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Old 10-25-2020, 11:36 PM   #1
Mini-Skoolie
 
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Question Air Ride Suspension Off Kilter

I'm looking for some advice on a potential problem with my air ride suspension on a 2007 IC 30' bus. The air ride is working, it's just not leveling both sides of the bus.

In April the dealership noticed the leveler valve was stuck, keeping one of the bags too full, so they replaced the leveler valve. We had not had any issues since then. However, yesterday I decided to go for a drive after not driving our bus for a week. As I was doing my pre-trip check, I noticed the passenger side was WAY lower than the driver side. I assumed the air had just been lost over the week. After starting him up, sure enough, the air bags filled up and looked pretty good. The passenger side was still lower than the driver's side, but I expected they would level out as I drove. I didn't notice any issues on my drive, but when I got home you could definitely tell the driver side was still higher.

This morning I checked again and they were still off. There was 3" of clearance from the tire to the top of the wheel well on the passenger side and 4.5" on the driver's.

My air pressure on the dash appears to be normal, with both tanks maintaining a steady pressure of 120 psi. I did notice on my drive last night that the air pressure seemed to be dropping closer to 90 psi on both tanks, then the tank release would happen and they would both immediately bounce back to 120 psi.

Before I call the dealership back and hope this repair is under warranty, do any of you have any suggestions on what I could look for? I haven't noticed any leaks in the air lines and I'm just curious why one side is lifting higher than the other. Is the passenger side air bag bad? I appreciate any suggestions!
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Old 10-26-2020, 12:11 AM   #2
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I seriously doubt there will be any warranty on a 13 year old bus. Check both air bags, make sure they match. Check air lines going to 'em for kinks, obstructions, etc. Check all the metal parts for anything bent, broken, damaged, missing, etc. Check the frame, hangers, mounts, air-bag pads, etc. These systems really aren't that complex and anything damaged should be somewhat obvious.
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Old 10-26-2020, 12:18 AM   #3
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Howdy Brad, thanks for the reply. I'm sorry, I only meant the warranty on the leveler valve they replaced in case it was faulty and causing the issue.

I've checked for leaks and didn't notice anything out of place, but I'll get back under and check really closely when I can. I just found it odd to be leaning and have just discovered this is apparently called air bag lean and happens more often in Freightliner vehicles. Learn something new everyday I suppose!
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Old 10-26-2020, 01:06 AM   #4
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Ah, yes. Leveling valve shouldn't cause it to lean one side or the other, typically these only have "Air In" and "Air Out" lines; both air bags *Should* get the same amount of air pressure, the system being T'ed at some point after the leveling valve. The most common failure of leveling valves is air leakage with age and wear.


I could see air bag lean being an issue if a vehicle is heavier one one side than the other, since both (in theory, at least) have the same air pressure. If by some chance the air bags don't have matching air pressures, then there's a problem that needs to be addressed.
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Old 10-26-2020, 01:53 AM   #5
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Response to air ride problems

My Crown had some problems with the air ride also. If you can get underneath your coach with soapy water in a spray bottle, spray the soapy water on the air bags, the leveling valves, and air lines. Any leaks will make bubbles. On my Crown the suspension would be very uneven the next day. Replacement of the leveling valve did not fix it. It turned out that the check valve had failed on the side that dropped. When you have a bad check valve (connected between the air source in your system and the leveling valve) as your air system bleeds down air pressure, the air in the airbags will pass through the leveling valve into your air system, resulting in uneven suspension. Since I replaced the check valve (the cheapest and easiest part of the air ride) after two weeks the bus still sits level. As for equal pressure, your gauges show what tank pressure is in your front and rear air systems. If you were to add 500 lbs of weight on one side of your coach, the leveling valve would allow more air pressure in the heavier side to again make the coach level. If you removed the 500 lbs the valve would let pressure out from the now higher side until the coach was level again. I hope this helps.
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Old 10-26-2020, 08:39 AM   #6
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mty carpenter bus has a slight lean to it.. one thing you *can* do if the slight lean is bothersome is install 2 leveller valves one for each rear bag and then level your bus accordingly.. the factory levelling system is a single valve and a simple 'T' that sends air to both bags based on the lever position.. the lever is normally set up to measure the center of the bus.. if the weight districution in your bus is heavier on one side than the other you can end up with uneven levelling since the same amount of pressure is sent to both bags..

