I am getting an intermittent Air Suspension Fault warning light on my 2005 XJ. Does this ALWAYS mean that the suspension is failing or is there a way to test to see if it's something as simple as a loose wire or bad sensor? Is there a way to see if, in fact, the air suspension system is failing without having to replace it?

No, no, yes. ;-)

The air suspension on an XJ is not one part but consists of several parts. The main difference you see are people that have the ASF message but the car is not riding lower over time or the car losing height (with or without ASF message). If the car doesn't loose height the air shocks themselves are good and it's probably related to either compressor and/or electronics. Reading the fault codes can help there. If it loses drops it's usually related to either air shocks and/or height sensors.

Guus

As Xag says, get the fault codes read.

If the suspension seems completely normal, like correct height etc, then I suspect you'll have C0203 indicating a failing compressor. This is a known short life part of the air suspension system, but is easily cured with a new piston seal. Our forum member 'bagpipingandy' makes and sells them for the Wabco compressor used by Jaguar. New compressors are around the £300 mark on the internet.

The car seems to be riding just fine so let's hope it's just the compressor pump. I did find the pumps on eBay that Bagpipingandy sells. Once I have had my mechanic confirm that it is just the compressor then I think I will buy one from him. I'm not much of a mechanic so I'll probably have to see if my mechanic will do it for me. Sometimes they don't like to install parts they haven't sourced themselves.

Hi GrahamPhotog,

I tend to agree with Guus and Fraser that the most likely suspect is a worn piston ring in your air compressor. Since Andy's replacement piston ring is so affordable, and the replacement job is relatively easy, it would be worth doing it as a matter of course on a nine-year-old car. Below are links to photos I took when I did the job, which may be helpful to your mechanic. Most folks don't bother replacing the desiccant beads as I did, but it would be a very good idea to at least open up the air dryer and exhaust valve to check for and clean any corrosion you may find:

Welcome to Jag-lovers - Members Photo Viewing Page
Welcome to Jag-lovers - Members Photo Viewing Page
Welcome to Jag-lovers - Members Photo Viewing Page
Welcome to Jag-lovers - Members Photo Viewing Page
Welcome to Jag-lovers - Members Photo Viewing Page
Welcome to Jag-lovers - Members Photo Viewing Page
Welcome to Jag-lovers - Members Photo Viewing Page


Please keep us informed.


Cheers,


Don

Don, thanks for the photos. You did clear one point up for me. I thought that Andy made and built the entire compressor, but now I see that it is only the piston ring. I couldn't understand his really low price until now.

I will definitely call my mechanic and ask him about replacing just the piston ring. The light hasn't come on in two days now which is leading me to believe that the problem is with the pump and not the shocks themselves. Of course, as soon as I start it up again the light will come on!

i wish i could offer compressors at £25, i would sell lots but probably wouldnt be in buisiness for long

it does sound like compressor issues for now, the error being very intermittant is a good sign its the compressor being weak,

any questions please just ask

regards
Andy

I called my mechanic and he still says that I need to replace all of the shocks. His reasoning is that the compressor pump is failing because the air shocks must be leaking. I also called the local dealership and they pretty much said the same thing.

Hi GrahamPhotog,

I must respectfully disagree with both your mechanic and the dealership. The piston ring or seal in the compressor is made of PTFE (Teflon), which is a relatively soft material. The piston and connecting rod are one solid piece, with no wrist or gudgeon pin, so as the piston moves up and down in the cylinder, it "wobbles," which promotes wear on both the leading and trailing edges of the seal. This wear happens whenever the compressor runs, regardless of the condition of the shocks; whether they are leaking or brand new. As the seal wears, the compressor loses its efficiency and its ability to pressurize the system within the 120 seconds alloted by the Air Suspension Control Module (ASM), before it shuts down the compressor to prevent overheating of the seal and cylinder. It is this failure to pressurize the system within the alloted time that triggers the ASF warning. Replacing the seal is inexpensive and not difficult, and since so many of us have had great success with bagpipingandy's new seal, I would highly recommend you give it a try before shelling out the high cost of replacement shocks.

Cheers,

Don

I doubt if you can feel a leak from the ride at this stage. Measure if it sags overnight or not.

