2004 XJ8 with (no prize for guessing) air suspension trouble. New compressor maybe two years ago. Rear end is up fine, front end in on the ground right now. I unscrewed an air hose and started the car, and found that there is air coming out of that pipe. It is as if the shock doesn't want the air!

Not sure if this is normal, but when I unlock the car doors, I always get a long hiss out of that front drivers side shock. Obviously no hiss now, the shock is flat.

I've read on the forum about a regularly faulty relay... does it only affect one end of the car? Is it a generic relay or something Jaguar specific?

Thanks all,

John

 

MG Do a search in this forum under air suspension. Look for posts from Stevetech. About 8 t0 12 months ago this subject was throughly explored and it would pay you to study up on it before you take the next step.

Pay particular attention to Arnott Industries as an after mkt. source for air shocks.

 

Today I have some more information... There are no OBDII codes related to the suspension (I did get a MAP code, unrelated). I sprayed soapy water on the two front air lines and on the distribution block in the trunk. There was no air escaping. Both front shocks are down all the way, the rears are up in the air like nothing has happened.

I did search and read stevetech's postings but did not really come across anything specific to front only failure other than to say that the front two shocks are connected but the rear aren't.

Thanks for any help,

John

 

Well, stevetech gets on here ever few days, so I'll change your title to catch his attention, and maybe he can guide you to another approach for diagnosis. Sit tight.

 

John,

By your description of symptoms it very much sounds like you've lost one of the two front air springs, barring any air pipe damage. The front air springs are connected together and fill (and deflate) as one unit.

If you used any commercial scan tool you will not read C codes. Does the dash computer produce any air suspension fault messages?

The crossover pipe for the two fronts is located on the front chassis member by the front grill. I would begin by removing one pipe at a time directly from the air spring. Cap it, start the car and see if one side of the front lifts. Then test the other side replacing the first pipe. If neither front side lifts, then you have a pipe leak somewhere.

Air springs usually leak around the top collar, but if it is leaking so badly that you can hear air hissing, then you'll not get enough inflation probably to even use soapy water.

I know I have one good used front air spring in my shop, but with the price and warranty of a rebuilt from Arnott, you're far better off going that way.

Hope this gets you started.

Best,

 

I'm confused by this idea that the front two shocks use the same air supply. On my car, there are three air lines going to the back of the car, one for the compressor and then one each for the two front shocks.

In this picture, the yellow and brown lines (4th and 6th) go all the way to the front shocks, and the 2nd hose, slightly off the line, goes to all the way to the front to the pump.

The blue and red (1st and 5th) are for the rear shocks. The pink obviously goes to the tank.

Is my car a little different than most XJ8's?

 

John,

Yes, there are four separate line feeds from the junction block. This is somewhat complex because we're talking in one of two different dimensions - static or dynamic. Statically, the front corners are treated as a single unit by the ASM. Dynamically, the ASM can control all four corners and, in certain situations such as braking, acceleration, or cornering, in pairs - both fronts to both backs - both lefts or both rights.

To diagnose a bad air spring which you'd be doing in a static mode obviously, you really have to work at the air spring itself for the fronts. Don't try to diagnose a front corner from the junction block in the trunk as you need to keep the ASM and system alive, but from the junction block the system is continually equalizing the front pair as a single unit so you have to make the ASM think it is equalizing the fronts. You cannot do the from the junction block.

 

I am also having a similar issue, a while back the "vehicle too low" light came on then went away. The light didn't come on for a while so i didn't think anything of it. Later the "vehicle too low" light started coming when I first started the car but it would shut itself off after the car was running for a little while. Now I notice the front of the car sits really low and the "vehicle too low light" comes on and sometimes turns in to "air suspension fault". If I shut the car off the "air suspension fault" goes away but it usually comes back shortly.

Yesterday i drove the car around and let it level out and when I got home I disconnected the battery and measured the height of the fenders. This morning (9 hours later) i went out and the rear was fine but the front had dropped about 2 inches and i think if i would have checked later it would have been even lower. I have noticed that when i don't use the car for a whole day it is almost sitting on the ground.

Any help would be greatly appreciated!

And yesterday i backed into a pick-up now i need a new trunk lid.
I'm about to lose it!

 

sounds very similar to the OP, I'd follow the steps above for diagnosis, perhaps you can nail it down to either an air spring or the line. Compressor sounds fine at the moment.

 

Ok so I got a bottle of soapy water and sprayed down the two lines at the top of the front air springs and also sprayed down the distribution block in the trunk and got no signs of a leak.

Then I disconnected the passenger side air spring, capped it and started the car. The compressor came on lifting the driver side a little then shut off. About 35 seconds later the compressor came back on for about 20 seconds then shut off for another 35 seconds.

Then I reconnected the passenger side air spring, disconnected the driver side air spring capped it and it did the same thing just on the opposite side. The time intervals for the compressor coming on and shutting off were the same as well.

What is the next step?

 

Hello again friends. This is perhaps a dumb question, but by what means have you capped the air line?

Although I don't recall hearing it a few days ago, today the front drivers side shock is hissing from under the wheel arch after the car is turned off. There is very little doubt that I need one of Arnott's rebuild air shocks.

The little doubt comes from the underside of the trunk mounted fuse box, which I found to be massively corroded (Greeeeeen). It appears that the trunk was full of water at some point. If I pull fuse F52, the compressor stops. If I pull F12, nothing happens. Both are "air suspension". If I can find one cheap enough I will be swapping out the fuse box before dropping $400 on the air shock. I guess my question is if there is anything programmable in that fuse box because it is a heck of a lot more than a fuse box (circuit board in there too). The corroded fuse box would explain to me the one dim reverse light so I want to change it anyway.

-John

 

I plugged it with my finger when I heard the compressor come on but that might not be acceptable.

If some one could look a t my previous post and let me know the next steps to take in figuring out this air suspension problem I would really appreciate it! Thanks for the help so far.

 

Guess what? The problem was electrical! The corroded fuse box was the cause of the bottomed out front suspension, and the cause of my A/C fan not working. I changed out the fuse box for a junkyard part ($65) and the nose came right up! But, unfortunately, the passenger side didn't come up the entire way. So the dash still reads air suspension fault and vehicle too low. The car seems driveable though.

Does the fuse box contain anything programmable? Sounds like I need to visit the dealer.

-John

 

So what would be the next step in trouble shooting the suspension system?

By the way when I get the "air suspension fault" while im driving, if i put the car in neutral and shut it off and then start it back up the fault will go away, the car seems to raise it self back up and the ride is much smoother. But its not long till the ride becomes bumpy and the light comes back on.

Any help would be appreciated.

Thanks

 

Hi VDP.....

I've been following your story - I noticed the thread kinda died a death a month or so ago - how are things now?

So far, I've "only" had the air compressor changed on mine (although the ******* charged me a total of almost GBP2000 as they insisted on a new suspension ecu too - terrible, eh!), although I'm rather scared of what the next suspension fault is going to be

How's your car now? Did you manage to get to the bottom of it without forum help?

Thanks..

 

Its going well getting a lot of info but i still want to check the spring itself for leaks before I buy new ones.

Can anyone tell me how to do this?