MS333,

The air suspension system includes a small accumulator that will provide air to the system even if the engine is off.

If you want to test this.

1. Unlock the car.
2. Open the trunk lid and sit on the trunk lip.
3. Wait circa 30secs and you'll feel the suspension raise slightly.

The air suspension compressor will run, if required, for a few seconds once the vehicle reaches 18 mph (30kph). It waits till this speed is reached so that road noise covers the compressor.

wombat

 

Yes, that is correct. While not necessarily the most accurate method, and generally not the spec found in shop manuals, but for a "quick and dirty" comparison number, our XJ's "ground to top of wheel opening", is 28.5" in front and 29" in the rear.

Unless you have a drive-on lift at your disposal, suspension work can be a hassle, especially when tightening fasteners after removing/replacing control and/or trailing arms. The car needs to be sitting on all 4 wheels, with the suspension fully loaded. The tricky part, even for a professional shop, is that the car has to be lifted and supported, so the wheels can be removed, in order to access/work on the suspension parts, but then the wheels have to be put back on, and the car dropped back on it's own weight, in order to properly tighten everything up.

 

The few times I've had to do it weren't so bad.
I just used a jack stand (IIRC, or something like that anyway) to support that corner at the hub, or rotor, or where the wheel would otherwise be, and finish tightening-up the fasteners with all weight on it as it would be with the wheel installed.
Then after tightening the fasteners to spec, jack it back up, move what I was supporting that corner with (jack stand or some something strong enough & at the right height that would fit under the hub, knuckle, rotor or whatever) out of the way & install the wheel.
BUT you've got to be really careful that whatever you have supporting the corner is solid & secure, for instance if you have a jack stand supporting the hub, it could easily be situated where it could slip off of the support.
Above all, I took time to make sure that it was solidly supported & couldn't fall.
And I also had a secondary support poised under the frame jacking point, not to support any weight, but to be there if the primary support failed.

 

Thanks! I realized the rear suspension will lower a bit when I reversed the car to park and inflate when I opened the door (after engine off and door locked).

 

I drove the car for awhile and after parking the car (mine is a RHD), I left the engine running while doing measurement and got these figures (plus minus for some human error):

Front (driver) 407mm
Front 404mm
Rear (driver) 407mm
Rear 411mm

Came back to the car around an hour later and re measure again (without engine running and door was still locked, so the rear is not raised yet by the small accumulator)

Front (driver) 407mm
Front 402mm
Rear (driver) 406mm
Rear 403mm

Does the air suspension lower a bit when the car is reversing? I had a visual check and a simple fingers measurement just before I reversed into the parking lot and realized it was lowered after I parked.
I will drive the car for a short distance tomorrow and do the measurement again with the engine running without reversing the car this time round.

 

Have 2011 XJL supercharged. Car was leaning to the passenger side quite a bit. Brought it in to dealer to have it checked, I suspected it was height sensor but needed to confirm. They said it was rear height sensors (both left and right) that needs to be replaced. After replacing ($1500), Dealer said they would like to leave it overnight to see if the car stays level after calibration. Next day, it was lower on passenger side. They said I now need to replace the rear right air spring. If i replaced the right read air struts ($3400), would it raise the front as well?
The wheel heights are still leaning to the right. If they had calibrated after the height sensor replacement, shouldn't the driver side be lower close top 15.8 or 15.9" ? here is the current height after the height sensor replacement (not replaced the air struts yet).

Front Driver: 16 5/8" Front Passenger: 15 "
Read Driver: 17" Read Passenger: 15"

Thanks

 

The X351 cars only have air springs in the back so not sure they would change the front height? I don't know how you can even change the front height? It's just a conventional coil spring front end.
We don't see many problems since Jaguar went to just the rear air springs so hardly any threads about it?
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