🏷️ Basic Information

Make:

Mercedes-Benz

Model:

W126 SEC

Year:

1981

Chassis Code:

W126

Body Style Code:

C126

👋 Introduction

Target Audience:

Mercedes-Benz W126 SEC owners, independent repair shops, and automotive enthusiasts.

Comparison To Generic:

Significantly more detailed and specific than generic repair guides; dealership-level accuracy.

Digital Benefit:

Single, easy-to-use PDF manual; no need to flip through multiple books; printable pages for garage use.

Completeness:

Covers all models and all repairs A-Z for the specified year.

📋 Manual Details

Covered Models:

All W126 SEC models for 1981

Estimated Pages:

Extensive (specific number not provided, but described as comprehensive for A-Z repairs)

Type:

Service and Repair Manual

Language:

English

Digital Format:

PDF

📖 Manual Coverage

Engine:

Complete engine service, including diagnosis, overhaul, and component testing.

Fuel System:

Fuel injection system (Bosch K-Jetronic likely), fuel pump, injectors, fuel lines, and fuel tank service.

Ignition System:

Ignition control module, distributor, spark plugs, ignition coils, and wiring.

Cooling System:

Radiator, water pump, thermostat, hoses, fan clutch, and coolant specifications.

Lubrication System:

Oil pump, oil filter, oil pressure, and lubrication intervals.

Emission Control:

Air injection, catalytic converter systems, and emission control component diagnosis.

Transmission:

Automatic transmission service, diagnosis, and repair (likely 4-speed automatic).

Drivetrain:

Driveshaft, universal joints, differential, and axle service.

Suspension:

Front and rear suspension components, including control arms, ball joints, bushings, and springs.

Steering:

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

Brakes:

Front and rear disc brake systems, hydraulic circuits, brake fluid specifications, and parking brake.

Electrical System:

Comprehensive wiring schematics, component testing, lighting, charging system, and starter.

Body And Interior:

Door locks, windows, seats, interior trim, engine hood, and exterior body panels.

Climate Control:

Air conditioning system service, refrigerant, and climate control unit operation.

Instrumentation:

Instrument cluster, gauges, warning lights, and related sensors.

Maintenance:

Regular maintenance procedures, fluid changes, filter replacements, and lubrication schedules.

Diagnostics:

Troubleshooting guides, symptom-based diagnostics, and fault finding for all systems.

Repair:

Detailed step-by-step instructions for component removal, repair, and reinstallation.

Adjustment:

Adjustment procedures for engine timing, idle speed, brake systems, and other critical components.

Specifications:

Torque values, clearances, fluid capacities, electrical resistance, and other critical data.

Depth:

Factory-level, comprehensive (A-Z coverage), suitable for professional technicians and advanced DIYers.

Illustrations:

Includes detailed diagrams and illustrations for clarity.

Schematics:

Complete wiring schematics for all electrical systems.

📊 Manual Specifications

Digital Format:

PDF

Compatibility:

Windows (Vista, XP, ME, 98, NT, 2000) and Mac OS compatible.

Printable:

Yes, all pages are printable.

Image Scaling:

Images can be blown up and printed at enlarged sizes.

Binding:

Digital (PDF), no physical binding.

Paper Format:

N/A (digital format, print as needed).

Reader Requirements:

Adobe PDF Reader (free).

Compression Requirements:

Winzip (free).

⚙️ Engine Specifications

Engine Type:

Likely M116 V8 (for 500 SEC) or M117 V8 (for 560 SEC, though 560SEC was later in W126 series).

Displacement:

For 1981, likely 3.8L (M116) or 5.0L (M117) V8.

Engine Code:

Likely M116 or M117 series.

Horsepower:

Variable by engine size, e.g., M116 3.8L approx. 155-160 hp, M117 5.0L approx. 230 hp (DIN).

Torque:

Variable by engine size.

Injection System:

Bosch K-Jetronic (CIS - Continuous Injection System).

Fuel Type:

Unleaded gasoline.

Coolant Type:

Proprietary Mercedes-Benz coolant or equivalent, typically 50/50 mix with distilled water.

🔧 Transmission

Transmission Type:

Automatic

Transmission Gears:

Likely 4-speed automatic transmission (e.g., 722.3).

Transmission Fluid Spec:

MB 236.3 (e.g., Dexron II or equivalent).

Transmission Fluid Capacity:

Refer to manual for exact capacity, typically around 8-10 liters for a complete fluid change.

📐 Dimensions

Body Style:

2-door Coupe (SEC)

Wheelbase:

2895 mm (114.0 inches)

Length:

4965 mm (195.5 inches)

Width:

1820 mm (71.7 inches)

Height:

1390 mm (54.7 inches)

Curb Weight:

Approx. 1700-1800 kg (3750-3970 lbs) depending on engine and options.

🛡️ Safety Features

Safety Standards:

Designed to meet rigorous Mercedes-Benz safety standards of the era, including reinforced A, B, and C pillars.

Antilock Brakes:

ABS (Anti-lock Braking System) was optional and increasingly common on higher-end models like the SEC.

Airbags:

Driver-side airbag was an option, becoming more common later in the W126 generation.

Seat Belts:

Front and rear seat belts, often with pre-tensioners as an option.

💡 Technology Features

Audio System:

Original systems would typically be analog radio with cassette player, often with premium sound options.

Cruise Control:

Factory cruise control was a common option.

Climate Control System:

Sophisticated automatic climate control (often vacuum operated with thermoelectric cooling elements) was a hallmark feature.

Connectivity Features:

Limited by modern standards; primarily analog systems, with no digital connectivity or infotainment integration.

🔧 Maintenance

Oil Change Interval:

Typically every 10,000-15,000 km (6,000-9,000 miles) or 12 months, depending on driving conditions and oil used.

Transmission Fluid Service:

Recommended every 50,000-60,000 km (30,000-37,000 miles) or as per manual, including filter and gasket replacement.

Spark Plug Replacement:

Intervals vary by plug type, but generally around 40,000-60,000 km (25,000-37,000 miles).

Engine Oil Spec:

API SF or SG classification, viscosity SAE 10W-40 or 15W-40, depending on climate. Always consult manual for precise spec.

Brake Fluid Spec:

DOT 3 or DOT 4 brake fluid.

Common Problems:

Vacuum leak issues related to the climate control and fuel system, biodegrading wiring insulation (especially later in the model's life), potential head gasket leaks on higher mileage engines, and wear on suspension bushings.

Preventative Maintenance:

Regular inspection and replacement of rubber hoses and seals, checking vacuum lines, and monitoring for any fluid leaks are crucial.

📚 Vehicle History

Brand Legacy:

Mercedes-Benz is renowned for engineering excellence, luxury, and safety, setting standards in automotive innovation.

W126 Generation:

The W126, produced from 1979 to 1991, succeeded the W116 S-Class and introduced significant advancements in safety and aerodynamics. The SEC (C126) was the coupe variant, known for its pillarless windows and elegant styling.

Production Period:

The W126 SEC (C126) was produced from 1981 to 1991.

Manufacturing Location:

Germany

🏆 Awards & Recognition

Market Perception:

The W126 SEC is highly regarded as a symbol of 1980s automotive luxury, engineering prowess, and timeless design, often considered a modern classic.