🏷️ Basic Information

Make:

Mercedes-Benz

Model:

300 D Turbo

Model Code:

W123 (specific variants may apply, e.g., 300TD Turbo)

Year:

1982-1985

Engine Variant:

OM617.952 (3.0L Turbocharged Diesel)

👋 Introduction

Market Position:

The Mercedes-Benz W123 series, particularly the 300 D Turbo models, represented the pinnacle of reliable, luxurious, and durable diesel sedans and estates of their era, favored by those seeking longevity and exceptional build quality.

Competition:

Competed against other European luxury marques and premium sedans, but stood out with its robust diesel engine technology and renowned Mercedes-Benz engineering, offering a distinct blend of performance and economy.

Key Features:

Robust OM617 turbocharged diesel engine, excellent build quality, comfortable ride, strong resale value, and iconic Mercedes-Benz design.

📋 Manual Details

Coverage:

Comprehensive repair, maintenance, troubleshooting, diagnostics, rebuild, refurbishment, and restoration

Page Count:

Approximately 1500-2000 (typical for detailed service manuals of this era and scope, actual count may vary)

Manual Type:

Factory Authorized Service Manual / Repair Manual

Manual Origin:

Factory-generated or authorized reproduction for service centers.

Language:

English

Format:

Digital (PDF) and/or Print

📖 Manual Coverage

Engine Mechanical:

Disassembly, assembly, inspection, repair, and overhaul of the OM617.952 engine, including cylinder head, block, pistons, crankshaft, camshaft, timing chain, valves, fuel injection system, lubrication system, cooling system, turbocharger system.

Engine Fuel System:

Detailed coverage of the Bosch inline diesel injection pump (e.g., PES 6M 100), injectors, glow plug system, fuel filters, fuel lines, and troubleshooting.

Transmission:

Repair, overhaul, and adjustment of automatic transmissions (e.g., 722.3) and manual transmissions (if applicable to specific models), including torque converter, valve body, clutch packs, and seals.

Drivetrain:

Front and rear axle assemblies, driveshafts, universal joints, differential, half-shafts, and wheel bearings.

Suspension:

Front and rear independent suspension systems, control arms, ball joints, tie rods, bushings, springs, shock absorbers, and sway bars.

Brakes:

Hydraulic brake system, front and rear disc brakes, brake calipers, master cylinder, brake lines, parking brake, and ABS system (if equipped).

Steering:

Power steering system, steering gear, steering column, steering linkage, and associated components.

Electrical System:

Detailed wiring diagrams, battery, starter, alternator, ignition system (if applicable to diesel variants), lighting system, instrumentation, dashboard controls, power windows, central locking, and HVAC controls.

Body And Chassis:

Body panel removal/installation, door mechanisms, window regulators, interior trim, exterior trim, bumpers, and chassis repair.

Heating Ventilation Air Conditioning:

HVAC system components, refrigerant service, blower motor, heater core, A/C compressor, and climate controls.

Maintenance:

Routine maintenance schedules, oil and filter changes, fluid checks and changes, lubrication points, belt tensioning, and battery care.

Troubleshooting:

Systematic diagnostic procedures for common and uncommon faults, symptom-based troubleshooting guides.

Repair:

Step-by-step repair instructions for all major vehicle systems, including component removal, installation, adjustment, and calibration.

Rebuild:

Detailed procedures for complete engine and transmission rebuilds, including specifications for machining, clearances, and torque values.

Diagnostics:

Fault code interpretation (if applicable), testing procedures for sensors, actuators, and control modules.

Body Repair:

Bodywork repair, panel alignment, rust prevention/repair, glass replacement, door and window mechanism servicing.

Diagnostic Tools:

Details on required specialized tools and testing equipment for accurate diagnostics.

Depth:

Expert level, covering from basic adjustments to complete engine and transmission overhauls. Includes detailed technical drawings, schematics, and specifications.

📊 Manual Specifications

File Format:

High-resolution PDF, searchable text content, bookmark navigation.

Print Quality:

Professional printing with clear diagrams and legible text. If digital, ensures clarity on digital displays.

Binding Type:

Perfect bound or spiral bound for ease of use in a workshop environment (for print versions).

Paper Type:

Durable, semi-gloss paper suitable for workshop conditions (for print versions).

Completeness:

Highly complete, intended for professional technicians and serious DIY enthusiasts. Covers all aspects of mechanical, electrical, and body repair.

