I've seen all the post about problems with air bags, compressors, sensors, etc. I dont think I have seen any info on a proper operating system.

I have test driven 2 LWB VDPs, the first car I heard the compressor pump up on start up and then nothing after that. The second car it ran a lot more frequently.

What is the normal cycle, will this vary with road conditions?

Will the car settle over night, if not over night how long will it hold the same height?

Last question how loud should the compressor be?

Thanks.

 

I can only speak for my 2005 VDP. (All VDP's 2005 and later are LWB)

My nose may or may not sink a little bit over night. If it does, it rises as soon as the car is started. The compressor kicking in right away.

If it doesn't, the compressor kicks in around 20-25mph, runs for maybe a minute (I don't get a mile down the road) and then shuts off. I assume it is "topping off".

If driving below 40mph with the radio off, I can barely hear the compressor. I don't think guests in my car even notice it. Going any faster, or any additional noise (radio, conversation, cell phone) and I can't hear it.

While many are justifiably scared of the air suspension, it is what makes the car ride so wonderfully and a large piece of why I like it so well. When I bought mine, I figured if all three of the major issues (compressor, shocks, throttlebody) with this car went bad, it would cost me about $5000. I added that (in my head) to the purchase price of the vehicle, drop the same amount in an interest bearing account and have no worries about future with this car.

Good luck with your search, pictures of my VDP in my user profile.

 

compressor only runs when needed. Car should not sink overnight, but can over several days. I have never heard my pump.

My technical notes give a full description, but it's hard copy and copyright Jaguar. There might be something on the Internet, have a try.

 

Appreciate the quick responces and reassurances guys!

 

I agree with wheelgun, the air ride, beside the history and performence is whats sets our cars apart. With that said I don't know whats normal with my air ride system either and I try to read all the threads. I do know with my car most of the time when you start it up, if you watch a fixed spot the car will sink a bit and raise right up and I never heard the compressor even though I try.

At times when stutting down you will hear it letting out air but I think it's purging water from the system.

 

I uploaded the 350nas_New XJ RANGE.pdf to the sticky section somewhere.
The document is over 11MB so it is a large file to download.

I also have the NP04 student guide from Jaguar training but it is a PAPER document.

Someone might have converted it to .pdf ????? and uploaded it somewhere.

bob gauff

 

Bob,
I'm not picking up what your putting down! LOL I'll go looking for it. I have no idea what I'll find.

 

One can read up on how the system operates and the components involved as THAT WAS THE ORIGINAL QUESTION!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!

bob gauff

 

Bob, Thanks for the help and yes that was my question, I'm trying to understand the principle of operation and what is normal. I don't seem to be able to find the file in the stickys, and have not done a search yet for the file by name. I'll try that, hopefully I'll have success. BTW I wasn't trying to be a smart*** just didn't understand the file.

Update: I have done a search using the file name and got only one return, which refers me back to this thread.

 

The question was what to do with the document.

bob gauff

 

You are probably going to see more posts from cars with issues than those without. Frasier and I have been fortunate, although I had a compressor replaced under warranty in the 30K+ range and the car always sinks overnight when temps reach below 40F and it can take 30 minutes to get air bags filled to proper height, I have been advised this is normal. I now have about 85K miles.

 

OK, back to basics !

The car air suspension consists of: -

- air compressor, used when demanded by the ASM to recharge the compressed air reservoir. A fairly short life component due to the seals wearing out, but reasonably cheap and easy to replace. Think of it like having to replace a couple of tyres. Found behind the front bumper LH side.

- four air spring units, one per road wheel. These have the shock absorber built in, its not separately replaceable. This makes the air springs a bit expensive to replace, even on the internet. Bushes at the bottom wear out quickly, but are very cheap items, although labour can add up unless you replace them it yourself. For some reason, the air diaphragms seem to fail more in the US than in Europe and elsewhere. Some US owners have converted the system to steel coil springs like some Land Rover owners have also. It can be a 'shock' when advised of the price of an air spring/shock for the first time. Used ones can be bought on the internet but could fail quickly or last for years.

- Air Suspension Module (ASM) - the electronic control box for the suspension. Supremely reliable, believed never reported as failing on this forum. Found behind the rear seat back.

- Air reservoir - tank holding the compressed air used to pump up the air springs. Capacity 4.5 litres at max pressure of 15 bar, but can be as low as 9 bar. Again supremely reliable so far. Found in the spare wheel well of the trunk.

- Valve block - block containing electrically-operated valves to pass air in/out of the air springs and the system. Five valves, one per spring unit and one for the reservoir. Compressed air is regularly blown to atmosphere via the compressor to blow water out of the water trap, normally shortly after engine shut down, and also as normal height adjustment. Found in the spare wheel well of the trunk. Very reliable normally.

