Hello all,

It's now happened to me. A few days ago I got the dreaded ASF & VTL messages with accompanying orange and red dash lights. Of course the car went "low rider" but I continued to drive home knowing that the roads were very level and bump free. I stopped a couple times to shut the engine down, "reset" the suspension, and allow the car to rise. The air shocks remained inflated for only a few minutes each time and ultimately I just drove with the shocks flat the rest of the way home. As a side note the outside temperature was a balmy 19 degrees F and I was driving with a passenger at highway speeds when all this happened.

Anyhoo, I've been pouring over the threads on this wonderful jaguar forum and found that I'm not just the only one having these troubles but there is a treasure trove of information regarding diagnosis. In fact this topic seems to be the top most discussed issue with this car. My question is if what follows is a logical approach to solving this dilemma?

So that was about two days ago. Since then the car hasn't been moved out of our garage but I did run the engine to inflate the shocks. I then shut the engine down, disconnected the battery, and measured the height of all four mudguard arches to the floor. I then allowed the vehicle to sit overnight for a minimum of 24 hours and then measured once again. There wasn't any meaningful loss of height or air for that matter.

My immediate reaction to that result is that there are no leaks coming from the the air shocks!

Now mind you I am nothing more than an average shade tree mechanic. I have some car smarts but at the time of this writing I have no specialized tools, i.e., no multimeter, pressure gauges, etc. This leads me to have to just go ahead and shoot in the dark hoping to find the cure. I'll start with the easiest and least expensive troubleshooting and work my way from there.

My next step would be to check the R1 Relay but because we know the compressor is turning well then that step can me omitted.

Now I'm guessing the next and least expensive thing to check would be the compressor piston ring. I can open that unit up and replace the ring fairly easily with one of BagPipingAndy's replacement parts. Great!

If that doesn't clear up the problem then we could go for a new car battery. I hear that a weak battery can easily have an owner running him or herself crazy. They'll be chasing little electrical gremlins here and there not knowing it was simply the battery causing all the fuss. Okay

Last on my list would be the air lines and the actual shocks themselves. I suppose that it is possible there is a leak that is partially "self sealed" in a fold of an air bag and since the car isn't currently in motion in the garage well then the leak won't expose itself. (I don't really believe that scenario but whatever).

Lets imagine that a leak is in fact at the shock and we say yes to replacement. Are the Arnott shocks OEM replacements? Do we loose ECATS or some other Jaguar functionality by using the Arnotts? Has anyone used SNG Barratt's air shocks and same question about loosing some functionality? Is the original Jaguar part head and shoulders above the aftermarkets in quality of build, is it to be trusted better? I don't know.

I think that this may be where I reach the end of the line. I suppose the glitch may exist at a computer somewhere onboard and if that is the case I'm done. Meanwhile I will keep my fingers crossed that one of the above solutions will work.

Is there anything else I'm missing or haven't thought of guys?

Thank you,
Norman

2004 XJR ~90,000mi

 

You don't mention anything about reading the fault codes. The system is recognising the vehicle is too low, so it looks as if your height transmitters are working OK. It is always wise to read the fault codes, (or get them read for you), before you start whacking out on parts that can be expensive.

If the compressor has been ignored up to now, (90k miles), I would indeed consider it is in need of attention or replacement. How long have you owned the car ?

Other thing to think about is this - normal pressure in each spring is 7-9 Bar, with up to 20 Bar on full bump. As the car stood OK overnight, but dropped whilst driving, it indicates maybe there is a leak somewhere, but it is only tested when driving. One or more of the top seals in the air spring units might be somewhere to look. If the main diaphragms were leaking the car would not stand OK overnight.

Try doing a leak test at the top of each air spring unit, starting with the front.

If you need replacement air springs, then you have a choice between the Arnott units or the OEM Bilstein ones. Now a recent thread here has indicated that Bilstein are only selling the springs that have the Comfort air spring; yours will be Sport as you have an XJR. The Bilsteins maintain the CATS system, the Arnotts don't so you can't really just replace one, you would have to put on a pair at least. There are a few companies that are putting on new air spring diaphragms. This is much cheaper, but doesn't deal with any possible leaks from the top seal.

Essentially, until you have got the fault codes read, you are in the dark. C0203 is the one for compressor taking too long to charge the reservoir. Two minutes is allowed and if the pressure is not attained, you get this code. It can also indicate a leak somewhere between the compressor and the reservoir.

 

Hi Fraser and thank you for your suggestions. I’ve owned the car for about two and a half years now. And you are correct, I haven’t read the codes because unfortunately I don’t have a code reader. Can you recommend one that will read Jag specific codes? Otherwise, do you know if it would be kosher to have a forum user in my local area that owns one be kind enough to drop by my place and help me out?