⚙️ Engine Specifications

Engine Code:

OM617.952

Engine Type:

Inline 5-cylinder, naturally aspirated diesel (pre-turbocharged versions exist, this manual covers turbo variant)

Displacement:

3.0 Liters (2998 cc)

Bore X Stroke:

87.0 mm x 100.0 mm

Compression Ratio:

21.0:1

Valvetrain:

SOHC (Single Overhead Camshaft), 2 valves per cylinder

Power Output Hp Ps:

Approximately 125 hp (93 kW) @ 4350 RPM (specifications can vary slightly by market and exact configuration)

Torque Ft Lb Nm:

Approximately 177 lb-ft (240 Nm) @ 2400 RPM

Turbocharger:

Garrett AiResearch (or similar), providing boost pressure for enhanced performance.

Injection System:

Bosch Inline Injection Pump (PES 6M 100) with mechanical governor and direct injection.

Fuel Type:

Diesel fuel

Oil Capacity:

Approximately 7.5 Liters (with filter change)

Recommended Oil Viscosity:

API CD or ACEA E2, SAE 10W-40 or 15W-40 (check manual for exact OEM specifications, often semi-synthetic or synthetic for turbo diesel).

🔧 Transmission

Transmission Type:

4-speed Automatic Transmission (e.g., 722.3 series)

Transmission Type:

4-speed or 5-speed Manual Transmission (less common on turbo diesel models, check specific market variants)

Automatic Features:

Hydromechanical control, torque converter lock-up (on some later models), efficiency-focused shift points.

Automatic Transmission Fluid:

MB 236.1 Specification (e.g., Dexron II compatible but MB spec is preferred).

Automatic Transmission Fluid Capacity:

Approximately 8-10 Liters (with torque converter).

📐 Dimensions

Body Styles:

Sedan (W123), Coupe (C123), Estate/Wagon (S123), potentially Landaulet/Limousine variants from coachbuilders.

Curb Weight:

Approximately 1500-1650 kg (depending on body style and equipment).

🛡️ Safety Features

Safety Ratings:

While formal crash test ratings from modern organizations are not directly applicable, W123 models were built to high safety standards for their era, featuring a robust chassis and impact-absorbing zones.

Active Safety:

Four-wheel disc brakes (standard on most models), power-assisted steering, independent suspension.

Passive Safety:

Reinforced safety cage, crumple zones, padded interior, collapsible steering column.

💡 Technology Features

Infotainment Features:

Basic analogue radio (often Becker), cassette player, rudimentary speaker systems. Focus on build quality and driving experience rather than advanced tech.

Driver Assistance Features:

ABS (Anti-lock Braking System) was optional and increasingly common on later models. Cruise control was also an option.

Connectivity Features:

No modern connectivity features like Bluetooth or USB. Analog telephone integration was a rare, high-end option.

🔧 Maintenance

Oil Change Interval:

Typically every 5,000-7,500 miles (8,000-12,000 km) or 6-12 months, whichever comes first, depending on driving conditions and oil used. Turbocharged engines may benefit from slightly shorter intervals.

Fuel Filter Replacement:

Every 15,000-30,000 miles (24,000-48,000 km).

Air Filter Replacement:

Every 15,000-30,000 miles (24,000-48,000 km).

Transmission Fluid Change:

Every 30,000-50,000 miles (48,000-80,000 km) or as recommended by the manual.

Valve Adjustment:

Check and adjust if necessary every 30,000-50,000 miles (48,000-80,000 km) or if engine noise is apparent.

Coolant:

50/50 mixture of Mercedes-Benz approved antifreeze and distilled water. Check manual for MB specification number (e.g., MB-Approval 325.0 or equivalent).

Brake Fluid:

DOT 3 or DOT 4 (check manual for specific type and change interval).

Known Issues Common:

Vacuum leaks (affecting central locking, climate control, engine idle), injector pump seal leaks, timing chain stretch (on high mileage), glow plug system issues, rust (especially wheel arches, door bottoms, trunk edges), climate control flap actuators failure, power steering hose leaks.

Turbo Specific Issues:

Turbocharger bearing wear, wastegate issues, intercooler leaks (if equipped).

📚 Vehicle History

Brand Heritage:

Mercedes-Benz has a long-standing reputation for engineering excellence, safety, and durability, particularly with its diesel engines.

Model Evolution:

The W123 series was introduced in 1976, evolving from the W114/W115. The 300 D Turbo variants, introduced later in the production run (around 1977 for some models, refining into the early 80s), offered significantly improved performance over their naturally aspirated predecessors, becoming a benchmark for diesel luxury cars.

Production Years:

W123 series: 1976-1986. Specific 300 D Turbo variants covered in this manual span 1982-1985 within that larger window.

Manufacturing Location:

Primarily West Germany.

🏆 Awards & Recognition

Recognitions:

The W123 series consistently received accolades for its durability, build quality, and comfort. Often cited in classic car circles as one of the most reliable Mercedes-Benz models ever produced. While specific 'awards' from consumer magazines of the era might be scarce compared to modern vehicles, its market reputation and longevity speak volumes.