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Old 03-12-2020, 07:03 AM   #1
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Help, Air bag suspension leaking?

Good morning. I recently purchased a 2005 International model PB10500 12 passenger handicap bus. When I first looked at it, the fenders were noticeably low on the tires. I asked the seller if the air bags needed to be replaced. He stated that when buses sit for awhile they will leak out. I verified this with 2 different reputable sources. I bought it, drove it home for 2hr30min and noticed the air pressure release valve was releasing air every so often as it normally does when the tanks build to optimum pressure. It held air overnight and for most of that day. Come evening, the bus was sitting low again. Anyone have any issues like this before? Any ideas on costs or repairs? Possible to repair myself?
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Old 03-12-2020, 08:28 AM   #2
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Once the system is charged up and the bus is sitting normally, chock the wheels, shut it off, set the brakes and crawl under the back. Something is bound to be leaking air. Bring a spray bottle of soapy water to help you find it.
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Old 03-12-2020, 09:34 AM   #3
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You're dealing with something that is 15 years old. You're bound to have tiny air leaks at every fitting, valve, etc.

The fact that you held air overnight and through most of the next day tells me you're fine.

The DOT says the max air leakage allowed without brakes applied is like 2 psi per minute, and you're well within that.

Truthfully, I think you'll be chasing your tail and opening up a pandora's box if you try and fix leaks that small.

Yeah, it's a pain to have to deal with a bus that goes flat after a day, but I'm going to tell you to get used to it.
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Old 03-12-2020, 10:21 AM   #4
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Originally Posted by Booyah45828 View Post
You're dealing with something that is 15 years old. You're bound to have tiny air leaks at every fitting, valve, etc.

The fact that you held air overnight and through most of the next day tells me you're fine.

The DOT says the max air leakage allowed without brakes applied is like 2 psi per minute, and you're well within that.

Truthfully, I think you'll be chasing your tail and opening up a pandora's box if you try and fix leaks that small.

Yeah, it's a pain to have to deal with a bus that goes flat after a day, but I'm going to tell you to get used to it.
I wouldn't sweat it at all. We have brand new buses that lose all their air overnight and older ones that hold air just fine. They all work and pass DOT inspections with zero issues. Just takes a couple seconds at startup for the compressor to play catchup.
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Old 03-12-2020, 12:09 PM   #5
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My air suspension goes down after a little while, probably fairly close to the 2 PSI per minute threshold, but once the air bags go flat it'll stay at 60 PSI for weeks, which is probably what my "Protection Valve" is set to. I expect the leveling valve is leaking (in addition to who-knows-what), it's like a $15 part and 30 minutes of DIY time to replace, and chances are high this is your problem too, if you want to bother fixing it.
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Old 03-12-2020, 02:13 PM   #6
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I have 2 busses with air suspension.. both ive had to replace the air levelling valves due to leaking. and one i had to replace the bags because there were dry-rot cracks and air leaked out after a couple hours.. the levelling valve on my red one has been replaced twice in the nearly 4 years ive owned it.. .. I found the leaks by mixing up a fairly stron solution of DAWN liquid. (real DAWN) and water in a spray bottle. did as another post suggested, ran the bus, shut it off, chocked the wheels, crawled underneath and started spraying everything air related.. the leaks were always revealed by soap bubbles..
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Old 03-13-2020, 07:39 AM   #7
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Quote:
Originally Posted by ermracing View Post
Once the system is charged up and the bus is sitting normally, chock the wheels, shut it off, set the brakes and crawl under the back. Something is bound to be leaking air. Bring a spray bottle of soapy water to help you find it.
this is how we did it in truck shops also dont be afraid to spray the leveling valve and hoses as the soapy water will not hurt anything under the bus
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Old 03-13-2020, 08:53 AM   #8
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Thank you to everyone that replied, I will make sure I do as stated and dig in deeper regarding this situation. If DOT pulls you over do they actually check for this type of thing? The school bus I purchased is being converted to an RV.
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Old 03-13-2020, 09:19 AM   #9
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Thank you to everyone that replied, I will make sure I do as stated and dig in deeper regarding this situation. If DOT pulls you over do they actually check for this type of thing? The school bus I purchased is being converted to an RV.
The only chances that would happen are:

If you are in an accident and they do a thorough inspection of the vehicles involved.

Your state DOT sets up a roadside inspection station where they go over the trucks with a fine toothed comb. If your rig is titled and registered as an RV then you should be able to skip these roadside checks.
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Old 03-13-2020, 09:46 AM   #10
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The only chances that would happen are:

If you are in an accident and they do a thorough inspection of the vehicles involved.

