Air suspension leaks and compressor wear
Every X7 rides on two-axle air suspension. With age and miles the air springs can leak and the compressor wears, usually after the warranty has ended; a single air spring costs less than a compressor, and both are known bills on older, higher-mileage cars.
How to check
Check that the car sits level at all four corners after standing overnight, listen for the compressor running often or for long spells, and look for suspension warnings on the dash.
