Category:
Luxury Diesel Sedan/Coupe
Key Competitors:
BMW 5 Series (E28), Audi 5000 (C2/C3), Cadillac Seville
Powertrain Reliability:
Renowned for the durability and longevity of its OM617 diesel engine.
Build Quality:
Exceptional Mercedes-Benz build quality, typical of the W123 era.
Fuel Economy:
Excellent fuel efficiency for its class and era, a major selling point for the diesel models.
Comfort Ride:
Supple ride quality and comfortable interior appointments.
Diy Savings:
Significant cost savings by empowering owners to perform routine maintenance and repairs.
Technical Expertise:
Provides factory-level technical understanding for enthusiasts and mechanics alike.
Primary Coverage:
Service, Repair, Maintenance, Troubleshooting, Diagnostics
Secondary Coverage:
Wiring Diagrams, Specifications, Procedures
Estimated Page Count:
1000+
Type:
Factory Service Manual (WSM)
Format:
Digital Download (PDF)
Powertrain:
Engine (OM617.952), Fuel System (Diesel Injection), Exhaust System, Cooling System, Lubrication System
Drivetrain:
Transmission (4-Speed Automatic), Driveshafts, Rear Axle, Differential
Suspension Steering:
Front Suspension (Independent), Rear Suspension (Independent), Steering System (Power Steering)
Brakes:
Front Disc Brakes, Rear Disc Brakes, Parking Brake, Hydraulic System, ABS (if equipped)
Electrical:
Battery, Alternator, Starter Motor, Ignition System (Glow Plugs), Lighting System, Instrumentation, Wiring Diagrams
Body Chassis:
Body Panels, Doors, Windows, Seats, Interior Trim, Chassis Components, Corrosion Protection
Maintenance:
Oil Change, Filter Replacement (Oil, Fuel, Air), Fluid Checks and Replacements, Tune-Up Procedures, Belt Inspection/Replacement
Repair:
Engine Overhaul, Transmission Rebuild, Brake System Repair, Suspension Component Replacement, Electrical Component Diagnosis and Repair
Troubleshooting:
Diagnostic Charts, Symptom-Based Troubleshooting, Component Testing
Depth:
Comprehensive: From basic fluid changes to complete engine and transmission overhauls, including detailed diagnostic procedures and electrical schematic interpretation.
Configuration:
Inline 5-cylinder
Displacement:
3.0 Liters (2998 cc)
Aspiration:
Naturally Aspirated Diesel
Horsepower:
85 hp @ 4200 rpm
Torque:
135 lb-ft @ 2400 rpm
Injection Type:
Bosch Inline Fuel Injection Pump (Mechanical)
Valvetrain:
SOHC (Single Overhead Camshaft)
Glow Plugs:
Yes, essential for cold starts
Type:
4-Speed Automatic (722.3)
Type:
5-Speed Manual (rare for 300CD)
Torque Converter:
Yes (for automatic)
Automatic Transmission Fluid:
MB Specification 236.1 or 236.2 (e.g., Dexron II compatible)
Body Styles:
Coupe (C123), Sedan (W123)
Wheelbase:
108.7 inches (2761 mm)
Length:
188.2 inches (4780 mm)
Width:
69.5 inches (1765 mm)
Height:
54.8 inches (1392 mm)
Curb Weight:
Approx. 3400-3600 lbs (1542-1633 kg)
Gross Vehicle Weight Rating:
Approx. 4500 lbs (2041 kg)
Crash Test Data:
Limited official crash test data from modern standards, but known for robust construction.
Brakes:
Four-wheel disc brakes (standard on many models/trims), optional ABS (Anti-lock Braking System).
Steering:
Recirculating ball steering system with power assist.
Seatbelts:
Three-point front seatbelts, lap belts in rear.
Construction:
Reinforced passenger safety cell, crumple zones.
Oil Change:
Every 3,000-5,000 miles or 6-12 months, depending on driving conditions.
Fuel Filter:
Every 10,000-15,000 miles (crucial for diesel longevity).
Air Filter:
Every 15,000-20,000 miles.
Transmission Service:
Every 30,000-40,000 miles (fluid and filter change).
Engine Oil:
API CD or CE rated Diesel Engine Oil, 15W-40 or 10W-40 recommended (refer to manual for specific viscosity based on climate).
Coolant:
Ethylene Glycol based antifreeze/coolant, typically a 50/50 mix with distilled water. Mercedes-Benz specifications should be followed.
Brake Fluid:
DOT 3 or DOT 4 brake fluid.
Engine Wear:
Potential wear on injection pump, injectors, and oil cooler seals over high mileage.
Suspension Components:
Worn bushings, ball joints, and tie rod ends are common due to age and mileage.
Climate Control:
Can be complex; vacuum actuators and compressor issues can arise.
Body Rust:
Rust can affect wheel wells, rocker panels, and door bottoms, especially in areas with road salt.
Electrical Connections:
Corrosion in connectors and wiring harnesses can lead to intermittent electrical issues.
Legacy:
Mercedes-Benz reputation for engineering excellence, durability, and luxury stretching back decades.
W123 Lineage:
The W123 generation (1976-1985) is famed for its build quality and reliability. The 300 CD model specifically was a unique coupe offering in the North American market, featuring the robust diesel engine.
Manufacturing Location:
Germany (primarily)
Production Period:
W123 series: 1976-1985. 300 CD variants primarily produced for North American market.
