't really tell direction from the video. Do you hear the air dryer blow off when it hits 120 psi? If so, it's not the moisture ejector valve.
The line that feeds the air beams from the leveler valve is 1/4" and it's split between the two beams. The one coming from the compressor is much larger than that. Also, the suspension is the last thing to get aired up. It doesn't kick in until somewhere around 65 psi. So, it's definitely possible for the system pressure to reach 120 psi with a large leak in one of the bags. It's going to cycle rather quickly, though, as it is doing. Based on the fact that one lobe of the front bag is not inflating, my professional armchair diagnosis is on that particular bag having a hole in it.
Thanks Gumpy. I guess my specific question in response to your last post is whether or not this airbag position (picture below) is within normal tolerances. I wasn't able to reach my hand back there, but by using an extension stick I manipulated the upper bag and thereby augmented the sound of the hissing. Perhaps that's not enough data to make a definitive determination, but again, my question is this: is the seating/position of the upper airbag normal and expected in a non-inflated state, or is the airbag placement in and of itself a "faulty" position? Once I can get the wheel removed I'll probably have a much better idea of what the problem is, but it seems to me like the airbag is in a non-standard/working position.
(https://busconversionmagazine.com/forum/proxy.php?request=http%3A%2F%2Fsites.sora.do%2Fwp-content%2Fuploads%2F2018%2F02%2Fimg_0542.jpg&hash=8755a58033bccdd0d88084095a97200a6aa1ecdd)
When the air pressure drops, does it go to zero or stop or noticeably slow when it gets below 85 or 65? If it noticeably slows, then major problem is in air suspension. Check in that gap with a prybar and flashlight. Good chance of crack or hole there. Do any of the air bags inflate. You can hit them with a stick. They should thump like a tire. You can check the area with a small hose placed to your ear and probe around that bag. I'd consider using an earplug incase noise is very loud. Or mechanic's stethoscope without metal end attached. Very useful item to have down the road for noise and air leak diagnostics. Not too expensive either.
Couple of things ... the air suspension has many components that all have to work together. You can have a leaky or torn bag, a bag out of place or incorrectly installed, leaks in an air beam, rust holes in brackets, problems with valves, leaking fittings or pipes etc. It can be difficult to sort out the difference because the effect of leaks from any source have similar effects on the overall air system of the bus. Once you have a major problem, you have to really dig down into all the parts of the air suspension system and positively locate the problem.
It is not uncommon also to have several problems at the same time. You can have a corroded mounting plate that's not sealed to the air beam at one place and has damaged the bag itself in another place. Or a bag that's slipped out of position might have bent the mounting plate. There are a lot of opportunities for "combination" problems. Probably, most of those components probably were installed at the same time so if one is deteriorating, there's a good chance that others are also damaged or reaching the end of their design life.
In my opinion, you're going to have to work through all the system and check out all the parts themselves, their installation, and their effect on the other parts around them. My guess (WAIG) is that you have multiple problems now and making the system right is probably going to require changing some parts that appear to be working OK now but are worn or damaged or ending their design lives and are just ready to fail.
Thanks for the photo. It helps for people to see how the parts really look when they're trying to understand what's going on on a bus.
At this point I would get the bus up in the air, front wheels off, and find the leak. Poking at it from the outside is pretty much a waste of time until you get stuck in. The air spring can certainly look like that if it's on a missing bumpstop and fully deflated for a long time. Might be OK, might not be. AD2 purge valve kits are still available from Bendix, PN 287053N. I have one on my desk that I will install when it's warm again.
Brian
Brian is right. The air bag can certainly be compressed to this extent if there are no bump stop rubbers left.
Understand the upper and lower lobes are not individual bags. There is only one chamber in there, with two lobes. If you augmented the air noise by messing with the bag using a stick, it's most likely a hole in the air bag itself. The photo does not indicate a problem in the seating, though it is possible. I've had one that developed a leak in a seat over a period of time due to a pinch that occurred when it was installed. I've also had one that cracked in the lobe where it gets stressed because of the severe deflation such as you have there.
As Brian says, get it jacked up and get the tire off and then you'll be able to confirm where the problem is. I expect you'll be replacing that air bag, which may well be the best scenario.
If it is the airbag and you have to replace it, you may as well do them all. Save a couple of the best ones for spares but you will probably never need to use them.
Thanks for the detailed info guys. So about getting this behemoth in the air....
Here's my current (limited/likely incorrect/incomplete) understanding of the steps I need to take. Please feel free to copy/paste and correct any of these items (or add new ones):
0) Loosen lugnuts on any tire which will need to be removed while wheels are still on the ground (thanks Buswarrior!)
1) Since I can drive it, should I pull the front end onto some blocks or ramps in order to get the majority of the height I need?
1b) Chock rear wheels (thanks Richard5933!)
2) Stick a couple 20 ton jacks under either the axle and/or vertical frame columns as shown at the bottom of this post: http://www.busconversions.com/bbs/index.php?topic=31266.0;all (http://www.busconversions.com/bbs/index.php?topic=31266.0;all)
2b) Remove wheel blocks or ramps
3) Once airborne, stick blocking under the axle and/or vertical frame columns as shown above
3b) Lower jacks until bus rests securely on blocks
4) Find a big @$# breaker bar and wrench (or large 1/2" socket of the correct size) to remove lugs
5) Take a short moment to lament ever wanting to own a bus. Recall the visions of waking up in the heart of Banff. Shake it off. Plow ahead.
6) Remove wheel, set aside
7) From here I'm fuzzy. I'm guessing I can take care of the air system inspection/airbag replacement (if necessary) without removing rotors or anything else wheel-related?