Anyway, if I’m understanding you correctly you postulate that there is in fact a leak at the top seals and not at the diaphragms as evidenced by the vehicle maintaining it’s height while parked in my garage?

I’ll do as you say and check those top seals. Am I right in checking them with soapy water spray, and right at the top of the towers (inside engine bay)? Or am I to spray soapy water inside the mudguards (wheel area). Not sure there.

So if the leak is in fact coming from the top seal then can this seal be replaced on its own without replacing the complete air shock?

When you said in your post that “This is much cheaper” were you referring to having aftermarket air shocks from whatever company, eg Arnott, as compared to Jaguar dealer original equipment air shocks?

Just to be sure the CATS system helps maintain vehicle ride height regardless of load, i.e., air is pumped into and out of the shocks as passengers and or cargo are moved into or out of the car. This will maintain the perfect height above the road at all times. Correct?

So if the above is correct then am I to assume that the Arnott units will have the air ride quality but due to not having CATS then it is possible that the car will drag when loaded heavily?

How would I know if an air shock unit is CATS compatible by just looking at it versus one that isn’t?

Lastly, with regard to the compressor. Are the compressor and the reservoir mounted together? Are the air lines easy to follow between them and see if they are leaking? Regardless of what I find I will be ordering Bagpiping Andy’s piston ring replacement later today and feel certain that this will have a positive effect on the compressor’s performance.

Incidentally I noticed you have an MG. I have a 1954 MGTF that needs a lot of work especially in the area of the body and I’m hoping to get started on it sometime in the near future.

Cheers!
Norman

2004 XJR ~90,000mi

 

Hi Norman

The CATS system has no input to the air spring system, it only switches the Bilstein variable dampers inside the units between Hard and Soft depending on inputs from accelerometers and speedo, (and possible driver engine demand). If you brake it switches the fronts to Hard, same for the rear when accelerating. Hard on left or right when going round curves really fast. Only the OEM Bilstein units have the internal solenoid and valve that supports the CATS system, certainly the Arnotts don't, (not yet anyway!).

I was looking at a Tesla today and that has an air spring option. The spring units looked remarkably similar to the Bilsteins on the Jaguar. If more cars have air springs fitted the unit costs come down and hopefully give lower prices. Jaguar dealers are still charging ey-watering prices for these things and even the Bilstein OEMs on the aftermarket are many hundreds of dollars/pounds. However, you can just replace them singly as there is no sacking out like with steel coils.

The ASM takes inputs from the height sensors, at front and rear and adjusts the vehicle height to bring it back to the defined height stored in memory. If the car is standing whilst you load it up with bags of cement in the trunk, it will adjust the air springs as the car drops under load to bring it back to the correct height. When you're driving the springs are going up and down a lot, so it only adjusts the suspension very slowly based on average height readings.

Air spring top seals cannot be replaced, only the part that is the "spring", i.e. the rubber diaphragm, (and the bottom bushes on the rears). For me, if a company is replacing the diaphragms, as some are doing, they really ought to put some sealant on the top seal from the inside to reseal it. I don't know if any do this or not. The damper, (or shock absorber) part is left alone as it is very long lived and has no maintainable parts. Clearly if the shock is found to be leaking oil when a defective air diaphragm is removed, it is pointless replacing it.

People here have used soapy water to test the top spring seals, but Jaguar tell you not to. I think it is OK if you mop it all up afterwards. There are, of course, special sprays you can get in aerosol cans to do this.

The compressor is mounted behind the front bumper on the left side in the direction of travel, but the reservoir and the valve block that supplies each spring with air is in the trunk underneath the spare wheel. This is normally a very reliable component and we don't usually see much on this forum about this, unlike the compressor.

I suspect your compressor needs to be your first port of call when trouble-shooting if you have not replaced it yourself, and there is not record of replacing before you bought the car.

BTW here's a couple of pics of the sports cars.

 

Fault codes would be a good idea just to see what is wrong, if the car lifts the compressor is at least working, but why it is sinking is strange, either air leak or for some reason the car is opening the valves to lower, a fault code may shed some light on this,


Link to compressor removal here for reference: http://www.bagpipingandy.com/compres...oval_Guide.pdf


check fault codes too, I don't think the kit will fix your issue, but it will improve the compressor performance


regards


Andy

 

A lot of you may be rushing to fix something that may fix itself when the WX warms up a bit.
This month has been somewhat colder here in Northern Florida, and when the temps got down to the 30's, things started to go wrong with my cars suspension system--ie--a suspension fault caution, and a couple of times the front air went south.
This was during a two week "drive the other car and give this one a rest" period, so just being idle could have been the cause, along with the cold. Now that I am giving the XK8 it's two week rest, all is back to normal with the XJ8L. and of course the temps are back to normal also with the Florida WX. No cautions, no flat front end and it's good to go.
I guess what I'm trying to say is, if it's real cold outside, you may have problems. New parts can fix the problem I'm sure, but maybe if you have the second car, warmer WX may also do the fixing and your not out the bucks.
Just a thought.

