🏷️ Basic Information Identification Make: Mercedes-Benz Model: 350 SD Turbo Year: 1991 Codes Chassis Code: W140 Engine Code: OM603.970 👋 Introduction Market Position Vehicle Segment: Full-size Luxury Sedan Historical Context: Flagship model for Mercedes-Benz during its production era Competitive Analysis Key Competitors: BMW 7 Series, Audi V8, Lexus LS 400 Key Features Engineering Philosophy: Over-engineered, robust construction, focus on comfort and durability Diesel Offering: One of Mercedes-Benz's premium diesel offerings, known for torque and longevity 📋 Manual Details Coverage Areas Primary Coverage: Vehicle Repair and Service Secondary Coverage: Maintenance, Diagnostics, Troubleshooting Page Count Estimated Page Count: 600-800 Manual Type Type: Repair Service Manual Language Language: English Format Format: PDF Download 📖 Manual Coverage Systems Covered Engine Mechanical: Complete overhaul, component testing, torque specifications, timing procedures Engine Management: Fuel injection system (Bosch KE-Jetronic), ignition system, emission control systems, sensor diagnostics Transmission: Automatic transmission (722.3/722.4) service, diagnostics, fluid specifications, valve body operation Brakes: ABS (Anti-lock Braking System) diagnosis and repair, hydraulic system service, pad and rotor replacement, fluid types Suspension Steering: Front and rear suspension components, hydraulic self-leveling suspension (optional), steering system, power steering system Electrical System: Wiring diagrams, component testing, fuse and relay identification, starter, alternator, battery service, lighting systems HVAC: Air conditioning system service, climate control operation, heater core replacement, blower motor diagnostics Body Chassis: Body panel removal and installation, door mechanisms, glass replacement, exterior trim, chassis components Procedures Included Routine Maintenance: Oil changes, filter replacements, fluid checks and top-offs, belt inspections and replacements Troubleshooting: System-specific fault finding, diagnostic flowcharts, common problems and solutions Repair Overhaul: Engine rebuild procedures, transmission disassembly and reassembly, component replacement guidelines Diagnostics: On-board diagnostics (OBD) interpretation for the era, sensor testing, electronic module troubleshooting Technical Depth Depth: Comprehensive (from basic maintenance to full engine/transmission rebuilds) Target Audience: Professional Technicians, Advanced DIYers 📊 Manual Specifications File Format Quality: High-resolution, searchable PDF Searchability: Full text search enabled Print Quality Printable: Yes, designed for printing specific sections or the entire manual Binding Type Digital Binding: N/A (Digital Download) Paper Type Digital Paper: N/A (Digital Download) ⚙️ Engine Specifications Primary Engine Engine Type: Inline 6-Cylinder Turbo Diesel Displacement: 3.5 Liters (3449 cc) Bore X Stroke: 91.0 mm x 88.3 mm Compression Ratio: 21.0:1 Aspirated By: Turbocharged Performance Horsepower: 148 hp @ 4000 rpm Torque: 232 lb-ft @ 2400 rpm Fuel System Fuel Delivery: Bosch KE-Jetronic Electronic Fuel Injection with Diesel Turbocharging Fuel Type: Diesel Fuel Fluid Specifications Engine Oil Type: API CD or CE, SAE 15W-40 (check manual for specific viscosity based on temperature) Engine Oil Capacity: 7.5 Liters (8.0 US Quarts) Coolant Type: MB 325.0 (Glysantin G48 or equivalent blue ethylene glycol coolant) 🔧 Transmission Standard Transmission Type: 4-Speed Automatic Transmission Model: 722.3 / 722.4 Optional Optional Transmission: None offered for 350 SD Turbo in 1991 Features Shift Modes: Comfort (C) / Sport (S) Fluid Specifications Transmission Fluid Type: MB 236.1 (Dexron II or equivalent) Transmission Fluid Capacity: 8.0 Liters (8.5 US Quarts) for total capacity, 3.5 Liters (3.7 US Quarts) for drain and fill 📐 Dimensions Exterior Length: 197.9 inches (5027 mm) Width: 74.0 inches (1880 mm) Height: 57.4 inches (1458 mm) Wheelbase: 118.1 inches (3000 mm) Weights Curb Weight: 4400 lbs (2000 kg) approx. Gross Vehicle Weight Rating: 5512 lbs (2500 kg) approx. 🛡️ Safety Features Ratings NHTSA Ratings: Not directly comparable to modern standards, but built to high safety standards of the era. Active Features ABS: Standard Anti-lock Braking System (ABS) Passive Features Airbags: Driver airbag standard Seatbelts: Pretensioning seatbelts Body Structure: High-strength steel construction, crumple zones 💡 Technology Features Infotainment Audio System: Factory premium sound system, often with cassette player and AM/FM radio. Driver Assistance Cruise Control: Standard electronic cruise control. Climate Control: Automatic climate control (often dual-zone). Connectivity Telephony: Optional integrated telephone system (era-appropriate, large handset). 🔧 Maintenance Service Intervals Oil Change Interval: Every 7,500-10,000 miles or 12 months, whichever comes first (refer to manual for exact spec). Transmission Fluid Interval: Every 30,000-50,000 miles (check for specific recommendation, often considered 'lifetime' by manufacturer but recommended for service). Air Filter Interval: Every 15,000-30,000 miles or as needed based on driving conditions. Fuel Filter Interval: Every 20,000-30,000 miles. Known Issues Common Diesel Issues: Glow plug failure, injector pump issues, turbocharger wear, pre-chamber issues, vacuum leaks affecting various systems. Common W140 Issues: Hydraulic suspension leaks (if equipped), SRS system issues, vacuum operated door locks/central locking faults, window regulator failures, biodegradable wiring harness degradation (later models, but potential for some). Fuel System Specifics: KE-Jetronic system can be complex to diagnose; requires specific tools and knowledge. 📚 Vehicle History Brand Heritage Brand Legacy: Mercedes-Benz has a long history of producing robust, high-quality diesel engines and luxury vehicles. Model Evolution W140 Introduction: The W140 chassis was introduced in 1991 as the successor to the W126 S-Class, representing a significant leap in technology and size. Sd Designation: 'SD' denotes the...