Your state DOT sets up a roadside inspection station where they go over the trucks with a fine toothed comb. If your rig is titled and registered as an RV then you should be able to skip these roadside checks.
Yes dot is mostly for commercial truck and buses. Only scale that I know of where RV is required to enter and weigh is in sturgis south Dakota
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Old 03-14-2020, 03:40 AM   #11
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Just to fill in another data point ... ours will usually leak out in 24 to 3 hours like yours does. Once the engine is started back up and the pressure goes over 80 PSI, the air bags inflate again. While using it as a moving van we have had to park it on a slanted drive a few times. As the load was slowly being removed, the leveler valve could be heard letting out excess air no longer needed to hold the frame up.

All in all, it is fine. While in operation with the engine running, there is no loss that is not handled by the compressor.


Perhaps some day I will go chasing down that rabbit hole with a spray bottle of soapy water.
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Old 03-14-2020, 09:06 AM   #12
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air bags can get worse and run your compressor to death they can get so bad it will not keep up.when your compressor runs it robs power and will have a effect on mpg. most will only leak slowly or a long time but there is no way to tell when it will blow out just like a tire. so the question is do you want to gamble with a flat air bag going down a mountain? in traffic? they get real rough to handle. changing air bags is easy just jack up the body, no need to even drain the tanks. if you purchase a new bag before installing it extend it out by hand [do not use air pressure] and soak it with a rubber preservative like armorall. i have changed many air bags and all leaks get worse over time. change it now when it is not a issue . some air bags seem to take a week to get . be sure to shop around or a good price. record the manufactures part number [eg firestone] as it makes it easier to find than the oem
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Old 03-14-2020, 10:11 AM   #13
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Quote:
Originally Posted by Graywolf View Post
Thank you to everyone that replied, I will make sure I do as stated and dig in deeper regarding this situation. If DOT pulls you over do they actually check for this type of thing? The school bus I purchased is being converted to an RV.

In the trucking world, what they will typically do is have you shut off the engine and listen for leaks, and watch the air gauge drop with a stopwatch running. As an RV conversion, which are typically exempt from such inspections, it probably won't be an issue as far as inspections go.


Quote:
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. . . . . record the manufactures part number [eg firestone] as it makes it easier to find than the oem

Several companies make air bags, you do *NOT* have to rely on any specific company/brand of air bag. Get a part number(s) for the old one(s), get some interchange numbers for other brands and keep these handy as you shop for replacements.
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Old 03-14-2020, 08:28 PM   #14
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Thanks again to all who chimed in. Many excellent points brought up. I am going to go ahead and order new bags just to be on the safe side. I started up the bus today to allow the bags to come to full inflation and after shutting it off the frame was back down around a few hours later. I noticed before I started it, my PSI was 0. I have never seen it that low before but maybe this is common? It usually sits around 30-40psi when left to sit without running for a few days.
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Old 03-15-2020, 12:53 AM   #15
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As I posted above, mine goes down to about 60 and generally stays there. It's not unheard of for some (many?) systems to go completely flat, even those that normally maintain some residual pressure. As long as the rate at which it goes down is within ~2 PSI/minute or less, you're within limits.
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Old 03-18-2020, 05:38 PM   #16
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My air bags go flat overnight, but there are "stops" that only let them go so far down. Most of the leakage is through the leveling valve, and not the bags themselves.
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Old 03-18-2020, 07:30 PM   #17
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hmmm. My last two air ride buses would leak down within minutes of shutting down the bus.
My current bus NEVER seems to leak down no matter how long I leave it.
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Old 03-18-2020, 09:02 PM   #18
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My air bags go flat overnight, but there are "stops" that only let them go so far down. Most of the leakage is through the leveling valve, and not the bags themselves.
That seems to be the case with our bus as well. I just am not ready to chase it down since it is not a real problem, yet.
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Old 03-19-2020, 12:51 AM   #19
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Originally Posted by Brad_SwiftFur View Post
My air suspension goes down after a little while, probably fairly close to the 2 PSI per minute threshold, but once the air bags go flat it'll stay at 60 PSI for weeks, which is probably what my "Protection Valve" is set to. I expect the leveling valve is leaking (in addition to who-knows-what), it's like a $15 part and 30 minutes of DIY time to replace, and chances are high this is your problem too, if you want to bother fixing it.
"protection valves" are only used on trucks that pull a trailer it only is in the brake system not air ride. i think you are thinking of the brake saver valve [yes look that one up] and it is set about 90 psi if it is going to 60 it needs replaced. i drive air ride trucks and i can return after a week off and find my air bags still full
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Old 03-19-2020, 12:56 AM   #20
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Originally Posted by Graywolf View Post
Thanks again to all who chimed in. Many excellent points brought up. I am going to go ahead and order new bags just to be on the safe side. I started up the bus today to allow the bags to come to full inflation and after shutting it off the frame was back down around a few hours later. I noticed before I started it, my PSI was 0. I have never seen it that low before but maybe this is common? It usually sits around 30-40psi when left to sit without running for a few days.
you have other leaks as air bags should quit leaking at 90 psi if the brakesaver valve is working. you are throwing money without really knowing what you issue is. your bags might be ok and after all that work be prepared to have the same issues. diagnose first then spend money
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