I am tired of the long waits for the bus to air up, so I am plating my air bags and bypassing the leveling valves. Not sure which is the culprit for the leak but I will not have to worry about either any more. I made some air valves whith pressure gauges, one for the fronts and one for the rears. I will use my portable air compressor to fill to the desired height and pressure and close the valve. I am going to mount the rear gauge in the engine compartment on the passanger side. And then i will mount the front inside the front driverside compartment. I am going to take pictures of the whole processs.
Sounds like you've had it with the OE system, huh?
No way you'd at least consider plumbing to the brake compressor for semi-automatic make-up air?
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yes not just because of air leaking down but sometimes when i go around a sharp corner it might take a mile or 2 to level back out. And also now when I am camping on unlevel ground it will be easy to level my bus.
Chart1- plating the air bags will make for a more firmer ride with the bouncing and rebounding at a faster rate. Using one gauge on the front is alright- that's the way it is plumbed from the factory. But using only one on the rear-your tipping when going around a corner may not ever recover. I highly recommend you to use left and right side fill points for the rear. Then the bus will right itself immediately when you come out of the corner.
Now my suggestion to your system. First off-you have a great air compressor on the engine that puts out about 12 cu/ft/minute. No way can an electric compressor put out that much-so your electric compressor time will be VERY long. Second-I would keep the automatic leveling system in place. If you get a pin hole in one of the air bags, or just a small leak-the air compressor on the engine will keep up with it-the little electric air compressor won't. Plus with your planned system, every time you need to add air to the system, you'd have to stop and manually add it at the front or the back.
Go ahead and plate off the air bags (if you're not going to mind the firmer ride) and keep the automatic air leveling valves. Then add a manual leveling system with a manual/automatic switch with the gauges and switches in the driver's compartment so you can manually adjust them while driving-if you want. I have this system, that I made, and it works great. If you ever have a leveling valve problem then you can just switch to manual. Good Luck, TomC
Several folks who plated their air beams went with rolling diaphragm air bags. They should make the ride quite a bit softer and have a good spring rate change as the spring is compressed.
If you are going to control the rear suspension, you can consider an electric valve to isolate the two springs where you need tighter handling. That way there is no air transfer from the loaded spring to the unloaded spring on curves. I did that on my truck toterhome and it really helped the handling on the curvy roads.
Jim
How about three mini air regulators in the system, then you would have automatic and adjustable pressure/leveling control, one front, two rear, and with guages. You could still put shut off valves upstream of the bags for after you shut down, to keep any potential backflow from causing an airdown.
Rolling diaphram, are those the bags with the ring round the middle?
I would get rid of the OE leveling system. Its great on a Bus in passenger service, people constantly getting on and off, loading and unloading baggag. But in an RV/motorhome, except for fuel burn there almost zero weight loss/gain or weight transfer going down the road. The OE leveling system seems to be a constant headache to keep working, and often leads to a air loss somewhere when you least need to deal with it. And without shutoffs, most leak down shortly after shutdown. Once the OE stuff is gone, your source of leaks will be greatly reduced, making for a more reliable Coach.
I guess if you are going to all the work I would also get the rolling lobe bags. I think my kits were around $1500 from Mohawk. Luke might be cheaper. You do have to remember that the cost of the plates and bolts will be included in either instance and you may find some questionable bags that need replaced anyways. Also add in the fact that you may have some trouble getting the existing bags to also seal and your ride will become somewhat stiffer. Look at it this way. It's a one time cost that sure eliminates some headaches. The only thing I wish I had also done was replace all the shocks at the time. Later
On my 4104 I have one plated rear side and the other side still has the original air beam. there are no plates on the front. All air bags and one rear valve are new. There is no detectable ride difference between the plated and the originals. The only detectable difference is the very fast air up time for the plated side.
Your bus is not supposed to use air bags to prevent leaning on a corner. There isn't enough time for the system to react to a curve. There is a built in time delay controlled by fluid inside the leveling valve, they are set up that way originally. The leveling valves are designed to adjust to passenger load changes, not highway curves.
If it leans after you leave a curve you have a bad valve or you are not on level ground.
The bags do not level the bus, they equalize the distance between the axles and the body to compensate for uneven loading.
Gus, I have to admit that stock buses do not use isolation valves. When you think about it, that would be way to complex for the driver to deal with.
On my truck, the center of gravity was higher than a bus and the aftermarket air springs were located a bit inboard. My truck would lean a lot on twisty roads. I custom made a pretty big sway bar and that helped. But when I put the isolation valves on, it made a big difference. My plumbing was a bit unique. I had a rather large air tank between the springs that served the same purpose as an air beam (larger volume for smoother ride).
I had a large handle toggle switch that I could hit as I approached a tight curve. Worked very quickly. It became instinctive for me.
When you think about going around a curve and transferring air from the loaded bag to the unloaded bag, it just does not make sense. That tends to make the lean worse.
Probably not a big issue on a bus, but it was quite a deal with the truck. That said, I sure see some leaning buses on our mountain canyons - even the new ones.
Jim
Jim
Great post Gus! Good to see a good explanation from someone who understands the levellling system.
My 5C came from the PO with, like Gus's, one rear side plated with convoluted bags, and the other side original with the convoluted bags and the air beam. NO noticeable difference between one side and the other.
