I have a 2005 XJ350 4.2 LWB that has been suffering from a leaking air suspension for a number of years. The car has been little used and am just restoring it in several ares at the moment leaving the Air Supension until last.

Diagnosing the root of the air suspension problem had so far confounded my mechanic so I wondered if anyone can point us in the right direction. So here goes with as accurate description of the symptoms as I can manage

When the car is parked up and left for a couple of hours there is no apparent drop in the suspension, however a period of about six hours the front of the car will gradually lower itself and possibly slightly more quickly on the front offside.

Starting the car will result in the car apparently doing nothing for a minute and the gradually returning to full height over another minute or so. Once up to height , the car drives normally but an 'Air Suspension Fault' warning light will sometimes come on and sometimes not.

If the car is left without starting for more than 3 - 4 days the suspension will gradually settle down all round. Then when starting the car it takes longer for the suspension to come up maybe 5 - 10 minutes before you can see it start to come up again.

If the car has been left without being started for more than a couple of weeks then even starting it won't see the suspension coming up even after it has been left running for 20 minutes. Driving the care carefully (and ignoring the 'Vehicle too Low' Warning Message) has usually resulted in the car suspension coming up.

On a couple of occasions the car was not started for several months. Starting the car, leaving it running for twenty minutes and then driving it did not produce any movement in the suspension. However on one occasion when this happened I put the front of the car on some simple carp ramps to investigate underneath and almost immediately after doing this the suspension came up. Having discovered this, if the car was ever like this and not coming up I put it on the ramps and it comes up more or less straight away.

Now I start the car every morning and in a couple of minutes the the car is up but by the evening it is down at the front again.

We ave checked all the obvious places with soapy water and there is apparently no sign of leak.

If anyone has any ideas on where we should start looking next or what to change first I would be extremely grateful.

Many Thanks Henry

 

Welcome to the forums Henry,

I've moved your question from General Tech Help to X350 forum. Members here with the same model will be able to help.

Please follow this link New Member Area - Intro a MUST - Jaguar Forums - Jaguar Enthusiasts Forum to the New Member Area - Intro a MUST forum and post some information about yourself and your vehicle for all members to see. In return you'll get a proper welcome and some useful advice about posting to the forum.

Graham

 

Many thanks Graham, Have done this. This is the first forum I have ever joined so any advice would be great.

Henry

 

Can you hear the pump running when you start the car after the suspension had sagged? The pump is in the bumper on the left/drivers side. If you cannot find a source of the leak and all sides drop equally then the pump may be going out. At least that was my case. Your story sounds similar to mine. When parked for a week or more the car would sag. It would sometimes take awhile for the shocks to pump back up. My pump had failed and was raising the car slow and also had a small leak.

Also regarding the car taking a long time to raise up when running. The pump will only run for a couple of minutes at idle to prevent the pump from overheating. From what I remember it won't run again until the car starts moving or the engine is restarted.

If you are feeling adventurous you can take off the tire and the wheel well shroud. That will reveal the pump. It will be far easier to tell if the pump is running with the shroud off. Put the tire pack on, turn the wheel so you can easily see the pump and start the car.

 

How many miles on the car ? The air compressor does not last forever, especially early ones, (improvements were made by Wabco). You have the normal symptom of it becoming less efficient and not replenishing the air reservoir within the time allowed. Eventually, of course, by switching off to cool, then on again, the compressor manages to replenish the reservoir, and a fault code is generated.

As for the car lowering, clearly there is a small leak somewhere, probably on a single air spring. The ASM is woken up every so often after the car is locked and attempts to keep the car level, but without using the compressor., so lets air out of the other springs to level the car up. So eventually the whole car will drop. You need to read the fault codes, but I would bet one of them will be C2303 "Reservoir plausibility error"

 

Thanks Fraser, it has about 125,00 on it now. Th problem began about 5 years ago but I have only done a couple of thousand miles in the last 5 years so it would have been around 123,000 on it then. The problem doesn't seem to have become worse during that time.

 

Many Thanks , will investigate later this week regarding pump noise. The bumper is already off to replace a headlight unit so can see the pump already.

 

If that is the original compressor you've done well, as I had to have a new one at 35k miles on my first X350. The new one was still on the car when I part-exed it at 115k miles for another X350, actually an X358 Sovereign. I had no trouble at all with the air suspension on the later car. Biggest problem for me with these cars is the short life of certain of the suspension bushes, i.e. they don't last 5 minutes ! OK I joke, but really what idiot designed the suspension so the full weight of the car is taken through the four quite small plastic bushes at the bottom of the air struts ? They last about 30-35k miles. Then there are the rear lower wishbone bushes, another notoriously short-life item and one has to replace the whole wishbone !! I could go on, but I did really like my car, but did curse Jaguar and Ford for their somewhat cavalier attitude to durabilty.

 

Google images "jaguar x350 leaking strut"

Lots of pics re leaks. You may need one of Bagpiping Andy's kits

to replace compressor seal.

