Hey all, I was able to do a quick "diagnosis" with some soapy water — no bubbles anywhere! Here's what I found.

First, I sprayed the top of the shock where it had been instructed by some other members, being careful not to spray the electrical plug directly:





I didn't see any bubbles at all escaping from the top of the shock, so then I went to the reservoir in the trunk. I didn't spray anything, because I didn't hear or see anything that would make me think there was a leak:





When I went back to the front of the car, I could audibly hear a hissing / air leaking sound coming from the wheel well next to the suspected shock. If I put my head right up to the wheel, I can easily hear the air escaping from what seems to be the side or bottom of the shock somewhere:





So it seems to be the shock that is the culprit. The only thing I want to confirm with you gents here is whether the air line going into the top of the shock is the only line in/out for air. Is there any other place on the shock where air could be escaping through a hose? Or if I'm hearing the leak coming from the side of the shock, does that mean it's definitely the shock?

Thanks again!

Justin

 

Hi Justin,

Yes, unfortunately, the air hose fitting is the only proper route for air to escape the air spring. The fact that your leak is inside the wheel well almost certainly means the air spring bladder has a leak. I'm not sure if any company is currently rebuilding these units, so it may mean you need at least one new air spring/damper unit.

Perhaps someone else can answer the question of whether it is possible to have your unit rebuilt or to purchase a rebuilt unit and receive partial credit for shipping the rebuilder your old unit.

Cheers,

Don

 

I actually already bought an OEM Bilstein shock — just so I'm clear, that's what you mean by air spring / damper unit? No other parts?

 

Yes, the OE Bilstein units are combined air springs/shock absorbers, or air springs/dampers in Jaguar-speak (the Queen's English).

You should be good. Please keep us informed.

Cheers,

Don

 

A service to replace these bladders would be really useful. Arnot used to do it, but have now given up.
There will be plenty of life left in the damper part. Essentially replacing a bladder is the same as replacing a broken steel coil on a Macpherson strut; you don't replace the whole strut just for the coil and this should be the same. Bilstein are no doubt rubbing their hands with glee at selling what is a very expensive item because a £20 air bladder has failed.

I for one am glad to see Jaguar finally getting rid of air suspension. Only the current XJ now still has it on the back wheels.

 

I have myself biten the bullet and bought a pair of Bilstein B4's for the front.
Because the front driver's side shock is now heavily leaking on a regular basis every cold morning and I have to wait that the engine is warm to have the top seal self-heal and the compressor succed in re-inflating it. Not practical anymore...
I will try selling the still good one on ebay.

 

Just got a quote from the British Automotive place I've gone once before:

$400 just to install/calibrate the new shock
$475 to diagnose the leak first and install/calibrate after

I could potentially also take the car to another very inexpensive mechanic to just install the new shock, and I'm estimating he'd charge me about $100. But of course, he would not be able to calibrate it, as he doesn't have the Jaguar software or anything.

How important is that software calibration? You guys think I could get away with not running the calibration and hoping the system adjusts the height automatically?

 

$400 is a lot of money for this job. Calibrating the air suspension can take about an hour, mostly due to how slowly the Jaguar SDD system operates. Installing a new front air spring/shock takes about an hour or less, and can be done by almost any do-it-yourselfer with basic skills. Except for a large Torx bit for the lower shock bolt, only basic wrenches and sockets are required.

Arnott Industries has pdf instructions and a YouTube video that show how to replace the air spring/ shock.

You could always try installing the new air spring/damper just pay for the calibration if the resulting ride height is too far off.

Cheers,

Don

 

I believe the secret with this sort of repair is to do it while the ASM is "not looking"

Park the jag,switch off, shut doors and leave for 30 mins then jack up and change the strut

then lower vehicle when complete.

I don't think calibration is necessary as long as the hight sensor is not removed or

damaged. The actual height is set in SDD and should not change.

You will need to confirm the details of the above procedure which was posted on this forum.

Maybe Don can remember it?

 

Yes, it seems not to be necessary to recalibrate with IDS-SDD if the correct procedure is followed.
Just take care of disconnecting the battery to start the job when the car is at normal height.

Also there are some adjustments to be made when lowering the car at the end of the process.
Look at the following video to install Bilstein B4's which is quite explanatory:

On the other hand, I understand that a full axles alignment (parallelism) has to be undertaken afterwards to avoid issues of bad tyres' wear.

 

Thanks for posting that video, it's helpful to see, even if I'm not doing the repair.

One problem is that there's not a way for me to disconnect the battery when the car is at normal height, because as soon as it's shut off, the shock leaks until it's bottomed out. So the battery would have to be disconnected when the front right shock is empty(ish).

 

My cheaper mechanic is going to do the installation for $120. I'm bringing it to him later in the week, so I'll try to get him to look at this Bilstein video prior to the work.

Hopefully the ride height will self-adjust after the work is done, but if it doesn't, I'll bring it to my Jag mechanic and have him calibrate it.

How necessary is the alignment after this is replaced? It doesn't look like any steering parts are touched, so could I get away with not doing one, or should I not risk it?

 

I'm puzzled why a recalibration of ride height is claimed to be needed after replacing an air shock.

