I have read many threads in this forum about this topic and have a knowledge base built as a result...but can a I get a few opinions from experienced owners?

I just bought a 06 XJ8 VP with low mileage. The air suspension fault message is coming on and for good reason. When it does, after about 2-4 minutes of driving, the suspension is gone. It is like driving a dump truck.

My trusted import repair shop says both front shocks need to be replaced and then they will be able to test further to determine if the air compressor is working properly and also determine any other leaks. This is a $1800 repair for starters and the Jag dealer quote $3200.

I am very interested in buying the Arnott coil spring/shock kit and not sinking money into a suspension money pit for years to come. My questions:
Are you glad you chose this option from a cost and performance perspective?
How many service hours are required? I read 8 hours in a previous post.
Anticipating...how did you get rid of error messages after disconnecting the system? I am assuming this will happen.

Thank you so much. I am pumped about the car and need to make a decision in the next couple of days.

 

What do you mean by "the suspension is gone" ? If the air compressor cannot maintain reservoir pressure, a fault code will be generated, plus a warning message on the dash panel. The normal message is "Air suspension fault", but can be "Vehicle too low", if the ASM cannot maintain vehicle height.

Has your "trusted import repair shop" read the fault codes ? You don't mention these at all, but I suspect that one of them will be C2302 which normally indicates a failing air compressor, the most common fault on these cars. This is cured by fitting a new seal to the piston in the compressor (see our member 'bagpipingandy'), or swapping out with a new compressor. Compressors can start to fail at low mileages, as in my case at 37k miles in 2010. Air springs are much longer lasting but failures do occur. Arnott Industries used to do a service exchange on air spring units by replacing the spring diaphragms, but now only supply new non-CATS units. Bilstein OEM units are now available on the aftermarket worldwide and I suggest you investigate their cost which I believe to be around $800 in the USA.

I have to say I find their advice a bit odd; have they worked on these cars before ? I mean, you do NOT spend a mint of money replacing the air springs at $800 a pop in order to check the air compressor !! You read the codes first, then decide what to do. The compressor is fairly cheap to fix compared to the air springs, yet they are suggesting you replace the most expensive parts first and then look at the compressor !!

 

Thank you for the response. The message on the dash is a constant "air suspension fault". As this is displayed there is a feeling of no cushioning whatsoever on the drive and it is riding low.

They did not supply the codes but I know they keep an electronic vehicle record which include all codes. I will get the codes.

I am going to get a second opinion before I make a move. I did see the bagpippingandy kit. That would be a wonderful solution if that is indeed the issue.

Cheers!

 

I was also told in 2010, when I had to have a new compressor fitted, (service exchange actually), that the CATS will default to "Hard" if you get "air suspension fault" come up. This explains the hard ride.

If vehicle is too low all round the compressor has to be the first suspect, but you haven't told us the mileage yet. I would ask your shop why both front shocks need replacing; are they leaking air badly ? If an air spring is removed from the car, the air line is disconnected, but there is a valve in the unit that keeps a minimum pressure in the unit to prevent the air diaphragm from damage by irregular movement off the car. A shock that won't retain this pressure obviously is leaking and needs replacing.

BTW, after a reasonably long run, the system will exhaust air from the reservoir back through the compressor to blow the water out of the water trap. You hear a "Whoosh" for a few seconds. This is a normal part of the air suspension operation. Maybe Jaguar should have mentioned this in the Owner Manual !!

 

Thank you Fraser for the insight on the CATS hard ride. The car has 55,000 miles on it and the assessment from 3 mechanics is a thumbs up clean!

There is a bizarre turn of event that just occurred this afternoon. I loosened a line to the front shock and a long burst of air came out...possibly indicating no or slow leak in the shock. MUCH air came out in a long burst. Also, the "ex-trusted" garage must have changed something because the "air suspension fault" is on constantly.

Next I took the car out for a 10 mile ride on a rough road and it rides like a dream! Now I am really wondering what is going on? The front is low when the car is off. Any further thoughts?

 

Have you downloaded this? http://www.mediafire.com/view/7rdkgg...ion_Sectio.pdf

 

Hi Jagzzz,

Welcome to the Jaguar Forums!

I agree with Fraser that the shop's recommendation to replace both front shocks before checking the compressor is suspect. For one thing, I'm not aware of any other report of two air springs failing simultaneously. Knowing the Diagnostic Trouble Codes the shop pulled from your car will help.

The fact that so much air came out when you disconnected the air line suggests that if there is a leak in that air spring, it is minor and not the cause of your issues.

One test you could do to see if your primary issue is a worn piston ring in the compressor is to start the engine, leave the transmission in Park and listen for the air compressor to start running. It may start within seconds, or it may take a full minute or so before it begins to run. The compressor is mounted in the front bumper cover near the left corner and it runs with a soft "knocking" pulsation. It will run for up to 2 minutes and then shut off to prevent the piston ring and cylinder head from overheating. When you hear the compressor shut off, turn off the engine and wait at least 45 seconds to allow the compressor to cool.

