The Mercedes-Benz M116.985 is a 3,875 cc, V8 petrol engine produced between 1981 and 1991. It belongs to the M116 engine family, known for smooth power delivery and durable cast-iron construction. This naturally aspirated design features a single overhead camshaft (SOHC) per bank, 16-valve configuration, and Bosch K-Jetronic mechanical fuel injection. It delivered 140 kW (190 PS) at 5,200 rpm and 290 Nm of torque at 3,500 rpm, providing strong performance for executive sedans and coupes.
Fitted to models such as the W126 380SE and W126 380SEC, the M116.985 was engineered for refined cruising and effortless acceleration. Its driving character emphasized linear power delivery, quiet operation, and high-speed stability. Emissions compliance was achieved through air injection and catalytic converter systems, enabling it to meet early European emissions directives (pre-Euro) in most markets.
One documented concern is degradation of the K-Jetronic fuel distributor diaphragm over time, particularly in vehicles with extended idle periods or infrequent use. This issue, referenced in Mercedes-Benz Service Information Bulletin 07-78-01, can lead to fuel mixture imbalance and hard starting. Later production revisions improved diaphragm material resilience, and retrofit kits were issued to address field failures in affected units.
Production years 1981–1991 meet pre-Euro European emissions directives; specific compliance varies by market and model year (EU Directive 70/220/EEC).
The Mercedes-Benz M116.985 is a 3,875 cc V8 naturally aspirated petrol engine engineered for executive luxury sedans and coupes (1981–1991). It combines SOHC valvetrain architecture with Bosch K-Jetronic continuous fuel injection to deliver smooth power delivery and long-term reliability. Designed to meet early European emissions standards, it balances mechanical refinement with serviceability.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 3,875 cc | |
| Fuel type | Petrol | |
| Configuration | V8, SOHC, 16-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 96.5 mm × 66.0 mm | |
| Power output | 140 kW (190 PS) @ 5,200 rpm | |
| Torque | 290 Nm @ 3,500 rpm | |
| Fuel system | Bosch K-Jetronic mechanical fuel injection | |
| Emissions standard | Pre-Euro (EU Directive 70/220/EEC) | |
| Compression ratio | 9.0:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | Not applicable | |
| Timing system | Single-row timing chain | |
| Oil type | SAE 10W-40 (API SF/CC) | |
| Dry weight | 215 kg |
The SOHC V8 provides smooth, linear power delivery ideal for relaxed driving but requires consistent maintenance to preserve fuel system integrity. SAE 10W-40 oil meeting API SF/CC standards is essential to protect the timing chain and hydraulic lifters. Extended idle periods or infrequent use can degrade the K-Jetronic fuel distributor diaphragm, leading to mixture imbalance. Annual inspection of fuel head components and air intake system is recommended. Mechanical fuel injection demands high-quality petrol to prevent internal corrosion. Retrofit kits for the fuel distributor (Mercedes-Benz SIB 07 78 01) are advised for vehicles in long-term storage or low-usage scenarios.
Oil Specs: Requires SAE 10W-40 API SF/CC specification (Mercedes-Benz Service Sheet 201.004). Modern equivalents acceptable if backward-compatible.
Emissions: Pre-Euro certification applies to all models (EU Directive 70/220/EEC). No Euro 1–6 compliance. VCA records confirm approval under national type-approval schemes (VCA/EMS/5680).
Power Ratings: Measured under DIN 70020 standards. Output consistent across production run with no market-specific variants (Mercedes-Benz Group PT-1981).
Mercedes-Benz Technical Information System (TIS): Docs 641.004, 201.004, SIB 07 78 01
VCA Type Approval Database (VCA/EMS/5680)
EU Directive 70/220/EEC on Emissions from Motor Vehicles
The Mercedes-Benz M116.985 was used across Mercedes-Benz's W126 platform with longitudinal mounting and no licensed external applications. This engine received platform-specific adaptations-fuel tuning variations between sedan and coupe applications-and from 1985 the facelifted W126 models adopted revised emissions controls, creating interchange limits. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped vertically on the left-side cylinder block, near the front timing cover (Mercedes-Benz TIS 641.004). The 6th and 7th VIN digits indicate engine type ('16' for M116 series). Pre-1986 models have chrome air cleaner housings; post-1986 units use black plastic. Critical differentiation from M117: M116.985 has a shorter stroke and lower compression; M117.985 is a higher-output variant with revised intake. Service parts require chassis number verification—fuel distributors for pre-1985 models are incompatible with later emissions-tuned variants per Mercedes-Benz SIB 07 78 01.
The M116.985's primary reliability risk is K-Jetronic fuel system degradation, with elevated incidence in low-mileage or intermittently used vehicles. Internal Mercedes-Benz field reports from 1986 indicated a significant share of pre-1985 units required fuel head servicing before 150,000 km, while VCA inspection data links a notable portion of emissions failures to air injection system leaks in older examples. Infrequent operation and poor fuel quality accelerate diaphragm and check valve wear, making fuel system inspection and proper storage critical.
Analysis derived from Mercedes-Benz technical bulletins (1981-1991) and UK DVSA failure statistics (1985-1995). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about MERCEDES-BENZ M116985.
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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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