Hi all -

I searched for awhile before posting this, as there are A LOT of threads on the air suspension. But I didn't see anything describing my question so here it goes.

I have an 09 Super V8 Portfolio, 65k miles, dealer maintained southern car that I purchased in Feb of this year. Ever since I got the car, both in cold weather and warm, the following events occur:

Come out in the morning, front end is low but not all the way down. Start car up, raises to normal drive height almost immediately. Would say it's a couple inches. Driving is fine, no faults or error messages. When I park, immediately upon shutting the car off, it lowers about two inches. You can hear the air leaving the struts, but it stops abruptly once the car reaches a certain height and then it's silent with no residual air leaking sounds.

Is this normal behavior for the car?

 

You can check for codes but sounds normal to me when I had air suspension.

 

Neither of my air suspended XJs have done that. Occasional changes in height as the car is unlocked, or started, depending upon how it was last driven (the suspension drops automatically at over 100mph, but doesn't rise again for several minutes after the pace drops below that figure), or when parked on uneven ground. It's probably a smart idea to plug it in for a diagnosis. My best guess is a failing front ride height sensor.

 

Are you parking on a level place ?

If I leave my car for a few days the front raises about 1" when I start the engine, and there are no faults displayed. However, my driveway has a slight slope and the car is parked up the slope. I suspect the slight weight transfer to the rear causes the system to level-up the car by lowering the front slightly. My last X350 did exactly the same thing, so it is obviously working as it should.

 

 

Have you actually measured the amount of drop when parked / rise when started, both front and rear? A couple of inches does seem a lot; perhaps it isn't that much. In any case if SDD shows no faults, then I wouldn't be too concerned unless the car's behaviour changes. You would have to be unlucky for there to be any serious fault at such a low mileage.

 

Sleep Mode

Sleep mode is invoked approximately thirty minutes after the ignition is switched off and the last door or luggage lid activity has been detected. The air suspension system shuts down when the vehicle is not in use and automatically wakes up every twenty-four hours to check the vehicle ride height. Twenty-four hour multiples are used to avoid temperature variation, for example to avoid the variability between day and night temperatures.

If the suspension level requires correcting, the suspension’s lowest corner will be used as the height value and the suspension will be lowered to meet that height. If the suspension lowers to the minimum height, the ASM makes no further adjustments. To conserve reservoir pressure and battery power the system does not raise the ride height when in sleep mode. When the SSP signal detects a door or luggage lid activity the suspension will switch to preliminary mode.

Inclination Mode

The ASM activates the inclination mode when the vehicle is parked on an uneven surface for example, with one wheel on a curb. If the ASM detects what is effectively a sufficient twist between the front and rear axles, the axles will be leveled as a pair. This avoids suspension leveling when the vehicle is moving away.

 

I am following with interest and working through the Air Suspension manual, available in the Stickys (First kind of man according to Box signature!)
Jeez it's complex - there are no less than 14 modes listed. And x^n sensors...

Reason is, I have a front corner go down when parked overnight or a couple of days (it varies). So I drive and it comes up.
-On one occasion it took a few km to come up (why does that guy keep stopping and checking his left tyre? Oh...it's a Jag)
-On another occasion it came up almost immediately.
-This morning I observed Preliminary Mode (just unlocking raised the car-if enough air in the reservoir)

According to the manual there are so many things affecting this -residual reservoir pressure-driving above 25mph-what I ate for lunch affecting load- that observed characteristics can vary and I remain slightly bamboozled with my computer-on-wheels.

As far as I'm concerned there's a leak, but not enough to worry about.

 

It was left overnight at my mechanic, and when he measured it the next morning it was 2" lower in front than when he parked it the night before. No change in the rear height.

Yeah, at this point I am not really concerned. More just perplexed and want to understand the behavior. I'm used to land rover's system but I've read there are differences with the one Jag used.

 

Sounds like it could be Sleep Mode, except that it lowers immediately after shutting the car off. My only concern really is that if I do have a leak, this behavior could be causing stress on the compressor.

 

Well that was pretty cool (I was prepared this time)...
My front suspension went down overnight as it usually does. I unlocked the car with the key fob and it rose to "riding height" within seconds.

"My only concern really is that if I do have a leak, this behavior could be causing stress on the compressor. "
Yes that's what I've read here. Your choice as to what is "excessive" compressor use.
My limited experience is that the suspension can be expected to go down whenever parked (it's not my daily driver)
Although in my case, it takes many hours at least. (flat parking)

You heard some "leaking air". Could you determine where that was coming from? I would think that unusual and possibly excessive.

 

If it were my vehicle, I would do a suspension calibration with SDD, and then see if the condition persisted.

 

I have noticed another symptom that I think might be related to the odd air suspension behavior: the HIDs are not leveling out as they should, and per the user manual, the HID level is determined by the air suspension. Here's a photo I took against the side of my house the other night:





As you can see, the lights are pointing upwards and the beam is hitting the top of my garage. Coincidentally, I just had my mechanic install new HID bulbs. Is there some kind of calibration that needs to be done afterwards? Could this odd behavior be related to the air suspension behavior I've been noticing?