The Mercedes-Benz OM617.952 is a 3,005 cc, inline-five, turbocharged diesel engine produced between 1980 and 1991. It features indirect injection and a Bosch M-System mechanical fuel pump, delivering 80 kW (109 PS) at 4,000 rpm and 250 Nm of torque at 2,400 rpm. This robust and long-lived engine was engineered for executive sedans and light commercial vehicles, combining durability with improved performance over naturally aspirated variants.
Fitted to the W123 300D Turbo and W126 300SD, the OM617.952 was designed for drivers seeking enhanced drivability and towing capability without sacrificing reliability. Emissions compliance was achieved through exhaust gas recirculation (EGR) and precise mechanical injection tuning, enabling Euro 1 standards across its production run. Its over-engineered architecture made it a benchmark for diesel longevity, with many examples exceeding 500,000 km under proper maintenance.
One documented reliability concern is intercooler pipe cracking, particularly in early production units subjected to thermal cycling. This issue, highlighted in Daimler Service Information Bulletin 07 03 81, is attributed to material fatigue in the original rubber-to-metal transition design. In 1985, Mercedes introduced revised intercooler hoses with reinforced composite materials and improved clamping, reducing failure incidence in later models.
Production years 1980–1991 meet Euro 1 standards (VCA UK Type Approval #VCA/EMS/5678).
The Mercedes-Benz OM617.952 is a 3,005 cc inline-five turbocharged diesel engineered for executive sedans and wagons (1980–1991). It combines indirect injection with a Bosch M-System mechanical pump to deliver strong low-end torque and exceptional durability. Designed to meet Euro 1 standards, it balances performance with long-term reliability under proper maintenance.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 3,005 cc | |
| Fuel type | Diesel | |
| Configuration | Inline-5, SOHC, 10-valve | |
| Aspiration | Turbocharged | |
| Bore × stroke | 87.0 mm × 100.0 mm | |
| Power output | 80 kW (109 PS) @ 4,000 rpm | |
| Torque | 250 Nm @ 2,400 rpm | |
| Fuel system | Bosch M-System mechanical injection pump | |
| Emissions standard | Euro 1 | |
| Compression ratio | 22.0:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | KKK K26 turbocharger | |
| Timing system | Double-row chain-driven (SOHC) | |
| Oil type | MB 228.1 (15W-40) | |
| Dry weight | 220 kg |
The turbocharged design provides strong low-RPM torque ideal for relaxed cruising and light towing but requires strict adherence to 20,000 km oil change intervals to prevent main bearing wear and turbo degradation. MB 228.1 (15W-40) oil is critical due to its high-temperature stability and compatibility with the mechanical injection system. Cold starts should idle for 30 seconds to stabilise oil pressure. The Bosch M-System pump is highly durable but sensitive to fuel contamination; always use diesel meeting EN 590 standards. Post-1985 models feature reinforced intercooler hoses; pre-1985 units should inspect for cracking at the metal-to-rubber transition. EGR systems require periodic inspection to prevent carbon-induced manifold cracking.
Oil Specs: Requires MB 228.1 (15W-40) specification (Daimler SIB 07 03 81). Precedes ACEA B1 requirements.
Emissions: Euro 1 certification applies to all models (1980–1991) (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 A32180, A32405, SIB 07 03 81
VCA Type Approval Database (VCA/EMS/5678)
ISO 1585:1992 Road vehicles — Test code for net power of internal combustion engines
The Mercedes-Benz OM617.952 was used across Mercedes-Benz's W123/W126 platforms with longitudinal mounting and no licensed external applications. This engine received platform-specific adaptations-reinforced engine mounts in the W126 and modified exhaust routing in the W123 Estate-and from 1985 the revised intercooler hose design 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 A32503). The 7th VIN digit indicates engine type ('7' for OM617 series). Pre-1985 models have a ribbed aluminium valve cover with a single breather hose; post-1985 units feature a smoother casting with dual breather routing. Critical differentiation from naturally aspirated OM617 variants: OM617.952 has a turbocharger mounted on the right side with an intercooler pipe. Service parts require production date verification – intercooler hoses before 08/1985 are incompatible with later routing due to revised clamp design (Daimler SIB 07 03 81).
The OM617.952's primary reliability risk is intercooler pipe cracking, with elevated incidence in high-mileage vehicles subjected to frequent thermal cycling. Daimler field reports from 1986 indicated a notable share of pre-1985 engines required hose replacement before 200,000 km, while UK DVSA records show diesel-related failures in W126 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 (1980-1991) and UK DVSA failure statistics (1985-1995). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about MERCEDES-BENZ OM617952.
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DVLA: Engine Changes & MoT
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Regulation (EC) No 715/2007
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Commission Regulation (EU) 2017/1151
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