This comprehensive service and repair manual is specifically designed for the 1977-1985 Mercedes-Benz W123 Series 300D, 300CD, and 300TD (Turbo) models. It offers detailed step-by-step instructions and clear illustrations, covering everything you need to successfully repair, maintain, rebuild, refurbish, or restore your vehicle. It encompasses all diagnostic and repair procedures, making it the ultimate resource for service and repair information.

This manual is structured to provide you with a complete understanding of your vehicle, covering a wide range of topics, including:

* **General Maintenance and Service:** Learn about routine maintenance procedures, service schedules, technical data, operating instructions, and essential information about service products like fluids. You'll also find instructions on jacking up, towing, and laying up the vehicle.

* **Engine:** This section covers everything from engine removal and installation, crankcase, cylinder head, engine breathing, crank assembly, engine timing, and valves, to various engine systems including the diesel injection system, carburetor system, gasoline injection systems (mechanically, electronically, and mechanically/electronically controlled), air cleaner, intake air preheater, exhaust gas turbocharger, air compressor, belt drives, intake manifold, exhaust manifold, engine brake, emission control system, electrical system engine (ignition system, preheating system, starter, alternator), engine lubrication, engine oil cooler, engine cooling system, coolant hoses, radiator, and engine mounting.

* **Drivetrain:** Dive into the intricacies of the clutch, manual and automatic transmissions, transfer case, pedals, throttle control, and frame.

* **Suspension & Steering:** This section details the suspension, front axle, rear axle, trailing axle, wheels, chassis measurements, propeller shaft, brake system (hydraulic, mechanical, pneumatic, and auxiliary brakes), and steering system.

* **Fuel & Exhaust:** Understand the fuel system, exhaust system, heat shield, and outer components.

* **Electrical System:** This section covers the electrical system, equipment, instruments, speed control systems, auxiliary drives, hydraulic and articulated systems, tools, test instruments, and equipment.

* **Body & Interior:** The comprehensive body section covers the body, understructure, front end, front wall, side wall, rear wall, rear end, roof, glass (panes) and windows, interior equipment, doors, trunk lid, fuel flap, slide roof (sun roof), top, racks, electrical system body (radio, windshield washer system, light range regulator), climate control, emergency equipment, sanitary equipment, kitchen, attachments, outside flaps, seats, cots, restraint systems, body noises, sound insulation, body sealing, anti-corrosion protection, paintwork, and technical literature.

This manual is an invaluable tool for any owner or mechanic looking to work on their 1977-1985 Mercedes-Benz W123 Series 300D, 300CD, or 300TD (Turbo). It provides the necessary information and instructions to confidently tackle any repair or service project, helping you keep your vehicle in top condition and save money on professional repairs.

The Mercedes-Benz W123, produced from 1976 to 1985, is a legendary model known for its robust build quality, timeless design, and exceptional durability. The W123 series was the first Mercedes-Benz to feature a unibody construction, offering improved safety and handling compared to its predecessors. This model offered a wide range of body styles, including sedans, coupes, station wagons, and even a pickup truck. The W123 also introduced several innovative features, such as a 4-speed automatic transmission with overdrive and a fuel-injected diesel engine, setting a new standard for fuel efficiency in luxury vehicles.

The 300D, 300CD, and 300TD models featured a 3.0-liter, naturally aspirated or turbocharged diesel engine, renowned for its reliability and longevity. The 300D delivered smooth performance with about 88 horsepower, while the turbocharged 300TD offered a considerably more potent 123 horsepower, making it remarkably quick for a diesel-powered car of its era. The 300CD was the station wagon variant, offering ample cargo space and versatility for families and outdoor enthusiasts. All three models were praised for their comfortable ride, spacious interiors with high-quality materials, and exceptional build quality, ultimately making them incredibly popular and sought-after vehicles even today.