Vehicle Class:
Full-Size Luxury Sedan
Target Audience:
Owners and independent repair shops specializing in classic Mercedes-Benz vehicles.
Competitors Era:
BMW 7 Series, Audi V8 Quattro, Jaguar XJ, Lexus LS (later in the period).
Vehicle Strengths:
Exceptional build quality, luxurious interior, powerful V8 engine, advanced (for its time) safety features, sophisticated ride quality.
Manual Utility:
Essential for maintaining the complex systems of this luxury vehicle, aiding in accurate diagnosis and repair, preserving the vehicle's value and performance.
Manual Coverage Years:
1986, 1987, 1988, 1989, 1990, 1991
Estimated Page Count:
Extensive (specific number not provided, but typical for comprehensive service manuals)
Type:
Service and Repair Manual
Operating Systems:
Win95/98/ME/XP/vista/7/8/Linux/MAC, iOS, Android
Delivery Method:
Instant Download
Powertrain:
Engine (M116 V8), Fuel System, Ignition System, Cooling System, Exhaust System, Automatic Transmission (722.3), Transfer Case (for 4MATIC), Clutch System (for manual transmission variants, though less common on SEL models)
Chassis:
Suspension (including Level Control, ADS, ASD), Steering System, Front Axle, Rear Axle, Brakes (including ABS), Wheels and Tires
Body And Electrical:
Body Structure, Water Leakage, Corrosion Inspection, Doors, Hood, Sunroof, Soft Top (if applicable), Wiper and Washer Systems, Lighting (Headlamps, Exterior Lamps), Electrical System (Warning Lamps, Indicator Lamps), Climate Control (AC, Heating), Hydraulic Systems (Top operation), Lubrication Points
Maintenance:
Oil and Filter Changes (Engine, Transmission, Axles), Fluid Level Checks and Corrections, Filter Replacements (Fuel, Air, Dust, Charcoal), Belt Inspections and Adjustments, Spark Plug Checks and Replacements, Valve Clearance Checks and Adjustments, Ignition Timing Adjustments, Coolant Replacement, Brake Fluid Replacement
Repair And Diagnostics:
Component Inspection, Line and Hose Inspection, Suspension and Body Structure Inspection, Fuel System Condition Checks, Steering Play Checks, Brake System Checks (Pads, Discs, Lines, Parking Brake), Hydraulic Top System Checks, Electrical System Diagnostics (Warning Lamps), Troubleshooting of Vehicle-Related Problems
Rebuilding And Assembly:
Disassembly, Inspection of Parts for Reuse, Rebuilding and Assembly of Components (general application across various systems)
Depth Of Coverage:
Comprehensive: Covers routine maintenance, diagnostics, troubleshooting, and detailed repair procedures for most major systems. Aimed at both professional mechanics and advanced DIY enthusiasts.
Engine Type:
V8, SOHC (Single Overhead Camshaft)
Displacement:
4.2 Liters (4196 cc)
Bore X Stroke:
92.0 mm x 78.9 mm
Compression Ratio:
9.2:1 (typical)
Horsepower Peak:
Approximately 220-230 hp (SAE net) depending on year and emission controls
Torque Peak:
Approximately 260-270 lb-ft (SAE net) depending on year and emission controls
Fuel Delivery:
Bosch KE-Jetronic Electronic Fuel Injection (with Lambda control)
Fuel Type:
Unleaded Premium Gasoline (91 Octane or higher)
Coolant Capacity:
Approximately 10.5 Liters (with heat)
Coolant Type:
Mercedes-Benz approved Antifreeze/Coolant (e.g., G05)
Type:
4-Speed Automatic Transmission
Transmission Model:
722.3 (e.g., 722.341 for 420SEL)
Type:
Rarely, a 5-speed manual was an option on lower trims, but highly unlikely on a 420 SEL.
Shift Modes:
Standard P-R-N-D-3-2 or P-R-N-D-4-3 depending on specific variant and year.
Fluid Type:
Mercedes-Benz Specification 236.6 or equivalent ATF (e.g., Dexron III for later years, but check manual for exact spec)
Transmission Fluid Capacity:
Approximately 2.5 Liters (for dry fill, pan fill is less)
Crash Test Results:
Generally rated highly for its era due to robust construction and safety features. Specific official ratings from modern bodies are not directly comparable.
ABS:
Standard Anti-lock Braking System (ABS)
Asd:
Optional Automatic Locking Differential (ASD) available on some models.
4Matic:
Optional All-Wheel Drive system (4MATIC) available on some models.
Airbags:
Driver's side airbag became standard in later years of the W126 generation.
Seatbelts:
Front and rear seat belts, including pretensioners for front belts.
Crumple Zones:
Designed with advanced crumple zones for occupant protection.
Audio System:
Premium audio systems available from Becker or Blaupunkt, often with cassette decks and AM/FM tuners.
Climate Control:
Automatic Climate Control (THERMATIC) and optional dual-zone climate control.
Cruise Control:
Standard cruise control system.
Level Control System:
Hydraulic self-leveling suspension (Level Control) on the rear axle for maintaining ride height under load.
Early Connectivity:
Limited to antenna mast operation and basic electrical connections. No modern Bluetooth or USB integration.
Oil Change Interval:
Typically every 7,500-10,000 miles or 12 months, whichever comes first. Refer to manual for specific recommendation.
Transmission Service:
Every 30,000-50,000 miles for fluid and filter change. Check manual for exact interval.
Air Filter Replacement:
Every 15,000-30,000 miles or as needed based on driving conditions.
Power Steering Fluid:
Mercedes-Benz Specification 236.3 or equivalent (e.g., Pentosin CHF 11S or equivalent hydraulic fluid for ADS/Level Control systems).
Brake Fluid:
DOT 4 Low Viscosity (LV) or DOT 3, depending on ABS system requirements. Always use fresh fluid.
Common Problems:
Wiring harness degradation (especially in the engine bay), vacuum leaks affecting climate control and engine operation, seal and gasket deterioration, potential for head gasket issues on high-mileage engines, ABS sensor failures, rust in common areas (wheel wells, rocker panels, door bottoms).
Maintenance Importance:
Proactive maintenance is crucial for these vehicles to prevent costly repairs and ensure reliability. The manual provides the guidance to achieve this.
Brand Focus:
Mercedes-Benz is renowned for its engineering prowess, luxury, safety, and durability.
W126 Lineage:
The W126 succeeded the W116 S-Class and was itself succeeded by the W140. It represented a significant advancement in automotive design and technology.
420 Sel Positioning:
The 420 SEL, with its long wheelbase (SEL), offered increased rear legroom and was positioned as a high-spec, comfortable luxury cruiser.
Manufacturing Location:
Germany (primarily Sindelfingen plant)
Production Period:
The W126 was produced from 1979 to 1991, with the 420 SEL model introduced later in its lifecycle.
