🏷️ Basic Information

Make:

Mercedes-Benz

Model:

300D

Year:

1981

Chassis Code:

W123

Engine Code:

OM617

👋 Introduction

Positioning:

The Mercedes-Benz 300D W123 of 1981 represented Mercedes-Benz's commitment to robust engineering, diesel efficiency, and enduring quality, positioning it as a premium, long-lasting vehicle in the luxury sedan market.

Competitors:

Competed against other luxury diesel offerings and gasoline-powered luxury sedans of the era, such as BMW sedans, Audi sedans, and upper-tier American makes, often favored for its fuel economy and durability.

Highlights:

Renowned for its reliable OM617 diesel engine, solid build quality, comfortable ride, and exceptional longevity. Key features included advanced (for the time) safety systems, sophisticated suspension, and understated luxury.

📋 Manual Details

Covered Models:

Mercedes-Benz 300D (1981)

Estimated Pages:

Estimates vary based on specific publication, typically 300-500 pages for comprehensive manuals of this era.

Type:

Service and Repair Manual

Language:

English

Format:

PDF / WinRAR

📖 Manual Coverage

Engine:

Detailed coverage including inspection, oil/filter change, valve adjustment, injection timing, fuel system diagnostics, exhaust system.

Cooling System:

Coolant level and antifreeze check, cooling/heating system inspection, coolant replacement.

Fuel System:

Fuel filter replacement (primary and pre-filter), injection timing adjustment, fuel system condition checks.

Air Intake:

Air filter cleaning and replacement, intake manifold seating inspection.

Exhaust System:

Exhaust manifold seating and system connection retightening.

Transmission Manual:

Manual transmission oil change, fluid level check and correction.

Transmission Automatic:

Automatic transmission fluid and filter change, fluid level check and correction.

Transfer Case:

Transfer case fluid change, fluid level check and correction.

Clutch System:

Clutch disk wear inspection, fluid level check and correction, system inspection.

Suspension:

Suspension and body structure inspection, self-leveling suspension inspection, level control system (ADS, ASD, 4MATIC) fluid level.

Front Axle:

Front axle oil level check, ball joint inspection (including with special tool).

Rear Axle:

Rear axle oil change, fluid level check and correction, rear axle mount limiting stop adjustment.

Wheels Tires:

Wheel inspection and rotation, tire inspection, tire pressure correction, wheel bolt tightening.

Brakes:

Brake fluid level check, brake line inspection, brake pad and disc thickness inspection, brake disc cleaning, parking brake adjustment and check, brake fluid replacement, brake test.

Steering:

Power steering fluid level check, steering play check, steering bolt retightening.

Electrical System:

Battery fluid level check, warning and indicator lamp checks.

Body Exterior:

Water leakage and corrosion inspection, cleaning water drains, lubricating door hinges and locks, lubricating hood, lubricating folding side mirrors, body for paint damage inspection.

Body Interior:

Removing and installing engine compartment lower panel, removing and installing lower noise encapsulation panels.

Heating Ventilation Ac:

Replacing dust filter for heating and ventilation, replacing active charcoal filter, replacing recirculating air filter, checking and correcting AC refrigerant charge.

Windshield Wipers Washers:

Windshield wiper and washer inspection, replacing windshield wiper blades, checking and correcting windshield washer fluid level.

Lighting:

Headlamp and exterior lamp inspection.

Convertible Top:

Hydraulic top fluid level check and correction, soft top locking tab check.

Safety Features:

Inspecting safety belts, checking backrest lock operation.

Maintenance:

Routine maintenance tasks such as oil changes, filter replacements, fluid checks and top-offs, belt inspections, spark plug checks.

Troubleshooting:

Diagnosing and identifying the cause of vehicle problems.

Repair:

Step-by-step instructions for component disassembly, inspection, rebuilding, and assembly.

Adjustments:

Adjustment procedures for valve clearance, idle speed, injection timing, parking brake, steering components, rear axle limiting stops.

Replacements:

Procedures for replacing major components like filters, fluids, belts, spark plugs, oxygen sensors, wiper blades, and air filters.

Depth:

Comprehensive, covering basic maintenance to detailed repair and rebuilding of major mechanical and electrical systems. Suitable for both DIY enthusiasts and professional mechanics.

📊 Manual Specifications

Digital Format:

PDF, WinRAR archive

Quality:

High-quality digital reproduction, ensuring clarity of diagrams and text.

