View Full Version : Air Bags

dale farley
04-03-2018, 06:48 PM
I was talking to a new member last week, and he was asking about replacing his air bags. There has been a lot of discussion over the years, and some have replaced them at a specific time and age of the bus, others have waited until they had a problem. I have owned three buses, and I needed to replace one air bag during that time. I had a 93 Marathon that one bag developed a leak, so I replaced it. That was one of the first jobs I tackled on a Prevost and I think I recall that it took between 1 and 2 hours. I now have a 1998 chassis with no visible leaks or cracks in my air bags.

My question is, "What is the current thought about air bag replacement?" Should I replace them all because they are 20 years old or should I wait until I have a leak? All comments welcome.

04-03-2018, 08:29 PM
Pump them up to full extension and take a look. They don’t look the same at ride height.


04-03-2018, 09:45 PM
Air bags 2000 Marathon H3 (99 shell) at appox 16 plus years of age. Exceptions to every rule of course but front bags get most wear.

dale farley
04-12-2018, 07:22 PM
I am wondering if my air bags have been replaced at some point. I raised the bus all the way and made pictures of each bag, and I see no cracks at all. The light is different on some of them so some look darker than others. There is also more dirt on the rear ones. If these are original, they look great to be 20 years old. Three of them look new the way the light is hitting them, but I know they haven't been replaced since I purchased the bus in 2013.

I don't know why the system turned all these sideways. I made all of them with my phone in a normal vertical position.

04-12-2018, 11:19 PM
Sure looks like bags were replaced at some point....I think your good to go.

Great pictures showing other members the good ones compared to bad ones.

Joe Camper
04-13-2018, 07:58 AM
Hey Dale couple things there you wrote down first IMHO a failure is not usually due to a road hazard. You almost never take one out with a road hazard. You have to drive over something pretty big and kick it up pretty far to take out the airbag. When they do fail they almost never go boom. They'll develop a slow leak. The difference in the age that you can get out of them is directly related to how you're storing the bus and where you park it and where you use it. If you stored inside and use it very little in colder climates they'll go a long way. That's normally what you run into at least what I do anyway. I use them until you develop a leak and then when you do start getting a lean then decide how much you want to do either do that corner or do them all.

It's also kind of surprising to hear the manufacturer say that they can last a lifetime. I I guess that would depend on what your definition of a lifetime would be.

I've seen coaches that get stored inside that r used in warmer climates with bags that are 20 years old look way better than bags on a bus that are stored outside and used in colder climates that are barely 10 years old.

Yours all look fine. What will happen is some other component will go bad, IE norgren, and start leaking and make you lean and then you decide whether you want to replace them at that point or not, along with the other problem.

When I'm replacing airbags I do it most frequently with people that just picked up a new bus to them but a used one and they want to put all new to start fresh because they either don't have service records or because the service records that they do have show them to be older than 10 years old. Needless to say I pull off a lot of really good looking airbags.

Those bags are date coded on that one picture you can see a little circle with an arrow in it it tells you the year and the month, picture 4. if I had a venture to guess I'd say most of the ones that you pictures are probably older than 10 years old.

The bags on the IFS require 95 PSI a great deal more pressure then drive axle and tag which are closer to 60 PSI at right height. If in doubt and budget permitting and wanting to be proactive that's probably a good place to start.

Hey Al the picture of those steer axle bags you took off as bad as they look I would definitely have replaced those and got them out of there. But. Take a minute and cut one open cut one of those two bags open and look at how the rubber is and look at the difference of the inside of it. I think that's why the manufacturer says coulf last a lifetime. I pulled airbags off that are so dry and cracked the outside of them is crumbly you can rub your hand on it and crumbles fall off of it but they still held air completely. I'm not saying leave that kind of stuff on your bus I'm just saying they CAN go a long long long way and frequently do. Even at that point they most frequently won't go boom they'll just begin to leak a little.

04-13-2018, 08:02 AM
The ones with vertical lines and rubber tips on them look newer than the others.

dale farley
04-13-2018, 08:31 AM
I wonder if it would do any good to clean the bags and spray with a non-petroleum based rubber conditioner?

04-13-2018, 09:28 AM
Service records and inspection are what should move owners to replace air bags. When a pre purchase inspection on our 2000 Marathon H3 showed front air bags with cracks the size of the Grand Canyon their replacement was made easy. At same time, all nine (9) Norgren's.
On Dale's bus in my opinion his bags look pretty good.
I have also heard on 2 separate air bag change out of some bags filled with water. This example is a direct ownership lack of care, don't give a damm about draining tanks or basic lack of any and all maintenance.

