1990 Mercedes-Benz E 3.0L Petrol · H557 CBC

UK ownership guides call out the same W124 rot spots: rust around all arches, rear sills around the jacking points, the crossmember below the sump and the front mounts of the rear subframe, with estates additionally trapping water where the rear quarter window seal sits, causing severe rust. Specialist maintenance writing for North American cars backs the pattern, flagging the front wheel arches behind the plastic cladding where moisture and dirt are trapped, and the jacking point areas, and noting that the factory protection only lasts so many winters of road salt. Structural corrosion at the subframe mounts or sill roots is an MOT failure, not an advisory.

Both the single-cam M103 and the 24-valve M104 six-cylinders are known for head gasket failure. Specialist guides describe the tell-tale symptoms as an oil leak, foamy coolant and high water consumption, and workshop writing on the model adds that the first sign is usually oil seeping externally from the front passenger-side corner of the engine, with oil and coolant emulsifying in the reservoir or on the cap in worse cases. Catching it early means a gasket job; ignoring it risks the engine, and the six-cylinder cars need substantial strip-down labour.