Mercedes Benz
OM 604, OM 605, OM 606
Manufacturer:	Mercedes Benz
Production period:	1993-2001
Style:	Four-cylinder OM 604 Inline five-cylinder OM 605  inline six-cylinder OM 606
Engines:	2.0 liters (1997 cc)  2.2 liters (2155 cc)  2.5 liters (2497 cc)  3.0 liters (2996 cc)
Previous model:	OM 601 (4-cylinder)  OM 602 (5-cylinder)  OM 603 (6-cylinder)
Successor:	OM 611 (4-cylinder)  OM 612 (5-cylinder)  OM 613 (6-cylinder)

The OM 604 series is a series four-cylinder diesel engine with prechamber injection from Mercedes-Benz . It is a further development of the OM 601 and has four valves per cylinder. Like its predecessor, the engine block is made of gray cast iron and the cylinder head is made of light metal .

The use of four-valve technology in a passenger car diesel was a world first at this time. Utilizing this technology not only increased torque and performance over a much wider engine speed range, but also reduced fuel consumption at full load by up to 8 percent. In addition, the particle emission in the exhaust gas was reduced by around 30 percent thanks to the optimized combustion process. Other measures for efficient exhaust gas purification were exhaust gas recirculation and the standard oxidation catalytic converter .

The OM 604 was first used in 1993 in the C-Class ( 202 series ) and 1995 in the new E-Class ( 210 series). These had the only Mercedes-diesel a distributor injection pump (electronic distributor injection pump, short EVE ) from Lucas instead of the proven in-line injection pumps from Bosch .

The gaskets of Lucas injection pumps become brittle and leaking over time. Since the replacement of the entire injection pump is very costly, a repair kit is offered in which the affected seals are replaced. 

OM 605 / OM 606

The series OM 605 (five-cylinder) and OM 606 (six-cylinder) were built on the same technical basis . From 1993, OM 605 and OM 606 (E 250 diesel and E 300 diesel) were installed as naturally aspirated engines in the 124 series , where parallel two-valve engines were used as a turbo engine.

In the first C-Class (W202) of the OM 605 was available with the introduction of the 1993 series, from 1995 then available exclusively as a turbo diesel with the designation C 250 TD. The larger OM 606 six-cylinder turbo diesel could be ordered now in the E-Class (210 series) and E 300 TD.

As of 1997, these engines were also available in the successor 210 series with an exhaust gas turbocharger .

With the exception of the OM 604 D20, which was produced in small quantities for the southern European market, the OM 604 four-cylinder engine, in contrast to the OM 605 and OM 606, had larger bore values ​​(89 mm) and stroke (86.6 mm). , but a smaller total cubic capacity of 2155 cc.