😎👍 Awsome !! Thanks, good info.
I have replaced my rear air shocks a year ago (jag 04 XJ8, 132,300 miles) and I need to replace now the front ones, the car seats low in "winter only" if it is 55 degrees also I think of a new compressor too since the one that is there is the OEM, I did change the piston rims though. I hear air coming out from the top of the front air shocks after the compressor fail in filling them
I guess it's a leak, I also have the CATS System Fault light on my dashboard so I'm thinking in replacing the front shocks with Arnotts.

 

Just a little note i descverd on mine concerning the tank, i dont think it actually acts as a resovior as some beleive , i fount it doesnt hold mutch air at all, as it acts as a "shock" overflow when the car hits a bump, after all the compressed air has to go somewhere to stop the bag exploding, after the car levels it get fed back via the compressed preasure
if this is not roughly the mechanics of the system can you please ad a little not so i can look further in to the suspension fault
thanks to all in the above

 

Hi Lukie,
I believe there is no possible air return from the shocks to the reservoir, because of the way the system is built, with one-way valves and higher pressure in the tank than in the shocks.
The shocks don't explode when the car hits bumps because when the tyre comes up, the volume in the bag decreases and its pressure increases through adequate movement of mechanical parts pressing on the bladder in the shock.
Others may chime in.

 

I think there is two way flow. Ride height would only adjust higher if there is no return.
The only venting I hear is from the compressor. I believe the One Way valves isolate the compressor from the air tank.

 

Hi lukie,

I would recommend that you carefully read the Air Suspension & ECATS section of the Dealer Training manual, which I scanned into pdf format and Graham uploaded to the forum download area. This is the most thorough explanation I have found of the air suspension components and operation. You can download it at this link:

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

Here are a few summary points that may be helpful, paraphrased from the manual:

Nominal pressure developed by the compressor is 15 bar / 218 psi. A safety pressure-relief valve on the compressor is set to relieve pressure above 17.5 bar / 254 psi. An air exhaust solenoid valve on the compressor provides for relief of excess pressure when lowering the vehicle and to backflow dried air through the air dryer to partially dry and reactivate the desiccant beads. You will sometimes see the air dryer described as the "water trap," but a water trap is a different type of device and there is no water trap in this stock system.

The reservoir has a capacity of 4.5 liters with a maximum design pressure of 15 bar / 217 psi. When fully charged the reservoir capacity is sufficient for at least one full lift of the vehicle at gross vehicle weight (GVW). The air suspension system does not deplete the reservoir contents below 9 bar / 145 psi under normal operating conditions.

From page 8: "This means that the system is operating within a pressure range. This is done to prevent the air pressure held in the air springs from being transferred into the reservoir."

Normal operating air pressure in the air spring bladders is 7 - 9 bar / 101.5 - 130.5 psi. Maximum "full bump" spring pressure at GVW is in the region of 20 bar / 290 psi. The air spring burst pressure (when new) is around 40 bar / 580 psi [note that the factor of safety or yield stress/working stress ratio is 2:1].

Pressure-retaining valves in each air spring ensure that a minimum of 3 bar / 43.5 psi remain in the air bladder to prevent folding or creasing of the rubber bladder that could cause damage. These are not "one-way" valves. They allow air to move in both directions so the Air Suspension Control Module (ASM) can increase or decrease the pressure in the bladder to level the car and maintain proper ride height under all conditions. They are only "one-way" in the sense that they will only allow the pressure in the air spring to be reduced to 3 bar / 43.5 psi and no lower. They will allow the pressure to be reduced from the typical maximum operating pressure of 9 bar / 130.5 psi down to 3 bar / 43.5 psi.

Here are a few examples of when air pressure is adjusted:

1. When the trunk/boot is filled with heavy luggage, the ASM increases the pressure in the rear air springs to re-level the car. When that luggage is removed, the ASM reduces the pressure in the rear air springs to lower the car to standard ride height.

2. When the vehicle exceeds 105 mph, the ASM reduces pressure in all four air springs to lower the ride height by 15 mm to improve aerodynamics and fuel economy. When the speed slows to below 80 mph, the ASM will increase the pressure in the air springs to return to standard ride height.

3. When the car is parked on an inclined surface, the ASM will relieve pressure in the air springs on the higher end of the vehicle to make it more level with the lower end.

System height is communicated to the ASM via the Hall effect height sensors mounted in the suspension (two at the rear and one at the front left corner, except on the earliest X350s which had height sensors at both front corners).

The pressure in each of the air springs is regulated by the ASM by way of the valve block. The rear corners are regulated independently, and the front corners are regulated as a pair (except on the earliest cars with four sensors).

In general operation, when an increase in pressure is required, the pressure is supplied from the air reservoir. The compressor is operated only as needed, and typically only when the vehicle is traveling at 25 mph or faster, or when the transmission is in Park. This is part of the overall NVH management strategy (Noise, Vibration and Harshness).