8) Find any and all air leak sources, film/photograph, and return and report...
Any other tools I need? Any other steps I'm missing? Any misconceptions? I'm sure there are things I'm missing here, and to be completely transparent I am quite apprehensive about getting the bus up in the air, properly blocked, and ready for the real work. I'm not really familiar with the anatomy of the bus structure/body yet, so when I hear references to "bulkhead", "axle jacking points", etc, I don't have a clear picture in my mind of what those mean. If you can be gentle in explaining this like you would to a newbie, this newbie would be ever grateful.
Ron
I cannot comment much on the air bag replacement itself. But, however you get the thing in the air, you need to properly chock the wheels and block the bus so that it cannot fall on you. The jacks cannot be relied on to hold up the bus without proper blocking. Proper wheel chocks need to be large enough to hold the bus from rolling and not just the little things used to chock a compact car.
Quote from: richard5933 on February 09, 2018, 08:52:20 AM
I cannot comment much on the air bag replacement itself. But, however you get the thing in the air, you need to properly chock the wheels and block the bus so that it cannot fall on you. The jacks cannot be relied on to hold up the bus without proper blocking. Proper wheel chocks need to be large enough to hold the bus from rolling and not just the little things used to chock a compact car.
Ahh, thank you. I added wheel chocking to the list (1b) and clarified removal of the jacks on 3b.
were i you i'd pray for experienced help.
if you need a $1000.00 worth of tools/stuff to do a $1000.00 job...
A small diversion, but a necessary one...
The busnut who waits until the bus has been jacked into the sky by manual methods without having FIRST loosened the wheel fasteners on the ground...
Will be cursed with both stuck fasteners and a rim which is rusted to the hub so badly that no human physicality will remove it up in the air...
And down it all has to come so you can break it free with the coach's own weight and the brakes...
These are not the things that a regular shop sees, only busnuts get to experience the foolishness of wheels that have not been removed in years.
Another vote for proper annual wheel end service, if for nothing else than ensuring the #$^& wheels will come off when you get a flat?
happy coaching!
buswarrior
Quote from: buswarrior on February 09, 2018, 11:32:44 AM
A small diversion, but a necessary one...
The busnut who waits until the bus has been jacked into the sky by manual methods without having FIRST loosened the wheel fasteners on the ground...
Will be cursed with both stuck fasteners and a rim which is rusted to the hub so badly that no human physicality will remove it up in the air...
And down it all has to come so you can break it free with the coach's own weight and the brakes...
These are not the things that a regular shop sees, only busnuts get to experience the foolishness of wheels that have not been removed in years.
Another vote for proper annual wheel end service, if for nothing else than ensuring the #$^& wheels will come off when you get a flat?
happy coaching!
buswarrior
Amazing. Great advice, and such obvious hindsight in a realization that you saved me from having to make just moments too late. Adding to the list as step 0 now. Bless you for speaking up. 🙏🏻
You'll need something to cut the airbag bolts off as they will turn the whole bolt rather than coming loose easily, unless...... the previous service used antiseize. The heads of those bolts have funky heads that set in a recess on the clamp ring. They might start to loosen, then spin. You can't get pliers or a wrench to hold them. This is assuming you will need to replace one of more airbags. Otherwise, nevermind.
Thanks chessie4905. I'll keep an eye out for that, and return for your suggestions if I end up being unlucky. :)
One other thing to keep in mind is the fact that jacking up and supporting the suspension of your bus does not support the body of your bus. This tidbit of information comes to you courtesy of experience, ie: the school of hard knocks. After raising and supported the front of my MCI 9 at the suspension lift points and axle, I was disconnecting air lines to the suspension to address some leaks, all while working under the bus in some fairly tight conditions. Upon pulling a 1/4" line loose the body started to lower into the area I was occupying and it quickly became apparent I had made a serious error. Praising God for allowing me to squeeze out just in time before getting crushed. Been working on vehicles most of my life, but buses and air suspensions were new to me. The body needs to be blocked if you are working under the bus. Some have mentioned this in previous posts by providing instruction to place blocks at the bump stops, but MCI has 4 location (at least for the 9) designated to support the body and I am now in the habit of using those locations to support the body anytime I go under the bus. Just to summarize.... supporting the suspension and supporting the body are two different things, make sure you have the body supported safely if you are getting under your bus.
Quote from: csrddcd on February 11, 2018, 04:38:27 PM
One other thing to keep in mind is the fact that jacking up and supporting the suspension of your bus does not support the body of your bus. This tidbit of information comes to you courtesy of experience, ie: the school of hard knocks. After raising and supported the front of my MCI 9 at the suspension lift points and axle, I was disconnecting air lines to the suspension to address some leaks, all while working under the bus in some fairly tight conditions. Upon pulling a 1/4" line loose the body started to lower into the area I was occupying and it quickly became apparent I had made a serious error. Praising God for allowing me to squeeze out just in time before getting crushed. Been working on vehicles most of my life, but buses and air suspensions were new to me. The body needs to be blocked if you are working under the bus. Some have mentioned this in previous posts by providing instruction to place blocks at the bump stops, but MCI has 4 location (at least for the 9) designated to support the body and I am now in the habit of using those locations to support the body anytime I go under the bus. Just to summarize.... supporting the suspension and supporting the body are two different things, make sure you have the body supported safely if you are getting under your bus.
Excellent advice and kind warning, csrddcd. I will definitely be sure to block both to make sure I'm not the unwitting wearer of a steel corset.