Vehicle Segment:
Mid-size luxury sedan/wagon
Brand Reputation:
Known for build quality, durability, and engineering excellence
Key Competitors:
BMW 5 Series, Audi 100, Volvo 240 series
Vehicle Focus:
Durability, comfort, robust diesel powertrain
Manual Benefit:
Empowers owners and technicians with factory-level knowledge for effective maintenance and repair
Model Years Covered:
1976-1985
Engine Variants Covered:
3.0L OM617 Diesel Engine
Body Styles Covered:
All Styles Covered (Sedan, Wagon, Coupe, etc.)
Estimated Page Count:
Hundreds of pages (printable)
Manual Type:
Complete Official Full Factory Service Repair Manual
Delivery Method:
Instant Download
Engine:
Detailed overhaul, troubleshooting, fuel system, lubrication, cooling, exhaust
Transmission:
Manual and Automatic Transmission service, overhaul, and troubleshooting
Drivetrain:
Axles, driveshafts, differential, clutch (if applicable)
Brakes:
Hydraulic system, calipers, master cylinder, parking brake, troubleshooting
Suspension:
Front and rear suspension components, alignment specifications, shocks, springs
Steering:
Power steering system, steering gearbox, linkages, troubleshooting
Electrical:
Ignition system, charging system (alternator), starting system (starter), lighting, instruments, wiring diagrams
Body And Chassis:
Body panels, doors, windows, interior trim, chassis components, rust repair guidance
HVAC:
Heating, ventilation, and air conditioning system maintenance and repair
Maintenance:
Scheduled maintenance, fluid changes, filter replacements, inspections
Repair:
Step-by-step repair instructions for all major components and systems
Disassembly:
Complete disassembly procedures for components and systems
Assembly:
Detailed assembly procedures with torque specifications
Troubleshooting:
Diagnostic procedures for common and uncommon issues
Cleaning:
Component cleaning procedures
Reinstallation:
Correct reinstallation procedures for all components
Depth Of Coverage:
Comprehensive: From basic maintenance to complete engine rebuilds and advanced diagnostics
Target Audience:
Professional technicians and experienced DIY mechanics
Engine Type:
Inline-5 Cylinder, Naturally Aspirated Diesel
Displacement:
3.0 Liters (2998 cc)
Horsepower:
Approx. 72-80 hp (depending on variant and emissions regulations)
Torque:
Approx. 123-134 lb-ft (167-182 Nm)
Fuel Injection:
Bosch Mechanical Direct Injection
Cooling Type:
Liquid-cooled
Oil Type Specification:
API CD or ACEA B3/B4 Specification Diesel Engine Oil (e.g., 15W-40 or 10W-40, consult manual for exact specs)
Glow Plugs:
Essential for cold starting
Valve Train:
Overhead camshaft (OHC)
Transmission Type Standard:
4-speed Manual (early models) or 4-speed Automatic (common)
Transmission Type Optional:
5-speed Manual (later models)
Automatic Transmission:
Mercedes-Benz 4G-Tronic (K4B040) – robust and smooth
Automatic Transmission Fluid:
MB-Approval 236.1 or 236.2 (e.g., Dexron-II)
Manual Transmission Fluid:
GL-4 Gear Oil (e.g., 75W-90 or 80W-90)
Crash Safety Philosophy:
Designed with a strong emphasis on passive safety and occupant protection for its era.
Body Structure:
Reinforced passenger safety cell, crumple zones
Interior:
Safety padded dashboard, energy-absorbing steering column
Glass:
Laminated safety glass for windshield
Oil And Filter Change:
Typically every 3,000-5,000 miles (5,000-8,000 km) or annually, refer to manual for exact interval based on usage.
Fuel Filter Replacement:
Recommended every 15,000-30,000 miles (24,000-48,000 km), critical for diesel health.
Air Filter Replacement:
Typically every 15,000 miles (24,000 km) or as needed based on operating conditions.
Coolant Service:
Flush and replace coolant every 2-3 years or per manual recommendation.
Engine Coolant:
MB-Approval 325.0 or 325.2 (Ethylene Glycol based, typically a 50/50 mix with distilled water)
Brake Fluid:
DOT 3 or DOT 4, high-quality glycol-based brake fluid.
Power Steering Fluid:
MB-Approval 236.3 (ATF, but specific properties required, consult manual)
Diesel Specific Issues:
Glow plug system reliability, injector pump maintenance, potential for oil leaks from seals and gaskets.
Common Wear Items:
Suspension bushings, ball joints, exhaust system components, HVAC blower motor.
Body Corrosion:
Prone to rust in common areas like wheel arches, rocker panels, and around windows; rust prevention is key.
Diesel Maintenance Importance:
Proper fuel filtration and maintaining the injection system is paramount for the longevity of the OM617 engine.
Manufacturer:
Mercedes-Benz, renowned for engineering and automotive innovation since the late 19th century.
W123 Introduction:
Introduced in 1976 as the successor to the W114/W115 (Stroke-8) series.
W123 Characteristics:
Known for its robust construction, exceptional longevity, and reliability, especially the diesel models.
W123 Diesel Significance:
The 300D became iconic for its fuel efficiency and durability, making it a popular choice globally.
Production Period:
1976-1985
Production Locations:
Various Mercedes-Benz plants worldwide, including Germany and Austria.