Cheers

 

Hi Fraser,

I understand now how the CATS system works, thank you for that. For clarification and if I understand correctly the Bilstein shocks do have CATS compatibility but the shocks are the “comfort” kind and not the “performance” kind like my XJR is originally equipped with? Would this have any implications in terms of driving the car? How about the Arnotts, what kind of ride could I expect out of those? Since there is no Arnott CATS system compatibility does that mean that the vehicle would pitch and roll significantly more than the bilsteins or original jag equipped cars would?

A few weeks ago I went into a Tesla showroom and was very impressed with their car. The sprung chassis was there too and like you I saw the air shocks. Quite an impressive car that was, especially with the acceleration. Never-the-less I didn’t think that the interior furnishings raised that car to the level of high end luxury that equally priced cars offer.

Yesterday I took the opportunity to call our local Indianapolis Jaguar dealership parts department and price out a front shock. They quoted me $1,481 each compared with Bilsteins sourced at the local autoparts store AutoZone; those came in at $1,448 each. Not much of a difference there at all. Huh!? I thought aftermarket parts automatically would save significant $$?? I don’t get that. I didn’t ask about warranties for either supplier, think I will do that.

I did do another measurement of the mudguard/wing arches this morning (the car hasn’t been started nor the battery reconnected). The front shocks had settled down just about 1 centimeter, but the rears remained inflated just the same.

Question. If the top seals aren’t replaceable, then that means the entire shock unit must be replaced?

Thank you for the MG pics. Unlike mine those cars look in great condition. I’ve never seen a late model MG personally, but I think I’d go for one if I could :-)

Norm

2004 XJR ~90,000mi

 

Hi Andy,

Thank you for your input. I’ve decided to go ahead and get a code reader after all. I’m thinking about the “icarsoft i930”, seems to be a good unit for the price that will give me specific Jaguar (and Land Rover) codes.

I just got done telling Fraser that while driving my Jag’s suspension was dropping out repeatedly and within a very few minutes of being fully inflated.

By contrast now that the car has been immobilized in my garage and with the main car battery disconnected, the air had initially seemed to maintain the vehicle height, but over the course of two or so days the front end has definitely begun to lose some air and dropped by by about 1 centimeter.

So we are definitely loosing air somewhere, either by “natural seepage” that can be expected especially of an older car, or by a bonafide leak. The valves you speak of could not have moved one bit since the battery has been disconnected.

I was going to order a kit from you asap, but I realized I will have to wait until I get a replacement CC from my bank in the mail. So an order is imminent

Best,

Norm

2004 XJR ~90,000mi

 

Hi Chuck,

Yeah I've been thinking of doing exactly that. We have a third car that loves getting attention and zoom zooming from here to there every now and then. I'm just doing some of the leg work now while it's cold out so that when the temps warm up in another few weeks or so, and if it is absolutely proven and necessary, I can pull the trigger on a new shock or two. In the mean time I think I will check for leaks using a soapy water solution, order Andy's compressor piston ring kit, order an icarsoft i930 code reader, and drive the spare car. The big man above knows I have no interest in doing major work in a non-heated garage space

Regards,

Norm

2004 XJR ~90,000mi

 

Hi Norman

The MG Midget is a '77 and was bought by a friend of mine in 1987 when it had done 18k miles. I went with him to pick it up and drive his other car back. When I bought it off him in 2010, it had been standing since 1996 and had 22k miles. Now, with me using it in summer and a member of the Midget and Sprite Club, it has got up to 36k miles. It's a lovely little car, but if you're over 6' tall forget it, you'll never get the seat back far enough, or even get in it !
The TF is one of the last few hundred that left Longbridge late in 2009, and is mostly Chinese after they bought the factory and designs after MG Rover went bust in 2004. The car was on 17k miles when I bought it, but is now on 24k. I bought it so I didn't have to use the Midget so much. It is a lot better on fast roads as it has a five speed gearbox. The car is a mid-engined 1.8 litre and the most economical car in our fleet, giving 35 mpg.

Anyway, back to Jaguars............

I think a bit of air leakage is going to be inevitable once these cars get a few years on them. The top seal isn't something that suddenly goes 'Bang' like the main diaphragm, but can commence a slow leak that obviously the compressor has to replace with new compressed air. I think a very slow leak here can be lived with, but the compressor has to be up-to-snuff to deal with it. Personally, I'm convinced that the top seal could be resealed with a suitable sealant if the main diaphragm is being replaced, as it is then exposed from the pressure side. Whether the firms that replace diaphragms do this, I don't know, so they need to be asked.