Greetings all lovers of these wonderful but sometimes problematic vehicles. Yes, I have RTFF but did not run across my issue specifically. Let me offer some clarity.

I purchased my 2004 XJR (VIN ending in 16398) about four years ago with 45k miles. Been a great daily driver; however started getting the dreaded air suspension fault a couple of years ago, but only so often. Had the car diagnosed, and it was a faulty relay. Of course all good things must come to an end and I lost a rear bad. I bit the bullet and changed all four corners to Arnotts. However, the car continues to occasionally throw the warning light. Weird thing is it is not logging codes. Took the car to the dealer; did the overnight leakdown and determined the front was dropping about a quarter inch, and the compressor came back within limits. I also just replaced a battery, with winter on our doorstep.

I started the car cold and bounced the suspension up and down for 5 minutes the other morning - certainly long enough to throw a compressor code, wouldn't you think? No light. It only happens when driving, and usually when the car hits a unexpected bump - perhaps only on the right side.

So...ride height sensor perhaps? I believe my vehicle actually has a right and left (though I haven't looked) based on the VIN. Any other ideas?

I bow to the wisdom of the board. Please help me extinguish that damnable yellow light I see in my dreams.

 

Bigsilvercat,

Welcome to the Jaguar Forums!

A number of possibilities come to mind, including a loose or oxidized electrical connector or ground point in the air suspension system.

From your post, I gather that the compressor is original and that you have not replaced the piston ring?

Regarding the Arnotts replacement shocks you purchased, were they rebuilt Jag units that preserve the CATS functionality or the proprietary Arnotts units that do not?

Please visit the New Member Area - Intro a MUST - Jaguar Forums - Jaguar Enthusiasts Forum and post an introduction to share some info about yourself and your car.

Cheers,

Don

 

Thanks for the welcome! Correct, the compressor has not been replaced or serviced. The arnotts are their manufacture, not rebuilt. I would think that were the compressor timing out, I'd get a C2303 code logged. I am on the cusp of replacing/repairing the compressor anyway just to see if it impacts it. Thoughts? Thank you!

 

My first reaction to your description of the behavior wasn't compressor timeout. Since you suspect the problem happens when you hit a bump, especially on the right side, I wondered if a loose or corroded electrical connection might be losing contact when jarred, triggering the ASF. The manuals only give a few circumstances under which the ASF warning appears, but they don't seem to explain all the ASF occurences reported here, so there are still some things we don't fully understand.

But one thought occurs to me: When the Arnotts shocks are installed, is there some modification to the system to account for the fact that the CATS functionality is lost? If this modification involves any electrical connections, could one of those be susceptible to bumps and jolts?

Since the compressor piston ring is made of PTFE (Teflon), it's relatively soft and wears out in time, and 10 years is plenty of time for that to happen. I would personally replace it as a matter of course. The part is inexpensive from forum member bagpipingandy, and the job is something almost anyone with basic tools and willingness can do. Below are links to photos showing the process. Most folks don't bother replacing the desiccant as I did:

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


This document at the link below contains the best explanation of the air suspension that I'm aware of:

http://www.mediafire.com/view/7rdkgg...on_Section.pdf


The X350 Workshop Manual provides some explanations fault modes (the Air Suspension is in the Chassis section):

http://www.mediafire.com/download/md...f+contents.pdf
http://www.mediafire.com/download/aa...nformation.pdf
http://www.mediafire.com/download/n3...2.+Chassis.pdf
http://www.mediafire.com/download/9b...Powertrain.pdf
http://www.mediafire.com/download/0i...Electrical.pdf
http://www.mediafire.com/download/4j...+and+Paint.pdf


Cheers,

Don

 

Hi, the compressor does not ussually run until you move the car above 15MPH hence bouncing it will not trigger it to start, if after 10 mins of driving you get the error light this would point me towards the compressor being weak and at fault, my repair kit should cure this

any question just ask

regards

Andy

 

Thanks All...what I fond so odd is that is that there is no apparent rhyme nor reason to when the light activates. I had driven the car for a week with no light; yesterday the light activates just after hitting a rough spot. nothing major like a pot hole just rippled pavement. I know these gremlins are hard to chase but this is making me crazy.

 

I think the following may happen. On my car I had the light come on quite often so I did a lot of measurements on the function of the suspension. One thing you see is that the pressure in the system is not always the same. After replacing the seal with Andy's the message was gone but I also had a leaking shock which was replaced last month or so. After that the car sits perfectly level but...

I've had the ASF light come on again twice, strange since I didn't have it for so long. What I think happens is that when the car is parked and the pressure in the system is lower you have a chance the light comes on next time you drive it. If there is enough pressure it won't. Also when you wait a short while before driving off the compressor may have a bigger change of filling the system in time. If you encounter a big bump the system can release air which then may need the compressor to fill the system again. At that point it might run out the set control cycle of 2-3 minutes.

Just my theory ;-)

Guus

 

That's as good as any, Guus...Another thought, maybe Andy can contribute here: When the compressor goes south, does it allow air to escape from the system as well, as a leaking shock would?

 

A worn piston ring won't allow air to leak from the compressor, but there are several places in the compressor where leaks could potentially occur:

1. Corrosion in the exhaust valve could prevent it from closing completely (some of the problems reported on this forum would seem to indicate that this is quite possible)
2. Rubber sediment build-up around the check valve could allow pressure to leak back into the cylinder
3. A hardened or damaged O-ring on the outlet air hose could leak (this has been reported)
4. Hardening of the large O-ring between the cylinder head and air dryer could potentially leak (probably unlikely at the current age of our cars, but in the future it may become very likely)
5. Even less likely but technically possible, a failing pressure relief valve or damaged leaf valve on the top of the piston could allow leaks.

For photos of these components see the links I posted earlier.

BTW, keep in mind that the system is designed to periodically open the exhaust valve to release air; for example, to backflow dry system air across the desiccant beads in the air dryer to partially reactivate them (often done right after shutting the engine off at the end of a drive), to relieve some pressure to make it easier for the compressor to restart, or to help keep the vehicle level when parked on an incline.

Cheers,

Don

 

+1 compressor piston ring

 

I would say the components on a the compressor will not cause the car to sink at all, you can remove the compressor from the vehicle completely and it should not sink, i agree their are valves on the compressor but the electrically controlled valve (n111 valve) on the compressor has 2 jobs, it is to relve the pressure from the line to the valve block every time the compressor stops, and it opens to lower the car to vent air out but only when the valve block in the boot opens the valve pairs to let air out it is vented back to the compressor and out the N111 valve. it is the valve block in the boot which holds all the air in the system, not the compressor

if the car sinks, the air can only leak out from the airbags themselves, the airbag o-rings/fittment, the airline connections and or fittings or the valves and fittings in the valve block in the boot not sealing, the compressors job is only to provide air for lift/adjustment.

edit:
i read it as the car was sinking sorry
if the compressor is not producing pressure this can be because of the list from Don B above, (along with the no1 reason, the pistin ring worn ) these would be leaks at the compressor to cause low pressure & weak compressor symptoms but the car would not sink at all because of these.

best regards

Andy

 

Just wanted to say thank you to all that have commented. I truly appreciate the feedback and input.