My XJ8 was built in 2003 and registered in 2004. It does have a ride height sensor at each corner. I replaced the front air struts about a year ago and also installed the bagpiping Andy piston ring on the compressor at the same time. The air suspension has been faultless since then until a couple of days ago. She has been standing in the garage for about a month and was low all around by about an inch or so. Suspecting it was just normal leakage I took her out for a ride. After a few miles the front was fine and one back wheel was OK but the other a bit low. After a couple more days of running my front wheels are almost bottomed out, one rear about perfect and the other an inch low. I inspected the rear fuse box and pulled the suspension fuse for a few minutes. Everything looks good. No evidence of any damp and all ground points are clean and shiny. Battery voltage is 14V and I also disconnected it for an hour or so after clamping both cables together. The valve assembly has no leaks and I disconnected both sensors and reconnected them with no effect. The compressor runs as soon as I turn on the engine in Park and behaves as normal, cutting out after a couple of minutes and occasionally restarting.
My LRII code reader only shows the usual plausibility error and the dash also shows the too low warning. I put the car on my lift and all of the ride height sensors are in place and intact as are the connections.
I haven't yet checked the ASM connections behind the back seat and will do that tomorrow but my gut tells me this is either a compressor that wont reach or maintain adequate pressure, an ASM problem or a pressure sensor problem at the valve block. Unfortunately I don't have the tools to reset ride height and my local indy dealer doesn't either. I am 50 miles from my nearest Jag dealer in Tampa.
I have scoured the forum looking for ideas but have come up empty. I would love to hear of any other tests I could run or any flashes of inspiration....
Steve

 

I just found this brilliant thread...

https://www.jaguarforums.com/forum/x...ension-118966/

I will report back after testing. I plan to use my shop compressor to pressurize the tank first to make sure the compressor is behaving itself. It was interesting to see the observation that the rear wheels are pressurized before the solenoids open for the front, so I also plan to disconnect and cap the rear left side as it is always low.
Steve

 

Steve;

Sounds like you've been methodical troubleshooting the problem. Here's a few additional thoughts;

1) 'tis the season (lower temps) for any weakness' in the air suspension system to reveal themselves. I've used a Bagpipe Andy's kit myself but soon after discovered the damage to the bore of my compressor was severe enough that in the end I needed to just replace the compressor (this was an '04 XJR with ~90 kmi). I purchased one from Meisner in Europe (if memory serves me correctly) and I've not had any more issues for two years. Prior to replacement I was also getting the plausibility error.

2) Does your code reader allow you to view Live Data? I'm assuming if you view the actual leveling data for each corner you can see the height sensors are not at zero. The purpose of this is to verify the issue is something other than the height sensors. You could also start the car several time to allow the reservoir pressurize, record the final pressure/position of each corner, turn the car off for several hours, and then without starting the engine (ignition switch in accessory position) come back to check the pressure/position of each corner. Maybe this will let you see where the air is leaking.

3) Also using Live Data, verify the pressure your reservoir is pressurizing to. The plausibility error you mentioned I assume is the error created when the reservoir does not reach the desired pressure in a reasonable time. This would suggest either insufficient pressure from the compressor, a leak between the compressor and the reservoir, or perhaps a pressure sensor (integral to the solenoid block) issue.

4) While I suppose it is possible you have leaks on all four corners this seems unlikely, especially given front air-spring replacement in the recent past. Did you use Bilsteins? Seems more probable the issue is something common to all four corners.

Let us know what you learn.

By the way, I grew up in Wildwood (Sumter county). Where are you located?

Best Regards, William

 

Not much progress today. I still cannot locate a source for something to screw into the top of the rear strut to get a pressure reading. I did however find a setting on my LR2 code reader that shows me the heights of each ride height sensor. I did manage to get all four corners to start inflating but as soon as the compressor stops two or more of them start to deflate. Reasoning that the system wanted to inflate the rear struts first, I tried jacking up the back of the car until I had the correct clearances and also noted that the values changed for the height sensors from a negative to a positive value.
I then disconnected the two sensors on the valve block, cleaned them with electrical cleaner and reconnected. It did make a difference. All four struts inflated nicely until the compressor cut out but would not inflate any further when it cut back in again. At this point I have all four corners to within 1 inch of the required height but all four are slowly losing air.
Utter frustration pushed me to do something I hate doing. I ordered a replacement valve block with new sensors for a great price of $85 and it will arrive on Monday. It is still possible that I have an ASM problem or even a ride height sensor but as I have readings from all four and they change when I jack up the car or when the compressor starts up this seems unlikely. It is also possible I guess that I have a faulty compressor or sticky vent valve. $85 seems a cheap price to at least knock the solenoids and two sensors off the list.....

