In the process of replacing all the air springs on my bus I have discovered that the steer axle bags had been replaced with larger diameter Firestone Bags by I believe Country Coach during their conversion process. It is my intent to replace them with the Goodyear 151 bags, does anyone know if this might present any issues?
It is my assumption that C.C. felt a need for larger diameter bags due to weight. Although that does not make complete sense to me as I've weighed my front axle and it came in well within the reported weights of others.
For everyones information that might also have this change in their bus when I disassembled the assembly I discovered that due to the increased diameter the Firestone bags were being rubbed by the upper housing to the point that approximately half the thickness of the bag had been rubbed away in an area about 6in long with a width of 1/4 to 3/8. It looks to me that if these bags had remained on the bus longer that they would have surely been comprimised and subsequently I would have suffered a catastrophic failure.
I have zero CC experience. I would talk to Prevost engineering to see their thoughts on the air bags you have versus the ones Prevost supplies as original equipment. There is a lot going on under the coach under various conditions that prevent us from verifying clearances. We cannot duplicate the different extremes up or down, wheels turned left, wheels turned right, etc. As you can imagine there are a lot of moving parts in proximity to the air bags and clearances are very small. Due to the risk of an air bag failure I suggest you speak directly to Prevost Engineering.
It is obvious what you currently have is not working. Having said that however, do not rule out motion on parts that should not move. Your air bags may be the correct size, but maybe there is a failing bushing or ball joint and the chafing you see is a result of that. I presume that is not likely but when you see such indications particulalry with steering involved it is better to verify the cause.
One final point. I am not familiar with IFS, but on my coach the shocks limit up travel. If you do not use original equipment air bags, make sure the substitute does not have insufficient up travel, or too much up travel such that the air bags can exert enough force to snap the end ring off. Insufficient up travel adversely affects your ability to level the coach.
John,
Thanks for your comments.
After speaking with Prevost personnel I am confident in the use of the replacement bags they recommend (151). Having thoughly examined the IFS components for wear it appears the only issue is with the bushings in one of the upper a-arms, I am pulling both upper arms and replacing all bushings. As the chafing is being done by the upper spring housing which is stationary and all the associated components are in excellent condition I feel it is highly probable that there was some poor engineering by C.C.. My concern would be with buses similar to mine. I believe other owners of the same era would be well served to check their steer axle bags. It is fairly easy to determine if they are Firestone bags, if they find them they should be examined. Although I felt replacing the bags at ten years (my bus is registered as a 2002 but the chassis is 2001) was a bit overly cautious I am a believer now.
Thought you might find my recent experience changing front (151) airbags and upper A arm bushings useful. I changed the A arm bushings about a year ago and am just finishing replacing the air bags. I found that the old airbags were soft and stretched, consequently with some judicious wiggling was able to remove them with the A arms in their lowest position. The new airbags however are very stiff and I found it impossible to install them without removing the chassis ends of the A arms. Since you are changing both bushings and bags, I suggest that you install the airbags while the A arms are removed.
In removing the A arms I loosened the 4 chassis nuts then removed the cotter pin and unscrewed the center nut so that it would protect the threads on the ball joint. WE then used a 9lb sledge and after several very sharp whacks were able to knock loose the tapered ball joint shaft. This is not a job for a little guy. Since the job was a little below JDUB's paygrade and he's seldom seen in the Northwest, I found a local farmboy/defensive tackle to swing the hammer. FYI we tried jacking the ball joint but stopped when we could see the axle flex.
After removing the A arms it's necessary to remove the snap rings from the bushings. In my bus they were rusted in so I waited for a couple of days while letting them soak in penetrating oil. I then used a hydraulic press to compress the bushings so the snap ring tool would fully extend through the holes. As to snap ring tools, conventional pliers will not get the job done. I finally found the Wright 9H87 shown below which is the true answer to the task.
When reinstalling the bushings, grease them well, you may need to rotate them slightly in order to get the bolts back in. You will need to compress the bushings in the press in order to install the snap rings and spacers.