Dale, no Foo-Foo on air bags.

Joe Camper
04-13-2018, 10:14 AM


Here is what air bags look like when the bus hasn't been stored inside and they're the original bags still and they're older than 20 years old. I just took this one off my Pete a couple of weeks ago cuz I'm doing the rear axle on it I think they were original and the truck is a 1990 so these would be 28 year old airbags. They leak down overnight there was no audible hiss coming from anywhere you could not hear them leaking but the leak was big enough it would go down overnight so now there's some real comparison pictures for you Al.

I've pulled bags like this off of buses more than a few times but it's not the normal 4 Prevost motorhomes.

04-21-2018, 10:29 AM
Here are more pictures of 2 different air bags. There's two take aways from these pictures. First, there's no such thing as a replacement schedule. Those that preach 10 years are almost surely throwing good parts and money away. Second, bags, like all air products need to be inspected to determine when they should be replaced. The environment the bags are subjected too makes a huge impact on their serviceable life. FWIW, STEMCO engineering, the owner of Goodyear air bags, says a catastrophic air bag failure is rare. In almost all cases air bags develop a leak before failure.

Here is an air bag that was in service for over 15 years. I know it was over 15 years given the manufactures date stamp, the coach's in service date, and the date it was replaced.


Here's an air bag that was still in service holding air at 27 years old! The point being even really bad looking bags can hold air, although I'm not suggesting this bag should have been in service. Clearly, it was years past it's reasonable replacement date.


Joe Camper
04-22-2018, 10:45 PM


Here is 1 of an original set of 3 bags I took off the right rear corner of a marathon in Manteno this week. A 96 chassis but the bags are dated September of 95. The little oval in the top pic thats stamped 95. 22yr old bag here folks. With leaks, it did recently develop a right rear lean and we pulled those 3 bags with the norgrens for that corner along with them.

This is normally what a set of bags look like that's in between 5 and 10 years old in my opinion. So how you store your bus combined with what type of environment you're always driving in goes a long way to how long the air bags last for sure.

Even though the LEFT rear on this bus still has all its original air bags that are 22 years old now they don't look that bad. With my suggestion the owners going to leave them in there. That left rear could go another five years before it develops a leak maybe longer. I can get away with that with this particular bus he's very close within an hour of my house. Normally I'm a little further away from home than that and I don't get the opportunity to play that option.

Gil the picture that you posted with the totally rusted-out base the one with the studs thats snapped off. When that base rusts through air can leak out I've seen bags were the bladder still good but the leak is in that base because the base has rotted through. I bet the lower base that bag sits on wasn't looking real good either was it. Was that bottom round plate jacking the bag up off of it from rust before you even took it apart did you notice? Probably was. The base on that bag looks like a bag that I normally pull off a dump truck not a Prevo. Nasty

One other thing worth mentioning everybody seems to want to pull that bottom Bell off the bag and extend the bag all the way out to expose that crack on the bottom of the bladder. Same picture GI'll posted with the base with the broken stud that's a big crack in the rubber.

Well.....all bags do that in that location and pretty quickly. When you're at ride height that bag is rolled down on itself down there and that that crack isint as exaggerated like that when you're in ride height. That crack at the bottom is squished together when you're at ride height.

Whenever I'm elevating a bus up above ride height close to the max to get my jack stands in there I never leave a bus sitting maxed out in level low for that very reason cuz almost all the bags after a very few years will already be developing those cracks there.

Where else do you get this kind of insight?

04-23-2018, 07:24 AM
Joe, the picture of the really old bag came from someone else. So, I can't tell you more than the picture.

Joe Camper
04-25-2018, 07:40 AM
That's alright Gill. One other thing everybody. The older drive axle bags used to come with coarse thread studs on the bottom but fine thread stud on the top. The new bags are all coarse thread top and bottom. Pierre did that.

The nuts do not come with the bags sometimes when you call to order parts they'll ask you if you want them but sometimes they don't.

Joe Camper
04-25-2018, 09:50 AM

Here is a brand new drive axle air bag that I just put on a bus that's about an inch or two above ride height but not all the way up. Zoom in Look at the cracks in the bottom were rolls up when it goes back down, brand new.

Joe Camper
04-25-2018, 09:54 AM

Here's the process I go through when I got bad parts. Doesn't happen too often but every now and then I'll get a leaker from Prevo. When I do this is the solution I isolate the three airbags I put the front three way norgren with the front drive bag and I put the two-way norgren on the gauge with the rear drive bag and then I air out the tag bag by itself with shop air to 60 PSI, and then you wait. All these new components on this corner of this bus and it was still going down in the right rear about a quarter of an inch a day. A dramatic Improvement in the lean that used to be there but it's still got a new lean nonetheless.

