Even without the heat from the trap oxidizers, the original #14 mold cylinder heads were weak and if overheated could crack.

[citation needed] In 1990 the 350SD/SDL debuted, using a larger-displacement 3496cc OM603.97 engine that had more torque and a lower top RPM.

The engine lived on in the W140 chassis after the W126 production ended, as the 300SD or S350, with a larger yet turbocharger and thus more power and torque.

However, in the 3.5L there exists a different situation that appeared on some engines; eventual head gasket erosion, and thus passage of oil into the #1 cylinder.

As the 3.0L engine uses the same head oil passage design, yet does not appear to exhibit the problem - it might be that the larger bore in the 3.5 engine, the higher pressures, and resulting smaller head gasket surface area could conspire to cause a gasket erosion issue.