U300 Air Suspension

Topic: U300 Air Suspension (Read 918 times) previous topic - next topic

U300 Air Suspension

June 26, 2017, 06:55:59 pm

I noticed today while idling that my coach rises up off the wheels, but that the left front is quite low. It has not been driven for two weeks. I can raise the left front with the outboard lever, but when I release it, it sags back down; I can hear air escaping.

Could this be due to idling (vs. higher power underway)?

Thanks for any insights.

Re: U300 Air Suspension

Reply #1 – June 26, 2017, 07:09:47 pm

Could be that corner is set too low, and seeks it's "correct" level when you let go of the manual adjustment.

Len

Re: U300 Air Suspension

Reply #2 – June 26, 2017, 07:12:52 pm

Yup, need to set RIDE HEIGHT.

Idling is not the issue-- assuming you have adequate air pressure.

Two ride height valves in back, one in front.

Re: U300 Air Suspension

Reply #3 – June 26, 2017, 07:36:54 pm

It acts that way. My Ooerator's Manual addresses the air system in a very vague way and I cannot derive any useful information from it. There is, for instance, no description of the location or operation of the controls. It refers to panels I cannot find.

Re: U300 Air Suspension

Reply #4 – June 26, 2017, 07:38:24 pm

Thank you. And are those controlled at the valve or by the leveling controls next to the driver's seat. I can find no useful description of the operation of the system in my manuals.

Re: U300 Air Suspension

Reply #5 – June 26, 2017, 07:46:17 pm

I notice reference to "HWH Leveling Panel" in some online FT documents, but I cannot find the panel. Does the '89 GV have this system?

Re: U300 Air Suspension

Reply #6 – June 26, 2017, 07:56:48 pm

No HWH auto leveling on your coach. Our 1991 U300 had the same manual levers on the floor by driver seat. Those are only adjusted when parked to level the coach if needed. The levers should be in the centered position to drive. When levers are centered, all 4 corners should be at ride height. My quick and dirty check was a closed fist should fit between each tire and top of wheel well with about a 1/2 inch of clearance. You adjust the ride height by moving the vertical rod at the height control valve. As Brett said, you can adjust each rear valve, only one adjustment for front valve. If the rear is even, but the front is not, you need to investigate why.

Re: U300 Air Suspension

Reply #7 – June 26, 2017, 08:06:07 pm

Thanks, this clears up much confusion.

It's strange--coach was fine when I parked it at storage facility, but now there is a noticeable difference left-to-right in front. I can raise the left side, but as soon as I return the lever to neutral, the left front corner drops back down; there is the sound of air escaping as it drops.

Re: U300 Air Suspension

Reply #8 – June 26, 2017, 08:09:17 pm

The issue will be in the rear unless you have a bad front left air bag

Re: U300 Air Suspension

Reply #9 – June 26, 2017, 08:11:27 pm

For what it's worth, the rear is dead level. Is there a troubleshooting reference for that particular model year/installation?

Re: U300 Air Suspension

Reply #10 – June 26, 2017, 09:18:16 pm

You need to find where that air is coming out when you return the levers to centre. It could be a bad levelling valve or even the linkage could have come off of the valve. It likely isn't an air bag as it would leak when using the levers as well. It could be a broken or split air line.

Re: U300 Air Suspension

Reply #11 – June 26, 2017, 09:21:03 pm

Quote from: RandallBrink – June 26, 2017, 08:06:07 pm

I can raise the left side, but as soon as I return the lever to neutral, the left front corner drops back down; there is the sound of air escaping as it drops.

Keep in mind that the left and right levers only adjust the rear wheels. You are essentially "twisting" the coach slightly to raise one side or the other. The escaping air is normal as the suspension adjusts from a higher setting to a lower setting.

