Over-inflated Air Bag

[Steve Huber]

I didn't see this problem in the forum so here goes. If I missed it, let me know.

I have an 8 bag system with 3 adjusters, 1 in front and 2 in rear. Coach levels perfectly when parked.

When at ride height, the drivers side front sat low. Rear was level. I checked the bag inflation levels. All were close to in-spec; 9 3/4" to 10 3/8" except the right front bag (passenger side in front of front axle). It measured 12". I switched the inputs on the front bags so that the right bag was getting air from the left valves/manifold and vise -versa. No change. The right front bag was still at 12" and the left with-in spec. Next,I put an air fitting on the line leading to the bags and filled each with 70 psi. All bags were at same height (~10") except the right front, it was at ~12".

This seems to point to a faulty bag but I don't understand how a bad bag would over-inflate in the "vertical" direction. I also checked to insure nothing is restricting the "horizontal" inflation space.  Anybody else run into this?  (Goodyear Bag# 566-22-3-143).

THX!

[Richard And Babs Ames]

One side has more weight on it than the other? Not a supension problem? have you weighed by wheel?

[Gerald Farris]

Steve,
There is a possibility that you have either a bent frame from previous damage or a shock that is binding.

Gerald

[Steve Huber]

Gerald,
Re the bent frame possibility; when I dump the air bags, the coach sits level.If frame were torqued, wouldn't it show in height from floor,  etc?
Steve

[Steve Huber]

My original reply apparently didn't post so will try again.
Coach is lighter on right side; 362 lbs on front axle and 1384 on rear. But, this should also impact the air bag aft of the front axle on right side. But it  is in spec at 10 3/8"'.
Problem has been with me through a complete shock change so doubt this is cause.
I purchased coach in 05. No indication of damage then and nothing since. Also, I would think a bent frame would impact both fore and aft bags on front axle. Also as mentioned, dumping bags results in level coach when sitting in my garage on level floor.
Thanks for the quick responses!  Steve

[Edward Buker]

From a geometry point of view the center valve ride height has to be satisfied in order to stop the air flow to both front air springs. They are tied to the same flow of air pressure from the air valve and manifold. In order for one side to go high it would imply that the other side must be low in order to have the center of the coach ride height valve rod length shut off point satisfied. It seems strange that was not what you found.

One suggestion is that the driver side is being stopped mechanically at some point and then the right side has to continue the rise untill the center point valve rod length is satisfied. You could test this by lowering the coach by letting the air out and while measureing coach frame to ground on both sides. During the rise of the driver side, see if there is a stopping point while air flow in the front suspension air springs continue to flow, and the passenger side then continues to rise. This could be the restricted driver side shock case Gerald mentioned. If both sides continue to rise until the valve is satisfied with no stopping then that could indicate the bent frame case.

 The last option that comes to mind, especially if both sides rise and the driver side air spring has normal height of 10 inches, is that the air leveling system used when the coach is parked (if you have one) is adding air to the passenger bag when it should not be. I'm not sure that is even possible but I thought it was worth considering if another air control system could be involved here.

With only one valve regulating the front height, the geometry of the frame has to be in control of the side to side offset given the rear of the coach ride height side to side is correct. You may also gain some insight as you let air out of the system, seeing which side nests first to the full drop position and if it appears that any frame twisting occurs in the last several inches of drop between the driver and passenger side.
Lastly, just measuring the frame spacings and configuration near the air springs on both sides when full in the ride position and empty in the lower position may reveal some frame configuration differences side to side that could help explain what is happening. Hope this helps.

Later Ed

[Steve Huber]

Ed,

Thanks for the tips. I'm beginning to think Gerald may be right about the torqued frame. I don't think it's an air problem as I switched the manifold outputs so the left manifold fed the right side, and vise-versa. The problem stayed with the right side.

Both sides will raise and lower with no problem. When I level the coach on a declining surface, the front raises to max with no problems or sounds and is level, as it is when I dump the bags.

I'm able to get a level ride height in the front by adjusting the rear adjusters but then the problem switches to the rear with the drivers side high.

Air dump from ride height results in low side hitting stops first as I would expect assuming equal volumes of air are dumped from each bag.

Thinking about it I remember that just after I got the coach it was having a problem with park leveling. It would level but would be preceded by a loud metal bang. Shop found that frame was hanging up due to a bad u-bolt on the left rear leveling pad. Replaced pad and properly positioned u bolt and no more noise with smooth leveling. Wonder if hang up was enough to torque frame(??).

I'm still having a problem getting my head around the bent frame idea because of the following:
-Hard to envision a bent frame would drive the front bag ~1.75" out of spec and the aft bag, less than 5' away stays in spec.
-Coach will sits level (front and rear) when I dump the bags, unless weight is enough to force frame to seat in stops.

I'll continue checking based on your input. My chassis service shop has a lift so will troubleshoot it there if I'm not successful. Worst case we should be able to "split the difference to get both front and rear close to level. Will let you know results in any case.

Thanks again,  Steve