 

Steve,

You might benefit from either borrowing a set of gauges from lcmjaguar, or devising your own based on his design, as I did:

https://www.jaguarforums.com/forum/x...2/#post1062760

I'm trying to envision two sensors on the valve body. I can think of only one, the pressure sensor on the end that is made by Denso that apparently measures reservoir pressure. I wonder if your early car has an extra sensor? I'm not sure what that would be for. Perhaps you are describing the electrical connector for the solenoids?

I assume you have read this post but just in case:

Air Suspension & ECATS System Summary: Components & Operation


Cheers,

Don

 

Thanks Don - yes I am pretty much saturated with air suspension posts lol. Yes of course you are right. One connection for the pressure sensor and the other for the solenoid connections. Things are slightly complicated by the fact that my car has 4 ride height sensors and the fact that we dont have a "decision tree" matrix to best understand how the ASM software works.
Steve

 

Todays update. I replaced the o rings at both ends of each airline including the vent line and tank to valve block. It does rather look like my rear suspension is now almost correct and not changing overnight. Still a couple of centimeters low but the will inflate further if I lift the front of the car off the ground with jacks. Both front wheels settle to the same ride height (2 inches low) and I can hear the compressor attempting to raise them. Both front struts are only a year or so old but I am waiting on a few brass connectors to build a test gauge.
My pressure sensor is topping out at 7.4 bar. A bit low but I figure it should be enough and the compressor is coming on and shutting off as designed.

My LR2 code reader gives me height sensor readings relative to correct height ie. + and - numbers in mm. When they reach 0 they are at the height programmed into the ASM which makes me think the ASM is working as designed.

My gut feel at this point is that a valve solenoid is not properly closing and allowing one front wheel to go down. The ASM then compensates by opening the other front wheel valve to level the car side to side. The replacement valve block gets here next week so I can test that theory. Any other thoughts?

 

I got totally peed of with my air suspension. It was unreliable & parts were very expensive. I also much preferred the the ride which all my previous XJ’s had given with conventional suspension, so I bought an Arnott’s conversation which gives conventional springs & shock absorbers. The change over is dead easy, the handling is better, & the reliability problems are eliminated.

 

I finally got the adaptors I needed and made the connection to the top of my front right strut. I tested each connection to make sure it had no leaks and started inflating through the Schrader valve. My small shop compressor is good for 135 lbs but I could not get the gauge to more than 110 lbs before the leak overcame the rate of inflation. That corner of the car did not raise at all and I can hear air escaping from the bellows of the strut. At least I know what my problem is.

I had replaced both front air springs with RMT rebuilt units in July 2018 and the car has done less than 1000 miles since then and been garaged here in Florida. I have mailed Rebuild Master Tech to advise them and to request a warranty replacement. I await their response with baited breath and will call them on Monday afternoon to follow up. I tested the other front strut with my bigger shop compressor and she went up to height immediately and is staying there. The faulty unit will be removed tomorrow!.
Steve

 

So I got the old strut off - I am getting good at this now. The pressure in the outer bellows have pushed the clamp off the bottom of the strut and lots of rusty water is coming out. The car almost never goes out in the rain but is washed frequently - even so something is odd. I would not expect the compressor to push out so much water even if the dessicant is compromised. It is possible I guess that the water just got in there through the bottom of the bellows once they became detached. In any event, the air springs themselves must be damaged to release air into the gaiter. I will update when I hear back from RMT.

 

Not to blame you, but it is this type of feedback (not the first one unfortunarely, there were many more in the past) that made be chosing the expensive but secure decision of buying new B4 Bilstein units.
Never any issue since the replacement.

 

R M T has been having some problems with rebuilding these shocks.
A set on the rear of mine, started to drop to the stops, within a week of installation.
Sent them back for a refund, put Arnotts on, life is good.
A set of R M T's on the front of the other one.
It now has developed an occasional clunk from the drivers side.
Still holds air and seems to work alright, just an occasional clunk.
Will not be buying anymore rebuilt shocks from them.
They had brand new air compressor pumps, for just under $200 delivered.
That has worked out very well, also has a lifetime warranty.
Those i do recommend, but they are new, not rebuilt.
All in all they do seem to try to do a good job,

 

At the end of my stuck air spring saga, I found copius amounts of orange liquid when I inverted the assembly with bad air valve removed.

Mine was a bit slick, but that 2 yo Arnott suffered a bad leaking shock as well. So I figured some light miscable solution.

I'm starting to believe, and there may be a post or two that hints at it, that those of us in areas prone to wild condensation are building loads fo water, and probably dwarfing the load of a few ounces of dessicant.

I replaced one young arnott with am RMT. The. company seems attentive. The next arnott failure was replaced with the bilstein. The rears are next. They hold air fine, but handle like worn springs. One rear feels like a dead shock as well.

They aren't 3 years old. Few, few miles.

So, what I'm thinking is my valves locked up because of the contamination of the water.

Then it acts like a more rigid member and you get a thunk at a bump in the road.
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