Segment:
Mid-size Luxury Sedan and Wagon
Target Audience:
Discerning drivers valuing durability, comfort, and engineering excellence.
Key Competitors:
BMW 5 Series (E28), Audi 100, Volvo 240/740 Series, Cadillac Sedan de Ville.
Competitive Advantage:
Exceptional build quality, robust diesel powertrain known for longevity, comfortable ride, and timeless design.
Vehicle Features:
Renowned for its durability, safety (pioneering crumple zones), comfortable interior, smooth ride quality, and legendary OM617 diesel engine.
Covered Years:
1976, 1977, 1978, 1979, 1980, 1981, 1982, 1983, 1984, 1985
Estimated Page Count:
1500+
Type:
Complete Workshop Service Repair Manual
Searchability:
Searchable text for quick access to specific information.
Printability:
Printable pages for on-the-job reference.
Quality:
High-resolution scans of original factory documentation.
Engine System:
Detailed diagnosis, overhaul, and repair of the OM617 diesel engine, including fuel injection, cooling, lubrication, and emissions control.
Transmission System:
Coverage for both manual and automatic transmissions (4-speed and 5-speed manual, 3-speed and 4-speed automatic), including clutch, drivetrain components, and differential.
Brake System:
Complete service procedures for hydraulic braking systems, including disc and drum brakes, power assist, ABS (where applicable on later models), and parking brake.
Suspension Steering:
Detailed information on front and rear suspension (independent front, semi-trailing arm rear), steering gear, power steering system, and wheel alignment specifications.
Electrical System:
Comprehensive wiring diagrams, troubleshooting guides for lighting, ignition, charging system (alternator), starter, instruments, and accessories.
Body Chassis:
Body repair, interior trim removal and installation, door mechanisms, glass replacement, and chassis lubrication.
Heating Air Conditioning:
Service and repair procedures for the HVAC system, including climate control, refrigerant handling, and component diagnosis.
Maintenance Procedures:
Regular scheduled maintenance, oil changes, filter replacements, fluid checks and changes, belt tensioning, and spark plug replacement (if applicable to specific variants, though primarily diesel).
Troubleshooting Diagnostics:
Systematic fault finding for engine performance issues, electrical gremlins, transmission problems, and brake system malfunctions.
Engine Overhaul:
Complete engine rebuilding procedures, including cylinder head removal and service, piston and connecting rod installation, crankshaft service, and timing component replacement.
Transmission Rebuild:
Detailed instructions for the disassembly, inspection, repair, and reassembly of both manual and automatic transmissions.
Brake System Repair:
Caliber overhaul, brake pad/shoe replacement, rotor/drum resurfacing or replacement, bleeding procedures, and master cylinder service.
Suspension Steering Repair:
Replacement of ball joints, tie rod ends, control arms, shock absorbers/struts, and steering box adjustments.
Electrical Troubleshooting:
Step-by-step guides for diagnosing and repairing electrical faults using wiring diagrams and test equipment.
Body Panel Replacement:
Procedures for removing and installing body panels, fenders, doors, and trim pieces.
Depth Level:
Comprehensive from basic maintenance to full engine and transmission rebuilds, including detailed diagnostic procedures.
Diagnostic Capabilities:
Advanced diagnostic information for the OM617 engine, fuel system, and electrical components, aiding in precise problem identification.
Special Tool Requirements:
Lists and illustrations of specialized tools required for specific repair procedures, ensuring correct execution.
Torque Specifications:
Precise torque values for all critical fasteners throughout the vehicle, essential for proper assembly and safety.
Tolerances Clearances:
Detailed specifications for component clearances and wear limits during engine and transmission overhauls.
Oil Change Interval:
Typically every 3,000-5,000 miles (5,000-8,000 km) or 6-12 months, depending on driving conditions. Consult manual for specific recommendations.
Fuel Filter Replacement:
Recommended every 10,000-15,000 miles (16,000-24,000 km). Crucial for diesel engine health.
Air Filter Replacement:
Typically every 15,000-20,000 miles (24,000-32,000 km).
Coolant Flush:
Every 2-3 years or 30,000-50,000 miles (50,000-80,000 km).
Engine Oil:
API CD or CE rated diesel engine oil, viscosity typically SAE 10W-40 or 15W-40. Check manual for specific grade based on climate. Capacity approx. 7.5 liters.
Coolant:
Ethylene glycol-based antifreeze (e.g., Mercedes-Benz 302.0 specification) mixed with distilled water (50/50 ratio). Capacity approx. 8.5 liters.
Transmission Fluid Auto:
Dexron III (or equivalent specification) for 722.1 / 722.3 automatic transmissions. Capacity varies, often around 5-7 liters for a fluid change. Consult manual for precise amount and procedure.
Brake Fluid:
DOT 3 or DOT 4 brake fluid.
Power Steering Fluid:
Mercedes-Benz Power Steering Fluid (000000002051) or equivalent ATF Dexron II/III.
Common Issues:
Vacuum leaks (affecting door locks, climate control, cruise control), rust (especially around wheel arches, rocker panels, and sunroofs), wear on front suspension components (ball joints, tie rods), potential for injector pump issues, climate control flap actuator failures.
Diesel Specific Issues:
Glow plug system maintenance, potential for hard starting in very cold weather if glow plugs or battery are weak, occasional fuel line leaks.
Heritage:
Mercedes-Benz has a long-standing reputation for engineering excellence, safety, and durability, particularly in their diesel offerings.
Model Lineage:
Successor to the W114/W115 ('Stroke Eight') series, the W123 expanded on its predecessor's strengths with improved aerodynamics, safety, and comfort.
Body Styles:
Offered in Sedan (Limousine), Coupe, Estate (T-model), and long-wheelbase Limousine variants.
Production Years:
1976-1985
Production Volume:
Over 2.7 million units produced across all body styles and variants.
Manufacturing Locations:
Primarily Sindelfingen, Germany, with some production in other global facilities.
