🏷️ Basic Information

Make:

Mercedes-Benz

Model:

300 CD

Year:

1985

Chassis Code:

W123

Engine Code Family:

OM617

👋 Introduction

Market Niche:

Luxury Diesel Coupe/Sedan, known for durability and European engineering.

Key Competitors:

BMW 324td, Audi 5000 Turbo Diesel, Volvo 740 GLE Diesel.

Vehicle Strengths:

Robust OM617 engine, excellent build quality, comfortable ride, distinctive W123 styling, strong resale value for its era.

Manual Value Proposition:

Provides DIY enthusiasts and professional mechanics with the authoritative information needed to maintain and repair this classic Mercedes-Benz.

📋 Manual Details

Primary Coverage:

Service, Repair, Maintenance, Troubleshooting, Diagnostics

Secondary Coverage:

Electrical Diagrams, Specifications, Torque Values, Component Locations

Estimated Pages:

700+

Type:

Factory Service Manual / Workshop Manual

Language:

English

Format:

Digital (PDF)

📖 Manual Coverage

Engine:

3.0L 5-Cylinder Turbo Diesel (OM617.952), Fuel Injection System, Cooling System, Lubrication System, Exhaust System

Transmission:

4-Speed Automatic Transmission (722.3) and 5-Speed Manual Transmission (G3/25-5)

Drivetrain:

Rear Wheel Drive, Driveshafts, Differential, Axles

Suspension:

Front Independent Suspension (Double Wishbone), Rear Independent Suspension (Multi-link), Shock Absorbers, Springs, Bushings

Brakes:

Front Disc Brakes, Rear Disc Brakes, Parking Brake, Brake System Hydraulics, ABS (if equipped)

Steering:

Power Assisted Steering System, Steering Gear, Steering Column

Electrical:

Battery, Starting System, Charging System, Ignition System, Lighting, Gauges, Switches, Fuses, Relays, Wiring Harnesses, Climate Control Electronics

Body And Interior:

Body Panels, Doors, Hood, Trunk, Seats, Upholstery, Trim, Glass, Wipers, Convertible Top (if applicable)

Climate Control:

HVAC System, Air Conditioning, Heater Core, Blower Motor, Controls

Maintenance:

Oil Changes, Filter Replacements, Fluid Checks and Replacements, Belt Adjustments, Spark Plug Replacement (gasoline models), Glow Plug Checks (diesel)

Repair:

Engine Overhaul, Transmission Rebuild, Brake Caliper Replacement, Suspension Component Replacement, Electrical Component Diagnosis and Repair, Body Panel Repair

Troubleshooting:

Diagnostic Flowcharts, Symptom-Based Troubleshooting Guides, Common Problems and Solutions

Specifications:

Torque Specifications for all fasteners, Engine Control Unit (ECU) data, Valve Clearances, Timing Specifications

Depth:

Comprehensive: Covers everything from basic maintenance to complete engine and transmission rebuilds, including detailed diagnostic procedures and electrical schematics.

📊 Manual Specifications

Quality:

High-resolution scans, searchable text, bookmarks for easy navigation.

Reproducibility:

Suitable for printing individual pages or sections for workshop use.

Binding:

N/A (Digital Format)

Paper Quality:

N/A (Digital Format)

⚙️ Engine Specifications

Engine Type:

Inline 5-Cylinder Turbocharged Diesel

Displacement:

3.0 Liters (2998 cc)

Bore X Stroke:

90.9 mm x 100.0 mm

Compression Ratio:

21.0:1

Valvetrain:

SOHC (Single Overhead Camshaft), 2 valves per cylinder

Fuel Delivery:

Bosch Inline Fuel Injection Pump with Turbocharger

Horsepower:

125 hp @ 4350 rpm (approx.)

Torque:

184 lb-ft @ 2400 rpm (approx.)

