OM603 engines appeared in 1983 simultaneously with a whole family of units with different numbers of cylinders and power and were installed on a number of popular models of the German concern, such as W124, W126 and W140. Three modifications of this diesel engine were offered, naturally aspirated and two turbocharged.
The 603rd series are 6-cylinder engines packed in steel blocks with an aluminum cylinder head, equipped with hydraulic pushers, a reliable injection pump and other progressive improvements. When developing OM 603, the engineers paid special attention to the control over emissions, these were improved models that allow to reduce the smoke of the outlet by 40%.
Specifications
| Displacement, cc | 2996 |
| Power, hp | 143 – 147 |
| Torque output, Nm (kg-m) at rpm |
267 (27) / 2400 |
| 273 (28) / 2400 | |
| Fuel type | diesel fuel |
| Fuel consumption, L/100 km | 7.9 – 9.7 |
| Configuration | inline, six-cylinder |
| CO2 emission, g/km | 209 – 241 |
| Cylinder bore, mm | 87 |
| Valves per cylinder | 2 |
| Power, hp (kW) at rpm |
143 (105) / 4600 |
| 147 (108) / 4600 | |
| Supercharger | Turbine |
| Compression ratio | 22 |
| Piston stroke, mm | 84 |
The camshaft and injection pump are driven by a duplex chain from the crankshaft. A separate single-row chain drives the oil pump. The camshaft acts on the valves using hydraulic tappets. The valve is automatically adjusted.
Fuel is injected into the pre-combustion chamber. The Bosch M injection pump with mechanical control and vacuum control is lubricated by connection to the engine oil circulation, the fuel lift pump is installed on the side of the injection pump. The preheating is carried out automatically by the glow plugs.
Due to the tightening of emission regulations in the US market, a diesel particulate filter has been created. Since they were installed on the cylinder head (modern ones are installed further), the heat from them caused the failure of the aluminum cylinder heads, and debris from the filters could damage the turbocharger.
Another typical malfunction of the Mercedes OM603 engine is strong vibrations. This causes the crankcase screws and bolts to loosen. The latter enter the oil pump or clog the channels, which ultimately leads to oil starvation, bearing damage and broken block rods.
Modifications OM603
| Modifications | Power, kW (hp) | Torque output, Nm |
| OM603.912 | 81 (109) at 4600 rpm | 191 at 2800 – 3050 rpm |
| 84 (113) at 4600 rpm | 185 at 2800 rpm | |
| OM603.960 and OM603.963 (4Matic) | 106 (143) at 4600 rpm | 267 at 2400 rpm |
| 108 (147) at 4600 rpm | 273 at 2400 rpm | |
| OM603.960 | 106 (143) at 4600 rpm | 267 at 2400 rpm |
| 108 (147) at 4600 rpm | 273 at 2400 rpm | |
| OM603.961 | 110 (148) at 4600 rpm | 273 at 2400 rpm |
| OM603.97x | 100 (136) at 4000 rpm | 310 at 2000 rpm |
| OM603.97x | 111 (150) at 4000 rpm | 310 at 2000 rpm |
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