-Christopher
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Old 10-26-2020, 10:13 AM   #7
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Thanks guys for the responses and information!

Brad - Yeah that was my thinking also. I've been researching YouTube and scrounging anything I could find about air bag lean and there's not much out there. About all I could find, and those were in short supply as well, was about the air leveling valve. It does seem like a fairly simple device; air in, air out. So I agree, I don't believe the leveling valve is my issue.

flattracker - Thank you very much for the detailed information. I will look much closer at the air line system, especially the supply going to the passenger air bag. And thank you for letting me know the check valve is the easiest and cheapest to replace, we're about out of funds at the moment and another trip to the dealership is not in the cards. We did add an adult changing table for our boys on the passenger side, but it's at most 200 pounds and had not caused any lean before.

cadillackid - First, let me say it is an honor to have you reply to my post! Not saying others aren't knowledgeable, but I have learned a TON reading other posts with issues that you have responded to. You are definitely a wealth of knowledge and I appreciate your time.

I had a friend that suggested we add a second leveling valve at some point. Our bus is a little different than most on here. Once COVID settles down, he will essentially be my daily driver as we have 2 boys that use wheelchairs for mobility and is the reason for getting him in the first place. My youngest has a wish through Make-A-Wish for a Magic School Bus and they are getting close to having us drop off RW1 to completely deck out the inside with new seats, lights, TVs, etc. This will help keep the boys occupied on our long medical trips to see specialists in Houston. Since I'm not sure how much weight will be added, I wanted to wait until that was completed before adding a second leveling valve.

All that being said, is if it is safe to drive the bus with the lean it currently has? My youngest son is also on the waitlist to get a service dog and we need to travel to DFW soon for some training. Do y'all think it will be safe to drive for a longer distance if I'm unable to find a leak?
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Old 10-26-2020, 10:27 AM   #8
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my busses are pretty much my daily drivers too..



safety - that really depends on what is causing the lean..

ie is the lean due to something underneath being rotted out , bent, or broken. ie the bag perch or spring perches up front (front spring issues can cause rear lean)..



if its weight related does the bus feel unstable and rock side to side or want to pull one direction when driven or cornering



or is the lean more of an annoyance



-Christopher
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Old 10-26-2020, 11:10 AM   #9
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curious, since on the subject

where does one get replacement bags?

never really thought about it till just now

might be handy to put this in the bus notebook
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Old 10-26-2020, 11:35 AM   #10
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True, I understand what you're saying regarding safety. The bus passed a full and thorough inspection in April and is where they found the issue with the old leveling valve and replaced it. No other issues were found and nothing is broken, rusted or bent that I saw. I'll need to get out there later this evening, I have my boys home doing virtual school as COVID would be a worst case scenario for us. I'll let you know if I see anything out of the ordinary.

The lean doesn't affect the driving characteristics that I can tell. It's not pulling to the right or causing excess roll during a turn, just something I noticed and found it odd. Originally I thought maybe the cooler weather was a factor (we just dropped from the 90's to the 60's with a cold front), but I didn't see how that would make the bus lean all of a sudden. Then again, I'm not a bus mechanic and stranger things have been caused by dropping temps and air pressure.
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Old 10-26-2020, 11:44 AM   #11
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Quote:
Originally Posted by RolesvilleMarina View Post
curious, since on the subject

where does one get replacement bags?

never really thought about it till just now

might be handy to put this in the bus notebook



the bags on most of our busses are pretty standard parts.. many truck parts houses carry them.. I got mine at Truck-Pro and they were i think around $120 a piece or so.. not hard to put on esp if the old ones still hold air.. i ran the suspension up and then lowered it down onto my Heavy jackstands to where it was still abut halfway extended then released all the air in the system, replaced the bags, aired it up, adjusted, and done.. took me a few hours if I remember right..



to the OP:

as far as the lean, im assuming you checked the air pressure in your tires?
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Old 10-26-2020, 11:55 AM   #12
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Yes sir, pressures were same on all tires at 98 psi. Not sure if that's too high or too low, but that's what I've settled on as a pressure.
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Old 10-26-2020, 12:03 PM   #13
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To be clear....