Fuel Type:

Diesel

Fuel Capacity:

17.4 gallons (66 liters)

Engine Oil Type:

API CD or higher, SAE 15W-40 or 10W-30 (depending on climate)

Engine Oil Capacity:

7.4 quarts (7.0 liters) with filter change

Coolant Type:

Ethylene Glycol based antifreeze with corrosion inhibitors

Coolant Capacity:

Approx. 9.5 quarts (9.0 liters)

🔧 Transmission

Transmission Type:

4-Speed Automatic (722.3)

Transmission Type:

5-Speed Manual (G3/25-5)

Automatic Features:

Hydraulic Torque Converter, Selectable Modes (e.g., Economy/Standard)

Automatic Transmission Fluid Type:

MB Specification 236.1 (e.g., Dexron II compatible)

Automatic Transmission Fluid Capacity:

Approx. 8.0 quarts (7.5 liters) for change with converter

Manual Transmission Fluid Type:

MB Specification 235.0, SAE 80W/90 GL-5 gear oil

📐 Dimensions

Length:

188.0 inches (4775 mm)

Width:

69.9 inches (1775 mm)

Height:

55.1 inches (1400 mm)

Wheelbase:

112.2 inches (2850 mm)

Front Track:

57.5 inches (1460 mm)

Rear Track:

56.7 inches (1440 mm)

Curb Weight:

3,350 - 3,500 lbs (1520 - 1590 kg) depending on body style and equipment

Gross Vehicle Weight Rating:

Approx. 4,300 lbs (1950 kg)

Towing Capacity:

Not typically recommended or specified by manufacturer.

🛡️ Safety Features

NHTSA Ratings:

Not available for this model year in a standardized format comparable to modern ratings.

Active Safety:

Four-wheel disc brakes, optional Anti-lock Braking System (ABS) on later models of the W123 chassis.

Passive Safety:

Reinforced safety cage, crumple zones, padded interior surfaces, three-point seat belts (front), lap belts (rear).

💡 Technology Features

Infotainment Features:

Original equipment typically included an analog radio (AM/FM/Cassette), mechanical HVAC controls, and basic speaker systems. Aftermarket upgrades are common.

Driver Assistance Features:

Cruise control (optional), power steering, power windows, power locks, headlight washers/wipers.

Connectivity Features:

No factory connectivity features (e.g., Bluetooth, USB) as per modern standards.

🔧 Maintenance

Oil Change Interval:

Every 3,000-5,000 miles or 6-12 months, whichever comes first (depending on driving conditions and oil used).

Air Filter Replacement:

Every 15,000-30,000 miles or as needed based on driving environment.

Fuel Filter Replacement:

Every 15,000-30,000 miles or annually.

Coolant Flush:

Every 2-3 years or 30,000-60,000 miles.

Transmission Fluid Change Interval:

Automatic: Every 30,000-50,000 miles. Manual: Consult manual for specific intervals.

Valve Adjustment:

Periodically, usually around 30,000 miles (specific interval in manual).

Common Problems:

Vacuum system leaks (affecting door locks, central locking, headlight aimers), overheating due to clogged radiator or inefficient cooling fan clutch, oil leaks from engine seals, rust in common W123 areas (wheel wells, rocker panels, window seals), brittle rubber components (bushings, hoses, mounts).

Diesel Specific Concerns:

Glow plug reliability, injector pump maintenance, potential for fuel gelling in extreme cold (requires anti-gel additive).

📚 Vehicle History

Brand Focus:

Mercedes-Benz is synonymous with luxury, engineering excellence, and automotive innovation, particularly in diesel technology and build quality.

W123 Generation:

The W123 chassis (1976-1986) is celebrated for its exceptional durability and reliability, earning the nickname 'The Tank'.

300Cd Variant:

The 'CD' designation typically referred to a diesel coupe model. In 1985, this was the final year for the W123 coupe.

Production Years W123:

1976-1986

Manufacturing Location:

Sindelfingen, West Germany

🏆 Awards & Recognition

Model Reputation:

The W123 generation is widely recognized by automotive journalists and owners for its exceptional build quality, longevity, and robustness, often lauded as one of the most reliable Mercedes-Benz models ever produced.

Consumer Reports Legacy:

Consistently ranked high for reliability in its era by publications like Consumer Reports.