🏷️ Basic Information Identification Make: Mercedes-Benz Model: 300D Chassis Code: W123 Model Years Covered: 1976, 1977, 1978, 1979, 1980, 1981, 1982, 1983, 1984, 1985 Codes Engine Code Primary: OM617 (Inline 5-cylinder Diesel) 👋 Introduction Market Position Segment: Mid-size luxury sedan/sedan-diesel Target Audience: Owners seeking to maintain and repair their classic Mercedes-Benz diesel vehicles Competitive Analysis Competitors: BMW E28, Audi 5000, Volvo 240 Diesel Key Features Vehicle Strength: Exceptional build quality, durability, fuel efficiency, comfort Manual Value Proposition: Enables DIY maintenance and repair, preserving the longevity and value of a classic vehicle 📋 Manual Details Coverage Areas Manual Type: Service and Repair Manual Language: English Format: PDF Download Manual Completeness: Comprehensive, covering all major systems and repairs 📖 Manual Coverage Systems Covered Engine: Detailed diagnosis, repair, overhaul, tuning for OM617 diesel engine Fuel System: Injection pump, injectors, fuel lines, filters, glow plug system Transmission: Manual and automatic transmission overhaul, maintenance, diagnostics Drivetrain: Clutch, driveshaft, differential, axles, wheel bearings Suspension: Front and rear suspension components, springs, shock absorbers, bushings, alignment Steering: Steering gear, power steering system, tie rods, linkages Brakes: Hydraulic system, brake calipers, master cylinder, wheel cylinders, parking brake, ABS (if applicable) Electrical System: Battery, charging system (alternator), starting system, ignition system, lighting, gauges, accessories Cooling System: Radiator, water pump, thermostat, hoses, coolant specifications Exhaust System: Manifold, catalytic converter (if applicable), mufflers, pipes Body And Chassis: Body panels, doors, windows, locks, upholstery, frame HVAC: Heating, ventilation, and air conditioning (HVAC) system Procedures Included Maintenance: Oil changes, filter replacements, fluid checks, belt adjustments, tune-ups Troubleshooting: Diagnostic flowcharts, symptom analysis, common problem resolution Repair: Step-by-step repair instructions for all major components and systems Overhaul: Complete engine and transmission rebuilding procedures Diagnostics: Detailed diagnostic procedures for mechanical and electrical issues Technical Depth Depth: Expert-level, covering everything from basic maintenance to complete engine rebuilds Diagrams: Includes detailed exploded views, wiring diagrams, and schematics Specifications: Precise torque values, clearances, measurements, and tolerances 📊 Manual Specifications File Format File Type: Digital PDF Searchable: Yes, text-searchable for quick information retrieval Print Quality Resolution: High-resolution, clear text and diagrams suitable for printing Binding Type Binding: N/A (Digital Download) Paper Type Paper: N/A (Digital Download) ⚙️ Engine Specifications Primary Engine Engine Type: Naturally Aspirated Inline 5-cylinder Diesel Engine Code: OM617.912 (typically) Displacement: 3.0 Liters (2998 cc) Performance Horsepower: Approximately 77-83 hp (SAE Net) depending on year and emissions standards Torque: Approximately 130-135 lb-ft (SAE Net) depending on year Redline: Approximately 4500 RPM Fuel System Injection Type: Bosch inline mechanical injection pump Glow Plugs: 4 (one per cylinder, plus an extra for faster warm-up on some models) Fuel Type: Diesel fuel (ULSD acceptable, LSD preferred for older engines) Intake System: Naturally aspirated, air filter element 🔧 Transmission Standard Standard Transmission: 4-speed manual transmission Optional Optional Transmission: 4-speed automatic transmission (e.g., 4G-TRONIC) Features Torque Converter Lockup: Yes, on most automatic transmissions for improved highway efficiency Transmission Fluid Type: Dexron III (or equivalent) for automatic; SAE 75W-90 or 80W-90 gear oil for manual 📐 Dimensions Exterior Wheelbase: Approximately 2794 mm (110 inches) Length: Approximately 4725 mm (186 inches) Width: Approximately 1790 mm (70.5 inches) Height: Approximately 1430 mm (56.3 inches) Weights Curb Weight: Approximately 1550 - 1650 kg (3417 - 3638 lbs) depending on options Gross Vehicle Weight Rating: Approximately 2100 kg (4630 lbs) 🛡️ Safety Features Ratings Historical Safety: Known for robust construction and safety features for its era Active Features Brakes: Front disc, rear drum brakes; optional ABS on later models Steering Assist: Recirculating ball, power-assisted standard Passive Features Seatbelts: 3-point front seatbelts, lap belts in rear Construction: Reinforced passenger cell, crumple zones 💡 Technology Features Infotainment Audio System: Factory AM/FM radio or cassette player, often with basic speaker setup Climate Control: Manual or optional automatic climate control (Thermatic/Thermomatic) Driver Assistance Cruise Control: Optional on many models ABS: Optional on later models Connectivity Connectivity Features: None by modern standards; basic antenna for radio 🔧 Maintenance Service Intervals Oil Change Interval: Typically every 5,000 miles or 6 months Air Filter Replacement: Every 15,000 miles or as needed based on operating conditions Fuel Filter Replacement: Every 15,000 - 30,000 miles or annually Transmission Service: Automatic: every 30,000 miles; Manual: inspect clutch, change fluid at higher mileage intervals Fluid Specifications Engine Oil Type: API CD or CE rated diesel engine oil, SAE 15W-40 or 10W-30 (depending on climate) Engine Oil Capacity: Approximately 7.5 liters (8 US quarts) with filter change Coolant Type: 50/50 mixture of Mercedes-Benz approved antifreeze (or equivalent) and distilled water Brake Fluid Type: DOT 3 or DOT 4 Known Issues Diesel Specific: Glow plug failure, injection pump seal leaks, injector issues, potential for overheating if cooling system is neglected Chassis Specific: Rust, worn suspension bushings, vacuum line leaks, HVAC system performance degradation, climate control unit issues Electrical Specific: Wiring harness degradation (especially around heat sources), instrument cluster issues, headlight switch problems...