The system gets its height information from the height sensors not from anything in the air spring unit which are completely dumb in this respect. When the new air springs are installed, they won't have enough air in them to maintain height, so the car will start off low. The height sensor will transmit the height reading and the system should then pass air into the spring unit to raise the car until the height reading matches that in the ASM memory. What else should happen ?

 

I'm on the same page as you. Seems like the system is designed to automatically detect height and adjust accordingly. Seems like the only reason a re-calibration would be needed is if the sensors themselves are no longer reading the right height, but that seems like it would be independent of the shock.

I'm planning to replace the shock and not re-calibrate right away, so I'll post the results here.

 

Well, I don't think it's quite that simple. Remember that the front right height sensor was eliminated from VIN G26872, yet the system retained the ability to calibrate the front left and right ride heights independently. How does it do that?

It must be able to do that through independent calibration of the air spring valves in the valve block so that any pressure differential in the air hoses to the front left and front right air springs is maintained, even as the pressure to both air springs is increased and decreased.

During the SDD ride height calibration procedure the pressures in the lines running to the left front and right front are adjusted independently and the height sensor reading is stored in the memory of the Air Suspension Control Module (ASM) for ongoing reference. I have used SDD to recalibrate the suspensions on two different X350s, and I can confirm that SDD can adjust the front corners independently even though both cars had only one front height sensor.

Once the calibration is complete and the vehicle is returned to service, the ASM adjusts both front air springs together as though they were one unit, yet somehow it maintains any pressure differential that was established during the calibration procedure. This pressure differential must be maintained by the ASM in conjunction with the air spring solenoid valves in the valve block.

So what happens when a new front air spring is installed with a new air bladder that may require a different air pressure to achieve the same ride height as the old air spring? Whether the new unit is on the right or left side, the ride height of the left corner should be relatively unchanged because the ASM will adjust the pressure until the height sensor signal matches the one stored in memory. But if the pressure required to raise the new air spring to the correct height is different than it was for the old air spring, the front right corner may be too high or too low because the calibrated pressure differential between the left and right air springs is maintained.

I think this is why recalibration may be required.

But if the pressure doesn't change much, the resulting ride height may be perfectly acceptable. So cross your fingers, MrWest!

Cheers,

Don

 

My fingers have been crossed since the day I bought this thing

 

Don,

What you say is very interesting.
I was wondering how the calibration and balance between right and left would work with only one sensor.

Could you please confirm that what you call calibration here is the process wherby the car is lowered first to a measured 380 mm height, then to 340 mm after 2 minutes as shown in the video (measured on one side but, I assume, realised on both sides by the suspension system during that phase when the suspensions are maybe still "soft")?

I guess that the memory then stores the possible pressure differentials between right and left so as to ensure a levelling between both sides once the process is completed.
Am I right?

 

Hi paydase,

When you use SDD to calibrate the air suspension, you measure each corner from the center of the wheel to the underside of the wheel arch in the fender/wing, and you enter this measurement in millimeters into SDD, one corner at a time. The system then goes through an automated routine and asks you to again measure each corner and enter the results. If the new measurements are within a +/- 15mm tolerance range, SDD considers the calibration successful. If one or more corners requires additional adjustment, the procedure is run again.

On both my own '04 XJR and a friend's '05 XJ8, the calibration routine would not bring all of the corners as close as we wanted to the factory specification, which is 386mm front and 373mm rear. So I used Cambo's technique of "lying" to SDD in order to bring the final results closer to factory spec. By "lying," I mean that if the front right corner was initially 15mm too low, and after recalibration was still 10mm too low, on the next run of the calibration routine I entered a value for that corner that was 20mm too low so the ASM would overcompensate, and by doing that by trial and error a few times I was able to get all four corners within a millimeter or two of spec.

Cambo's excellent post on how to lower your X350 is just as valid if you want to calibrate to factory specified ride height:

How to Lower Your X350


Yes, I think you are right. That is my assessment.

Cheers,

Don

 

Alright folks, update time.

I had the new shock installed yesterday by my non-Jaguar guy (he charged $120, as opposed to my Jag place, who quoted $465).

When the car first came off the lift and was turned on, the rear shocks seemed to be all the way up, and the front basically all the way down. Nothing happened for about five minutes of the car running — all four corners stayed this way. I didn't hear the air compressor come on or anything.

The mechanic connected his diagnostic thing to the car and cleared a code (not 100% sure what code, but C2780 appeared after this). After a re-start of the car, the compressor turned on and the front inflated like normal, but the rear remained high. To compensate for this (I presume), the front also inflated about 1-2" higher than normal.

He decided to try disconnecting the battery and connecting the negative terminal to the positive, and leaving the battery unplugged for about five minutes. Same thing when the car turned back on — all four corners about 1-2" too high.

I've driven the car three times since yesterday, and it seems to be at the same height still, so it looks like I'll need to have the shocks calibrated on the Jaguar tool.

One weird side effect — I heard/felt a little tire rub on the inside front passenger wheel well (the corner with the new shock) on my drive this morning. Both times the car was turned almost full lock. What's strange is that this corner is higher than normal. Not sure how that would lead to tire rub.

 

Hi Justin,

Try the solution in the thread below that helped wardf:

04 XJ8 raised and doesn't come back down

Cheers,

Don