I have an '04 XJR that seems to have a leak in the air suspension system. After sitting over night, approx 12 hours, the vehicle drops about 1/2 inch (10 mm). I've disconnected the #4 relay/fuse to see if there is a specific shock leaking, and the car does not drop at one individual corner. The compressor pumps up fine, and car returns to normal height after about 90 seconds after start up. Approx 6 mos ago, I used Bag Piping Andy's rebuild kit to replace the compressor piston ring, and that has been working fine.

I've mixed soapy solution, and sprayed all of the shock connections, as well as the distribution block and tank in the trunk, and have not found any leaks or bubbles.

The thing that makes this different from every other thread that I've been able to research is that I get an air suspension fault after I drive the car for approx 25 minutes/20 miles. I have a 30 minute/25 mile commute into work, and 4 out of 5 times, the ASF will come on 5 minutes before I arrive at my destination. When it comes on, the suspension gets very bouncy. When I stop the car, the ride height seems correct.

My experience with the two Jag dealers that are over an hour away in opposite directions has been very poor when it comes to the suspension, so I haven't taken it in to get any codes read and am reluctant to do so. Does anyone have any suggestions before I roll the dice with one of these dealers?

 

Hi QuikCat,

My initial thoughts are:

1. Having the codes scanned might help narrow down the problem. If you have an old Windows XP Pro laptop or can set up an XP Pro virtual machine on a Windows 7 laptop (not hard), you might consider investing in the "Mongoose" cable and an older version of JLR SDD software so you can read the codes yourself. Search this forum for information on affordable sources for these items.

2. It seems possible that either the exhaust valve or check valve (non-return valve) in the compressor may not be sealing properly and allowing pressure to leak down over time. You would need to remove the compressor and partially disassemble it to check these valves.

3. Under normal operating conditions, the system will not allow the pressure in the reservoir to fall below 9 bar / 145 psi. This is to prevent pressure from the air springs from transferring back to the reservoir. It might help track down your problem if you could rig up a pressure gauge to test your system pressure at various points. Search this forum for posts from owners who have fabricated gauge adapters for use with the X350 air suspension.

4. It might be worth cleaning the electrical connectors at the valve block and the Air Suspension Control Module (ASCM or ASM - behind the rear seat) and their associated grounds to reduce the possibility that high resistance in the circuits is causing incorrect ASCM behavior.

Hopefully others will have more ideas.

Cheers,

Don

 

Were do you measure this?

Guus

 

It is well known that the struts can leak in very cold weather and it is

possible therefore that a strut can leak when the ambient temp. is not

particulaly cold.

I would suggest that you make yourself (two ideally) pressure gauges to fit

in the the top of the struts.

These fittings will need a 'T' piece fitted with a valve to pressurise the strut.

You will then be able to pressure test each strut individually.

 

Don -
Thanks for the great suggestions.
1. I don't plan on keeping the car much longer as I seem to be experiencing one thing after another and have lost confidence in driving it long distances.

2. How would I check the valves? I did have the compressor out when I replaced the piston ring. I do recall hearing a sound when the compressor finishes filling and shuts off that I didn't use to hear about the same time I ran into this problem.

3. Does anyone have one of these that they may be willing to loan out? I'd be happy to pay for shipping.

4. I will try this as well.

I was measuring from the fender lip to the ground when I first parked it and then again next morning.

 

Front and rear and left and right and lowered the same amount all around? That would be very strange.

Guus

 

I didn't measure the distance drop on the rears. I measured the fronts and they both dropped the same amount. I started the car and got out immediately to watch the rear rise and then the front (like it's supposed to).

Still looking for a response on how to determine if the check valves in the compressor are bad.

 

I was under the impression that the #1 relay in the engine box was the Air Suspension. #4 is the wiper on/off.

 

Hi QuikCat,

The check valve in the compressor is at the outlet of the compression cylinder and entrance to the air dryer. The only two ways I can think of to test it would be to:

1. Attach a pressure gauge to the outlet of the compressor, let the compressor run until it shuts off, and watch the gauge to see if the pressure holds or leaks down. If it leaks down, then either the check valve, exhaust valve or pressure relieve valve is not holding, or less likely, there is a leak somewhere else in the compressor assembly; and/or

2. Remove the compressor from the car, remove the cylinder head and disconnect the air dryer and inspect the check valve for any signs of trouble such as corrosion, built-up gunk, deteriorated rubber seal, a bent or weak spring, etc.

See the links below for photos I took of the check valve while rebuilding our compressor. Check valve disassembly begins with Photo 6 in the first album, and reassembly is shown beginning with Photo 4 in the second album:

Welcome to Jag-lovers - Members Photo Viewing Page
Welcome to Jag-lovers - Members Photo Viewing Page

For the rest of the photo albums related to the compressor just click on the "My Photo Albums" button.

Cheers,

Don

 

Ok, was a bit wondering because of your first post.

Easiest solution would be to use an SDD and measure the pressure or measure the pressure at the outlet of the pump. But that wouldn't explain at all why you get the message have way through a drive...

Guus