OM604

Arriving in 1993 to replace the single-cam OM601, the OM604 opened a new family of four-valve diesels with the five-cylinder OM605 and six-cylinder OM606. The head carried twin overhead camshafts, four valves and split intake ports, a gear on the exhaust cam turning the intake cam; underneath, the iron block, hydraulic bucket tappets and duplex chain were much as before. Combustion still went through a prechamber. The extra valves were about breathing and refinement, not about direct injection, which was still four years away.

The odd choice was the pump. Where the rest of the range used Bosch inline units, this engine was given a Lucas EPIC electronically controlled rotary distributor pump, and its seals harden and weep with age — the defect that now defines the engine among owners. Naturally aspirated throughout its life, it came as a 2.2 for the C 220 D and E 220 D and a 2.0 for the C 200 D and E 200 D, with 75 PS taxi calibrations of both. It lasted barely five years before the common-rail OM611 arrived, though SsangYong later took the architecture, turbocharged it and added common rail to create the D20DT.