 

Many Thanks for the advice. Have the front bumper off to change headlight unit and car has settled down all round over the last week. So tried your suggestion and switched the car on, the compressor was running for a couple of minutes and then cut out, with no visible raising of the car . Switched car off and then waited a minute and switched on again and compressor started running straight away and after a minute or so the car started to rise and after about another minute was full height all round before the compressor cut out.

When the car goes down it does seem to begin at the front off side and then front nearside follows almost straight away. Both fronts are down in about 7 hours and then after a couple of days the rear follows. I was wondering if this would indicate the leak was coming from the front offside and the rest of the car settling was due to the automatic the automatic level compensation? If we disconnect the battery would this disable the automatic level compensation and give a stronger indication that the problem was in the front offside?

 

Many thanks Fraser,

Have checked and the compressor seems to be fine. The car has been standing for about a week in the garage. Started it again and compressor ran for a couple of minutes with no visible movement on the suspension and then cut out. I switched the car off waited a minute and switched on again the compressor started straight away and within a minute started to rise and within another minute it had reached full height when the compressor cut out. This would seem to indicate the compressor is OK?

There is obviously a leak somewhere but soapy water tests have failed to produce any results. Unfortunately my mechanic does not have a diagnostic that gives results on these cars. When the suspension starts to sag after a 5 or 6 hours it does seem to begin at the front offside and the front nearside seems to follow a centimeter or so behind and both fronts are completely down after 7 or 8 hours. The rears come down a day or two later. Would this point to the leak being in the front offside ? Could the rest of the car coming down something to do with the automatic height adjustment system? I was thinking if I disconnect the battery would this disable the automatic adjustment system to reinforce the evidence that it is a problem in the front offside?

 

Hello Henry, hwaiken,

Regarding your:
[QUOTE=When the car is parked up and left for a couple of hours there is no apparent drop in the suspension, however a period of about six hours the front of the car will gradually lower itself and possibly slightly more quickly on the front offside.

Starting the car will result in the car apparently doing nothing for a minute and the gradually returning to full height over another minute or so. Once up to height , the car drives normally but an 'Air Suspension Fault' warning light will sometimes come on and sometimes not./QUOTE]

Well,
1. It's not going to be that cheap.
2. Whether it's your front shock absorber/s or rear... this is simply the time period where the air suspension rubber dries, crack and start leaking as a result of its age... it lost its strength.

I was suffering from this situation not less then you are and to cut the whole bullshit, I ordered a year ago 2x genuine "Bilstein"'s rear shock absorbers P/N 44-069506
(from "British Parts UK), and 2x genuine "Bilstein"'s front shock absorbers P/N 44-069483, (from ebay - Mosseurope) and assemble it by myself according to:
and
(It's not that complicated).

And follow all instructions and orders for all the necessary torques, replacement nuts, (according to "X350 Workshop Manual.pdf" guide) and since then, my friend,
I was back into peace of mind, everything return to a "Peace Of Mind" mode.

The rest, compressing, vehicle height level, absorbers strength & softness became perfect.

The shock absorbers inflation, height etc., its a behavior and result of the car's computers

FYI.

 

Curiouser and Curiouser

With the really useful information coming in, thats so much for this, and the car having happily pumped it self up to full height yesterday afternoon. We decided to do an experiment to see if only the front offside went down we decided to disconnect the battery. Returning to the garage today some 20 hours later the suspension had not dropped at all! It is always down on the front after 6 of 7 hours. Now very mystified. Has anyone any ideas on what this would indicate?

 

Hwaiken I think Fraser has sent you down the correct path here. You most likely have faulty struts (or a strut) up front. The compressor only feeds the reservoir tank, not the struts directly. The fronts share a single height sensor on later models so they can fool you a little. However I just finished dealing with a similar situation so I will explain as it seems similar. I had replaced both front struts with rebuilt units earlier this year. After I had done it, I still felt the dampener in the front right unit wasn't working correctly as despite the shocks holding air the right front was floaty and made bad noises over bumps. I eliminated bad bushings as a problem so I just lived with the car. Fast forward to a few weeks ago and upon uncovering the car, there was the front laying on the ground. I could start the car and it would air up and I could drive it but the front would completely drop overnight. I had no obvious leaks at the tops of the struts, soapy water and all. As Fraser has also mentioned, I could "wake" the car up by unlocking the doors and the car would come up with the air stored in the reservoir. This to me ruled out the tank, supply lines, etc.. I finally had decided to just swap the car to coil overs when a new Bilstein strut came up on Ebay for half price. I gambled and bought it and swapped out what I had always felt was the faulty right front despite having no obvious leaks. Well not only did it solve the issue but it is the first time the suspension has felt correct since I bought the car last Fall. What a nice ride!! The car stays up overnight and the ride is spot on. Struts are pricey but I would look at B4 Bilsteins over rebuild units (rebuilds are done to 15 yr old +/- parts, my opinion of course, do as you will), and with the mileage on your car it would be well worth replacing the piston ring in the compressor to make sure it is as efficient as possible as it only will run in two minute intervals by design. My experience with two XJ8's so far has been that the front struts are the weak point as they get older. Stay patient and you can get it sorted out.

