Target Audience:
Mercedes-Benz 300 SD Turbo owners and independent mechanics seeking detailed repair and maintenance guidance.
Value Proposition:
Provides comprehensive, year-specific service information for a critical period of the W126 chassis diesel models, essential for maintaining these robust vehicles.
Key Features:
Covers multiple model years, detailed diagnostic and repair procedures, component inspection guidelines, fluid specifications, and troubleshooting tips.
Engine Systems:
Engine disassembly, inspection, rebuilding, component condition, oil & filter change, valve clearance adjustment, injection timing, fuel system, air intake, cooling system, V-belts, exhaust system
Transmission Systems:
Manual transmission oil change & level checks, Automatic transmission fluid & filter change, fluid level checks, transfer case fluid change & level checks
Suspension And Steering:
Suspension and body structure inspection, self-leveling suspension, level control (ADS, ASD, 4MATIC) fluid level, front axle oil level, rear axle oil change & level, ball joints, steering play, steering bolts, throttle linkage
Brake Systems:
Brake fluid level, brake lines, brake pads & disk thickness, brake disks, parking brake cable & adjustment, brake fluid replacement, parking brake check
Electrical Systems:
Warning & indicator lamps, battery fluid level, antenna mast, headlamp & exterior lamp inspection, windshield wiper & washer system
Body And Chassis:
Water leakage & corrosion inspection, wheel inspection & tightening, drive shaft flexible coupling, lower noise encapsulation panels, engine compartment lower panel removal/installation, door hinges & locks lubrication, sunroof maintenance, soft top checks, body paint damage inspection
Climate Control:
AC refrigerant charge, dust filter replacement, active charcoal filter replacement, recirculating air filter replacement, windshield washer fluid level
Maintenance Procedures:
Routine fluid changes (oil, coolant, transmission, axle), filter replacements (oil, fuel, air, dust), belt inspections, spark plug checks, tire pressure adjustment, lubrication points
Diagnostic Procedures:
Troubleshooting vehicle problems, component condition inspection, line and hose inspection, suspension inspection, corrosion inspection, idle speed adjustment, injection timing checks
Repair Procedures:
Disassembly, inspection of parts for reuse, rebuilding, assembly of components, fuel filter replacement, air filter replacement, oxygen sensor replacement, spark plug replacement, coolant replacement, engine mount adjustment, clutch disk wear check, brake fluid replacement
Technical Depth:
Comprehensive; covers basic maintenance to component rebuilding and diagnostic procedures for mechanics and knowledgeable DIY enthusiasts.
Engine Type:
Inline 5-cylinder, turbocharged diesel
Displacement:
3.0 Liters (2998 cc)
Horsepower Approx:
123 hp @ 4350 rpm (varies slightly by year and specific output)
Torque Approx:
184 lb-ft (249 Nm) @ 2400 rpm (varies slightly by year and specific output)
Fuel Injection System:
Bosch inline injection pump with mechanical governor
Recommended Fuel:
Diesel fuel
Valve Adjustment Interval:
Typically every 10,000-15,000 miles or as specified in the manual.
Injection Timing Adjustment:
As needed, especially after fuel system work or if performance issues arise.
Glow Plugs:
Essential for cold starting; manual covers inspection and replacement.
Transmission Type:
4-speed automatic (common), 5-speed manual (less common for SD Turbo models, but covered in general W126 manuals)
Automatic Transmission Model:
722.3 (e.g., 722.303)
Automatic Transmission Fluid Type:
Dexron III (or equivalent specification as per Mercedes-Benz)
Automatic Transmission Fluid Capacity:
Approximately 7-8 liters for a complete fluid and filter change (refer to manual for exact capacity).
Manual Transmission Oil Type:
GL-4 or GL-5 gear oil (specific viscosity recommended in manual)
Engine Oil Change Interval:
Every 3,000-5,000 miles or 6-12 months, depending on driving conditions (refer to manual for specific recommendations).
Fuel Filter Replacement Interval:
Typically every 15,000-20,000 miles or as indicated by symptoms.
Cooling System Service:
Coolant flush and replacement every 2-3 years or as recommended.
Engine Oil Specification:
API CD or CE rated diesel engine oil, viscosity 15W-40 or 10W-40 (refer to manual for exact MB approval).
Coolant Specification:
Mercedes-Benz approved coolant (e.g., G05 or equivalent)
Brake Fluid Specification:
DOT 3 or DOT 4 hydraulic brake fluid.
Known Issues:
Vacuum system leaks (affecting door locks, climate control), rust in common areas (wheel wells, door bottoms), injector pump wear, glow plug system faults, potential for head gasket issues if overheated.
Brand Heritage:
Mercedes-Benz has a long-standing reputation for engineering excellence, durability, and luxury, particularly in its diesel models.
Model Evolution:
The W126 S-Class, introduced in 1979, represented a significant step forward in automotive safety and comfort. The 300 SD Turbo (often referred to as the 'SD' in North America) was the entry-level diesel model, known for its fuel efficiency and longevity.
Production Period W126:
1979-1991
300Sd Turbo Production Years:
1980-1985 (primarily for the US market, later models were 300SDL)
Manufacturing Location:
Germany
