Self-leveling rear suspension
The 3.6-liter M5 has a hydraulic self-leveling rear suspension. Its struts and the lines that feed them leak, new struts are hard to find so refurbishment is the usual repair, and many owners have converted to conventional shocks and springs.
How to check
Look for oil on the rear struts and lines, check that the rear sits level with a load in the trunk, and ask whether the system is original, refurbished or converted.
