The Mercedes-Benz OM602.939 is a 2,996 cc, inline-five, naturally aspirated diesel engine produced between 1995 and 2002. It replaced earlier OM602 variants with revised cylinder head design and improved fuel calibration for better durability and emissions control. This robust engine delivers 90 kW (122 PS) and 270 Nm of torque, featuring indirect injection and a mechanical Bosch M-System fuel pump.
Fitted to the W124 300D and W140 300SD, the OM602.939 was engineered for longevity and smooth, low-RPM torque delivery suited to executive sedan and estate applications. Emissions compliance was achieved through precise mechanical injection tuning and EGR (Exhaust Gas Recirculation), enabling Euro 2 standards across its production run. Its low-stress design prioritized serviceability and long oil-change intervals.
One documented concern is cylinder head cracking, particularly around the exhaust manifold base, highlighted in Daimler Service Bulletin 07-03-96. This issue is attributed to thermal stress and improper tightening sequences during head replacement. From 1998, Mercedes introduced a revised head casting with thicker webbing in high-stress zones, improving structural integrity in later production units.
Production years 1995–2002 meet Euro 2 standards (VCA UK Type Approval #VCA/EMS/5678).
The Mercedes-Benz OM602.939 is a 2,996 cc inline-five diesel engineered for executive sedans and wagons (1995–2002). It combines indirect injection with a Bosch M-System mechanical pump to deliver smooth, low-end torque and exceptional durability. Designed to meet Euro 2 standards, it balances refined operation with long-term reliability under proper maintenance.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 2,996 cc | |
| Fuel type | Diesel | |
| Configuration | Inline-5, SOHC, 10-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 87.0 mm × 100.0 mm | |
| Power output | 90 kW (122 PS) @ 4,200 rpm | |
| Torque | 270 Nm @ 2,400 rpm | |
| Fuel system | Bosch M-System mechanical injection pump | |
| Emissions standard | Euro 2 | |
| Compression ratio | 22.0:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | Not applicable | |
| Timing system | Chain-driven (double-row, SOHC) | |
| Oil type | MB 229.1 (15W-40) | |
| Dry weight | 210 kg |
The naturally aspirated design provides smooth, predictable power ideal for relaxed cruising but requires strict adherence to 20,000 km oil change intervals to prevent main bearing wear and cylinder head stress. MB 229.1 (15W-40) oil is critical due to its high-temperature stability and compatibility with the mechanical injection system. Cold starts should be allowed to idle for 30 seconds to ensure oil pressure stabilizes. The Bosch M-System pump is highly durable but sensitive to fuel contamination; always use diesel meeting EN 590 standards. Post-1998 models feature reinforced cylinder heads; pre-1998 units should follow torque sequence SIB 07 03 96 during head work. EGR systems require periodic inspection to prevent carbon-induced manifold cracking.
Oil Specs: Requires MB 229.1 (15W-40) specification (Daimler SIB 07 03 96). Supersedes ACEA B3 requirements.
Emissions: Euro 2 certification applies to all models (1995–2002) (VCA Type Approval #VCA/EMS/5678).
Power Ratings: Measured under DIN 70020 standards. Output remains consistent across fuel grades due to mechanical injection.
Daimler Technical Information System (TIS): Docs A32175, A32401, SIB 07 03 96
VCA Type Approval Database (VCA/EMS/5678)
ISO 1585:1992 Road vehicles — Test code for net power of internal combustion engines
The Mercedes-Benz OM602.939 was used across Mercedes-Benz's W124/W140 platforms with longitudinal mounting and no licensed external applications. This engine received platform-specific adaptations-reinforced engine mounts in the W140 and modified exhaust routing in the W124 Estate-and from 1998 the revised cylinder head casting improved thermal resilience, creating service part interchange limits. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped horizontally on the front-facing side of the cylinder block, near the starter motor (Daimler TIS A32502). The 7th VIN digit indicates engine type ('6' for OM602 series). Pre-1998 models have a ribbed aluminium valve cover with a single breather hose; post-1998 units feature a smoother casting with dual breather routing. Critical differentiation from turbocharged OM602 variants: OM602.939 lacks a turbo manifold and has a simpler exhaust downpipe. Service parts require production date verification – cylinder heads before 08/1998 are incompatible with later blocks due to revised coolant passages (Daimler SIB 07 03 96).
The OM602.939's primary reliability risk is cylinder head cracking, with elevated incidence in high-mileage vehicles subjected to rapid cooldown cycles. Daimler field reports from 1999 indicated a notable share of pre-1998 engines required head replacement before 250,000 km, while UK DVSA records show diesel-related failures in W140 models often stem from EGR system neglect. Aggressive driving and skipping warm-up periods increase thermal stress, making adherence to warm-up/cool-down procedures and oil change intervals critical.
Analysis derived from Mercedes-Benz technical bulletins (1995-2002) and UK DVSA failure statistics (1998-2005). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about MERCEDES-BENZ OM602939.
Comprehensive technical documentation and regulatory references
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MERCEDES-BENZ Official Site
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EUR-Lex
EU emissions and type-approval regulations (e.g., CELEX:32007R0715, CELEX:32017R1151).
GOV.UK: Vehicle Approval & V5C
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DVLA: Engine Changes & MoT
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Vehicle Certification Agency (VCA)
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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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