🏷️ Basic Information

Make:

Mercedes-Benz

Model:

W126 SEL

Year:

1980

Chassis Code:

W126

Body Style Code:

SEL (Long Wheelbase Sedan)

👋 Introduction

Positioning:

The W126 chassis represented Mercedes-Benz's flagship luxury sedan of its era, setting benchmarks in comfort, safety, and engineering. This manual is targeted at owners and independent repair shops seeking authentic, dealership-level repair information.

Advantage:

This manual's primary advantage is its specificity: it is not generic but directly applicable to the 1980 W126 SEL, providing the exact same information used by authorized Mercedes-Benz technicians. This contrasts with generic repair guides that may lack crucial details or specific procedures.

Ease Of Use:

Presented in a single, searchable PDF, eliminating the need to flip through multiple physical volumes.

Digital Convenience:

Printable pages, allowing users to carry only necessary information to the workshop without risking damage to the original digital file.

Diagnostic Tools:

Includes diagnostic procedures and troubleshooting trees essential for complex repairs.

📋 Manual Details

Primary Coverage:

1980 Mercedes-Benz W126 SEL

Secondary Coverage:

All W126 models and sub-variants for 1980, comprehensive A-Z repairs

Estimated Page Count:

Likely over 1000 pages (typical for factory service manuals covering all systems)

Type:

Factory Service and Repair Manual

Language:

English

File Format:

PDF

Digital Delivery:

Speed Download

📖 Manual Coverage

Engine Mechanical:

Detailed disassembly, inspection, repair, and reassembly of all engine components.

Fuel System:

Fuel injection system (Bosch K-Jetronic), fuel pumps, lines, injectors, pressure regulators, and troubleshooting.

Emission Control:

Exhaust gas recirculation (EGR), air injection systems, catalytic converter operation, and emissions troubleshooting.

Cooling System:

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

Lubrication System:

Oil pump, oil filter, oil cooler, oil pan, and lubrication specifications.

Ignition System:

Distributor, ignition coil, spark plugs, ignition control module, timing specifications.

Charging System:

Alternator, voltage regulator, battery, and charging circuit diagnostics.

Automatic Transmission:

Four-speed automatic transmission (e.g., 4G-TRONIC), hydraulic control, valve body, torque converter, and maintenance.

Drivetrain:

Propeller shaft, universal joints, rear axle differential, and axle shafts.

Suspension:

Independent front suspension (double wishbone), independent rear suspension, springs, shock absorbers, and bushings.

Steering:

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

Brakes:

Hydraulic braking system, front disc brakes, rear disc brakes, brake calipers, master cylinder, ABS (if equipped for the year/model), brake fluid specifications.

Parking Brake:

Mechanical parking brake system, cables, and operation.

Climate Control:

Air conditioning system (compressor, condenser, evaporator, refrigerant), heating system, and climate control panel operation.

Electrical System:

Complete vehicle electrical system, including lighting, instrumentation, power windows, central locking, and power seats.

Body And Interior:

Door mechanisms, latches, window regulators, exterior trim, interior trim panels, seats, and headliner.

Wiring Schematics:

Detailed wiring diagrams for all electrical systems, including power distribution and component connections.

Routine Maintenance:

Oil changes, fluid checks and replacements, filter replacements, spark plug replacement, belt inspection and adjustment.

Engine Repair:

Engine overhaul, piston ring replacement, valve seat grinding, crankshaft and connecting rod bearing replacement.

Transmission Service:

Automatic transmission fluid and filter change, transmission overhaul, and clutch adjustments (for manual transmission variants if applicable).

Brake Service:

Brake pad and rotor replacement, brake caliper service, master cylinder replacement, brake bleeding, and ABS troubleshooting.

Suspension And Steering Repair:

Ball joint replacement, tie rod end replacement, shock absorber replacement, power steering pump service.

Electrical Diagnostics:

Troubleshooting electrical faults using wiring diagrams, component testing, and fuse/relay identification.

Climate Control Repair:

Refrigerant system service, component replacement (compressor, drier, expansion valve), and HVAC system diagnostics.

Body Repair And Adjustment:

Door alignment, window adjustment, lock mechanism repair, and exterior trim installation/removal.

Depth:

Comprehensive, from basic maintenance to complete component overhaul and advanced diagnostics, mirroring dealership technician procedures.

📊 Manual Specifications

Compatibility:

Windows (Vista 32/64, XP, ME, 98, NT, 2000) and Mac compatible

Printability:

All pages are printable, with the ability to enlarge images.

