Vehicle Segment:
Full-size Luxury Sedan
Target Audience Manual:
Owners seeking to maintain, repair, or restore their Mercedes-Benz 420 SEL, DIY enthusiasts, independent repair shops.
Contemporary Competitors:
BMW 7 Series (E23/E32), Audi V8 quattro, Jaguar XJ6, Cadillac Fleetwood Brougham, Lincoln Town Car.
Vehicle Features Highlight:
Long wheelbase (SEL designation), powerful V8 engine, sophisticated suspension, luxurious interior, advanced safety features for its era.
Manual Value Proposition:
Provides professional-level repair and maintenance information, empowering owners with the confidence and knowledge to service their vehicle independently.
Applicable Years:
1986, 1987, 1988, 1989, 1990, 1991
Specific Models:
Mercedes-Benz 420 SEL
Estimated Page Count:
Comprehensive (Specific number not provided, but implied to be extensive)
Manual Type:
Service and Repair Manual
File Format:
PDF / WINRAR (Digital Download)
Engine:
Engine mechanical, fuel injection, ignition, lubrication, cooling, exhaust
Transmission:
Manual Transmission (if applicable to specific VINs), Automatic Transmission (4-speed 4G-TRONIC)
Drivetrain:
Rear Wheel Drive (RWD), Front axle, Rear axle, Driveshaft
Suspension:
Front and rear suspension, Level control systems (ADS, 4MATIC), ball joints
Brakes:
Hydraulic braking system, parking brake, brake fluid, pads, discs, lines
Steering:
Power steering system, steering column, steering play
Electrical:
Battery, charging system, starter, lighting, ignition, wiring schematics
Body And Chassis:
Body structure, corrosion, water leaks, door hinges, locks, hood, sunroof, soft top, exterior lamps
Climate Control:
Heating, ventilation, air conditioning (HVAC), dust filters, refrigerant charge
Maintenance:
Regular service, oil and filter changes, fluid checks and replacements, belt inspection, spark plug replacement
Diagnostics:
Troubleshooting, component condition inspection, system checks (fuel, ignition, cooling)
Repair Rebuild:
Engine rebuild procedures, transmission overhauls, brake caliper replacement, suspension component replacement
Adjustments:
Valve clearance adjustment, idle speed adjustment, injection timing adjustment, parking brake adjustment
Inspections:
Component condition, lines and hoses, suspension, body structure, water leakage, corrosion, brake system, steering play
Depth Of Coverage:
Comprehensive: Covers basic maintenance to advanced diagnostics and full rebuild procedures, mirroring professional technician information.
Detail Level:
Step-by-step instructions, detailed diagrams, illustrations, and wiring schematics.
Engine Type:
Naturally Aspirated V8
Displacement:
4.2 Liters (4196 cc)
Bore X Stroke:
92.0 mm x 78.9 mm (approximate)
Compression Ratio:
9.2:1 or 10.1:1 (depending on specific market/emission standards)
Horsepower Peak:
Approx. 180-228 hp (DIN/SAE, depending on model year and market)
Torque Peak:
Approx. 310-320 Nm (229-236 lb-ft) (depending on model year and market)
Fuel Delivery:
Bosch KE-Jetronic (CIS-E) or similar mechanical/electronic fuel injection system
Fuel Type:
Premium Unleaded Gasoline (91 Octane or higher)
Transmission Type:
4-speed Automatic Transmission (4G-TRONIC)
Manual Transmission Availability:
Rarely, if ever, offered for the 420 SEL model in most markets. Primarily automatic.
Automatic Transmission Features:
Lock-up torque converter, multiple driving modes (e.g., S/E - Sport/Economy)
Crash Test Data:
Limited official crash test data from this era readily available. Known for robust German engineering and build quality.
Driver Assistance Era:
ABS (Anti-lock Braking System), ASD (Automatic Slip Differential) on some models, ADS (Adaptive Damping System) on some models, 4MATIC all-wheel drive available on some variants.
Passive Safety:
Reinforced chassis, crumple zones, safety steering column, padded interior, seat belts.
Audio System:
Factory AM/FM stereo cassette player, optional premium sound systems.
Climate Control Tech:
Automatic climate control with manual overrides, often featuring recirculating air function and cabin air filters.
Advanced Features Era:
While not considered 'driver assistance' by modern standards, features like ABS, optional ASD/ADS, and the robust chassis design were at the forefront for their time.
Connectivity Features:
Very limited by modern standards. Primarily focused on vehicle mechanics and comfort. No Bluetooth or integrated smartphone connectivity.
Oil Change Interval:
Typically every 7,500 - 10,000 miles or 12 months, using high-quality synthetic oil.
Major Service Intervals:
Refer to manual for specific mileage/time-based major service recommendations (e.g., coolant flush, transmission service, spark plug replacement).
Engine Oil Spec:
API SG or higher, SAE 10W-40 or 15W-40 (check owner's manual for specific temperature ranges and approvals).
Automatic Transmission Fluid Spec:
MB-Approval 236.1 or 236.6 (e.g., Dexron II or equivalent with MB approval)
Coolant Spec:
Ethylene glycol based coolant with corrosion inhibitors (MB-Approval 325.0 or 326.0)
Brake Fluid Spec:
DOT 3 or DOT 4
Common Wear Items:
Fuel lines (especially rubber components), vacuum lines, fuel pump relay, ABS sensors, suspension bushings, valve cover gaskets, distributor cap/rotor (if applicable to specific year/variant).
Engine Specific Concerns:
Timing chain tensioner wear (M116), potential for oil leaks, vacuum system integrity is crucial for fuel injection performance.
Mercedes Benz Legacy:
Pioneer in automotive engineering, luxury, and safety, with a reputation for quality and longevity.
W126 Generation Development:
The W126 succeeded the W116 S-Class and was a significant evolution in aerodynamic design, safety, and technology. The 420 SEL was introduced in 1985 as part of a mid-cycle refresh.
Production Period:
The W126 generation was produced from 1979 to 1991. The 420 SEL specifically was produced from 1985 to 1991.
Manufacturing Location:
Germany (primarily Sindelfingen Plant)
Automotive Press Acclaim:
Consistently ranked among the finest luxury sedans of its era by automotive journalists for comfort, build quality, and engineering.
Reliability Perception:
Generally considered to be well-engineered and durable, though maintenance history is critical. Parts can be expensive but are often high quality.
Safety Certifications Era:
Met all prevailing safety standards for its production years. Mercedes-Benz often exceeded baseline requirements.