Start the engine and once again allow the compressor to run again as long as it will. If it runs for 2 minutes again, the system is still not fully charged, so you'll need to shut off the engine for 45 minutes again and then repeat the cycle.

If the compressor shuts off in less than 2 minutes, the system may be fully charged, so try taking a drive. If the AIR SUSPENSION FAULT or VEHICLE TOO LOW warnings do not reappear, this would strongly suggest that your compressor is not charging the system as quickly as it should due to a worn piston ring, and bagpipingandy's kit will correct what is probably your primary (if not only) issue.

The document Six Rotors provided the link to contains the best explanation of the air suspension that we're aware of. It doesn't answer all of our questions, but it does help us understand how the system is supposed to behave under most circumstances.

Cheers,

Don

 

I have a 2005 XJ8L.
Last year I put in the Arnott conversion. It took about 6 hours doing it myself. I think it would go quicker the second time.

My suspension was low and needed to be re-calibrated. Twice in cold weather I got a low suspension warning but it did not recur. The nearest Jag dealer is 100 miles away and the local indys I spoke with didn't have the full Jag diagnostic scanner. I just didn't want to deal with it. I did buy the Arnott Sport tune set instead of the comfort set; you may need to get in touch with the factory directly as the authorized retailer didn't know about this option.

OK, so about six months later:

No regrets with the Arnott system. No error codes, but I disconnected the CATS module before uninstalling the air shocks and there were no codes active at that time.

Since then I bought a Mongoose clone diagnostic tool for troubleshooting the ABS DSC system. If I had done that first and been able to trouble shoot and re-program the CATS system I probably would have kept the air suspension just because it is the original design intent.

Bottom line; the Arnott conversion is great. Suspension height is right on spec, handling and ride are good. There might be a tad more road noise, but I replaced upper control arms and tires at the same time so it's hard to tell what differences there might be.

At the time my options were:
1. Drive four hours round trip and pay a minimum $200 fee to get the system scanned, then repeat when problems recur. The $200 did not include calibrating they ride height, whcih they said they could / would do if there were 'no other deficiencies'
2. Let the local guys do 'parts replacement' trouble shooting, which still would not have reprogrammed the ride height.
3. Replace the air suspension with Arnott or other mechanical suspension. I choose to go this route.


With your low miles, compared to my 140,000+, you really have a completely different decision process. I would be concerned about a recommendation to replace both front shocks without some more data.

I have no regrets with my decision to go with the Arnott conversion, but it seems a bit drastic for a 55K mile car unless you WANT to get rid of the air system, or have some additional information on diagnostics and trouble shooting.

 

I can't see both front air springs failed at that kind of mileage. The ASM controls the front as a single axle so one failed unit means the front drops evenly each side. And if only one air spring is duff, it is surely cheaper to replace with a kosher OEM Bilstein new unit ? This has to be the cheapest option, surely ? Of course the compressor may need attention, but a piston seal kit should cure that.

If it were me, I'd not be doing full-on suspension swaps at that kind of mileage.

Of course, I live in England so am not far away from a Jaguar independent shop and also an very good main agent. I realise it is not like that in the US unless you live in the East or the West sides, the middle can be a bit short of Jaguar experts. Lets face it, the cars don't sell in hundreds of thousands.

 

Fraser, Don and Jim...Thanks for the information. After reading your latest material I jacked up the front of the car, pulled the wheels off and the plastic wheel wells and exposed the compressor. Here is what happens if I:

• Have the car locked, unlock it and open the door, air flows from the auxiliary tank to the front shocks and raises the front of the car...at that point air leaks in the front can be heard.
• Starting the engine, the compressor starts immediately...after 2 minutes it stops for about 5 seconds and runs again and again in sequence. The air is rushing out of both front shocks...at least very close up that is what it sounds like to me. This is not air leaking from the top connection that we see with the hood elevated.
• I had new tires put on today and now the faults are "air suspension fault" and "low ride". The body is barely clearing the tires.

There are many import car repair shops in this area and several Jaguar dealers. The dealer I called insists that all 4 shocks need to be replaced (sight unseen) based on the year of the car and the hot climate in Texas. (You cannot imagine their cost for performing this task) YES they just want to sell lots of expensive parts and labor and really don't care about efficiency when it comes to service. That has been my experience.

With all this said, it appears as though both front shocks are leaking. I asked the mechanic from last Friday for the codes...he said there were old codes and they quickly determined the issue was a leak in the front shocks and "codes are useless if leaks are the issue". What a mess but I am determined to get my machine on the road asap. Thank goodness there are no other issues.

