Positioning:
Premium mid-size luxury sedan, renowned for build quality, comfort, and durability.
Competitors:
BMW 5 Series (E28), Audi 100, Volvo 240/740
Build Quality:
Exceptional German engineering and robust construction.
Comfort:
Supple ride, comfortable seating, and quiet cabin.
Reliability:
Known for longevity and ability to withstand high mileage with proper maintenance.
Years Covered:
1976, 1977, 1978, 1979, 1980, 1981, 1982, 1983, 1984, 1985
Estimated Page Count:
Approximately 1200+
Type:
Factory Service Repair Manual
Engine:
M110 2.8L Inline-6 Cylinder (DOHC)
Engine Management:
Bosch K-Jetronic Fuel Injection
Transmission:
4-speed Manual, 4-speed Automatic (4G-Tronic)
Drivetrain:
Rear-Wheel Drive
Suspension:
Independent Front (Double Wishbone), Independent Rear (Multi-Link)
Brakes:
Front Ventilated Discs, Rear Discs (Power Assisted)
Steering:
Power Assisted Recirculating Ball
Electrical:
12V System, Charging System, Ignition, Lighting, Instrumentation, Accessories
Bodywork:
Chassis, Body Panels, Doors, Windows, Trim, HVAC System
Maintenance:
Scheduled maintenance, fluid changes, filter replacements, lubrication
Troubleshooting:
Diagnostic procedures, symptom-based troubleshooting, electrical fault finding
Repair:
Engine overhaul, transmission rebuild, brake system repair, suspension component replacement
Diagnostics:
Component testing, pressure testing, electrical continuity checks
Specifications:
Torque specifications, clearances, timing, fluid capacities
Depth:
Comprehensive (from basic maintenance to complete engine and transmission overhauls)
Engine Code:
M110.984 (US/Canada), M110.987 (Europe)
Engine Type:
Naturally Aspirated, SOHC 24-Valve (early models), DOHC 24-Valve (later models)
Displacement:
2.8 Liters (2799 cc)
Bore X Stroke:
86.0 mm x 80.25 mm
Compression Ratio:
8.2:1 or 8.7:1 (depending on market/model year)
Horsepower SAE Net:
145-155 hp @ 5250-5500 RPM (approx.)
Torque SAE Net:
165-175 lb-ft @ 3000-3500 RPM (approx.)
Fuel Injection:
Bosch K-Jetronic CIS (Continuous Injection System)
Fuel Type:
Unleaded Gasoline (Premium Recommended)
Oil Capacity:
7.5 Liters (approx. 8 US Quarts)
Recommended Oil Viscosity:
SAE 15W-40 or 10W-40 (depending on climate)
Standard Transmission:
4-speed Manual
Optional Transmission:
4-speed Automatic (4G-Tronic)
Automatic Transmission Features:
Hydraulic torque converter, selective gear engagement, torque converter lock-up (later models)
Automatic Transmission Fluid Type:
Dexron III/Mercon (or equivalent MB specification)
Federal Motor Vehicle Safety Standards Compliance:
Designed to meet 1970s/early 1980s US safety standards.
Braking System:
Four-wheel power disc brakes with dual-circuit hydraulic system.
Seatbelts:
Three-point inertia-reel seatbelts in front, lap belts in rear.
Steering Column:
Collapsible steering column for improved occupant protection.
Body Structure:
Reinforced passenger compartment, crumple zones.
Oil And Filter Change Interval:
Every 10,000 km (6,200 miles) or annually.
Air Filter Replacement Interval:
Every 20,000 km (12,400 miles) or annually.
Spark Plug Replacement Interval:
Every 40,000 km (24,800 miles) or as needed.
Coolant Flush Interval:
Every 2 years or 40,000 km (24,800 miles).
Valve Adjustment Interval:
Every 40,000 km (24,800 miles) for M110 engine (requires expert inspection).
Coolant Type:
Mercedes-Benz Specification 325.0 (Glysantin G48 or equivalent blue/green silicate-based coolant)
Brake Fluid Type:
DOT 3 or DOT 4 (Low Viscosity)
Power Steering Fluid Type:
MB Specification 236.3 (ATF Type A or equivalent)
Common Wear Items:
Fuel pump, fuel accumulators, vacuum lines, fuel injectors, ignition components, suspension bushings, exhaust system.
Corrosion Prone Areas:
Wheel arches, rocker panels, door bottoms, jacking points, trunk floor.
Electrical Issues:
Wiring harness degradation, instrument cluster issues, aging relays and switches.
K Jetronic Diagnosis:
Requires specialized knowledge for fuel pressure and mixture adjustments.
Mercedes Benz Legacy:
Globally recognized for engineering excellence, safety, and luxury since the late 19th century.
W123 Introduction:
Launched in 1976 as the successor to the W114/W115 series, establishing new benchmarks for durability and refinement.
W123 Body Styles:
Offered as Sedan (Saloon), Coupe, Estate (Wagon), and Limousine.
W123 Updates:
Received minor facelift and feature updates throughout its production run, including improved aerodynamics and interior refinements.
Production Years:
1976-1985
Manufacturing Locations:
Germany (main), various international assembly plants.
