Hi everyone, I'm new to this forum and hope I can get some help from those of you that are experienced and willing to offer some insight....

Here's my issue with my air suspension:

About a month ago, I was driving to church when I drove over a massive pothole. After church, the whole way home, I could tell the suspension wasn't working, The back end was bouncing all over the place. The next day, I went to get it checked out, but to my surprise, the bags had filled up and the suspension was working fine again, but, when I had it looked at, I was told that one of the bags on the back end had a leak in it. I then took it to get a second opinion because NTB told me it would cost $1200 to replace that bag. At the second shop, i was told they were both fine. So i decided to go about my business and not fork out the $1200.

A few weeks later after getting home from a 3 day trip, upon picking up the navigator, I noticed that again the car was bouncing around on the road. I pulled off the side of the road and the bags were indeed flat. After about 5 minutes of sitting, though, they were completely inflated again and the drive home was perfectly fine. (I'm not sure if this matters, but the temperature was around 40 degrees, which was about the same temperature when I was going to church when the problem first started).

Since these 2 occasions, I haven't had any problems with the bags not being full. It's driven perfectly fine, however, over the past week, I've had the message on the dash that's said "Check suspension". Does anyone know what the problem could be? or any troubleshooting ideas? Like i said, Its riding perfectly fine, there's only been those two instances ( 1 - After driving over the massive pothole, and 2 - The car sat for 3 days in the bitter cold) Any suggestions would be appreciated. Thanks ahead of time!!

 

Check all of the ride height sensors to make sure none of them broke loose from their mount.

 

oakley_kobe-
I've been working on my 05 expedition's air ride suspension lately too. Here's a few things to look for:
1. Can you hear when the compressor runs? Kind of a low pitched vibration that comes and goes for a few seconds each time it runs.
If you can hear it running, and it runs more than usual before you get the "Check Suspension" light, you likely have a leak somewhere and the compressor is working really hard to try and keep up with it.
2. Do you have a scan tool that can read MS-CAN sensors? You can use a PC program called "Forscan" that will show you the outputs of all of the air ride computer's sensors (and a lot more). It's really handy to troubleshoot these kinds of problems. You can do a search on the forum if you don't have one. There are several other threads that detail how to get into that.
3. When you are parked with the car off, do you ever hear air leaks or hissing sounds?

Now to bring it all together:
The air ride system uses a compressor, air tank, hoses, solenoid valves, air springs and sensors to maintain you vehicle at the proper height and "tilt". The vehicle's VDM (vehicle dynamics module) computes the input from the ride height sensors. There is one on each front wheel and one for BOTH rear wheels. It uses that input to either open or close the solenoid valves on each air spring to air it up or let it down. It has a vent that opens if it needs to let it down. It is supposed to be in a lowered state (about 1" lower) when parked (to make it easier to get in and out), then once you are started, with the door closed and out of park, the air springs will rise back up. As you drive down the road, the ride height sensors will be moving around a lot. The VDM takes that input and uses trends and averages to keep the vehicle riding at the right height. It also make adjustments as you make turns, speed up and slow down, or put it into park. It's a pretty neat system.
So, here's what is happening on mine, which sounds similar to what you are seeing... The air bags are thin rubber. They sit in one position most of their lives (while parked) and that rubber starts to dry rot. As it does, one of the dry rot slits will make its way all the way through the rubber and when the bag is in the right position, that slit opens up and air leaks out. The compressor comes on and pumps it back up until the leak gets so bad, the compressor can't keep up. Then "Check Suspension" light comes on. That's the cars way of saying "I give up". It shuts off the system and the leak eventually drops the vehicle so it is riding on nothing other than the rubber stops inside the air spring. It will seem to ride very low at this point, and VERY rough. Like, throw you out of your seat when you hit a bump, rough. The system may shut down with one or more bags still holding air. The car may seem to lean at that point and be rougher than usual, but not as bad as if they all went down.

In my case, I had a rear bag that was leaking as I described above. I replaced both rear bags myself. You can buy them for about $80 each. After I got it all back together, I started it up and it wouldn't air up. That's when I heard one of the front bags leaking. If I picked up on the truck just enough to get the leak to slow down, the compressor could overcome it and the system would air up properly and hold for a while. However, I've seen on these forums, and noticed myself directly, that when it is colder, the leaks are worse, and the system has a harder time stabilizing. So, I ordered two front bags and am about to go out there right now and change them out too.

Here's a little advice if you plan to change them yourself. Find out what O-Rings the bag seals take and get them beforehand. If you want to do it right, Ford sells an install kit with new hardware and the orings but it is about $50 each bag, almost doubles the price. You can't get these sized orings at the hardware or autoparts store. I could only find them at the hydraulic overhaul shop in my town.
Consider doing all 4 bags at the same time. The cost will likely end up being the same, so you might as well plan on it up front.
Have a big pipe to use as a cheater bar. Those 30mm nuts are a bear.

Alternatively, I have read many people who convert back to coil springs. There are endless threads on here about that. Personally, I thought it was cheaper and nicer to keep the air ride going on mine, but that's a personal decision worth considering before you invest any time or money on repairing your system. More than one person put a lot of money into repairs, just to give up and do the conversion later out of frustration. I might even end up that way!

Good luck. I'll be back on the forum more today if you have any more questions.