I am glad you mentionned that Gus, I thought I had the only odd bus in the world, LOL...
Yes in theory, more air volume would deliver a softer ride. But in practice, if there is a difference, it is minimal, unnoticeable.
If my bags needed replacement, I would buy rolling lobe ones, but in the meantime, it doesn't matter.
JC
Chart -Quote from: chart1 on February 27, 2011, 07:57:57 PM
. . . sometimes when i go around a sharp corner it might take a mile or 2 to level back out.
Welcome to the world of MCIs, or at least, pre-96/102A models. MC-7s, 8s, and especially 9s are notorious for "cornering on the rub rails," primarily because MCI didn't spend the extra bucks to install anti-roll bars on their chassis. Later models starting with the "A" series all have them, making a big difference.
If it's taking one - two miles to level back out, then there's something wrong with the rear leveling valves - probably the originals and most likely worn out. They're not that expensive, and should be part of your chassis restoration maintenance program. When operating properly, it only takes a minute or so to level the coach. (Or at least do what Gus said - equalize the distance between the axles and the body.)
As for leveling in campgrounds, seriously consider a system that allows the suspension to operate normally and automatically while on the highway, but can be switched to a manual mode for campground use. Best of both worlds, and you don't have to always be fiddling with the various valves to get the ride right. Pete Pappas (RTS/Daytona), who frequents BNO more than he does this bbs, used to sell a complete kit to do just that. Might see if Pete can give you a hand with this project.
Understand that the ride height specified in the Maintenance Manual is that for a reason. Besides giving a good ride and proper suspension travel, it also has an effect on the driveshaft angle coming off the transmission and into the rear axle.
Which also means, while you're in there replacing the factory leveling valves, replace the rubber axle bump stops, too. Most likely, they're worn beyond specifications also.
As mentioned, no significant ride difference between plated and non-plated, best results with rolling lobe-style kits.
Use your electric compressor only for airing up the coach in the morning before leaving the campground, NOT while running down the road.
FWIW & HTH. . .
;)
PS: Since you're a newbie, it would be helpful if you'd put your bus make/model and the city/state where you're located in your signature line. That way, fellow busnuts in your area might be able to help, as well as we'd be able to direct you to various vendors as needed. Or put the info in your profile, either way, we can help you better.
Jim,
I don't understand your post about transferring from one air bag side to the other. No original bus system does this that I know of. There would be no reason for it since the valves are designed to adjust for loading, not driving.
Left and right rear bags are independent as are both front sides. They have no effect on one another via air lines. There is no air transfer between sets of air bags and certainly not from the loaded to the unloaded. I can imagine that the loaded bags get compressed but not that they unload air pressure.
Unless your installed large air tank had very large air lines to it I don't see how it could serve as an air beam, those holes are huge and directly connected to the air bags via their huge holes.
As already posted, original leveling valves have so much time delay built in that no normal curve would ever have any effect.
I certainly agree that rolling diaphragm bags are far superior. The difference in ride between my 4104 and 4107 is phenomenal and the weight difference is only about 4,000 lb!
I'm thinking that if you are unhappy with the bus leveling after a turn you sure won't be any happier after plating and staying with the older bellow type bags. But others have stated otherwise. Hard to refute that. I'm still happy with my conversion and would not even think twice about doing it again. I love the ride!
My only complaint about bellows bags is that they are so bouncy underway that I almost get seasick - almost!!
The rolling diaphragm bags don't seem to have this problem.
Gus, my apologies about not understanding the plumbing on buses. If they are truly isolated, then my scheme does not apply.
On my truck, they were tied together and it was not fun to drive.
I have studied air springs for many years. At Gates, we developed some real interesting technology and did a bunch of testing on Lincolns with air springs. I talked them into giving me a set of springs that I adapted to my 56 Chevy long before the commercial kits became available (~~1990). I had a ball tailoring the ride from soft comfort to bad @$# handling. Also fun to drop it on the ground when I got to a show. Still have the car and it still has the Lincoln springs on the front.
The Lincoln had a solenoid valve in each spring, making them totally independent. The solenoid valves were not durable and they are expensive. I machined up some fittings to put in place of the valves. Unfortunately I only had one aftermarket solenoid valve and that prevented the springs from being isolated. Really messed up the handling. Have the extra valve but never had a chance to install it.
Jim
on most buses with airbags suspension the rear are isolated left and right, but the front are tied together both sides. Otherwise you could end up with a twisted bus.
First if you have a leaking problem you need to fix that first.Your brakes work on air.Second if you replace the leveling valve you will solve the leaning problem. you will be safe and spend a lot less money.
Jim,
No apology necessary, it took me a long time to figure out that leveling valves don't level and that here was only one in front!! Even after I had read it in the manual a truck repairman had to explain it to me after he repaired a valve link and I complained the bus wasn't level when one wheel was sitting in a hole!
Those Lincoln air suspensions are a disaster once the car is a few years old. A rebuilt air suspension on the rear alone costs more than the book value of the car. I often see a saggy Lincoln sitting by the road with a "For Sale" sign on it.
I replaced the rear air shocks on my wife's '89 Cadillac Deville a few years ago. They weren't all that expensive, nothing like Lincolns, but a real pain to change. They aren't isolated, all they do is raise the rear when rear seats and trunk are loaded.