Binding:

N/A (Digital Download)

Paper:

N/A (Digital Download)

⚙️ Engine Specifications

Engine Type:

Naturally Aspirated Inline 5-Cylinder Diesel

Engine Displacement:

3.0 Liters (2998 cc)

Bore X Stroke:

87.0 mm x 84.0 mm

Compression Ratio:

21:1

Horsepower:

Approx. 77-83 hp @ 4000 rpm (varies slightly by market/specification)

Torque:

Approx. 125-130 lb-ft @ 2400 rpm (varies slightly by market/specification)

Injection System:

Bosch Inline Fuel Injection Pump

Fuel Type:

Diesel Fuel

Oil Capacity:

Approx. 6.5 Liters (with filter)

Recommended Oil:

API CD or equivalent diesel engine oil (e.g., 15W-40, 20W-50 depending on climate)

Filter Part Number Oil:

Typical part numbers include Mann W917, Bosch 0451103250 (consult manual for exact fitment)

Filter Part Number Fuel:

Typical part numbers include Mann WK 80, Bosch 0450905211 (consult manual for exact fitment)

🔧 Transmission

Type:

4-Speed Manual Transmission

Type:

4-Speed Automatic Transmission (optional)

Manual Fluid:

GL-4 Hypoid Gear Oil SAE 90

Automatic Fluid:

Mercedes-Benz Specification 236.3 Automatic Transmission Fluid (e.g., ATF Dexron II or equivalent)

📐 Dimensions

Length:

Approx. 4725 mm (186.0 in)

Width:

Approx. 1790 mm (70.5 in)

Height:

Approx. 1440 mm (56.7 in)

Curb Weight:

Approx. 1450-1550 kg (3200-3420 lbs)

Gross Vehicle Weight Rating:

Approx. 1950-2050 kg (4300-4520 lbs)

🛡️ Safety Features

Crash Test Data:

While official NHTSA ratings for this specific year are not readily available in modern formats, Mercedes-Benz vehicles of this era were known for their robust construction and safety engineering, including crumple zones and reinforced passenger cells.

Features:

Four-wheel disc brakes (on most models), advanced suspension design for stability.

Features:

Reinforced passenger compartment, energy-absorbing steering column, potentially optional airbags (early adoption).

💡 Technology Features

Features:

Basic analog radio, cassette player (optional). Focus was on mechanical reliability rather than advanced electronics.

Features:

Cruise control (optional), power steering, four-wheel disc brakes. Advanced electronic driver aids were not prevalent in this era.

Features:

No modern connectivity features such as Bluetooth or USB were available.

🔧 Maintenance

Oil Filter Change:

Recommended every 5,000-7,500 miles (8,000-12,000 km) or annually, whichever comes first.

Air Filter Replacement:

Recommended every 15,000-20,000 miles (24,000-32,000 km).

Fuel Filter Replacement:

Recommended every 15,000-20,000 miles (24,000-32,000 km) or as needed based on fuel quality.

Valve Adjustment:

Recommended every 30,000-50,000 miles (48,000-80,000 km) or if noisy operation is detected.

Transmission Fluid Change:

Manual: Every 30,000-50,000 miles (48,000-80,000 km). Automatic: Every 20,000-30,000 miles (32,000-48,000 km).

Brake Fluid:

DOT 3 or DOT 4 (consult manual for specific type and compatibility)

Power Steering Fluid:

Mercedes-Benz Specification 236.3 Automatic Transmission Fluid or equivalent.

Coolant:

Ethylene glycol-based antifreeze mixed with distilled water (50/50 ratio typical). Consult manual for MB-specific approvals.

Common Problems:

Rust (especially around wheel arches, sills, and sunroof), vacuum system leaks (affecting central locking, climate control, cruise control), glow plug issues, injector pump wear, potential radiator and hose degradation due to age.

📚 Vehicle History

Heritage:

Mercedes-Benz has a long-standing reputation for engineering excellence, safety, and durability, tracing its roots back to the invention of the automobile.

W123 Generation:

The W123 chassis, produced from 1976 to 1986, was a monumental success for Mercedes-Benz. The 300D variant became synonymous with reliable, fuel-efficient luxury diesel motoring. The 1981 model represents a mid-cycle refinement of this highly successful platform.

Production Years W123:

1976-1986

Production Location:

Various Mercedes-Benz factories globally, primarily Germany.

🏆 Awards & Recognition

Accolades:

While specific awards for the 1981 model year are not widely documented, the W123 platform as a whole is widely recognized by automotive critics and enthusiasts for its exceptional durability, reliability, and engineering quality, earning it numerous accolades for longevity and value retention.