As with many jobs around the bus, this one is all about having the right tools for the job, in this case that included a very big guy willing to work for beer. Have fun.
I find this discussion very interesting, though I have no idea of which you speak.
How/when did you all learn to do things like this? I have no training as a bus mechanic and assume you don't either. When we finally find "the one" I would like to learn to do maintenance and repairs on it, but will need some tutelage.
Thanks Brian.
I have completed the removal of the a-arms and bags and as you report one of the best tools is a guy to swing the hammer. Luckily I have a brother in law that just can't seem to say no when I volunteer him to help. Lucky me. Once we had them removed we didn't baby the snap rings, we used a punch to remove them destroying them in the process. However, I already had the replacements and knew they came with new snap rings. We haven't yet reinstalled the bags and arms but when we installed the rear bags we compressed them by pushing down with our weight and then put a 1/2 in. plug in the air hole which assisted in keeping them compressed. Seem to work pretty well and we will repeat the process on the front bags.
I do like the looks of the snap ring pliers you show, nothing like having the proper tools. As I am doing the work on my bus in Eric & Debbie Faires' barn utilizing their pit for various other maintenance items including brake chamber and hose replacements I will see if they have one of those great snap ring tools. They seem to have about every other tool I could possibly wish for. LOL Nothing like having good friends when you want or need to work on these things!!!
Sawbonz,
Once you find the "one" and have made a couple of subsequent trips to a Prevost Service Center to have some work done it will quickly dawn on you that bus mechanic or not you will educate yourself to perform as much work on these things as possible. Unless of course money is no issue and if that be the case I'm in the Dallas area stop by anytime your near and we'll go out for dinner and drinks, of course your treat!!!!!!!!
I can easily speak to the issue of doing bus maintenance. First despite what others may think I did not start out working on my coach. I did nothing on it. Zip, nada, nothing. From 1990 to around 1994 or 1995 someone else did some or all the work. I started with oil changes, then I started greasing it, laying on my back on my barn floor. But the year Prevost moved their Jacksonville shop from Wilson Ave to the present location all that changed. They put a chain across the bays and decided owners could no longer observe the service work. That policy I believe has changed, but not before I made up my mind I could do my own work.
My first serious job was replacing air bags. As anyone who has done that knows, air bag replacement is not sophisticated. It just involves some bigger than normal tools and a willingness to get dirty.
From that I made the coach leak free. Don't laugh. That was a serious project and involved rebuilding all the Norgrens and bench testing them plus chasing every other leak source in my then 10 year old 1987 coach. Eventually I ended up replacing brake chambers, brake linings, trouble shooting problems, hub seals, alternator, fan clutch, plus all of the other routine and not so routine maintenance and repairs.
Speaking solely for myself I now know nobody, and I mean nobody cares as much about my coach as I do. During the time since 1995 I had Carrier replace a OTR compressor because I did not have the time to do it myself and as a result my coach caught fire within 400 miles of their efforts. I am certain there are many skilled mechanics and there are certainly a whole lot of people who know more about my bus than I do, but the bottom line is I care about it. That is why I spend hours looking underneath it. Aside from the fact it is cool in the pit on 90 degree days, I take the time to look for chafing, wet spots, leaky hub seals, brake pad and lining thickness, broken clamps or loose wires, hoses or tubing.
When I do a repair I always make it a point to look at stuff I usually cannot see when everything is together and in place. If it has rust I paint it, If it is dirty I clean it, and if I see something else that needs to be fixed I take the time to do that. If whatever broke created a problem I try to figure a way so that next time I can work around the problem. that is why I have inverter by pass switches, a hose accessible for engine priming and two pressure switches on my water pump. Anal is a good description, but at this point also call me confident. I know the coach, I know how to fix stuff, and if I am on the road and have to have someone else do a repair you can bet I won't be a victim.
If it is worth doing, it is worth overdoing so I know I am premature when it comes to part replacement and service intervals, so I likely haven't saved a penny, but I have gotten a very valuable education in Prevost. And that is priceless.
Air Springs
Reply With Quote
