Positioning:
The Mercedes-Benz W123 series, particularly the 280S, represented a significant step in luxury and engineering for its era, known for its durability and build quality. This manual targets owners and technicians seeking to maintain and repair these classic vehicles.
Competitors:
Competed with luxury sedans from brands like BMW (e.g., 5 Series), Audi, and Cadillac during the late 1970s and early 1980s, often lauded for its robust construction and advanced features for the time.
Manual Selling Points:
Comprehensive coverage, detailed diagrams, step-by-step procedures, instant download availability, printable format, DIY friendly, professional mechanic resource.
Covered Model Years:
1976, 1977, 1978, 1979, 1980, 1981, 1982, 1983, 1984, 1985
Type:
Workshop Service Repair Manual
Engine:
Complete engine overhaul, diagnosis, and repair (M110 engine family)
Fuel System:
Bosch K-Jetronic fuel injection system troubleshooting, diagnosis, and repair
Ignition System:
Ignition timing, component testing, and repair
Cooling System:
Radiator, water pump, thermostat, hoses, and fan diagnosis and repair
Exhaust System:
Component inspection, repair, and replacement
Transmission:
Automatic and Manual transmission service, overhaul, and repair
Drivetrain:
Driveshafts, differential, axles, and CV joints maintenance and repair
Suspension:
Front and rear suspension component diagnosis, replacement, and alignment specifications
Steering:
Power steering system, steering box, and linkage repair
Brakes:
Hydraulic system, disc brakes (front and rear), brake pads, rotors, calipers, and parking brake service
Electrical System:
Wiring diagrams, starter, alternator, battery, lighting, and accessory circuit troubleshooting and repair
Body And Chassis:
Body panel repair, door mechanisms, window regulators, bumpers, and chassis components
HVAC:
Heating, ventilation, and air conditioning system service and repair
Interior:
Seat removal, dashboard disassembly, and trim panel service
Routine Maintenance:
Oil changes, filter replacements, fluid checks, lubrication
Troubleshooting:
Comprehensive diagnostic procedures for all major systems
Repair:
Detailed step-by-step repair procedures for all components
Disassembly Assembly:
Complete instructions for component removal and installation
Adjustments:
Specific adjustment procedures for engine, brakes, suspension, etc.
Diagnostics:
System-specific diagnostic charts and procedures
Wiring Diagrams:
Comprehensive electrical schematics for various circuits
Depth:
Comprehensive, covering everything from basic maintenance to complete engine and transmission rebuilds.
Engine Type:
Inline 6-cylinder, Naturally Aspirated
Engine Code:
M110.984 / M110.988
Displacement:
2.8 Liters (2781 cc)
Bore X Stroke:
86.0 mm x 80.25 mm
Compression Ratio:
8.0:1 or 8.2:1 (depending on specific market/year)
Horsepower:
Approximately 136-145 hp (DIN) at 5000 rpm
Torque:
Approximately 220-230 Nm (162-170 lb-ft) at 3200 rpm
Fuel Injection:
Bosch K-Jetronic Continuous Injection System
Fuel Type:
Unleaded gasoline (minimum 91 octane recommended)
Oil Capacity:
Approx. 7.5 Liters (7.9 US Quarts) with filter
Recommended Oil Viscosity:
10W-40 or 15W-40 (depending on climate, refer to manual for exact specifications)
Transmission Type:
4-Speed Manual Transmission (common on early models or specific markets)
Transmission Type:
4-Speed Automatic Transmission (e.g., 4G-TRONIC)
Automatic Transmission Features:
Hydromechanical control, torque converter lock-up (on later models)
Automatic Transmission Fluid:
Dexron II (or equivalent)
Manual Transmission Fluid:
GL-4 Gear Oil (e.g., 75W-90 or 80W-90)
Length:
Approx. 4725 mm (186.0 in)
Width:
Approx. 1785 mm (70.3 in)
Height:
Approx. 1430 mm (56.3 in)
Curb Weight:
Approx. 1450-1550 kg (3197-3417 lbs)
Gross Vehicle Weight:
Approx. 2000-2100 kg (4409-4630 lbs)
Wheelbase:
Approx. 2795 mm (110.0 in)
Crash Test Results:
While formal crash test ratings like modern NCAP were not prevalent, the W123 was renowned for its structural integrity and safety features for its era, incorporating crumple zones and a robust safety cell.
Braking System:
Four-wheel disc brakes (front ventilated), power assisted
Steering Column:
Collapsible steering column
Seat Belts:
Three-point inertia reel seat belts
Body Structure:
Reinforced passenger compartment, crumple zones
Oil Change Interval:
Every 10,000-15,000 km or 12 months, whichever comes first (refer to specific manual recommendations)
Transmission Fluid Change:
Automatic transmission: Every 60,000-80,000 km. Manual transmission: Typically inspected and serviced as needed.
Coolant Flush:
Every 2-3 years or as recommended by fluid type
Coolant Type:
Ethylene glycol based antifreeze (e.g., MB 325.0 specification)
Brake Fluid Type:
DOT 3 or DOT 4
Common Problems:
Rust/corrosion (especially in wheel arches, door bottoms), vacuum system leaks (affecting door locks, climate control), fuel distributor leaks (K-Jetronic), hardened rubber hoses and mounts, potential for timing chain stretch (M110 engine).
Maintenance Focus:
Regular lubrication, attention to vacuum lines, timely replacement of cooling system components, and rust prevention are critical for longevity.
Mercedes Benz Legacy:
Mercedes-Benz has a long-standing reputation for engineering excellence, luxury, and durability, establishing a benchmark in automotive quality.
W123 Development:
The W123 was launched in 1976 to replace the W114/W115 series. It was designed to be more robust, safer, and more comfortable, building on the 'built to last' philosophy of its predecessors.
Production Years:
1976-1985
Production Volume:
Over 2.7 million units produced across all body styles (sedan, coupe, wagon, long wheelbase).
