I think I have this figured out.
Installed the new air fitting on the pump. Cut off a little first, installed new olive, put on new air fitting. Just snugged down.
I checked the air controller under the spare with soapy water and the air compressor running for bubbles. Also the air compressor outlet connection. No bubbles, but replaced the fitting anyway.
The system will shut off sometimes without timed shutdown and throwing the C2302 Plauibility code. But after driving a few miles it throws the code.
Car can sit for weeks without dropping.
Installed a seal and o-ring from Andy. Pulled and checked to verify correct orientation of seal. Cleaned the cylinder surface again to check for wear.
While checking for bubbles at air controlled, pulled and reattached the plug on controller. It threw two codes and reset these.
I have four paths left.
1. Crack in airline from compressor to controller in trunk.
2. Reed valve on Compressor piston is leaking. Allowing blowback.
3. Cylinder is worn and even a new seal will not fix.
4. Air dyer is plugged and not getting air to compressor.

I am not sure how to pressure test airline. Guess I can rig the old fitting and a line to check compressor output. Without the controller I assume it will pump until it cannot. I can let it run open ended to see if it is really pumping.
Seen mention here of air compressors that did not respond to a seal kit. Replacement was needed. Whether cylinder wear, dryer, or reed valve this is very possible.
One thing I noticed the first time I pulled compressor the hiss from the air line was short but loud. Second time just a whiff. I did not hear a bleed off yesterday.
Think the problem is getting worse. But it still will shut down due to reaching proper pressure sometimes.

 

Hi Panelhead,

I've got to run but will throw out a couple of additional possibilities:

5. Exhaust valve on compressor leaking due to internal corrosion
6. Electrical problem such as corrosion on electrical connectors in the air suspension system (e.g. at the ASM or the pressure sensor on the valve body) or on grounds used by the air suspension system (behind rear seat, in trunk, etc.).
7. Height sensor has developed a dead spot or there is a problem in its electrical connection or harness such that it is not reporting its position accurately.

It doesn't sound to me like you have a pressure problem since your car does not seem to lose ride height quickly, but lcmjaguar fabricated some test gauges that you might find interesting:

https://www.jaguarforums.com/forum/x...s-loan-126934/

Hopefully others will have additional ideas.

Cheers,

Don

 

Don,
I have narrowed it down to an air supply issue. Yesterday I sprayed soapy water on outlet fitting about 20 times wishing to see a leak there.
When starting sometimes the compressor would run for 20 -30 seconds and stop. I would crawl out and check instrument cluster for yellow light and air suspension failure message. Usually the compressor would run for a couple minutes and then shutdown. This always results in a code.
When I finally decided there was no leak on the old connector it did not make much noise when unscrewed. Whether is not building much or it is leaking off I do not know yet.
Going to make a fitting to screw into compressor outlet. Then check to see how much air. Plus volume. Suspect it is compressor.
One go thing is I have learned a lot chasing this. Cleaned ASM connectors, air control valve in trunk connectors, and grounds in trunk and behind headlight. This will pay off down the road as less "ghost" electrical issues.
I plan to use the old fitting and find a hose to check compressor output. I think the hose between the compressor and control valve can be checked with my trusty basketball hand pump and fitting. It has a gauge. The needle should fit inside the line to allow pressure testing.
If the issue is the compressor, exhaust valve, reed valve, or blowby is my best option just purchase a new one? They are available from Arnott for a little less than 500.00.

 

With your skills it would certainly be worth opening the compressor to check for corrosion on the leaf valve and in the exhaust valve. $500 will go a long way toward some other project your Jag will need down the road....

 

The list just gets longer. I want to replace O2 sensors after 105,000 miles. Plus now thermostat housing.
I already had 6 1/2" subs and sparkplugs planned after getting C2302 code straightened out.
The thermostat housing looks like a real butt kicker. Might let my Jamaican mechanics fight this. They are way more skilled than I am.

 

Replacing the thermostat housing is really not a big problem.

I took mine off to replace the supercharger and while I was at it I replaced the thermostat, hoses and belts as well as the water pump.

I replaced the housing gaskets as well which surprised me as they were not rubber rings but had a flat band like profile. They "scrunch" up when in place.

The only slightly awkward aspect was the fact that two torx bolts were relatively "hidden" so had to get at those mostly by feel.

Also draining the coolant is somewhat of a pain because I had to remove the under body front panel to get at the radiator drain plug.

I created a problem because I put a support bracket on the inside of a bolt hole rather than on the outside by accident. So had a nice leak which took a while to find.