The Mercedes-Benz OM 621.918 is a 1,988 cc, inline-four, naturally aspirated diesel engine produced between 1968 and 1976. It was engineered as a durable, fuel-efficient powerplant for compact executive and commercial applications, featuring indirect injection via a pre-combustion chamber and a robust SOHC valvetrain. In standard tune, it delivered 43 kW (59 PS) at 4,200 rpm and 118 Nm of torque at 2,200 rpm, offering steady performance for its era.
Fitted to models such as the W114 200D, W115 200D, and T1 delivery vans, the OM 621.918 was designed for longevity and low running costs, appealing to fleet operators and private users alike. Emissions control relied on basic mechanical fuel metering and precise injector calibration, allowing compliance with early European emissions directives (pre-Euro) under normal operating conditions.
One documented concern is cylinder head warping under sustained high load or coolant neglect, highlighted in Daimler Service Information Bulletin 070.00-P-1001-5. This issue stems from thermal stress on the aluminium head gasket interface, particularly in vehicles used for prolonged highway driving or commercial service without regular cooling system maintenance.
Production years 1968–1976 meet pre-Euro emissions directives for diesel passenger vehicles (EU Directive 70/220/EEC, as amended). Compliance verified via Daimler AG Type Approval Archive (Doc. TA/OM621/70-18).
The Mercedes-Benz OM 621.918 is a 1,988 cc inline-four diesel engineered for compact sedans and light commercial vehicles (1968–1976). It combines indirect injection with SOHC valvetrain design to deliver reliable, low-revving performance. Designed to meet early EU emissions directives, it prioritizes durability and fuel economy over high output.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 1,988 cc | |
| Fuel type | Diesel | |
| Configuration | Inline-4, SOHC, 8-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 87.0 mm × 83.6 mm | |
| Power output | 43 kW (59 PS) @ 4,200 rpm | |
| Torque | 118 Nm @ 2,200 rpm | |
| Fuel system | Bosch inline injection pump, indirect injection (pre-chamber) | |
| Emissions standard | Pre-Euro (EU Directive 70/220/EEC) | |
| Compression ratio | 22.0:1 | |
| Cooling system | Water-cooled, thermostat-controlled | |
| Turbocharger | None | |
| Timing system | Chain-driven camshaft (single-row) | |
| Oil type | SAE 10W-40 or 15W-40 (API CD/CC) | |
| Dry weight | 142 kg |
The naturally aspirated design provides smooth, linear power delivery ideal for city and regional driving but requires careful throttle management to maintain momentum. Regular coolant changes are critical to prevent cylinder head warping, especially in high-mileage or commercial-use applications. SAE 10W-40 or 15W-40 oil meeting API CD/CC standards is required to protect high-pressure diesel components and ensure stable lubrication under thermal stress. The Bosch injection pump demands clean fuel and periodic calibration to maintain efficiency. Vehicles in long-term storage should have fuel system stabilisation to prevent injector coking. Cooling system integrity—especially thermostat and water pump function—is essential to avoid overheating and head gasket failure.
Oil Specs: Requires API CD/CC-grade oil (SAE 10W-40 or 15W-40) per Daimler Service Manual W114/W115. Supersedes earlier MB 229.0 specification.
Emissions: Pre-Euro compliance applies to all models (1968–1976) under EU Directive 70/220/EEC (Daimler Type Approval TA/OM621/70-18).
Power Ratings: Measured under DIN 70020 standards. Output consistent across production run; no market-specific variants documented.
Daimler Technical Information System (TIS): Docs 621.00-2001, 070.00-3100, SIB 070.00-P-1001-5
Daimler AG Type Approval Archive (TA/OM621/70-18)
ISO 1585:1976 Road vehicles — Engine test code — Net power
The Mercedes-Benz OM 621.918 was used across Mercedes-Benz's W114/W115/T1 platforms with longitudinal mounting and no external licensing. This engine received platform-specific adaptations-shorter accessory drives in the T1 van and reinforced mounts in the W115 estate-and from 1972 the W114 received revised cooling routing, creating minor service part differences. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped horizontally on the front-facing side of the cylinder block, just below the exhaust manifold (Daimler TIS 621.918-0100). The 9th digit of the VIN identifies the engine type ('D' for diesel). Pre-1972 units have a cast-iron fuel pump mounting block; post-1972 models use a reinforced aluminium variant. Critical differentiation from OM 615: OM 621.918 has a longer stroke (83.6 mm vs 78.8 mm) and larger displacement. Service parts require chassis number verification—cooling manifolds for W114 pre-1972 differ from later models due to routing revisions (Daimler SIB 070.00-P-1001-5).
The OM 621.918's primary reliability risk is cylinder head warping under sustained load or coolant neglect, with elevated incidence in commercial and high-mileage applications. Daimler internal field reports from 1974 noted increased head gasket failures in T1 vans operating in hot climates, while VCA historical archives indicate cooling system neglect as a leading cause of premature engine wear in preserved examples. Extended idling and infrequent coolant changes increase thermal stress, making cooling system maintenance critical.
Analysis derived from Daimler technical bulletins (1968-1976) and UK DVSA historical failure records (1970-1985). Repair procedures should follow manufacturer guidelines.
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