 

According to the manual that Six Rotors provided the link to, the Air Suspension Control Module (ASM) allows the compressor to run a maximum of 120 seconds at a time, but will time out the compressor for generally 30-45 seconds to cool before allowing it to run again. If your compressor is only stopping for 5 seconds, that seems highly unusual. Perhaps it has to do with the volume of air being lost through the leaks.

Regarding the leaks, in addition to the air hose fittings on top of the air spring/damper units, there is a seal around the central area of the top of the unit around the CATS electrical connector. You can test for leaks on the tops of the units by spritzing soapy water on the air hose fittings and around, but not on, the CATS connection. Bubbles indicate a leak.

The other possible leak source is the air spring bladder, which is concealed by the cylindrical metal cover and the corrugated plastic gaiter, so you can't use the soapy water trick to test for bladder leaks. It would be at least worth doing the test on the tops of the units just to rule out the air hose fittings for certain.

Cheers,

Don

 

If both are leaking, it is unusual. But not reason two cannot fail at the same time. But take a look at the ride height adjuster.
I just purchased four XJR shocks off eBay. They look new in the pics. They have the red sticker. Supposedly off a 2004 with 32,000 miles. Should they on in a week. But from the DFW area. So freezing winters and 110 degree summers.
The previous owner replaced one with an Arnott. Seems indentical in ride. Not sure if it was a Comfort or Sport shock.
If you really have two bad shocks, either find a used pair, and repair the seal in the compressor, two rebuilds, or spring for the conversion.
These conversion kits are over priced. These are 100 - 150 dollar shocks. There is a Bilstein distributor here, ProAm, most are 100.00 each. The KYB rears are 60 - 75 dollar shocks. A conversion kit should be 700.00. The brackets and adapters are cheap in lots of 20. But the 800.00 Bilstein OEM are 1200 - 1500 at the dealer. Sets the price bar. A conversion kit is the price of a single shock from the dealer.

 

From your description, it does indeed look as if both front spring diaphragms are leaking. The compressor appears to be working normally, and obviously cannot keep up with the leaks !! Eventually this heavy demand for air will wear out the compressor, so best to get things fixed asap.

If you are short of dough, another option is to buy and fit used Bilstein units bought off the internet. They'll get you going for a bit until you have run the car for a while. Of course, Texas is a place that gets very hot, so I suspect the air diaphragms have a much shorter life there. You could also fit the Arnott air springs, but you'll lose the CATS at the front, because so far Arnott have not introduced CATS-compatible shocks; their units spoof the CATS module to think it is there when it isn't.

 

Thank you Fraser and everyone for bringing all the options to this string.

After considering the difficulty in putting a finger on good local Jaguar repair talent, evaluating the effects of high heat on the air suspension diaphragms in Dallas and my desire to have a car on the road versus the garage (for the last 3 weeks) I have ordered a set of coil spring shocks from Strutmasters. It is a pity since Jaguar has built in a complex system on the air ride and I am in effect throwing it out the door. However, I do not wish to have ANY further issues with suspension for the life of the car and my choice should get me there with a lifetime warranty on the equipment.

Hopefully the equipment will be installed tomorrow. I will update this string with my impression of ride and handling early next week in case others would want to consider Strutmasters.

 

Update on suspension conversion...

After several weeks of garage time, my Jag is back on the streets. Not sure if the kit was worth $1400 but I bought a kit from Strutmasters which included 4 assembled coil over struts and an electronic black box to take care of any suspension error codes that might appear.

The installation is straight forward and I am hoping this is the last suspension repair I must make...or at least pay for...the equipment has a lifetime warranty. Maybe I can sell my rear air shocks and compressor to offset some cost?

The ride is very solid. It is not as soft. Loosely I would describe it more to the sport feel which is fine with me. I can feel slight (normal) road vibration in the steering wheel with the struts and did not feel this with air. Leaning into the corners seems better controlled and there is no front or rear car bounce with the struts when encountering challenging road elevation.

I posted some pictures of the Strutmasters equipment. Looking closely you will notice a Bilstein label on the strut. Also the company really boasts about the Ibach coils. I am guessing this equipment is way over priced but my cost alternative buying new air equipment was worse. The bottom line is I believe the ride is good, it is safe to drive and I no longer appear as a low rider with only 1/2" clearance from top of tire to wheel well.

If I can be a resource to anyone considering a conversion, please add to the string or send me a message and I will be glad to share my experience thus far.

Once again, thank you to all that provided information, sources and much much more!

 

The Bilsteins will probably ease up a bit after a few hundred miles; they certainly did on my MG TF when I put a set on. A set of Bilstein monotube shocks was the recommended fitting on these TFs to get the "Comfort" ride. Well, it is still pretty hard, but now not uncomfortable. Before the Bilsteins I think the fillings in my teeth were getting loose !!