Air suspension fault light
 

Hi,


I have a 2004 VDP with 148K miles, and wondering what is waiting for me ahead with the air suspension. Little over a year ago, I started getting the air suspension fault warning light, but the car never went low while driving. During that time the battery was weak, so I replaced it and didn’t see the warning light until about a month ago, when the light would come on at the slightest sudden lane change or turn. The light goes off after the car has been parked overnight or for an extended period of time, usually few hours. The ride quality does not change when the light comes on neither the car suspension as long as the car is running. The suspension have gone down from the front after the car was parked, but it rises immediately as soon as it is unlocked if it was locked or started if it was unlocked. On two occasions, I heard hissing coming from the front passenger side over the air shock area. In these occasions, the car would go low from the front, but again, as soon as I unlock or start it the front would raise again immediately. I am in California and it is currently winter, but the weather is not that cold. It could get around 35-40 degrees Fahrenheit at night.
Any thoughts on what might be going on with the air suspension? It is normal operation or a sign of bad things to come?

Thanks.

Replacing the compressor seal may eliminate the light.

It would be worth doing since it obviously worries worries you.

Sounds like the right front air shock may be leaking which might explain the hissing sound. This is a relatively common problem with this MY car as it ages and it will cause the compressor to run more that it should. There is a lot of info on this forum on how to troubleshoot this issue and how to fix it. The air shock will leak around the top seal and you can test that by carefully spraying a soap solution on the top seal being careful not to soak the electrical connection. If it's leaking there are replacement parts you can get or you can convert it to a coilover. It's something that can be fixed and can be done by a DIYer with the proper tools. Good luck with it.

Thanks for your replies. I downloaded couple documents about the air suspension. I'll read the material and will diagnose the problem and report back my findings when I have them.

Hi,
I did the piston ring seal upgrade and it certainly helped the suspension, but mine definitely had at least one leak somewhere else in the system
This could well be the case for you too and it's such a hard problem to diagnose; the 4 shocks themselves, the compressor, the air tank, solenoid valves, any of the plastic air line tubing etc etc and they're not easily accessible parts...or cheap!!
I ended up going the coilover route and it's brilliant! Not that i'm trying to convert you or anything, just letting you know how I fixed my air suspension :icon_razz::icon_goofygrin:

your problem could well just be the compressor tho, in which case the seal kit is a good idea for only £25
I also had a terrible problem with the tiny flexible hose that attaches to the compressor (the most important one!) it just kept leaking air where the pipe comes out of the brass fitting and that brass fitting screws into plastic on the compressor which is very easily over tightened (ask me how I know!)
This would regularly leak air and was audible from outside the left fender.
I used some of that squishy putty 2 part epoxy stuff (looks like jb weld) and smushed that all around the fitting and tbh it actually worked.
I had the air suspension fault light come on permanently though so I had other issues with the system as I said, but i would recommend the repair kit as a start

hope u get it sorted

Since I wrote the initial post, the passenger front air shock went bad and it wouldn't hold air anymore. I identified the fault due to the air coming out of shock. I bought an Arnott replacement and after a lot of procrastination and watching the very good Arnott replacement video, I decided to take on the task of replacing the shock. I removed the shock successfully and placed the new one in. Now I am up to the step where I need to screw in the upper A arm to the hub assembly mount, but they are so far apart that I have not been able to bring them together after at least 1 hour of trying. I thought of using a ratchet straps, but I couldn't get it to work, so now I have been trying with the strap and pure muscle, but still can't get them to meet. I was thinking of jacking up the hub assembly but I am reluctant to try it. Want to check for suggestions first. The new shock is full of air and that's what Arnott recommends. Maybe if it wasn't full of air, it would make the job easier. Any suggestions to how to bring the hub assembly and the upper arm together?

https://cimg9.ibsrv.net/gimg/www.jag...f3fb9ee046.jpg
That's how far apart they are

https://cimg9.ibsrv.net/gimg/www.jag...2c26f24ced.jpg
that's how close I am able to get them with the strap. Even if I get them to meet, the screw will not go through the hole because of the hook.

wow! You are so lucky your area doesn't salt the roads during winter!
Yes you are correct, just put the floor jack (maybe with a piece of wood) under the lower control arm ball joint and jack it up until the hub extender arm and upper A arm meet... or until the vehicle reaches a ridiculous angle :D
I would disconnect the air line from the shock before jacking it up though, just to make it easier.
For peace of mind, I had to jack my last vehicle (x type) to a 45* angle to refill the transfer case oil... so you'll be fine!

This may be a dumb question but is the front end jacked up with both front wheels off the ground?

Yes, the front was jacked up from both sides.

Jacking up the control arm did the trick.

I'll summarize the account of the events and the resolution for others with the same issue.

I started getting the suspension fault error intermittently. Initially, it would come up maybe once a week, then the frequency started to increase over a period of 4-6 months until it started to appear every day. Once I heard a hissing from passenger front side, so the indication was that something might be wrong with the passenger front strut. One day while I was at a stop light, I felt something like a big puff of air and the car immediately lowered and I got the "car too low" warning. I was not far away from home, so I drove back and parked it. I did not do any further testing, I just concluded that the issue had to be passenger strut and decided to replace it myself. I bought an Arnott S2888 replacement from Rock Auto.

Arnott has a very good installation video and it seemed something that I could do, but I also read a lot about people having a hard time unscrewing one or more of the bolts, so before I ordered part, I took the front passenger side tire out, sprayed the bolts with penetrating fluid and tested to see if was going to be able to unscrew the bolts, and I had no issues. It probably because the car never seen snow or salt. There was no rust whatsoever.
After the part arrived, I started the replacement by jacking up the front of the car from both sides. I then followed the Arnott video step by step, so there no need for me to add pictures. Removing the strut took little time, but I could tell it was doable. Putting the new one in was a struggled because I could not get the upper A arm to meet the hub assembly until I used a jack to push the hub assembly up. The whole process took me around 3 hours, but if I was to do it again, it will not take more than an hour. When I started the car, it raised up immediately and everything worked perfect.

​​​​​​​When I did mine, I jacked up one side at a time, mainly because of space limitations but also just because the car is more stable on 3 wheels
I had a nightmare with mine because of salted roads and those steel subframes are just coated with plastidip or something completely useless.. though I was doing the coil-over conversion, the same problems would have applied if I was replacing the air shocks too
If you're bored you can see my post on this thread:
https://www.jaguarforums.com/forum/x...rience-195923/

Good luck to anyone who lives in a salted area :icon_violin:

@WLinSTL, thanks for pointing me to your post. Great post by the way. I was considering a conversion to a coil-over but decided that I'll replace just one strut and sacrifice the cost, and if I continue to encounter issues, then will do the conversion. The car is very clean and well maintained, but with a lot of miles, so it might be just a matter of time before a conversion is needed.

mhannaoui
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Thread Starter

The arms will pull down easily if you loosen the mounting nuts a little.
The floor jack works as well,.
Waiting to tighten the two mounting bolts, makes things work a lot easier for me.