Hello!

My 2005 X350 XJR has been air suspension fault free since I bought it (18 months).

But suddenly now the front drops while standing. Over about 3 days it is flat on the ground (tyres touching the wheel well ceiling - so much for that valve in the strut which keeps a minimum or air pressure inside).
I think the rear then also sinks, but I have not given it enough time to be sure.

So far I could not find a leak (soapy water).

This kind of general / total sag probably points to the valve block, but now my paranoia is setting in:
Suppose 1 front strut is leaking and dropping. Then suppose the ASM (in Sleep mode) notices that and drops the other side to level out the car again.
This way I can't be sure what is really happening.
(part of my suspicion is that I now notice one front side is slightly lower than the other, during my frequent measurements at the moment)

So I want to disable the ASM while the car is parked, so that I know what is happening purely physically without car "intervention".

So in my Owners manual there are 2 fuses that is listed as "Air Suspension", both in the luggage compartment (boot / trunk).
They are F12 & F52.

Can I pull either (or both) of these to temporarily disable any air suspension operation, while the car is parked, so that I can rule out that possibility and see only the physical effect of whatever is going on?
Any dangers / caveats to doing this?
Any other suggestions?

Thanks!

 

Pulling the fuses will NOT troubleshoot a leak, it will simply not allow the system to try to correct for a leak.

If the car is settling that badly, you most likely have a leak in the strut airbag itself, and not in the lines or valves anywhere, because like you said, there is a check valve that should keep it from dropping to the ground.

 

I had the same "dropping over days" issue for years. Didn't matter coz suspension was fine apart from slightly more compressor usage.
I thought the valve block was likely, but then a front strut popped internally and settled the matter for me.
Theoretically pulling the battery should disable the self-levelling ("self-settling") so one can find out which strut, I think someone tried it on here and his results were indeterminate.
I don't know if pulling fuses would disable self-levelling, might just disable the compressor?

 

Thanks Chris,
All my shocks are relatively new (aftermarket) so I really hope it's not any of them!
There is another fuse, I think in the engine bay, labelled "Air compressor", so I am thinking/hoping that either one of the 2 in the boot will pause the ASM sleep mode, without the ASM losing memory or creating any other new problem.

I had a valve block issue in my previous XJ. But my symptoms were slightly different - the rear would initially rise while the front dropped (cross leaking in the valve block). Also the soap test clearly confirmed bubbles coming from the seam between the aluminium & the plastic part of the valve block.

Hey, perhaps I can just unplug the valve block connector! Then the ASM should retain memory. A fault code might pop up can could be removed.

Have a great weekend!

 

Hi,

I do not yet know exactly where my leak is (can't spot bubbles anywhere), but I can confirm with 99% certainty that the "sleep mode" of the ASM, which will lower certain corners to level the car, will interfere with your ability to diagnose where the leak is.

I have now done weeks of testing (in between having to drive - so not all tests were long enough).
The ASM sleep mode will lower the other corners to compensate for the one that is sinking due to a leak.

By removing F12 & F52 in the boot fuse box (which are both marked as ASM in the owners book) you stop this sleep mode action.
Doing this I found the whole car does not continue to sink, only the one corner sinks (so yes it points to that corner line somewhere).
It might not go down all the way as far as when sleep mode is active (fuses installed) (perhaps of the reducing weight on that corner as it sinks, who knows).

After seeing which corner it likely is, I have also confirmed my theory by putting a block under the jack point on the suspect corner.
Even with the fuses in the car will sink to this point (where the block holds up this corner), but no further. I must still try this at another corner, but I believe the suspect side will keep on sinking.

I don't much like the sleep mode anymore, because apart from the issue above, it also means more stretching of the other corner shocks, and more lift required when the car is started - more compressor time.
I wish there was a setting to disable the "level during sleep" feature.

Anyway, don't forget to re-install Fuses F12 & F52 before driving, else the car might go too low and you might not know in time. I left the spare fuse cover on the driver seat as reminder whenever I took out the fuses or put a block under the far side corner.

Regards

 

Hi All,



I need some advice from the air suspension experts!



The Fundamentals:

• For almost 2 years of ownership my X350 XJR had perfect air suspension – never did it sag & almost never did I notice the compressor running. Now and again I heard the tshhhh as it let some air out, 30 minutes (I think) after coming home. It could be standing 2 weeks and hold its height.
  
• Suddenly it sags while standing a day or two.
  
• Careful testing confirmed that the “self levelling” feature of the ASM in sleep mode will lower other corners to level with the sinking one, thereby making it difficult to find the problem. Therefore I have taken to switch off the ASM while car is off, by removing fuses 12 & 52 in the boot.
  
• The front end sags first, and after some time the rear also, but the rear does not go all the way down like the front.
  
• My theory is that I won’t develop more than 1 fault at the same time (e.g. both front corners suddenly leaking)
  
• Experience with my previous XJ8 showed that the valve block can leak internally (between air lines, as in the rear goes up while the front sags under the engine weight), as well as externally (as in bubbles visible between the aluminium block and the plastic resin part of the valve block. I had a video of my previous car doing this here: https://www.jaguarforums.com/forum/a...-video0469.avi
  
• On this car I cannot see any bubbles. I tested all 4 corners and the valve block. I see no bubbles.
  
