🏷️ Basic Information Identification Make: Mercedes-Benz Model: 300SEL Year: 1990 Generation Chassis Code: W126 Codes Engine Code Prefix: M103 👋 Introduction Market Position Segment: Luxury Sedan Competitors 1990: BMW 7 Series (E32), Lexus LS 400 (UCF10), Cadillac DeVille Key Features Vehicle Attributes: Exceptional build quality, refined ride, potent inline-six engine, advanced safety features for its era, spacious interior. Manual Value Proposition: Essential for DIY enthusiasts and professional mechanics to maintain and repair the sophisticated W126 chassis, providing detailed, factory-accurate information at a fraction of dealership costs. 📋 Manual Details Coverage Areas Primary Focus: Service and Repair Page Count Estimated Pages: 1000+ Manual Type Type: Factory Service Manual / Workshop Manual Language Language: English Format Format: Digital (PDF) 📖 Manual Coverage Systems Covered Powertrain: Engine, Fuel System, Cooling System, Exhaust System, Transmission (Automatic) Chassis: Suspension (Independent Front & Rear), Steering System, Brakes (ABS), Drivetrain (RWD) Electrical: Wiring Diagrams, Lighting, Ignition System, Battery, Charging System, Starter, ECUs, Sensors, Instruments Body And Interior: Body Panels, Doors, Windows, Seats, HVAC System, Climate Control, Sunroof, Interior Trim Procedures Included Maintenance: Routine Service, Oil Changes, Filter Replacements, Lubrication, Inspections Troubleshooting: Diagnostic Procedures, Symptom-Based Troubleshooting Guides, Fault Code Diagnosis Repair: Component Removal and Installation, Overhaul Procedures, Adjustment Procedures Diagnostics: OBD-I diagnostic codes, component testing, sensor data interpretation for the era. Engine Rebuild: Detailed procedures for cylinder head removal, piston and connecting rod installation, crankshaft bearing replacement, camshaft timing. Transmission Service: Torque converter replacement, valve body diagnostics, seal replacement, clutch pack inspection. Electrical System Repair: Component testing for injectors, fuel pump, ignition coil, starter motor, alternator; wiring harness repair and continuity testing. Suspension And Steering Repair: Replacement of control arms, ball joints, tie rods, steering gearbox overhaul, shock absorber replacement, leveling system (if equipped). Technical Depth Depth: Comprehensive (from basic maintenance to full engine rebuilds and electrical system diagnostics) 📊 Manual Specifications File Format Searchability: Searchable Text Print Quality Resolution: High-Resolution Scans Suitable for Printing Binding Type Binding Type: N/A (Digital Format) Paper Type Paper Type: N/A (Digital Format) ⚙️ Engine Specifications Primary Engine Engine Type: Inline 6-Cylinder, SOHC Displacement: 3.0 Liters (2962 cc) Bore X Stroke: 88.5 mm x 80.25 mm Performance Horsepower: 188 hp @ 5700 rpm (SAE Net) Torque: 195 lb-ft @ 4400 rpm (SAE Net) Fuel System Fuel Delivery: Bosch KE-Jetronic CIS-E Fuel Injection Fuel Type: Premium Unleaded Gasoline (91 Octane or higher) Engine Management Ignition System: Electronic Ignition with Knock Control ECU Type: Bosch Motronic (specific model varies) 🔧 Transmission Standard Transmission Type: 4-Speed Automatic (4G-Tronic) Torque Converter Lockup: Yes Optional Optional Transmission: N/A (Only Automatic Offered in US Market for 300SEL) Features Shift Modes: Economy (E) / Sport (S) Fluid Specifications Fluid Type: MB Spec 236.1 (e.g., Dexron II, ATF-T-IV compatible with MB spec) 📐 Dimensions Exterior Wheelbase: 115.9 inches (2944 mm) Length: 201.0 inches (5105 mm) Width: 70.2 inches (1783 mm) Height: 56.1 inches (1425 mm) Weights Curb Weight: approx. 3,800 lbs (1724 kg) Gross Vehicle Weight Rating: approx. 4,784 lbs (2170 kg) 🛡️ Safety Features Ratings NHTSA Front Impact: N/A (Not tested by NHTSA under current protocols) IIHS Side Impact: N/A (Not tested by IIHS under current protocols) Active Features ABS: Standard (Anti-lock Braking System) Traction Control: Optional (ASR - Acceleration Slip Regulation) Passive Features Airbags: Driver's Side Airbag Standard Seatbelts: 3-Point Inertia-Reel Seatbelts Front & Rear Crumple Zones: Yes (Front and Rear) 💡 Technology Features Infotainment Audio System: Factory AM/FM Stereo Cassette Player with optional CD Changer and premium sound system (Becker units common). Climate Control: Automatic Climate Control (Klima-automatik) with cabin temperature sensor and adjustable airflow. Driver Assistance Cruise Control: Standard Memory Seats: Optional (Driver and Passenger) Connectivity Connectivity Features: N/A (Analog systems, no integrated Bluetooth or USB) 🔧 Maintenance Service Intervals Oil Change Interval: Every 5,000-7,500 miles or 6-12 months (depending on driving conditions and oil used) Major Service Interval: Refer to manual for specific mileage intervals (e.g., 30k, 60k, 90k miles) for spark plugs, belts, coolant, etc. Fluid Specifications Engine Oil Type: API SG/SH, ACEA A2/A3 (e.g., Mobil 1 15W-40, 10W-30, 5W-30 depending on climate) Engine Oil Capacity: 7.4 Liters (7.8 US Quarts) with filter change Coolant Type: MB Spec 325.0 (Ethylene Glycol based, typically 50/50 mix with distilled water) Brake Fluid Type: DOT 3 or DOT 4 Known Issues Common Wear Items: Ball joints, tie rod ends, shock absorbers, flex discs, fuel pump relay, idle control valve, climate control vacuum leaks. Electrical Common Failures: Door lock actuators, window regulators, instrument cluster warning lights, wiring harness insulation degradation (especially around engine bay). Engine Maintenance Tips: Regularly check and replace the fuel distributor O-rings, ensure proper function of the air flow meter, maintain correct CIS pressure. 📚 Vehicle History Brand Heritage Brand Reputation: Renowned for engineering excellence, durability, safety, and luxury. Model Evolution W126 Generation: Second generation of the S-Class, representing the pinnacle of Mercedes-Benz engineering in...