Simple & inexpensive leveling system for early GM coaches with air suspension

[dtcerrato]

On the subject of levelers. I just completed an effective & rather simple & inexpensive leveling system for camping or just periodic level parking. I teed in 12 vdc air solenoids at each leveler supply line (3 total, 2 back,1 front) I also put a solenoid at the dry tank (last tank all the way up front that feeds the air suspension & accessories). When we get in position where we want to level, I shut down the engine and purge air from the dry tank until it's down to 65 psi. After doing that I use the solenoids at each leveler to bring the coach to level. Once establishing that she'll sit that way for days. If we need more time than that I simply block it so it can't drop. This system keeps me from having to drive up on wedges to level. If the leveling is too extreme for the space the bags to chassis gives then I drive on wedging but much lesser than originally needed. This system also maintains the original "3 legged design". It's great. And in bringing the system to 65psi, more air will not move into the suspension system and there's plenty air in the system yet for brakes. The whole system cost less than $50. We love it!

[Kevin]

Hi Dan,

Sounds like an inexpensive yet effective set up. Good job!

Kevin

[Oonrahnjay]

   That's the system most people have used, Dan - thanks for the complete writeup.  Do you have part numbers and source for the solenoids?  Do you have gauges for your individual lines?   Thanks,  BH

[TomC]

I have a similar setup, although a bit more complicated. Each of the suspension positions has three 12v air solenoids. One normally open and two normally closed. In line between the automatic leveling valve and the air bags is the normally open valve that allows normal automatic leveling valve operation. Then between the normally open valve and and air bags is a T with the two normally closed valves also T'd in together-one as the exhaust, one tied into the air system.
In operation, I activate the normally open valve and that cuts off supply from the automatic leveling valve. Now I can use either of the two valves to add or exhaust air from the air bags. When overnighting, it takes all of about 2 minutes to level. If I'm staying more than 2 nights, I will level with blocks, then exhaust all air down to the bumpers. Then I don't even need an outside step to get into the bus. Good Luck, TomC

[dtcerrato]

Attached is the solenoid details & a photo of installation, similar unit sold by Grainger is almost $50 a pop, I got imports from Banggood on sale with 10% off coupons - paid under $6 a piece free shipping. The specs make these comparable units! Just a simple Tee in the leveler supply line (3 places) and one on the dry tank (for expelling air in suspension reservoir tank down to 65 psi) There isn't any need for additional gauges as your not overriding the auto levelers. You can't over inflate the bags with this setup. You're maintaining the engineered system - just creating a path to exhaust air for leveling purposes. The only gauge monitored is the master pressure gauge on the dash. Just a matter of plumbing in the solenoids and wiring with toggle switches (12 vdc) to the dash area (for convenience). It is a very simple and effective design. I'm still carrying the blocks but only use them a fraction of the time... 

[Lin]

As I have mentioned before, airbag leveling, which we also use, is limited.  Assuming that normal ride places your airbag roughly in the middle of its inflation, letting all the air out of a bag just drops it about 3 inches.  Filling the bag completely raises it about 3 inches.  Therefore, one can only achieve 6 inches of differential at most from back to front.  If the system you are describing only allows leveling by exhausting air from the bags, then you will only get about 3 inches difference from back to front, and save you the use of one 3 inch block.  That can certainly help, but if your axles are 30 feet apart, a three inch difference only deals with an incline of about 1/10 of an inch per foot, which is a pretty minimal incline.

The side to side benefit though is much better.

