Positioning:
The W126 was Mercedes-Benz's flagship S-Class sedan, representing the pinnacle of luxury, engineering, and safety for its era. This manual serves owners and independent technicians seeking to maintain and repair these sophisticated vehicles.
Comparison:
Competed with high-end sedans from BMW (e.g., 7 Series), Jaguar (XJ), and Cadillac (Fleetwood).
Distinctive Elements:
Known for its aerodynamic design, advanced safety features for the time (e.g., ABS on later models, early SRS concepts), robust build quality, and luxurious interior. The SEL denotes the long-wheelbase version, offering increased rear passenger space.
Powertrain:
Engine (M110, M117), Fuel System, Cooling System, Lubrication System, Ignition System, Starting System, Charging System, Emission Control System, Automatic Transmission (e.g., 4-speed 722.3)
Chassis:
Front and Rear Suspension, Drive Shaft, Differential, Axles, Brakes (Hydraulic, Parking), Steering System (including Power Steering)
Electrical:
Complete Wiring Schematics, Lighting, Instrumentation, Wipers/Washers, Horn, Power Accessories (windows, locks, seats), Meter/Audio/Visual Systems, Air Conditioning, Cruise Control, Supplemental Restraint System (SRS - early forms), Engine Immobilizer (if applicable)
Body:
Body Shell, Doors, Hood, Exterior Trim, Interior Trim, Glass/Mirrors, Seats, Instrument Panel
Maintenance Procedures:
Scheduled maintenance, fluid checks and changes, filter replacements, belt inspections and adjustments
Diagnostic Procedures:
Troubleshooting guides, fault code interpretation (if applicable), component testing
Repair Procedures:
Step-by-step instructions for engine rebuilds, transmission overhauls, suspension component replacement, brake system repairs, electrical system diagnosis and repair, body panel repair and replacement
Technical Data And Specs:
Torque specifications, clearances, timing settings, fluid capacities, electrical values, diagnostic parameters
Depth:
Factory level, enabling complete diagnosis, maintenance, and repair from basic servicing to major component overhauls.
Engine Code And Type:
Likely M110 (2.8L Inline-6) or M117 (3.8L or 5.0L V8), depending on specific SEL variant for 1981.
Horsepower And Torque:
Varies by engine. For example, the 3.8L M116 V8 (often found in US SEL models) typically produced around 155-160 hp. The 5.0L M117 V8 would offer more power. (Specific figures in manual).
Fuel Delivery:
Bosch K-Jetronic (CIS - Continuous Injection System) or potentially early electronic fuel injection (EFI) depending on the specific engine and market.
Standard Transmission:
Likely a 4-speed automatic transmission (e.g., 722.3).
Optional Transmission:
Manual transmission options were rare on SEL models, especially in the US market.
Transmission Features:
Torque converter lock-up, hydraulic control.
Wheelbase:
W126 SEL (Long Wheelbase) has a significantly longer wheelbase than the standard W126, typically around 3086 mm (121.5 inches).
Length:
Approx. 5170 mm (203.5 inches) for the SEL.
Curb Weight:
Varies by engine and equipment, but typically around 1700-1900 kg (3750-4200 lbs).
Historical Safety Focus:
Mercedes-Benz placed a strong emphasis on safety, incorporating crumple zones, safety cage construction, and advanced restraint systems for the era.
ABS:
Anti-lock Braking System (ABS) became available on W126 models, though may not have been standard on all 1981 SEL variants.
Airbags:
Driver's airbag was introduced later in the W126's lifecycle, so likely not standard on 1981 SEL. Supplemental Restraint System (SRS) was a developing technology.
Audio System:
Factory-installed Becker radio/cassette players were common, often with options for power antenna and multiple speakers.
Cruise Control:
Cruise control was available and a significant technological feature for its time.
Early Electronics:
The manual will cover the extensive electrical system and early integrated electronics for climate control, power accessories, and instrumentation.
Oil Change Interval:
Typically every 5,000 to 7,500 miles (8,000 to 12,000 km) or annually, depending on driving conditions and specific engine oil used. (Manual will specify).
Major Service Intervals:
Includes spark plug replacement, fuel filter replacement, and transmission fluid service, often at intervals of 30,000 miles (48,000 km) or more. (Manual provides detailed schedule).
Engine Oil Type:
API SF or SG classification, viscosity SAE 10W-40 or 10W-30 recommended for many climates, but specific grades are critical. (Manual is the definitive source).
Transmission Fluid Type:
Typically MB-Approval 236.3 Dexron II (or equivalent) for the automatic transmission. (Crucial to use correct fluid).
Coolant Type:
Ethylene glycol-based antifreeze. Manual specifies mixture ratio and MB approval number.
Common W126 Concerns:
Biodegradable wiring insulation (often needs replacement), vacuum leak issues affecting climate control and engine operation, potential rust in specific areas, aging rubber components (suspension bushings, hoses), fuel distributor issues (K-Jetronic).
Mercedes Benz Legacy:
Mercedes-Benz has a long history of automotive innovation and luxury, dating back to the invention of the automobile.
W126 Introduction:
The W126 S-Class was introduced in 1979, succeeding the W116. It was a significant redesign, focusing on aerodynamics, weight reduction, and improved safety and comfort.
Manufacturing Period:
W126 production ran from 1979 to 1991. The 1981 model is part of the early production run.
