Long story short: I know the front springs are controlled together by the suspension module, but they are valved separately, correct? So if the car is sitting, and one spring leaks out, the other 3 will stay inflated?

The whole story: my garage queen nearly stranded my family and me 500 miles from home this week. Had to go to NJ for a funeral, so took my car being the roomiest. Drove up there with no problem. Parked on the street overnight, low was in the teens or 20s. The next morning I came out to find the front right corner was down, all others were fine. Started up the car and it raised it back up, but upon taking off the pump was running a lot trying to keep it level while cold. Drove it around some, and after the engine warmed up and the sun warmed things up, the car was back to normal.

That same day, after the sun set the temps dropped to single digits. We came out of the restaurant after a few hours, this time I got the "Air Suspension Fault" and then "Vehicle Too Low." For some reason it wasn't just the front right, or just the front, but all 4 corners dropped to their lowest level. Managed to get the few blocks to my aunt's house, where she let me park in the garage and put her Mercedes on the street... the good news is that after staying the 40F garage overnight it started up and raised back to normal, and we made the 500 miles back home without incident.

I'm fairly confident the RF strut is the problem, read plenty of stories on here about these springs leaking when cold. I'm going to replace that, (pricing out options now ,one or both fronts, tbd). But I'm not sure why the whole car dropped down like that if just the RF spring was leaky.

Also surprised this issue has never presented itself before now. Granted I park in my garage that's 55F at the lowest, but we've had some days here last month 12-15F where my car was parked outside all day at work, and it had no issues. I had no warning that anything was remotely wrong with the ASM. Still really miffed about that.

That cat must have known how mad I was--about to fix it and sell it Luckily it was flawless on the drive home.

 

I recall from other posts that you have a 2006 XJ8 thus there is one ride height sensor for the front and two in the rear for each rear side. When the one shock in the front leaks air the air suspension system, when the car is off and thus not running, will release air to level out the car. Thus as the front side drops some more from the leak in the one air shock, the air suspension system will again release more air to keep leveling out the car until finally the car is fully down. Since the engine is not running, the compressor can not turn on and thus pump air into the system to rise up the car to level it to proper set height. There are many posts on this.

Use soapy water on the top of the shock to see were the leak may be, if it is from the center it maybe a bad air shock, if it is from the brass fitting to the air line it could be a rubber O ring issue that you can simply replace the O rings.

 

Yes, it is an 06 xj8. I do recall the ability of the asm to lower while parked, and since the sensor is on the front left it makes sense that the FR side could drop without pulling down the FL. I'm just wondering why the front and rear dropped to the bottom while the car was running... If the problem is just in the front strut. Car is working fine now, just worried there's some other asm fault affecting the whole system.

 

I would think that either the leak is to large in the front shock and/or the compressor ring is worn out and the compressor can not deliver the sufficent amount of air to raise the whole car so the cars self leveling mode ends up lowering teh car at all the shocks.

 

Ah, indeed the RF shock is the fault. Today found it was gushing air out the top of the shock (not at the air line fitting). Will be sourcing this quicker than I expected. I think it's lucky I replaced the air pump ring last summer, it's probably the only reason the pump can even get the front lifted a bit.

Anyone know if the Arnott reman shocks really look like this photo? No metal shield around the bladder or a dust boot on the shock rod?

 

I do recall that Arnotts does not put a cover over the air bladder - you might check the photos on their website to confirm. If I'm not mistaken, their rebuilt air spring/dampers come with a warranty, so there may be a chance that they would repair yours under warranty, or perhaps for a reasonable fee.

Please keep us informed.

Cheers,

Don

 

The Arnott air spring is a different design, (Arnott will probably say it's better !!). However one thing is it doesn't have a switchable damper so they really should be replaced in pairs, although I suspect most owners wouldn't notice any difference, but ask Arnott about this. You still have to connect up the CATS lead to the shock as Arnott have "spoofing" kit in there to fool the ASM into thinking the shock is a kosher Bilstein unit !

Personally, I think CATS is an unnecessary complication. Cars need to get a bit simpler and easier to maintain in my opinion !

