🏷️ Basic Information Identification Make: Mercedes-Benz Model: 350 SD Turbo Year: 1991 Codes Chassis Code: W140 (S-Class) Engine Code: OM603.970 👋 Introduction Market Position Positioning: Luxury German sedan known for its engineering prowess and comfort, targeting the executive market Competitive Analysis Competitors 1991: BMW 7 Series (E32), Audi V8 Quattro, Lexus LS 400, Jaguar XJ Key Features Diesel Performance: Torque-rich turbodiesel engine offering a blend of performance and efficiency for its class Luxurious Appointments: High-quality interior materials, advanced comfort features, and sophisticated design Engineering Excellence: Reputation for robust construction and advanced automotive technology 📋 Manual Details Coverage Areas General Coverage: Comprehensive repair, maintenance, rebuilding, refurbishment, and restoration Diagnostic Coverage: All diagnostic and repair procedures in great detail Page Count Estimated Pages: High (typically 1000+ pages for factory-level manuals) Manual Type Type: Service and Repair Manual Language Language: English Format Format: Digital (likely PDF), potentially printed 📖 Manual Coverage Systems Covered Powertrain: Engine (diesel, turbo), fuel injection, exhaust, cooling, lubrication, transmission (automatic) Chassis: Suspension (independent front/rear, self-leveling rear suspension), steering, brakes (ABS), wheels, tires Electrical: Wiring diagrams, lighting, ignition, charging system, starting system, instrumentation, comfort systems, power accessories Body: Body construction, exterior trim, interior trim, climate control, doors, windows, seats Procedures Included Maintenance: Scheduled maintenance, oil changes, filter replacements, fluid checks and changes, inspections Repair: Engine overhauls, transmission repairs, brake system repairs, suspension component replacement, electrical component diagnosis and repair Troubleshooting: Diagnostic procedures, fault code interpretation (if applicable), common problem diagnosis Technical Depth Depth: Factory-level, including detailed disassembly/assembly, specifications, tolerances, and torque values 📊 Manual Specifications File Format Digital Searchability: High (if PDF with OCR) Printable: Yes (standard for service manuals) Print Quality Illustrations: High quality, detailed diagrams and photographs Text Clarity: Excellent, professional typesetting Binding Type Binding: N/A (for digital), or professional binding (for print) Paper Type Paper: N/A (for digital), or high-quality, durable paper (for print) ⚙️ Engine Specifications Primary Engine Engine Type: Inline 6-cylinder Turbocharged Diesel Displacement: 3.5 Liters (3449 cc) Bore X Stroke: 91.4 mm x 110.0 mm Compression Ratio: 21.0:1 Performance Horsepower Ps: 148-150 PS @ 4000 rpm (approximate) Torque Lb Ft: 236-250 lb-ft @ 2400 rpm (approximate) Fuel System Injection System: Bosch VE Rotary Injection Pump with Turbocharging Fuel Type: Diesel Fuel Cooling Cooling System: Water-cooled, pressurized system 🔧 Transmission Standard Transmission Type: 4-Speed Automatic (4G-TRONIC) Gear Ratios: Detailed in manual (typical ratios for this era) Features Transmission Features: Torque converter lock-up, electronic control (for later models, but likely hydraulic control in 1991) 📐 Dimensions Exterior Length Mm: 5113 mm (1991 model year W140) Width Mm: 1886 mm (1991 model year W140) Height Mm: 1484 mm (1991 model year W140) Weights Curb Weight Kg: Approx. 1850-1950 kg Gross Vehicle Weight Kg: Approx. 2400 kg 🛡️ Safety Features Ratings Crash Safety Era Considerations: Designed to 1990s safety standards, advanced for its time but not comparable to modern NCAP ratings Active Features ABS: Standard Anti-lock Braking System (ABS) Passive Features Airbags: Driver airbag standard, passenger airbag likely optional or introduced later in the W140 lifecycle Seatbelts: Pre-tensioning front seatbelts Body Construction: High-strength steel safety cage 💡 Technology Features Infotainment Audio System: Premium Becker or Blaupunkt cassette-based audio systems, often with CD changer pre-wiring Climate Control: Automatic climate control with dual-zone capability Driver Assistance Cruise Control: Standard cruise control Parking Assistance: Parking Assist System (PAS) - optional, typically rear parking sensors were not common in 1991 Connectivity Connectivity Features: Limited by 1991 standards; no integrated Bluetooth or smartphone connectivity 🔧 Maintenance Service Intervals Oil Change Interval Km: Typically 7,500 - 10,000 km (or annually), consult manual for exact recommendations Air Filter Replacement Km: 30,000 - 40,000 km (or as needed) Fuel Filter Replacement Km: 20,000 - 30,000 km (crucial for diesel engines) Coolant Change Interval Years: Every 2-4 years Fluid Specifications Engine Oil Specification: MB 229.1 or equivalent API CG-4/CF spec, SAE 10W-40 or 15W-40 (viscosity dependent on climate) Engine Oil Capacity Liters: Approx. 7.5 Liters Transmission Fluid Type: ATF DEXRON II/III or MB 236.6 specification Coolant Type: Mercedes-Benz Coolant/Antifreeze Concentrate (e.g., G05 or G48, mixed 50/50 with distilled water) Known Issues Diesel Specific Issues: Glow plug system failure, injection pump issues, potential turbocharger wear, carbon buildup in intake manifold General W140 Issues: Vacuum system leaks (affecting door locks, HVAC), electrical gremlins, biodegradable wiring harness degradation (later models, but worth noting), suspension self-leveling issues 📚 Vehicle History Brand Heritage Mercedes Benz Reputation: Long-standing reputation for engineering excellence, luxury, and durability Model Evolution W140 Introduction: The W140 S-Class was introduced in 1991 as the successor to the W126 S-Class, representing a significant leap in size, technology, and luxury. 350 Sd Turbo Significance: The 'SD' designation signified a 'Saugdiesel' (naturally aspirated diesel) initially, but the 'Turbo' suffix clearly denotes the turbodiesel variant, a move towards more powerful and efficient diesel engines for Mercedes-Benz luxury cars. Production Production Period W140: 1991-1998...