Hello, I really am trying not to be redundant with this post. I did search for a similar issue, but most results were the "my suspension just dropped... What could be wrong?!?!" Mine is a little more specific.

The car: 2006 Super 8 Portfolio with 93k on the clock

The Problem:

At random times the car drops the rear suspension, but only the on the left rear. All the other shocks stay at the same height. No warning messages display and the only way I know it's happening while driving is the alignment is suddenly off and the ride quality deteriorates.

At random the car realizes the height is not correct, and it pumps air into the shock from the reservoir. If let sit, the shocks do not leak down even when undisturbed for over a week. Sometimes the shock pumps up when the trunk is open or someone gets in the car through the rear doors. Perhaps a pure coincidence, but one I noticed completely by accident.


Things I have done so far:

Checked all grounds in the cabin. Apparently water had gotten into the cabin at some point and I found corrosion on almost all the grounds. The ones under the front seats especially. Before this repair was done I also had battery drains. The drains are now gone, but this suspension issue remains.

When I did have battery drains the trunk didn't latch without me being aware of it, so water has gotten into the trunk once or twice. I've cleaned the trunk and checked all the electrical connections in that area. We've had heavy rains recently and I have not seen a return of water in the cabin or trunk.

I've soap tested the shocks and junction boxes and couldn't find an issue.


Further background on the car: this one has a repaired history. I picked it after something broke the windshield and the driver ran over a curb. Minor damage, but enough for the insurance company to take possession. I replaced the right fender, wheels (three of four were broken), and the windshield. I've also replaced a lot of the static parts of the suspension not because of the accident but because of play in the joints. If my memory serves me correctly I replaced the upper control arms on both sides, tie rods on both sides, and at least one lower arm on both sides.

Haha, part of me is thinking I'll just convert to coilovers and not even try to find the solution as the best long term effective "repair." I say this partly to avoid headache as the years go on of replacing the rest of the shocks and partly because I suspect the previous owner didn't take the greatest care of the car mechanically. Nearly every ball joint on the car having play to me is a sign of neglect even if cosmetically the rest of the car is in good shape.

Any thoughts to my issue?

Thanks for your time!

Prolix

 

All vehicles require service. Coming close to 100k miles and 10 years, the items you describe are part of that. More than likely the module you are having issues with is beginning to leak at the upper seal. It's not uncommon. Part of ownership of the X350 series, is the same as with all manufacturers who utilize air suspension modules on their vehicles, and that it is about that time to laying aside money for the air modules. 100k/10 years is about the lifespan. I suggest that on all the grounds, use this;

http://www.gardnerbender.com/en/ox-100b

 

I would suspect some kind of wiring fault from the left rear height sensor to the air suspension ECM. The ECM is located behind the rear seat and the ground/earth point for the air suspension is below the rear seat (G17).

Given your water incursion issues, I would pull the rear seat and clean/check the ground/earth connection. I would also use a good quality contact cleaner (not WD40) to clean the contacts and all connections from the height sensor to the ECM, as well as inspecting the wiring.

Have you pulled all the DTCs? If the ECM isn't getting a signal from the height sensor, even intermittently, it should throw a DTC, but it might not trigger a message center warning.

EDIT - When you noticed that a passenger entering the rear seats seemed to correct the issue, did they enter through the right side door or sit on the right seat?