This car was owned by one family before I bought it. It still had the original "Ever-Level" air suspension system which was installed in the factory in Southgate, California, and it worked just as bad as the ones which were removed within a year or two after delivery. The system leaked air everywhere, and there were many, many air connections in the system which ran 145 Pounds per square inch pressure. The repair parts were gone about 50 years ago as everyone scrambled to repair the systems - then, as few were left in service, the parts disappeared.
The main valve which operated the system had a thin rubber part which was shaped like a top hat, and it had a hole in it. That meant what air was pumped into the system quickly escaped, and the car ended up sitting "on the ground". There not being a replacement part anywhere in the universe, I explored around the garage over a period of days and finally looked at container that held rubber patches for bicycle tire tubes - the scuff-the-tire, then apply glue, then clamp for while, and your tube was ready to go type patches. In my case, I didn't need to glue anything, I just needed to trim the patch so that it would fit correctly inside the air chamber. It had to be clamped around the edges well enough to hold the air pressure. After carefully trimming the patch, it was placed between the two parts of the valve and the system was pumped up by the on-board compressor. IT WORKED!
That patch is still in place after being used for several more years. The remainder of the parts and connections continued to preserve the bad reputation of the system and a more modern air suspension system was adapted to the car and is now functioning as the designers of the original system had intended.