When pressure in one or more air springs must be reduced, the only exit path is via the exhaust valve in the compressor. The appropriate solenoid valve in the valve block opens to allow pressure from the air spring to escape, and the exhaust valve in the compressor opens to allow the pressure coming through the valve body to escape to the atmosphere. When the pressure declines to the desired level the valves close. (this is stated cryptically on page 14 of the manual)

The air springs/dampers were made for Jaguar by Bilstein, but the rest of the system is made by WABCO, founded in the U.S. in 1869 as the Westinghouse Air Brake Company, but now headquartered in Brussels, Belgium. In addition to Jaguar, the company supplies many automakers including Audi, BMW, Land Rover, Mercedes Benz, Rolls-Royce, Volkswagen and Volvo. Jaguar cleverly calls the system ECATS, or "Enhanced Computer Active Technology Suspension," but it is actually Wabco's ECAS system, or "Electronically-Controlled Air Suspension." You can download the Wabco ECAS brochure at the link below:

https://www.google.com/url?sa=t&rct=...93990622,d.b2w

I hope the above summary and linked documents will help answer any remaining questions you may have.

Cheers,

Don

 

Wow, Congrats, perseverance sure commands success, and Dave, you actually figured it out yourself ... inspiring to read your thread. Would you mind sharing mileage on your car? ... and what other issues you have conquered through its history of ownership.

 

I just bought a compressor from Arnott. The sold me a Wabco.

 

Great information, do you guys have any idea of for how long the car would stay up
Parked in cold weather conditions like 5 degrees. It is going to be parked for 20 days.

 

It depends on the health of your shocks and on the temperature.
If really cold, and as I understand from your post #21 above that your shocks are not in good shape, one night would be enough to empty them.

 

I don't know how that could be predicted. If your system is completely sealed, then theoretically the car might sag a little if the temperatures fall even lower, causing the air in the system to lose volume. But whether a sealed system would drop all the way to the bump stops I don't know. If you have any leaks at all, I think it is inevitable that the car will come to rest on its bump stops eventually.

Cheers,

Don

 

Hi Don P.
The only other big improvement I made was the front rotors. I put 3 new sets of rotors on the front and after about 500 miles each set would start to shimmy like it was warped. I didn't even suspect the rotors at 1st because they were basically new. After the 3d set was warrantied out I replaced them with R1 Concepts top of the line drilled and slotted rotors. I have 30,000 miles on them and they still outperform any rotor I've ever had. Anyone that gets them should get their pads with it as a package. (I also put them on a suv we have because they stay cool driving through the mountains; no brake fade).They work the best with their pads (no squeal) but will work with any other. They are a little pricey but worth more than they ask.
The only other thing I'll ad is that I use 2004 Lincoln LS suspension and steering parts. They seem to fit and work perfectly. I'm probably the only Jag owner that has grease fittings on my suspension. I'm partial to Moog. They make a lot of the LS stuff. If Moog doesn't make it then I use Ford. It usually comes in a Ford labeled bag but the part has Jaguar molded into the aluminum. Ford is still way cheaper than Jag. I also do my own 4 wheel alignments. I do it with a tape measure and works perfect for me. I feel like I'm rambling so hope I didn't bore you. If I can help with anything just send me a message. BTW the car has 110,00 miles and I've had it since 49,000

 

thanks, my front shocks and rear are new Arnotts replaced by myself and since then I have not heard the compresor again except when I replaced the front shocks and of course it started to fill them with air after installation which means no leaks I guess, the car is always up and nice ride.
I drove it to Kansas and it was about 10 degrees and not problem the new Arnotts always up

 

Hi Dave,
I have a similar problem after changing out the struts. I have the Arnott struts installed now but I'm still getting the 2303 code. I also bought the icarsoft i930 reader. Please tell me how to set it up to get the live data on the air susp. compressor. I have read the ASM module and cleared the codes. I have tried the live stream but I don't get the live readings. I must be doing something wrong, any help will be appreciated.

Thanks

never mind I accidently figured it out.

thanks anyway

 

Hi Bob,

The most common cause of the C2303 "Reservoir Plausibility Error" code is a worn piston ring/seal in the air compressor. The piston ring is made of Teflon and when it becomes worn the compressor can no longer pressurize the system within the time alloted by the ASM. The ASM interprets this as a major mechanical or pneumatic fault such as a large leak or disconnected pipe and flags the code.