 

Many thanks. I just understand why if there is a leak somewhere why disconnecting the battery apparently stops it. Or at least stops that car going down?

 

Well I am not 100% sure not being able to see the car, but as mentioned the car will wake up and check itself periodically. As it does this a few times without the car running it will slowly deplete the reservoirs supply of air and then especially since the front shares a height sensor the car will attempt to keep the car level which can only happen to the height of the weakest link. Eventually with no air supply left you find her sitting on the ground. Disconnection the battery means this attempt at leveling and height maintenance doesn't happen and if it is a slow leak it will appear to have not lost air.

It is a little strange that you say it has lost none but you may be lucky in that, without the car moving (attempting to adjust itself), the weak point in which ever strut is not being stressed by movement is allowing it to hold air. On my previous XJ8 I had a strut that would only leak air going over a bump. It would air up and sit perfectly but if you drove it with the window down you could hear air leaking when the wheel rode over bumpy surfaces. It finally blew the air spring out internally at the bottom where the air spring was clamped to the dampener. It is a long shot but maybe with the battery disconnected you could bounce each corner manually and possibly find the faulty unit.

 

Hi Henry,

You've received some great input already. Here are a few thoughts:

First of all, the post at the link below explains the components and operation of the air suspension and may help you diagnose your problems:

Air Suspension & ECATS System Summary: Components & Operation

Just to echo some of the input you've already received, my suspicion is that your front offside air spring has a slow leak, probably from the top seal. Leaks from the top seal are very, very common, and are often temperature dependent, being more likely to leak in cool or cold weather and less likely to leak in warmer weather.

Your compressor piston ring/seal is no doubt worn out and your compressor is struggling to pressurize the system. As explained at the link above, there is no temperature sensor on the air compressor so to protect it from overheating, the Air Suspension Control Module (ASM) limits its run time to 2 minutes, after which it will not run again for at least 45 seconds to allow it to cool down. Under normal conditions, the compressor does not feed the air springs directly, but instead feeds the reservoir, which in turn is used to fill the air springs. However, when the system pressure is very low or zero, the valve body will open up the valves to the air springs so the compressor can fill them directly. But it can take at least two and sometimes more 2-minute runs of the compressor to develop sufficient pressure to raise the suspension.

Our member lcmjaguar developed an inexpensive gauge setup to monitor leakage in individual air springs. I built my own set based on his design. You only need one gauge to test each air spring individually, but having at least two allows you to test both fronts or both rears simultaneously. The shut-off valve allows you to isolate the air spring from the rest of the system, which is very helpful on the fronts because they are tied together in the valve body on the later cars like yours with only one height sensor.

https://www.jaguarforums.com/forum/x...4/#post1062760

The top seals are not replaceable, but I have been experimenting with methods for re-sealing them and have been having success, so I'll try to post a report soon.

Cheers,

Don

 

R M T has new compressors for just under $200 delivered.
I purchased two, both cars have their front shocks replaced.
I now have a set of rear shocks for both, just purchased this month
A new compressor, with two front shocks.could solve your woes, for now.
But the rears will eventually need replaced.
Stop bitching, and get busy, things wear out, and need replaced.
Its just the cost of doing business.

 

The air suspension leaks (or can leak). The handbook even warns so. Get used to it.

Mine can go down after a few days, or next time a few weeks. What's the difference? The difference is that it has moving seals or valves which might or might not seal at a molecular level with any certitude on any particular occasion.

I've had this enjoyable discussion with DonB before. He enjoys "perfect seals". I need to visit my shrink to handle my suspension going down in a few days or weeks.

Now obviously the compressor is a weak point. OF COURSE, the faster your suspension goes down, presumably the more the compressor will be used and "wear out".

However, no-one, that's NO-ONE, has given any actual data on how much air is expected to be used in normal in-use CATS ride compensation. So why would you rave on just about at-rest leakage?
(it's a serious question)

 

Hi Chris,

Since the ECATS adaptive damping system adjusts the valving in the shock absorbers, which are filled with nitrogen and oil, there is no air involved in "CATS ride compensation."

Air is only used to fill and level the air spring bladders, and "how much" (by weight? mass? volume?) depends on ambient temperatures and barometric pressures. What matters is that the proper pressures are developed and maintained in the reservoir and individual air springs.

The general understanding of the word "leak" is an undesired and unintentional loss from a container of a substance such as a gas, fluid, powder, etc. So in that sense, the air suspension is not designed to "leak." The system is designed so the ASM periodically "wakes up," compares the signals from the ride height sensors, and if necessary, intentionally opens the exhaust valve and the appropriate air spring valve(s) in the valve body to release pressure to lower one or more corners to bring the entire vehicle closer to level. In a leak-free system, the vehicle should never drop all the way to its bump stops as a result of ASM adjustments.

Cheers,

Don