All W124 wagons use a rear self-leveling suspension (SLS) driven by an integral power-steering/SLS pump; without it the rear sags. The accumulators/spheres leak with age and need periodic replacement, and along with rear seal and A/C are cited as the expensive-but-known wagon repair items. …
Wagon self-leveling rear suspension (SLS)
Mercedes-Benz W124 E-Class · mechanical