- Pneumatic lines - interconnect the components in the compressed air circuit

- Height sensors - two rear, one by each wheel, and one front, (early cars had two at the front).

Operating Modes
1. Sleep Mode
Invoked 30 mins after ignition is switched off, and last door/trunk lid activity. System shuts down, and auto-wakes each 24 hours to check reide height. If correction is needed, the lowest corner is used as a datum, and other springs lowered to meet the lowest corner. No raising is done.

2. Preliminary Mode
Activated on detection of: -
- door or trunk lid opening, also when car is in 'Post' mode.
- engine switched off in 'Stance' mode

Lowering allowed. Raising allowed using reservoir only.
On engine start system switched to 'Stance' mode
If no unloading or door activity for some time, system switches to 'Post' mode.

3. Post Mode
Activated if no loading/unloading/door activity detected for some time.
Raising allowed to standard ride height, but compressor inhibited.
Door/trunk activity switches to 'Preliminary' mode
No activity causes switch to 'sleep mode

4. Stance mode
Activated from 'Preliminary' mode on engine start, (car stationary).
Car levelled to precise tolerance using reservoir unless insufficient pressure, in which case compressor is invoked. All height sensors use a fast filter signal to speed up levelling.
Movement above 0.6 mph (1 kph) causes switch to 'Drive' mode
Engine shutdown reverts to 'Preliminary' mode

5. Drive Mode
Only invoked above 0.6 mph. Above a defined speed (circa 30 mph ?), compressor is used to raise the car, and also recharge the compressor. Height sensor filtering switched to slow.

There are a number of system tricks as follows: -

- Rough road detection - inhibits Speed Lowering, but this only occurs over 100 mph, so not really useful.
- Leveling inhibit - significant cornering, braking and acceleration inhibits suspension lowering.
- Jacking Mode - the ASM detects car jacking activity and inhibits suspension adjustment until normal height is resumed, or speed of 2 mph is detected.
- Inclination Mode - ASM detects if vehicle is not parked level , and levels front and rear together.
- diagnostics - ASM stores fault codes for diagnosis using WDS

There is also adaptive damping is the system called "Computer Active Technology Suspension", (CATS). Dampers, (shocks), can be rapidly switched between 'Soft' and 'Hard' based on how the car is being driven and the road conditions. Not all cars may have this fitted.

 

Thanks for taking the time to provide that info. I would have nver guessed it would have that many modes. I can hear the wife now, LOL "the car is crooked again!"

 

Thanks for taking the time to provide that info. I would have nver guessed it would have that many modes. I can hear the wife now, LOL "the car is crooked again!"

 

Well I found the file mentioned earlier in the general section. It was loaded to a fricking cloud that wont give the file up. Can someone else try this file and let me know if its just my home compter that is having trouble?

Free Cloud Storage - MediaFire

Dave

 

The link works for me but it may not be what you are actually trying to find:

Issue:
This bulletin provides specific recommendations when diagnosing and servicing the hoses of the air suspension on 2004 MY-on XJ range vehicles.

Action:
When carrying out air suspension pipe repairs, follow the workshop procedure outlined in JTIS section 204-05 Vehicle Dynamic Suspension, general procedures, air leaks.

Caution: When diagnosing leaks in the air suspension, do not use soapy water as a means for detecting the source of an air leak.

Water can be harmful to the air suspension system, if it enters the air tubing. Use only Gotec Leak Detection Spray, part number C2C
22398, for this purpose.

If instructed to cut the air pipe, you must use one of the hose cutters outlined below:
• Hose cutter - 204-494 available from SPX OTC.
• Hose cutter - YA 1000A available from Snap-On.

 

Nope if that's what the file was!

 

The front of my xjr drops equally and I hear air when ever I turn my car off. It comes back up just opening the door. Do the front run off the same system because the back doesn't do that?

 

Let's ask a couple of question first. Is the area that you are parking level? If not the ASM will try and keep the body of the car even and level. Are you are parked on a slope? here again the ASM will auto correct, but in this case it will drop the road side of the car to protect the curb side from getting trapped. HUH? Yup I read that in the theory of operation.

In my case I thought I needed the ASM calibrated because in my mind the front right was always high. (My drive way is sloped) This was all with in the first 48 hours of ownership as well. ROOKIE LOL

The ASM will work the suspension level, allowing air out while parked. The compressor will not operate unless the key is on.

As far as the front and back being tied together you betcha. The part about opening the door and it rises could be because the module was sleeping and you woke it up. Sounds to me like you don't have an issue.

BTW Fraser has a good post a few thread up.

 

I park on level ground. I just know when I bought my 2004 XJR it did not make any aired noise and now it seems to be getting louder.