Segment:
Executive Sedan, Luxury Mid-Size Car
Competitors:
BMW 5 Series (E28), Audi 100, Volvo 240, Jaguar XJ6
Reliability And Durability:
The W123 platform is renowned for its exceptional build quality, durability, and longevity, often referred to as 'over-engineered'.
Comfort And Refinement:
Offered a high level of ride comfort, quiet cabin, and premium interior appointments for its era.
Engineering Excellence:
Embodied Mercedes-Benz's commitment to advanced engineering, safety, and build quality.
Model Years Covered:
1976, 1977, 1978, 1979, 1980, 1981, 1982, 1983, 1984, 1985
Estimated Pages:
Over 1000 (typical for comprehensive workshop manuals of this era)
Type:
Workshop Service Repair Manual
Format:
Digital (likely PDF)
Powertrain:
Engine, Fuel System, Ignition System, Exhaust System, Transmission (Manual & Automatic), Drivetrain
Chassis:
Suspension (Front & Rear), Steering, Brakes (Hydraulic, Parking), Wheels & Tires
Electrical:
Wiring Diagrams, Lighting, Instrumentation, Power Accessories, Starting & Charging System
Body:
Body Structure, Interior Trim, Exterior Trim, Doors, Windows, Seats, Climate Control System (HVAC)
Maintenance:
Routine Service, Oil Changes, Filter Replacements, Fluid Checks & Replacements, Belt Adjustments
Diagnostics:
Troubleshooting Guides, Fault Diagnosis Charts, Symptom-Based Repair Procedures
Repair:
Component Removal & Installation, Rebuild Procedures, Component Adjustment
Engine Rebuild:
Detailed instructions for engine disassembly, component inspection, measurement, and reassembly, including piston ring replacement, bearing replacement, and cylinder head overhaul.
Transmission Rebuild:
Procedures for manual and automatic transmission removal, disassembly, inspection, repair, and reinstallation, including clutch replacement for manuals.
Electrical Diagnostics:
Extensive wiring diagrams for all vehicle systems, troubleshooting charts for electrical faults, and procedures for testing and replacing components like alternators, starters, and ECUs (if applicable).
Depth:
Comprehensive (from basic maintenance to complete engine and transmission overhauls, electrical system diagnostics, and body repair)
Diagnostic Tools:
Covers identification of common diagnostic tools and methods applicable to the era, including multimeters, pressure gauges, and basic oscilloscope use.
Engine Code:
M123 (Inline-6)
Engine Type:
Naturally Aspirated, SOHC (Single Overhead Camshaft)
Displacement:
2746 cc (2.7 Liters)
Bore X Stroke:
82.5 mm x 85.0 mm
Horsepower:
Approx. 127-135 hp (DIN) at 5000 rpm (depending on market and specific tuning)
Torque:
Approx. 210-215 Nm (155-159 lb-ft) at 3000 rpm
Fuel Delivery:
Bosch K-Jetronic (CIS) Fuel Injection
Fuel Type:
Unleaded Gasoline (Octane Rating Varies by Market, typically 91 RON / 87 AKI)
Oil Capacity:
Approx. 6.5 Liters (with filter)
Coolant Capacity:
Approx. 10.0 Liters
Transmission Type:
4-speed Manual Transmission
Transmission Type:
4-speed Automatic Transmission (Optional)
Automatic Transmission Features:
Hydraulic Torque Converter, Smooth Shifting
Manual Transmission Fluid:
GL-4 Gear Oil (e.g., SAE 80W-90)
Automatic Transmission Fluid:
MB 236.1 Specification (e.g., Dexron-II compatible)
Length:
Approx. 4725 mm (186.0 in)
Width:
Approx. 1790 mm (70.5 in)
Height:
Approx. 1425 mm (56.1 in)
Wheelbase:
Approx. 2795 mm (110.0 in)
Curb Weight:
Approx. 1450-1550 kg (3200-3417 lbs)
Gross Vehicle Weight:
Approx. 1950-2050 kg (4300-4519 lbs)
Trunk Capacity:
Approx. 500 Liters (17.6 cu ft)
Crash Test Performance:
While formal crash test ratings as we know them today were not standardized, the W123 was designed with a strong emphasis on occupant safety, featuring a crumple zone design and robust safety cage.
Braking System:
Four-wheel disc brakes (front ventilated discs, rear solid discs), Dual-circuit hydraulic system.
Steering System:
Recirculating ball steering, with optional power steering.
Seat Belts:
Three-point inertia-reel seat belts (front), lap belts (rear, later models may have three-point).
Construction:
Reinforced passenger compartment, energy-absorbing steering column, impact-resistant doors.
Audio System:
Typically an AM/FM radio with cassette player. Optional upgraded sound systems may exist.
Cruise Control:
Optional cruise control system available on some models.
Climate Control:
Manual ventilation system with optional air conditioning and automatic climate control (Thermostatic system).
Connectivity Features:
None by modern standards. Primarily mechanical and basic electrical systems.
Oil Change Interval:
Typically every 5,000-10,000 km (3,000-6,000 miles) or 6-12 months, whichever comes first.
Major Service Interval:
Valve adjustment and spark plug replacement typically recommended around 40,000-60,000 km (25,000-37,000 miles).
Engine Oil Specification:
API SG/SH or higher, SAE 10W-40 or 15W-40 (consult manual for specific climate and year recommendations).
Coolant Specification:
Ethylene Glycol based coolant with corrosion inhibitors (e.g., Mercedes-Benz specification 325.0, typically a 50/50 mix with distilled water).
Brake Fluid Specification:
DOT 3 or DOT 4 Hydraulic Brake Fluid.
Common Wear Items:
Rubber suspension components (bushings, ball joints), vacuum lines, fuel pump relay, heater control valves, rust (especially around wheel arches and door bottoms).
Fuel System Maintenance:
K-Jetronic system requires specialized knowledge for tuning and repair; periodic cleaning of injectors and air flow meter may be beneficial.
Engine Cooling:
Radiator, water pump, and thermostat are critical; ensure regular coolant flushes to prevent overheating and corrosion.
Mercedes Benz Legacy:
Mercedes-Benz has a long-standing reputation for engineering excellence, safety, and luxury in the automotive industry.
W123 Lineage:
The W123 replaced the W114/W115 'Stroke Eight' series and was succeeded by the W124 E-Class. It represented a significant advancement in Mercedes-Benz design and engineering.
Production Years:
1976-1985 (for the W123 chassis, sedan variant)
Manufacturing Locations:
Germany (main production), with assembly plants in various countries globally.
Sales Figures Impact:
The W123 was a massive commercial success, with over 2.7 million units sold across all body styles, solidifying Mercedes-Benz's market position.
Industry Acclaim:
Consistently ranked as one of the most reliable and durable cars ever produced by various automotive publications and owner surveys. Highly regarded for its build quality and longevity.
Owner Satisfaction:
Very high owner satisfaction due to its robustness and low cost of ownership over the long term when properly maintained.
Design Awards:
While specific design awards are not readily documented for individual model years, the W123's timeless and functional design is widely appreciated.