You have air bags on the rear only? One per side? And one ride height valve?

As said, the height valve will put equal pressure to the rear bags. (Of course, unless there's a kink in a line or something) Front suspension checks out ok?
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Old 10-26-2020, 12:16 PM   #14
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ennonne - Yes, that is correct. Air ride suspension on rear only, one per side, only one ride height valve on driver side. Front suspension is spring.

Other than the lean, I haven't noticed anything else broken or bent. Even the air bags appear to be at the same height when inflated.

Y'all are giving me good things to inspect again though, I'll double-check the air pressure in all tires and inspect the springs again this evening.
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Old 10-27-2020, 11:53 PM   #15
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I would suggest breaking out a tape measure and finding out where the discrepancy is. I’ve had a pickup that had a small lean and finally realized the core support was a little rotten under the battery. The frame was still level but the front clip wasn’t. Not saying it’s a rotten core support on your bus, just that you could measure the height of each airbag and the tire to body height etc to at least see Where it’s not “level”
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Old 10-28-2020, 01:16 AM   #16
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What FAC said. Best to determine where the discrepancy actually is before looking all over the vehicle.

First, check all tires and make sure they are the correct size and match.

Second, check the suspension springs for cracks, damage or shifting.

Third, check the suspension mounts for cracks or damage.

Any of these can cause one corner of a vehicle to sit low.
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Old 10-28-2020, 01:20 AM   #17
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Quote:
Originally Posted by ennonne View Post
You have air bags on the rear only? One per side? And one ride height valve?
Quote:
Originally Posted by RaisingWheels1 View Post
ennonne - Yes, that is correct. Air ride suspension on rear only, one per side, only one ride height valve on driver side. Front suspension is spring.

Most conventional truck chassis (I suspect that is what OP's bus is based on) do not have air ride on the steer axle standard, only as an option on some models. Class 6/7 truck chassis generally do not. Air-ride steer axles are typically a coach / transit bus thing.
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Old 10-28-2020, 10:35 AM   #18
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Hi RaisingWheels1
Since nobody has mentioned it yet, I will caution you to NEVER get under an air-ride vehicle unless you have properly set jack stands or blocking first. Any failure or mistake could result in the vehicle dropping, perhaps suddenly, entrapping or injuring you. Safety first.
That said, unless you are parked on a dead flat surface, any suspension measurements you make should be made between the axle and chassis. As others have implied, variations in tire size/pressure can add small errors.
I have been chasing air suspension issues for a year and still haven't got mine to where I want it. Good luck.


Rich
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Old 10-29-2020, 11:02 AM   #19
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Quote:
Originally Posted by CHEESE_WAGON View Post
Most conventional truck chassis (I suspect that is what OP's bus is based on) do not have air ride on the steer axle standard, only as an option on some models. Class 6/7 truck chassis generally do not. Air-ride steer axles are typically a coach / transit bus thing.
Exactly. Just wanted to be sure since what the OP has wasn't mentioned.
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Old 10-29-2020, 03:22 PM   #20
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I haven't seen anyone mention one particular point about air ride suspension, that it doesn't get air pressure until your system reaches a certain pressure. On my Crown, the suspension would not level out until the system pressure exceeded 90 psig. The Crown's air ride suspension has four air bags, two leveling valves and check valves. All of this is supplied through one air line through a tee fitting. When the air ride has to fill up it is a slow process. Before replacing the check valve, one side would drop down overnight and I would start the bus to build up air before working under it. It was about a 20 minute exercise from start to finish. Make sure that the suspension is getting air flow in your troubleshooting. As far as parts sources go I go to Fleetpride in Klamath falls Or. Fleetpride is a chain store with locations in Oregon and California. I think you would find an equivalent store in all parts of the country since there are OTR truckers everywhere.
My experience with Crowns is that while they made the frames and the bodies, they bought everything else from manufacturers making parts for trucks and school buses.
For instance the differentials on my new Crown were made by Rockwell, using models also used on trucks. On my old crown the front axle was also used by other brands of school buses. This came in handy because when I went to get a front end alignment the alignment machine did not list Crowns, but did list a make of school bus that used the same axle, thus providing the needed alignment specifications.
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