Okay. I finally nailed it. Last night the temp dropped to 32 degrees F here in central Fla. I had Brutal's test kits all set up on both front shocks.

Left: 3:30 pm, 51 degrees F, 27 7/8", 100 lbs
7:00 am, 32 degrees F, 26 3/4", 96 lbs

Right: 3:30 pm, 51 degrees F, 27 1/2", 100 lbs
7:00 am, 32 degrees F, 25 3/4 , 45 lbs

So, the left shock lost 4 lbs and 1 1/8". It leaks, but I'm not too concerned about that and will worry about it later.

The right shock lost 55 lbs and 1 3/4". Clearly a bad one. Moreover, when I aired it back up to 100 lbs I could hear the air leak and feel it coming out under the shock tower. Will replace it after Christmas.

Thanks Brutal.

 

I guess the one good thing about air springs is that they are easy to replace! It was a PITA to compress the springs on my previous Lexus. Looks like it's just a few bolts on the Jag!

 

All you have to do is take of the tire/wheel, the sway bar end link, disconnect the upper a arm from the verticle link at the ball joint. Unbolt spring and turn the hub. Brake assembly so the caliper is closer to the car to not stress the brake hose. Then push the lower control arm down using the top off the verticle link as a lever and take out the spring. Reverse to reassemble

 

Does anyone know what the electrical connection to the top of the air strut does. The drawing says "solenoid"'. How does this work?

Bob

 

Electrical connection, ride selonoid, controls the ride quality. Air supply controls ride height. Some inter relationship involved, but in general these are the basic functions.

 

Does the air compressor only inflate for a certain amount of time before it automatically shuts off
My compressor seems to start running when I start the engine, but only runs for a few seconds. I have to stop and restart the engine to get the compressor to resume as I am trying to do anything to get the 'air suspension fault' message to go off.
Another interesting point.....my 'air suspension vault' message is never on with my first start up every morning. It only comes on after I've driven a while

formworks

 

Great stuff here. Thanks.

But let me ask a question. Every few days lately and as the weather cools, I come out to find my 2004 XJR fully lowered. Temperature doesn't seem to be a major factor, but I suspect the cooler weather is somehow contributing.

Should I be looking at leaks at all four corners or something more centralized? And if so, where would be a good place to start?

After starting, is only takes 30-45 seconds to come up to normal ride hight.

Thoughts.

Bob
Liberty MO

 

Having looked at a lot of posts on this pesky air suspension system, it is clear to me that nobody has all the answers, maybe not even Jaguar themselves !!

The following is based on information in the Jaguar technical notes 2003.5, but changes could have been made after this.

The compressor is always timed out after 2 minutes run-time. This time period should be sufficient to fully charge the air reservoir, so it it doesn't a fault code is generated. Also it is shut down if its defined operating temperature is exceeded, so as to prevent heat damage. As those who did physics at school will know, compressing air generates heat, and this can get to an excessive level which could damage the seals on the piston and elsewhere. Once heat reduces the compressor resumes operation if needed by the system.

Once the car has been shut down for 30 minutes the system goes into a 'sleep' mode, but wakes up each 24 hours to check the ride height. If adjustment is needed the lowest wheel is taken as the datum, and all others adjusted downwards until eventually the vehicle is at the minimum height. No raising takes place in sleep mode.

The system starts to prepare itself before engine start, using door or trunk lid activity as an indicator, then on engine start, leveling takes place using the compressor if necessary.

On drive-off (speed exceeds 1 km/h), the system goes into 'Drive' mode. Cornering, braking and acceleration inhibits suspension levelling until car is once again in a steady state.

 

Would someone please show me where this alleged overheat temperature sensor is located. I have thoroughly scoured the compressor laying in pieces on my bench and do not see one. There is also no wiring for it. There are two wires for power and two for the exhaust valve. Don't see one in any of the schematics. Not saying it doesn't exist but I can't find it.


The new kinder gentler Eddie

 

Nope fraser that's pretty much it, always has been. The issues are intermittent leaks( ican useally get these everytime with air gauges hooked up and cycling the suspension up and down on the lift and watch pressures upon setting. There are spots on the bad seals riding surface that will seal fine in 1 area and leak like crazy on another spot. Most of the air compressor can easily be diag by monitoring the run time and the amount of pressure the reservoir fills to with all else closed off.

 

Eddie i think the "overheat" is a calculated run time not to be exceeded. As in engineered parameters, run too long and overheats. I know that when i jump the relay and run the compessor. The 10 guage wire and connectors i use get pretty hot. Knowing that they probobly tested and found that anything over the run time limit induced too much heat. Thats why i know when i run a system with the computer it will run for a period, shut off, and then run again

 

The Shop Manual indicates:
"Re-activation of the compressor depends on vehicle activity and is generally no longer than 120 seconds" .