• I didn’t test at the compressor, but in my understanding the line to the compressor is not kept under pressure, so that the compressor can start up.
  
• Even though I could find no evidence either way, I still suspected the valve block, because what else can explain the whole front sagging, and the rear partially, while the ASM sleep levelling in off, when a few weeks ago there was no issue at all.
  
• So I took a chance and ordered a replacement valve block from China (see next post for more on that).
  
• I carefully installed the valve block. I did not re-seat the little olives, nor cut the tubes shorter. I could see no bubbles, except one fitting that didn’t have an o-ring! (but there were signs of some grease being used previously) But yet – the sagging is worse now! So either I have disturbed whatever the problem is, but still undetectable, or the new valve block is pretty junk to begin with and also leaks.
  
• So yesterday I put the original valve block back. This time I replaced all the o-rings (with 6mm & 9mm, but I think 8mm would be a better fit). I even dabbed a hint of lithium grease on the o-ring seat, on the thread and behind the olive. Minute quantities – won’t get near the air line. Again I did not cut the tubes or re-sear the olives. No bubbles. Still sags, quite aggressively now. In a few hours. If you are near the car you can hear the suspension creak as it sinks.
  
• I really don’t know where to look next, this is driving me crazy!
  
• My old car did not sink as fast as this one does now, and the bubbles on the valve block were easy to see.
  
• My air shocks are not OEM, but are relatively new
  
• Any help & suggestions welcome please!
  

 

Side note on the Chinese Valve Block:

I ordered the one that looks exactly like the OEM one, but was disappointed to receive one with a square metal part. I didn’t want this one since it looks like a cheap plastic thing with a sheet metal cover (on website photos). But I was pleasantly surpised that it is also a solid aluminium block, and weighs about 140g more than the OEM. I think the OEM version just machined away all the unnecessary weight. The Chinese block is a bit taller and the angles of the fittings go straight up. This caused a bit of strain on the tubes when I put back the foamalite cover & spare wheel, but it wasn’t the cause of a leak. Other than than, the new block clicks louder than the old, but superficially does not look cheaper built than the OEM.

When I first powered it up I got an “Air Suspension Fault”, but it turned out to be codes relating to unplugging the pressure sensor cable & solenoid control cable. Subsequently I removed fuses 12 & 52 while swopping, and this error did not come up again.

 

id convert to coil overs and never look back! Best decision ive made for my XJL yet. And the stance is better than before.

 

I agree with the conversion. Chased air issues for weeks after getting my XJ8L, After disassembling the compressor and finding its "dryer" was actually a water tank, and the exhaust vent valve was rusted solid, I abandoned the air, and like indyx358 above, have never looked back. I did mine with Arnott struts, and they came with the module to kill the CATS error and light. (I'm not sure the 2005 will get that error after conversion.)

These systems are WAY beyond their design lifetimes, and the lack of a serviceable dryer (the dryer is a chamber internal to the compressor) is a fundamental design flaw, not just for Jaguars, but ALL automotive air suspension systems. Once water is in the system, there is no way to remove it. Valves will rust, and water that has collected in the tank and struts continues to get circulated, forever. Get rid of it.

 

I also fought a 2006 XJ for weeks until wfooshee explained the design flaws in the Jaguar air system. I finally went to springs and it was a good swap! Car is dead reliable now and the ride is so close that I don't know that you will feel a difference.

On the 2006 and up models you will need the bypass box but others have posted that before 2006 just unhooking the air suspension module is all that's needed.
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Part of my problem is that I'm in South Africa and the nice coilover kits you have do not exist here.
Here will be lots of "yes we can do it" experts who've never done an XJ and who will shrug if they mess anything up in the process.
Importing the kits here will be very expensive + finding someone to install it properly....

So far I am holding thumbs to sort it, but I see your point...

 

If you can operate a car jack and a wrench, the installation no really not that difficult. The hardest part, literally, is removing the back seat for physical access to the air suspension module. Nothing that affects alignment is touched, other than the possibility that a slightly different ride height could affect camber. As for importing, I can't tell you anything that might help there, but if you can change a flat, you can probably install the struts yourself. Obviously, use jack stands to support the car while working under it, not just the jack itself. You can do one strut at a time, both struts at one end of the car, or both struts on one side of the car, however you want to do the lifting.

 

I also installed the coil kit at home. Now I did have a 2 post lift so that helped my old back for sure.
But no alignment needed as posted above. My car also settled some with time as it looked a bit high when first installed.
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I'm curious about this module you speak of! I have coilovers in my 2006 XJ8 and have installed resistors in the connectors at the shock towers, but I still get the "air suspension fault" warning in the info center. Will this module solve that? Where can I find one?

 

Air suspension fault, or CATS fault? Two different things. If the Air Suspension Module is still getting power after installing coilovers, it's going to throw a fault. What the resistors fix is the CATS fault that comes from struts that do not have the CATS system to change between soft and firm settings. The connectors to the air suspension module should be unplugged.