A mechanic put my car up on a rack to change.

This was a miserable system to start with, and Ford has done a very poor job of supporting their older products. You will not find the needed replacement air springs available from the dealer but a number of aftermarket suppliers offer retrofit kits that allow you to remove that system and install the more reliable coil springs. You'll never have to worry again about a leak, a failed compressor, a corroded sensor, or a failed computer module. You won't notice any difference in ride quality.