 

I ordered the remanufactured Arnott. The one without the metal shield is actually a remanufactured factory Bilstein. In theory it should come with an active damper because Arnott simply re-uses the Bilstein core from an old factory unit. The air bladder on the reman Arnott is exposed. Arnott also makes a brand new unit with an inactive damper that uses a spoofing system but that unit has the metal shield. Finally Arnott makes a kit that completely eliminates the air suspension and replaces the bladder with a coil spring. To be clear... Arnott sells three different units for the XJ8 (reman factory, aftermarket air w/o CATS, aftermarket coil over w/o CATS)

 

mhamilton,

There is an embossed logo on the air bladder of your air spring, but the photo resolution is insufficient to make it out. Can you read the information on the air bladder, and if so, could you please post all of it including all words and numbers? We're trying to locate a bladder manufacturer who might be willing to supply DIYers, and you may be in the perfect position to provide that information!

Thanks!

Don

 

Hi Don, that photo is not my strut. I have the OE parts on my car currently. The photo above is from an auction for the Arnott unit (see here for the eBay listing--no connection with the seller).

PCMOS and Fraser, yes I have been looking at the various aftermarket options for this strut. I don't think I want to get rid of the air springs or the E-CATS just yet. Simpler may be longer lasting, but I like the functionality of the original design. I'm leaning toward either a known good OE strut or will replace the fronts with the reman Arnott units.

The one sticking point for me on the reman using the old Bilstein (and the missing metal shield). I know the shocks last long, but I would have no idea if the shock I'm getting is at the end of life or only had 30k miles on it. Wonder if Arnott does anything to shock... I seem to recall Bilstein can reman any of their shocks if you pay them.

 

Mine looked factory fresh when it arrived and the gas charge was much stronger than the one I removed so I suspect they do something pretty significant to the shock in the reman process. The only problem is that since I've installed it my ecats is throwing a code for an open circuit on that shock. I haven't diagnosed it yet. I'm going to plug in the old shock in the trunk and see if the code goes away. I'm also going to check the resistance against the other factory original.

 

Hi Andrew,

I'll be curious to learn what you measure between the two ECATS solenoids. Cambo has shown that the ECATS signal is pulse-width modulation at 400Hz, IIRC, so the measurement the ASM is looking for is probably impedance rather than resistance. Another member (Guus?) posted a photo of the device Arnotts ships with its new air springs/dampers to fool the ASM/CATS system and the device is wrapped in the type of white mesh tape used on wire coils as found in solenoids, speaker voice coils, etc., and my assumption is that its an inductor coil meant to mimic the impedance of the original CATS solenoid.

You should still be able to measure a DC resistance on your old and new shocks for comparison, but whether or not the measurements will be conclusive remains to be seen, since impedance is a much more difficult quality to measure. Let us know what you find!

Cheers,

Don

 

once you sets a CATS code you need a dealer level scanner to erase the code.

 

Basically, shock absorbers wear out because the seals fail, and the oil leaks out. Bilstein are one of the top manufacturers in Europe, if not the world, and I would expect the shock part to last a lot longer than the spring diaphragm. In fact if one looks at the steel coil equivalent, steel coils fail regularly, but nobody thinks of replacing the shock just because the spring has failed, and here it is the same thing. All Arnott are doing is replacing the steel coil equivalent on the unit. Let us thank them for taking the trouble to do so ! So buy a rebuilt Arnott unit with confidence. However bear in mind the shock part of the unit has a life that could end whilst you own the car.

Of course there are also new OEM Bilstein units available too, but these are expensive, although cheaper than buying from Jaguar main agents. There are also used and new old-stock units on the internet. I have four on my car.

 

Arnott is no longer offering their rebuilt shocks and are not taking anymore blown units in trade. I was searching for some replacements last week and was told all they now offer are their new shocks.

 

Here is a UK supplier with the Bilstein OEM units. It's the cheapest I've seen for a Bilstein unit, although still eye-watering if the British 20% sales tax is added on !!

 

Where is the link?