 

I agree but Languid keeps talking about a thermal shutdown. I don't think it exists. The ASM limits duty cycle to control temp. I did the same as you with a jumper when I was troubleshooting mine. I just limited the run time to a min on and 30 secs off.

 

Tarheal, the only thing sobbing over spilt milk does is increase the size of the puddle!

I think the principal of operation is the same between the Jag & the Rangie air . The BecM monitors the height sensors even when the car is stationary. It will then adjust the 'springs' to keep the car level, and uses the lowest common denominator. I've also been fooled by thinking it was one corner, & the fault turned out to be another.

Also, when the suspension is not at full height, the fold in the rubber bag can control a small leak until either the height rises or movement allows the leak to become exposed.

Another thing, the EA computer on the Rangie is pretty reliable, but the valve control box is somewhat less so. If it is playing up, all sorts of frustrating events occur, such as random height adjustments, and overnight settling even when you can't find any leaks.

Brutal or u102768, you may know the answer to this. For the Rangie I bought an OBDII/USb data cable off ebay for about $45, and downloaded the free software that came with it to work on the Rangie's air suspension. It enables me to read (and adjust the height of) the sensors & just about everything else including fault resets from my laptop. Can you buy the same thing for Jags?
IMO, well worth the investment if you can.

Cheers,

Languid

 

Tarheal,

I'd suggest replace them both at the same time. If one has gone, the other will be close.

Cheers,

Languid

 

The principle is pretty much the same for all air suspensions. The Devil is in the details. My RV has one. It is built on a Freightliner Chassis. Uses height sensors, great big air bags, and the same compressor used for the air brakes. You can set the ride height on it with a wrench. You can also manually dump it.

I searched for software that would do what you said and have found none.

 

RCSnyder,

Suggest start with the high tech very soapy water in a spray bottle to check for leaks. It doesnt take that big a leak to drop the system overnight, so watch with some patience.

My earlier post also has some clues about the air suspension bags themselves. The rubber is usually good for 8 to 10 years before age exerts its influence, but if your mileage is up or your roads make the suspension work a little harder, you can get leaks around the folds that are not always obviuos at first glance. The other item that can 'throw' you is the valve body controller. They do play up, and an early sign is random adjustment for no obvious reason, or an indicator light sequence that doen't quite make sense. Because it's a 'random' fault, it can be frustrating to identify. The clue is often in the random behaviour.

Cheers,

Languid

 

formworks,

You need to provide some detail about your car, such as year model, mileage etc.

But the indications that I get from your question are either the compressor or the relay control. I had an almost identical problem on my Rangie, and the fault was the thermal cut-out inside the compressor. Pull the compressor relay and 'jumper' the compressor connections to see if the compressor runs for more than a few seconds. If it does, it is probably the control box. If it doesn't, you'll probably have to replace the compressor, as the thermal cut-outs are part of the brush mount board, and not repairable (so far- I'm looking). One of the causes I have identified for this is a worn seal on the compressor piston, which results in the compressor motor working much more than it should. Because the thermal prtection system is solid state it gradually becomes more & more sensitive and eventually 'jacks up' almost as soon as current starts to flow through it. Once the system gets to a 'hard fault' situation, you may also have to take it to a workshop who can clear the fault message out of the BEcM.

As I have mentioned elsewhere in this thread, I bought an OBDII cable for my Rangie, and downloaded software that enabled me to sort all this out at home. I've asked Brutal if he knows whether this is available for the Jags, and I will also look further into it myself, and post to the Forum if I can locate such. I haven't got a problem with the Daimler (touch wood) so I haven't previously looked into this for Jags. Sorry.

Cheers

Languid

 

Dear Lanquid,

How many brush mount boards for an X350 Jag have you actually seen?

 

MK82,

I will research further myself to see if I can locate a source for the software, & post it to the Forum if & when I do.

Meantime, I'm very interested in some info about your Presidio. I have plans to come over to the USA & buy something around that size to explore the country in. I can get a 10 year Visa, and plan to spend at least a year at a time on the road. The but is, that I need to be careful to buy one that I can convert to RHD to eventually bring back to Aus. Which means I must have the ability to put an access door on the left or the rear, and the overall width must not exceed 2500mm excluding mirrors & indicators. There are a few other 'compliances' to be met, but those are the main ones. Freightliner sell trucks here so the steering shouldn't be a problem.

Any thoughts on which RV's might be suitable would be appreciated.

Cheers,

Languid