Well, it happened, I went out to the car and it looked very low in the front so I unlocked the car, which must have activated the air suspension and I heard a loud hissing in the right front wheelwell. The car did not rise up so I'm sure the right front shock is leaking big time. I started the car and backed it up and the "vehicle too low " came on. I looked long for the thread where Brutal outlined the steps to replace one of these and got tired looking. Does anyone know where this is? Many thanks in advance.
I ordered two new shocks from Arnott, I'll just replace them both, assuming that if one is gone, the other can't be far behind.

 

https://www.jaguarforums.com/forum/s...ad.php?t=35024

It's all in there! Good luck!

PS Good idea on replacing both front shocks!

 

Thanks for the link.

I'll replace the right front first since there is no height sensor there. I'll just jack the car up remove the wheel and pull the shock. The other side requires the battery disonnect procedure.

 

g'luck oldmots!

 

I was just thinking about the symptoms and realized that although only the right side was hissing as it dropped, both fronts went down together. This must mean that either the fronts are on a common air supply or the other front went bad at exactly the same time (very unlikely). I hope that since there is only one height sensor for both fronts, they share an air line. I still plan to replace both shocks but I started worrying about my diagnosis.

 

Both front shocks are connected, so when one goes bad the entire front of the car sinks. I believe the rears are independent of each other.

If you can HEAR hissing from a particular shock, I'm pretty sure your diagnosis is correct.

 

Thanks, you gotta love this forum!

 

Are you sure about this? I am certainly not an expert on the air suspension on these cars, but when a rat gnawed through the air line to my LEFT front shock recently (07 XJ8), only the LEFT front of the car dropped down each time I shut it off. There were two small holes in the line, but the compressor could still provide enough air to raise the shock, but the hissing after the engine was shut off was quite noticeable until the air line was empty.

Furthermore, after I completed the repair, the suspension system was apparently locked in "jacking" mode and refused to raise the left shock at all until I drove the car for about a mile. I did not understand this at first, so my troubleshooting included checking the compressor and air supply - when I loosened the line to the right front shock, there was obvious high-pressure air in that line while the left front was still completely empty. In addition, I saw that the air lines to the front shocks are independent lines that run from the control manifold in the trunk and up through the left front fender well.

 

https://www.jaguarforums.com/forum/s...earchid=828445

All I know I learned from glancing at the thread above! Maybe I am incorrect.

 

This begs the question : if there is only one level sensor on the front left, how does the shock on the right side know how much pressure to run to level the car if the lines are separately controlled?

 

Oldmots,

If 1 front shock collapses the system will lower the other front shock to keep the front end level, left to right. It does this by checking the level every 30 mins or so, I think.

The actual job of replacing a shock is not so bad. I did it in a non hurried 3 hours. The second took me 1 1/2 hours.

 

Once the car has gone in to sleep mode which happens 30 minutes after switch off and all doors closed it only checks every 24 hours.

Each air spring has a pressure retaining valve whose purpose is to retain 3 bar (43.5 psi) within the air spring at all times. That protects the air spring membrane by preventing it from creasing. Therefore if you have one bad spring the other one shouldn't fully deflate.

Because it manages the front as a pair. They have seperate air feeds but it will keep the two front springs at the same height. You could argue that they could probably do away with one of the rear sensors as well but there are two because the rear loading can change quite a bit from side to side. The valve block in the boot has 5 individual solenoid valves, one for each air spring and one for the reservoir.


Once you start jacking the car up the system will try and correct it for around 10 seconds then will inhibit further corrections. Once in jacking mode it won't switch back to normal mode until the vehicle height returns to normal or a wheel speed signal of 2mph or more is detected.

It has a similar feature for vehicle hoists.

 

You are right when you say that the fronts are managed as a pair also there is an air supply to each shock but I have not seen an air line between the two front shocks????

Does this mean that the two fronts are only managed electronically??