Binding:

Digital (PDF format), offering no physical binding but the convenience of printing specific pages.

Digital Medium:

Digital file, replacing the need for physical paper and preventing wear and tear.

⚙️ Engine Specifications

Engine Type:

Likely a V8 gasoline engine, such as the M116 (3.8L) or M117 (5.0L).

Horsepower Torque:

Specific figures vary by engine displacement. For example, the 5.0L M117 engine produced approximately 230-240 hp and 300-320 lb-ft of torque in its early W126 iterations (subject to specific market regulations and tuning).

Injection System:

Bosch K-Jetronic (CIS - Continuous Injection System)

Fuel Type:

Unleaded gasoline (Octane rating as per Mercedes-Benz specifications for the era, typically 91-92 RON)

🔧 Transmission

Type:

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

Type:

Manual transmission was not typically offered on the SEL (long-wheelbase) models; it was available on the standard wheelbase W126 sedans (SE).

Hydraulic Control:

Sophisticated hydraulic control unit for smooth gear shifts and precise operation.

📐 Dimensions

Wheelbase:

Approx. 3080 mm (121.3 inches) for the SEL (long wheelbase)

Length:

Approx. 5160 mm (203.1 inches) for the SEL

Rear Legroom:

Significantly increased compared to the standard W126 SE, offering executive-class rear passenger comfort.

Curb Weight:

Typically in the range of 1800-1900 kg (3968-4189 lbs) depending on engine and options.

🛡️ Safety Features

Crash Safety:

The W126 was a pioneer in passive safety for its time, featuring a reinforced passenger cell, crumple zones, and an advanced steering column design. While formal crash ratings like NHTSA's were not as comprehensive then, the W126 was considered exceptionally safe.

ABS:

Anti-lock Braking System (ABS) was an optional or standard feature on higher-end models by this era.

Airbags:

Driver's side airbag was becoming available as an option or standard on some models/markets around this time, but might not have been standard on all 1980 models.

Seat Belts:

Three-point seat belts for all occupants, with pre-tensioners becoming more common.

💡 Technology Features

Audio System:

Factory-installed radio/cassette player, often with premium sound options. Manual would cover removal, installation, and basic troubleshooting.

Cruise Control:

Optional cruise control system, detailed in the manual for operation and troubleshooting.

Multiplex Communication:

While not 'CAN' in the modern sense, the W126 featured complex electrical systems with interconnected modules. The manual details these connections and diagnostic approaches relevant to the era.

🔧 Maintenance

Oil Change:

Typically every 10,000-15,000 km (6,000-9,000 miles) or 6-12 months, whichever comes first. Specific interval may vary based on driving conditions and oil type.

Transmission Service:

Fluid and filter change typically recommended every 50,000-80,000 km (30,000-50,000 miles).

Engine Oil:

API SF or SG grade, SAE 10W-40 or 15W-40 recommended for moderate climates. Consult manual for specific viscosity by temperature.

Transmission Fluid:

Dexron II or equivalent (MB Specification 236.8 or similar)

Coolant:

50/50 mix of ethylene glycol antifreeze and distilled water. MB Specification 325.0 or similar.

Brake Fluid:

DOT 3 or DOT 4 (MB Specification 331.0 or similar)

Wiring Harness:

Degradation of insulation on older wiring harnesses can lead to electrical issues. The manual would detail testing and repair procedures.

K Jetronic Problems:

Fuel distributor leaks, cold start valve issues, and air flow meter sensor problems are common with K-Jetronic systems. The manual provides diagnostic steps.

Climate Control Failure:

Aging O-rings, seals, and compressor clutch failures can impact A/C performance.

Suspension Wear:

Worn control arm bushings, ball joints, and tie rod ends are common due to age and mileage, leading to steering looseness and tire wear.

📚 Vehicle History

Mercedes Benz Legacy:

Mercedes-Benz has a long-standing reputation for building durable, luxurious, and technically advanced vehicles. The W126 continued this legacy.

W126 Introduction:

The W126 S-Class was introduced in 1979 as the successor to the highly acclaimed W116 S-Class. The SEL designation denotes the long-wheelbase version, emphasizing rear-seat passenger space and luxury.

Production Years:

The W126 chassis was produced from 1979 to 1991, with various updates and facelifted versions during its production run.

🏆 Awards & Recognition

Automotive Engineering:

The W126 S-Class was widely recognized for its engineering excellence, comfort, and safety innovations, often cited in automotive journals of the time as a benchmark luxury sedan.