Many of us have resolved this code by installing a new piston ring from our forum member Andy at bagpipingandy.com. At the links below I show how I did it (most owners don't bother replacing the desiccant beads as I did). Unfortunately Jag-Lovers is still migrating their photos to a new server so you can only view my thumbnails and not the larger images, but hopefully the descriptions will be helpful:

Air Compressor Piston Ring Replacement - Part 1 of 7
Air Compressor Piston Ring Replacement - Part 2 of 7
Air Compressor Piston Ring Replacement - Part 3 of 7
Air Compressor Piston Ring Replacement - Part 4 of 7
Air Compressor Piston Ring Replacement - Part 5 of 7
Air Compressor Piston Ring Replacement - Part 6 of 7
Air Compressor Piston Ring Replacement - Part 7 of 7

Cheers,

Don

 

Hi Don,

Once again thanks for the help and advice. I'm still trying to work through this thing. I bookmarked Andy the bagpiper's site just in case, it sure seems the way to go. I figured out the icarsoft 930i live stream so I know how my compressor is working now. I have no issues with struts leaking, I've been through all that.
When I unlock the doors after the car sitting all night I hear a short burst of air from the reservoir. I suppose there is a small leak somewhere. When I start and drive the car the compressor comes on after a bit and runs for about 15-30 seconds then shuts off and a couple minutes later comes back on for about 30 seconds and that's it. The reservoir stays off. If I were as mechanical as most of you seem to be I would just pull it out and change the ring but I will have to find someone to do it for me. I don't believe I face a compressor failure any time soon but the air suspension warning is irritating.

Thanks again for all your help.

Bob

 

Hi Bob,

In normal operation you can't hear air entering and exiting the reservoir, which is in the trunk. The way the system is designed, the compressor pressurizes the reservoir and pressure for the air springs is provided by the reservoir unless it has become depleted for some reason, such as a leak.

The escaping air you hear when you unlock the doors is completely normal. It's the exhaust valve on the compressor opening, presumably to allow the suspension to level prior to you entering the vehicle.

For a summary of how the system operates, see the post at the link below:

Air Suspension & ECATS System Summary: Components & Operation

While it's true that your compressor is probably not facing imminent failure, the fact that it can't charge the system as quickly as it should means it has to run more often, so the mechanical components are being subjected to more rapid wear. It would be good to replace the piston ring sooner rather than later. Any competent mechanic can do it - just show him or her the photos I linked to earlier.

Cheers,

Don

 

what I tend to do, and it has worked every time, after struts replaced do the usual hard reset, let air out of the air tank in boot disconnect the electrical plugs and wait about five minutes for air to escape.
put all back together , reconnect battery start car and go for a drive, get her up to over 2000 revs.
that usually get my system to kick in and everything runs as it should, the compressor only runs for short periods at a time anyway
dont ask me why this works, but it's worked three times when I couldn't get things going proper after replacing suspension parts in the past
good luck

 

Hi Don,

I bought the kit from Andy and bought a kit for the dryer. Everything is now working fine, no message on dash and no codes.

My questions is this: Since the desiccant was completely saturated do I need to evacuate and replace the air in the system or will it all dry out over time?

Your advice is appreciated.

One comment: Andy's instructions do not mention the dryer which might lead some to believe it is not important. In my case it was probably my biggest problem.

One other thing: There are many kits available now. I don't know about the quality but they are very inexpensive. One has the piston ring, seal and desiccant for less the $20.

Thanks again

Bob

 

Hi Bob,

That's great! Congratulations on a successful repair.

There is no mechanism for moisture to escape once it makes its way into the system, which is why I am contemplating adding a true water trap one of these days. Given that your desiccant was saturated and no doubt allowed excessive moisture to enter your system, it wouldn't be a bad idea to purge the system to whatever reasonable degree you can.

An efficient method might be something like this:

1. Run the engine and allow the air compressor to fully charge the system with air dried by the new desiccant;

2. Carefully loosen the fitting at the valve block for the hose from the air reservoir and allow the air from the reservoir to purge. Some of the trapped moisture should escape with the air;

3. Repeat the last two steps a few times to help purge moisture from the compressor-to-reservoir lines and the reservoir;

4. Run the engine to recharge the system again;

5. One at a time, loosen the fitting for the air hose at each air spring and allow the air to purge. Newly-dried air from the reservoir should force moist residual air through the lines and out through the loosened fitting, and as the air spring sags it will force some of the moist air from the bladder out as well.

Someone else may think of a better procedure, but short of having a large supply of dried, compressed air, this seems like a practical method to me.

I'm glad you opened your drier to check or the problem would have continued to worsen. The next time I rebuild a compressor (probably soon on a friend's Super V8), I am going to also remove and disassemble the exhaust valve and pressure relief valve to clean any moisture and corrosion.

I don't know anything about the other sellers, but since Andy owns an Audi that uses the same air compressor as our Jags, and is a precision machinist by trade, and is a frequent and helpful contributor to this forum, I am always happy to recommend that members buy their kits from Andy with full confidence that he will be available to provide knowledgeable and friendly customer service should any be required.

Cheers,

Don

 

I have been having a CATS system fault since like 6 months ago but my suspension is up and not issues I'm wondering
what it would be

i have been