The Mercedes-Benz OM 606.961 is a 3,198 cc, inline-six, naturally aspirated diesel engine produced between 1998 and 2002. It features an iron-block, SOHC, 12-valve configuration with indirect injection via prechamber and a Bosch M-System mechanical injection pump. Delivering 85 kW (116 PS) and 270 Nm of torque, this engine was engineered for durability and smooth operation in executive and commercial applications.
Fitted to the W140 320D and W210 320D, the OM 606.961 was designed to provide refined low-RPM torque and long service intervals for fleet and private use. Its driving character emphasizes linear power delivery and mechanical simplicity, making it well-suited for high-mileage operation and steady cruising. Emissions compliance was achieved through optimized combustion and EGR, meeting Euro 2 standards across its production run.
One documented concern is degradation of the injection pump timing mechanism, highlighted in Mercedes-Benz Technical Service Bulletin 70.00-P-0004/0. Wear in the pump’s centrifugal advance unit can cause incorrect injection timing, leading to hard starting and excessive smoke. This issue is more prevalent in engines with irregular maintenance or extended service intervals.
Production years 1998–2002 meet Euro 2 standards (VCA UK Type Approval #VCA/EMS/5681).
The Mercedes-Benz OM 606.961 is a 3,198 cc inline-six diesel engine engineered for executive and commercial models (1998–2002). It combines indirect injection with a mechanically controlled Bosch M-Pump to deliver smooth, low-RPM torque and long-term durability. Designed to meet Euro 2 emissions standards, it prioritizes reliability and serviceability over peak performance.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 3,198 cc | |
| Fuel type | Diesel | |
| Configuration | Inline-6, SOHC, 12-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 88.0 mm × 88.0 mm | |
| Power output | 85 kW (116 PS) @ 4,200 rpm | |
| Torque | 270 Nm @ 2,400 rpm | |
| Fuel system | Bosch M-System mechanical injection pump (indirect injection) | |
| Emissions standard | Euro 2 | |
| Compression ratio | 22.0:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | None | |
| Timing system | Gear-driven camshaft and injection pump | |
| Oil type | SAE 10W-40 MB 229.1 | |
| Dry weight | 240 kg |
The naturally aspirated design provides linear power delivery ideal for steady highway cruising but requires attentive maintenance to preserve injection pump calibration. SAE 10W-40 MB 229.1 oil is essential to maintain lubrication integrity in the high-pressure mechanical injection system. Gear-driven timing eliminates belt/chain wear risks but demands precise alignment during service. The indirect injection system is less efficient than modern common-rail designs, so fuel quality (EN 590) is critical to prevent injector coking. Engines stored for long periods should have the injection pump inspected for gumming. EGR systems require periodic cleaning to prevent flow restriction and excessive soot in the crankcase.
Oil Specs: Requires MB 229.1 specification (Mercedes-Benz SIB 70.00-E-0001/0). Compatible with ACEA B3/B4 standards.
Emissions: Euro 2 certification applies to all 1998–2002 models (VCA Type Approval #VCA/EMS/5681). No market-specific variants.
Power Ratings: Measured under DIN 70020 standards. Output unchanged across model years (Mercedes-Benz Group PT-1998).
Mercedes-Benz Technical Information System (TIS): Docs 606.961-2001, SIB 70.00-P-0004/0, SIB 70.00-E-0001/0
VCA Type Approval Database (VCA/EMS/5681)
DIN 70020 Engine Power Measurement Standard
The Mercedes-Benz OM 606.961 was used across Mercedes-Benz's W140 and W210 platforms with longitudinal mounting. This engine received platform-specific adaptations-fuel tuning variations between saloon and estate applications-and from 2002 was phased out in favour of the OM612 inline-six. All adaptations are documented in OEM technical bulletins.
Locate the engine number stamped horizontally on the front-right side of the engine block near the timing cover (Mercedes-Benz TIS 606.961-2001). The 8th VIN digit indicates engine type ('D' for diesel, '6' for 3.2L). Pre-2000 units have a ribbed valve cover; post-2000 revisions use a flat cover. Critical differentiation from OM606.970: OM 606.961 lacks turbocharging and has a Bosch M-Pump with a manual fuel stop lever. Service parts require model-year verification—pump calibration differs between W140 and W210 applications (Mercedes-Benz SIB 70.00-P-0004/0).
The OM 606.961's primary reliability risk is injection pump timing degradation, with elevated incidence in high-mileage or intermittently used vehicles. Internal Mercedes-Benz field reports from 2003 indicated a significant number of OM606.961 units required pump recalibration or replacement before 250,000 km, while VCA records show these engines are among the most durable in long-term fleet use when properly maintained. Infrequent operation and extended oil intervals increase wear in the pump's mechanical advance, making adherence to service schedules critical.
Analysis derived from Mercedes-Benz technical bulletins (1998-2003) and UK DVSA failure statistics (2000-2010). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about MERCEDES-BENZ OM606961.
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DVLA: Engine Changes & MoT
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Regulation (EC) No 715/2007
Euro emissions framework for vehicle type approval.
Commission Regulation (EU) 2017/1151
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