Re: U300 Air Suspension

Reply #12 – June 26, 2017, 09:21:08 pm

It's a pretty simple system. You have 3 levers on the left side of the seat. The levers have teleflex cables like on a speedboat steering/throttle. and rotate the leveling valves letting air in "raise" or out "to lower". Moving the lever forward lets air out dropping that side and pulling lever back lets air in and up you go . The left handle rotates the left side rear valve letting air in or out. The center lever controls the front. There is only one valve in the front that controls both left and right front air bags. The right lever controls the right side rear air bag. All left and right rotation is done with the rear air bags using the left and right levers. Front to back leveling is done with the middle lever either raising the front or lowering it.
If your left front is dropping you could have a leak in the air bag or maybe the air line to it is leaking.
If you crawl under you will see the air valve with the cable attached to it also the air lines going to each air bag. It should not be hard to figure out what is going on. No computers no electronics just simple simple mechanical system.

Re: U300 Air Suspension

Reply #13 – June 26, 2017, 09:21:49 pm

I have also seen where the levers for the old style leveling system (basically change the orientation of the ride height valves) gets hung up from lack of use. So, centering the lever doesn't really return the ride height valve to its "original an upright position".

So, make sure that this part of the system works freely.

Re: U300 Air Suspension

Reply #14 – June 26, 2017, 11:09:25 pm

Maybe you got under control now but here's an old post with the same info but worded differently:
leveling problem

Re: U300 Air Suspension

Reply #15 – June 27, 2017, 07:21:39 am

A point that might be confusing for a new owner with the manual leveling system is, when you move a lever to raise or lower the coach, you leave the lever at that position while parked, and then center the lever when you are ready to drive.

Re: U300 Air Suspension

Reply #16 – June 27, 2017, 12:15:42 pm

Ah, good point; didn't know. I'm going to move the coach today to level asphalt to determine if there is a problem, or whether it is my imagination, over-stimulated as it is by the discovery of unanticipated coach problems.

Thanks very much.

Re: U300 Air Suspension

Reply #17 – June 27, 2017, 04:51:02 pm

Flip your dash up and look on the passenger side and see if There is a piece of paper stapled there with the toe setting for the alignment and the air bag ride height measurement. I have one on my coach and the ride height airbag measurement is 8 1/4 inches.

Re: U300 Air Suspension

Reply #18 – June 27, 2017, 06:40:31 pm

I do have the placard inside the glovebox lid. Where is the measurement taken/read?

Re: U300 Air Suspension

Reply #19 – June 27, 2017, 07:01:56 pm

Measure from the bottom of the top metal plate the air bag attaches to and the top of the bottom plate. Levers in the middle travel position you'll feel the indents and no level light on.

Re: U300 Air Suspension

Reply #20 – June 28, 2017, 01:13:00 pm

Thanks--so just to clarify, I am measuring the total height of the bag itself from top to bottom.

Re: U300 Air Suspension

Reply #21 – June 28, 2017, 03:10:16 pm

Quote

I am measuring the total height of the bag itself from top to bottom.

Correcto. It's kind of hard to do with a tape but you can make a no cost measuring tool. Just take a 1X1 or whatever and drive two nails into it 8 1/4" apart. Then you just slide the nails toward the air bag and you'll be able to get it just about right.
jor

Re: U300 Air Suspension

Reply #22 – June 28, 2017, 04:55:24 pm

The low side sits at 7 1/2, whereas the right- or "normal" side is 9 1/2". Pressure, front and rear, is 118 psi.

But at 7 1/2, that leaves the coach floor only about 3 inches from the tire on the left front.

(FWIW, the ground is not totally level, with a dip at approx the same position as L-front tire.)

Re: U300 Air Suspension

Reply #23 – June 28, 2017, 06:46:09 pm

it must be level to measure properly. Looking at your measurements if the left side was 1" higher and the right 1" lower you would be spot on, so maybe it is correct. Find a parking lot or? that is level and recheck.
JohnH

Re: U300 Air Suspension

Reply #24 – June 28, 2017, 07:44:56 pm

Thanks John. I'm hoping it is entirely due to the uneven ground at the storage facility. I'll check it on asphalt before worrying further.

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