If it turns out it was a loose fitting that's my bad otherwise it's more labor. Its not too bad to isolate the back corner all I had to do was take the tag tire off and undo 2 fittings in the system to get all three jigs hooked up. 1 at the tag bag and one at the two position spool on the inside of this frame rail here. Takes about an hour to get to this point to check and then you wait.

04-25-2018, 10:25 AM

Just a guess, but I believe those lines that look like cracks are manufactured into the bag. The picture of my old bag shows the same. I guess is that this is done to allow water drain paths in the bag where the bag contacts the metal cone. Again, just a guess.

BTW, great setup for checking for leaks.

Joe Camper
04-25-2018, 11:10 AM
So if some mechanic tries to sell you some bags because there's cracks down there you know better.

That last pic I posted, those are cracks you're looking at not lines. Eventually those little cracks develop into them big splits.

Those rigs I set up for checking leaks not always necessary but sometimes they are. When the leak only has the bus going down on that Corner a quarter of an inch a day you might get lucky and find that leak with soapy water or better yet you might be able to go in there and find it with an ultrasonic leak detector but when it's only going down that's slightly you're not always going to find the leak even with an ultrasonic leak detector you got to split everything up and put these rigs on there and then you find it guaranteed. Every now and then one of these corners of suspension requires me to pull all the tricks out of the bag!!

Oversized oil-filled gauges that are calibrated to the pound very easy to monitor any drop and as quick as it's going to be humanly possible.

07-29-2018, 01:27 AM
I have a 1999 Marathon XL that has 120,000 miles on it. I purchased it in 2010 with about 99,000 miles on it. Recently I checked all the air bags (6 rear - 2 front)....it looked like one front air bag was starting to deteriorate, but all the rest looked great. I decided to change out the two front air bags myself and while I was at it I wanted to replace the shocks. They looked fine but it seemed like the thing to do. I read everything I could find on the task and wished there was more. Upon further inspection the upper "A" arm suspension has 2 rubber bushings each that attach the arm to the frame. The bushing were starting to break down so I elected to replace them as well. I did the right side first and it was pretty tough sledding. I used a torque multiplier for the lug nuts which worked great. With careful jacking you can get the tire out of the wheel well but it takes a little planning. Oh, did I mention I did this by myself. (don't forget - loosen the lug nuts prior to jacking and the left side has left threads) I do not see how you can change out the airbag without removing the "A" arm and the shock comes off and on with the "A" arm removed - not sure if you could get the upper shock mount off with the "A' arm in place. The four bolts holding the "A" arm to the frame are tough to manage (I cut a open-ended wrench making it 3 inches long to hold the bolt while the nut was removed and then when replaced. Once I got into it, it became obvious that if i had both front wheels off and could co-ordinate the jacking on both sides I could greatly improve the geometry it takes to get the 'A" arm and the air bags off and then on. (On this '99 coach the torsion bar inter-connecting the independent suspension will play a huge factor in working one side or the other. I really fought the right side but was able to navigate my way through the project but hind sight tells me it would have been a lot easier had I done both side at the same time. The left side was a lot easier once I got my act together. I ruined two bushing pressing the four bushings in the two "A" arms (you need a dam good press (20 tons) and you need to very carefully compress the bushings if you want to get the keeper keys properly placed. Taking the old bushing out is simple but putting the new ones in takes very careful symmetrical jacking to get even compression and placement of the keeper rings). Be sure to double block both sides of the coach with good blocking fore and aft of the wheels on the coach frame less you may kill yourself in the process (you will spend all your time in one wheel well or the other so do not plan on remaining clear of the coach should it fall if not properly blocked). Would I do it again .... SURE, but then I know what to do now! Oh, by the way both old air bags turned out to be ion great condition and I really did not need to replace them. The shocks were fine but again why not replace them while in there. Give me a call if you plan to try this yourself and I will try to talk you through it (AT LEAST GIVE YOU A LITTLE MORAL SUPPORT). For those that care if you cannot identify some problem with the air bag my best advice is to leave well enough alone....I just do not subscribe to EVERY TEN YEARS but then everyone has their point of view. (the air bag has a stamp on the end of it that can only be read once removed giving the year and month the air bag was manufactured .... in my case these two air bags were original equipment. Ted Beck bigskyted@aol.com

Joe Camper
07-29-2018, 06:49 AM
What did u do about the dirt boot for the ball socket?