Hello everyone,

I've been receiving random "Air Suspension Fault" messages on the dash for about three weeks. There didn’t seem to be any rhyme nor reason to the timing. Since I had successfully rebuilt the compressor 10 years ago and found it to be a simple procedure, I decided to do it again (along with throwing some fresh Akebono pads on the front wheels while my hands were refreshingly dirty).

Naturally, that didn't resolve the issue.

By accident, I discovered that the car was still running on its original battery—making it over 20 years old (see photo below)! I immediately replaced it with an Interstate H8 AGM from Costco. At $180 it was a bargain compared to other sources for the same battery.

The suspension error messages went away for a bit, but yesterday the fault came back on after about 10 minutes of driving. Today, it popped on instantly right after hitting a sharp bump (railroad tracks).

Mechanically, the suspension seems perfectly fine. The car pumps up beautifully and doesn't sag. After sitting for 15 hours, the ride heights (measured from the floor to the fender lip) are holding steady at:

• Front Driver / Passenger: 28 ľ”
  
• Rear Driver / Passenger: 27 ľ”
  

Before I rebuilt the compressor, I scanned it and somehow deduced the pump was the culprit, though I can't recall the exact code. Given that the car holds its height perfectly but throws a dashboard fault randomly, I'm starting to suspect a glitching height sensor or a wiring issue rather than a physical air leak.

Before I dive back into searching the threads, I thought I’d ask this august and highly esteemed body of refined scholars, gentlemen and fellow grease monkeys for suggestions. Any insights would be greatly appreciated!

Carpe diem,

Steve S.

 

Just in passing, AGM batteries are not preferred for the X350, they don't like the high voltage loads of the X350.
I concur with your view of a maybe not firmly attached or failing sensor or wiring issue: to be checked.

 

I'm firmly in the camp of stop throwing money at the air suspension and put coilovers under the car. Suspend it with steel the way God intended, 100% always usable and 100% reliable.

The air system is far beyond its design lifetime. Yes, folks have them still working well, but most still have the occasional glitch.

My two major dislikes with the air system...

1. There is no way to remove any water that gets past the "dryer" in the compressor. I put dryer in quotes because it is woefully inadequate in its capacity to remove water from the air going into the system. For a function so important, not making it a separately serviceable part is insane. Yes, it's "serviceable," but only by disassembling the compressor. (OK, you can get a perfectly dry system by replacing the struts, the reservoir, and the valve body, and by blowing out the air lines while you do all of that. You haven't removed water, you've replaced expensive parts. Even a drain plug on the reservoir would have helped, but they don't have one.)

2. I lied about there being two major dislikes. ALL of my issues with ALL currently available air suspension systems on the market come down to inadequate and unserviceable dryer function. Valves rust and will stick, and even if repaired will rust and stick again because the water in the system is still in the system, in the reservoir and in the struts.

My own car was drivable for only 15 minutes or so before I'd get air suspension fault messages. When I disassembled the compressor, the dryer section was a water tank and the outlet valve was rusted solid. I ordered Arnott struts, put them on in an afternoon in the driveway, and have never looked back. The car is more comfortable than before because in my case, the failed air system was very harsh-riding. My steel-sprung XJ8L is the best-riding car I have ever owned, and that includes several large American sedans known for their ride quality, and I never have to wait two minutes for it to raise up in the morning like I did before, or wonder why one corner wants to stay at maximum height; I get in and drive.