[TomC]

This is the reason I have both exhaust and pressure adding capability to the air bags. Also, the nice sideline is that I have one lazy air leveling valve that doesn't inflate very fast. I can pump it up in the manual mode, then running down the road, it works sufficiently well. Same if you blow an automatic leveling valve, can switch to manual mode. I have had the connecting rod on the air suspension either break or just plainly fall off. No problem, just switched to manual control, readjust the height, and went on down the road. Good Luck, TomC

[dtcerrato]

Hi Lin & Tom
I'm not familar with air suspension on an MC5A or AM General or the chassis design
Our 53 - 4104 has double convoluted bellows that have a ride height of 3" to 3-1/4" between axle & bumpers with a max air pressure of 75psi.
As with most all engineered systems (& body lines, lights, etc) on our coach - through the years we have tried to keep it as original as possible
Original design has three levelers, 1 front & 2 back thus "3 legged" which prevents undo torsion and stresses on the mono coupe design.
Curious - how many valves do you level with 3 or 4?
The assumption of "level" being at the middle of the bellows position I don't think is accurate with the 4104 design.
It is more at it's upper position although I don't know what the bag pressure is at that point.
I understand what your saying about limited up and down movement.
After leveling the ole' girl with blocks under the tires for over 35 years - with the new addition of the ability to level up to 4-1/4" (rubber bumpers do compress an inch) was awesome.
I know your system gives you more vertical differentiation for leveling (wondering if it's 3 way or 4 way) but ALSO wondering what kind of torsional stresses are you putting on the frame or "box" if you will...
With the ability to "twist" diagonal corners with you design - but again we're not comparing apples to apples

[Dave5Cs]

But Lin Remember we have 7 to 8 feet overhangs (depends on your coach)and 3" at the axle. So if mine is down all the way in front and up all the way in the rear it actually measures 11" of difference at bumpers. I have 4 corner leveling with 4 paddle valves next to drivers seat with 2 gauges with double needle registers in each. We rarely use blocks. Unhooked leveling valves out years ago. Ours hold at pressure for as long as we want them too.
Dave5Cs

[dtcerrato]

Was the original design three or four leveling valves?
Frame chassis or mono coupe?
At the bumpers I am at 6-1/2" differentiation
Not bad for $50 and two days labor!

[Dave5Cs]

I think your system is neat. Mine was original 5C saudie coach three Monocoque". One up front and 2 in the rear.  Did ours to all four corners or 2 pair on each corner. They fill and exhaust through the valves at the driver area.
Other nice thing is if you need the height in the rear in a gully you just adjust as you need it. I run 85 in the front and 80 in the rear on the road just a nice cushy ride. If i need it can go to 130 in any bag but must places I am at 90 PSi in bags.
Never had any problems with twisting etc. and have heard all the scarey stories but it works well. also 35 ft coach single axle.

[Lin]

Dave- I understand that the overhang means that there is more differentiation if you measure at the bumpers, but using the axles just is an easy calculation.  Also, measuring at the bumpers does not really change the rate of incline anyway.

DT- The MC5a also has three point ride height control and is monocoque.  I think the systems are pretty similar.  Our leveling is as bare bones as you can get.  We replaced the ride height control linkage with push/pull cables that can be used to inflate and deflate the air bags as required.  It works fine but suffers from the same limitations.  We have been in Forest Service parks that had twice the incline even at their most level sites.  Hence, we still needed 6 inches of blocks.

[TomC]

My AMGeneral has 4 double convoluting air bags per axle (instead of the air beam, each air bag has an aluminum "can" at the top for additional air capacity) and the single air leveling valve at the front and two leveling valves at the rear. So my system is almost identical to the 4104. Good Luck, TomC

[Scott & Heather]

Monocoque structure coaches like ours do flex a bit so the tripod design of the suspension is a good thing, but some here have hydraulic levelers on four points and claim they work fine. My friends S&S Rv happens to have three hydraulic levelers one in front and two in back same design as our Monocoque coaches... I am going to remove the auto leveling valves in my coach and replace with manual solenoid control and add dash gauges because the single most commons point of air bag leakdown are those Presley auto leveling valves which were more designed to fix level issues when you are constantly adding and removing large passenger and luggage loads throughout the day, something we won't ever be doing with a converted coach.


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[gg04]

Simplest and easiest is still 4 air seat valves and 4 gages..no twist... three air valve system will twist coach if used for leveling..three valve system works if only one contact point like three cylinder hydraulic systems.. rdw