Guus

The system also vents air out when functioning fully normal so needs the compressor to add air again. It doesn't has to be leaking shocks at all. If the car doesn't sag if left alone for a while then you don't have a problem with the air shocks themselves. I very much dislike people that dispense advice like this without being able to decently explain why it is actually needed. There's absolutely no logic behind replacing shocks on a car that doesn't sag.

Guus

I think it has to be accepted that with air under the sort of pressures it is in the system, that there is bound to be some leakage of air. Think about your air con system in the car. Why check it every year if the gas cannot possibly escape ? Yet we all know that some gas is lost every year, although not much. Of course, with the air suspension system, air is exhausted after most runs to clear out the water trap, so must be replenished when necessary, hence the air compressor. Clearly, if shocks are leaking significantly, the compressor will be called in by the ASM to recharge the reservoir more than normal, so can wear out. However, in the case of this thread, it looks much more likely the compressor seal has worn out. And as replacing that is the cheapest remedial action, this is the first line of attack. Never spend a lot of money when a little works just as well.

I think I will go and buy one of Andy's kits. Since I am not mechanically inclined enough to remove the existing compressor myself I'll have to find someone else other than my current mechanic to remove and reinstall. I do know of a local mechanic that sometimes works on Jags. He is a bit of a curmudgeon so don't know how he will react to installing a part that he didn't source himself. I'll also measure to see if the car sags overnight. By eyeballing it I don't think it is sagging.

Hopefully your curmudgeon will understand that the part you have sourced is not available through normal channels. Show him the photos I linked in an earlier post and hopefully they will help speed things up for him. Please keep us informed!

Cheers,

Don

Maybe this helps to convince him too.

http://www.bagpipingandy.com

Guus

If the car doesn't sink this means their are no leaks, its a good one!! Keep it!!
Only if the car was sinking down when parked, would we then suspect leaking airbags/shocks, if the car doesn't sink the mechanic is wrong.

it the error is intermittent and the car doesn't sink, & the system appears to be working other than the intermittent error, then a weak compressor is the issue.

any questions just ask.

best regards

Andy

Last night I took the car for a 30 minute drive and checked the height of the car from floor to the top of the wheel well. I subsequently checked the height after the drive and again this morning. The height dropped overnight by about 1", but went back up to 28 1/2" after I started the car up. I also used a builder's level back to front and side to side, and the car is level.

Interestingly Arnott's website states that with respect to their own pump that
" Airsprings Need To Be Changed Prior To Time Of Compressor Replacement~ Failure To Repl Airsprings Will Result In Premature Compressor Failure." They are also selling some overstock Wabco compressors and for them they state, "Air suspension compressors typically burn out when there is a leak in the air suspension system. After installation, Arnott recommends testing your system for leaks.". So, for their own compressor it sounds like they are recommending that one replace the air springs at the same time, whereas with the Wabco they only say to test the system for leaks. I will call them today for a clarification.

I have since called Arnott and spoke to a really helpful tech by the name of Marvin. After explaining the car's symptoms (or lack thereof other than the light) he suggested that one of the wires to the air shock might be loose or corroded. I have just unplugged and re-inserted the two front wires, and I will see if that does the trick. If not, I will do the same with the rear which are a little harder to get at.

Ok, monitor this sinking, (only when parked) if it sinks to the bump stop if left for longer then you have a leak, it may only be very small if it doesn't sink all the way to bump stops.
If it sinks every night the same spray the top mount with soapy water, it may just be the airline connection leaking

you do not have to change airbags before fitting a compressor but you must repair any leaks or it will shorten a compressors life, a big leak is a car sinking in less than 1 hour, the fact yous sunk 1" overnight could be a small leak hence monitor it over the next few nights or when left parked, then use soapy water to source the leak, it may not be the physical airstrut could simply be the airline fitting.

arnott will gladly sell you 4 airsprings and a compressor which would probably fix it, but its not diagnosing the source of the problem and fixing it economically. Which is where you guys and the forum comes into its own

best regards

Andy

After much dithering I finally resolved my Air Suspension Fault light on my 05 XJ. I had a set of new Bilstein coil shocks installed today. The ride is a bit firmer (in the past the car just seemed to glide), but it still very comfortable. I didn't like spending the money, but at least I don't have this hanging over my head any more.

Graham, thanks for the update and good to hear you have it fixed!

Guus