Market Segment:
Full-size Luxury Sedan
Target Audience:
Owners of Mercedes-Benz 420 SEL (W126), Independent Repair Shops, Automotive Enthusiasts
Key Competitors Era:
BMW 7 Series (E23/E32), Audi V8 quattro, Jaguar XJ, Cadillac Fleetwood, Lincoln Continental
Vehicle Hallmarks:
Exceptional build quality, refined ride comfort, powerful V8 engine, sophisticated engineering, advanced safety features for its time.
Dealer Equivalence:
Same Repair Service manual used by local dealers
Access Method:
Instant Download
Engine Systems:
Engine Mechanical, Fuel Injection (Bosch KE-Jetronic), Ignition System, Cooling System, Lubrication System, Emission Control Systems
Transmission Drivetrain:
Automatic Transmission (722.3/722.4), Driveshaft, Rear Axle, Differential
Chassis Suspension:
Front Suspension, Rear Suspension, Steering System, Level Control System (Hydropneumatic), ADS (Automatic Differential Suspension), 4MATIC All-Wheel Drive System (if applicable to specific sub-models/options)
Braking System:
Hydraulic Brake System, Anti-lock Braking System (ABS), Parking Brake
Electrical System:
Battery, Charging System, Starting System, Lighting, Instrumentation, Fuses, Relays, Electronic Control Units (ECUs), Power Accessories (Windows, Locks, Mirrors, Sunroof, Seats), Climate Control Electronics, Windshield Wipers/Washers
Body Interior:
Body Structure, Exterior Panels, Doors, Hood, Trunk Lid, Bumpers, Interior Trim, Seats, Headliner, Convertible Top (if applicable to other W126 variants, though less common for 420SEL), Audio System, Climate Control Unit
Maintenance Procedures:
Oil Changes, Filter Replacements (Oil, Air, Fuel), Fluid Level Checks and Top-offs (Coolant, Power Steering, Brake, Transmission, Differential), Belt Inspections and Replacements, Spark Plug Replacement, Valve Clearance Adjustment, Cooling System Flush and Refill, Brake Fluid Flush and Bleed, Air Filter Cleaning/Replacement, Lubrication Points
Diagnostic Procedures:
Troubleshooting Guides, Diagnostic Trouble Codes (DTCs) if applicable to onboard diagnostics, Inspection Procedures for all systems, Component Testing
Repair Procedures:
Engine Component Removal and Installation (e.g., cylinder heads, fuel injectors, manifolds), Transmission Overhaul and Repair, Suspension Component Replacement (shocks, struts, bushings, ball joints), Brake Component Replacement (pads, rotors, calipers, lines), Electrical Component Diagnosis and Replacement, Steering System Repair, Body Panel Repair and Alignment
Adjustment Procedures:
Idle Speed Adjustment, Injection Timing Adjustment, Parking Brake Adjustment, Clutch Adjustment (if manual transmission equipped, unlikely for 420SEL), Steering Alignment Specifications
Technical Depth:
Comprehensive: From basic maintenance and fluid changes to advanced engine diagnostics, transmission overhauls, and electrical system troubleshooting. Includes detailed diagrams, torque specifications, and step-by-step repair instructions.
Transmission Type:
4-Speed Automatic Transmission
Transmission Model Code:
722.3 or 722.4
Optional Transmission Type:
N/A for 420 SEL models
Transmission Features:
Comfort-oriented shift points, selectable modes (e.g., Economy/Sport, though less common on early models).
Transmission Fluid Type:
MB 236.3 Specification (e.g., Dexron II or equivalent)
Transmission Fluid Capacity:
Approximately 8 Liters (17 pints) for complete fluid change, less for drain and fill.
Oil Change Interval:
Every 15,000 km (9,300 miles) or 12 months (using synthetic oil)
Transmission Fluid Interval:
Every 60,000 km (37,000 miles) or 2-3 years
Engine Oil Specification:
MB 229.1 or higher quality synthetic oil (e.g., SAE 10W-40 or 15W-40)
Coolant Specification:
MB-Approval 325.0 (Glysantin G05 or equivalent)
Power Steering Fluid:
MB 236.3 Specification (Dexron II or equivalent)
Common Wear Items:
Fuel lines, vacuum hoses, distributor O-rings, climate control blower motor, suspension bushings, window regulators, headliner sagging, ABS sensor failures.
Engine Specific Considerations:
KE-Jetronic system can be sensitive to vacuum leaks and requires precise adjustment. Distributor cap and rotor wear. Spark plug fouling if oil control is poor.
Brand Reputation:
Mercedes-Benz renowned for engineering excellence, durability, luxury, and safety.
W126 Development:
Successor to the W116 S-Class, marked a significant advancement in aerodynamic design, safety, and technology. The W126 was produced in two main phases, with significant updates in 1985 (facelift).
420 Sel Positioning:
The 420 SEL was introduced in 1985 as a response to market demand for a slightly smaller V8 engine, positioned below the 500 SEL and 560 SEL, offering a balance of performance and efficiency.
Production Period For Model:
1986-1991
Manufacturing Location:
Sindelfingen, West Germany
