Segment:
Full-size Luxury Sedan
Key Selling Points:
Exceptional build quality, advanced engineering, luxurious interior, powerful V8 engine, comfortable ride, high safety standards for its era.
Primary Competitors:
BMW 7 Series (E23), Jaguar XJ-S, Rolls-Royce Silver Spirit, Cadillac Fleetwood.
Distinguishing Features:
W126 chassis's aerodynamic design, reputation for durability and longevity, sophisticated engineering, plush interior appointments.
Engine Mechanical:
Engine assembly, cylinder head, valve train, crankshaft, connecting rods, pistons, lubrication system, cooling system, fuel injection system (Bosch KE-Jetronic), exhaust system.
Engine Electrical:
Ignition system, starter motor, alternator, engine control unit (ECU) diagnostics, wiring diagrams.
Transmission:
Automatic transmission (e.g., 722.3 series), torque converter, hydraulic control, shift linkage, transmission fluid and filter service.
Drivetrain:
Drive shaft, universal joints, rear axle assembly, differential, half-shafts.
Suspension:
Front suspension (independent, double wishbone), rear suspension (independent, multi-link), shock absorbers, springs, bushings, steering knuckle assembly.
Steering:
Power steering system, steering box, steering column, tie rods, linkage.
Brakes:
Front disc brakes (ventilated), rear disc brakes, brake hydraulics, ABS (Anti-lock Braking System) if equipped, parking brake.
Electrical System:
Battery, charging system, lighting system (headlights, taillights, interior), power windows, power seats, central locking, climate control system electronics, instrument cluster, fuse box and relay locations.
Bodywork:
Body panel removal and installation, door mechanisms, hood, trunk lid, interior trim, weatherstripping.
HVAC:
Air conditioning system components, heater core, blower motor, control panels, refrigerant handling.
Routine Maintenance:
Oil and filter changes, spark plug replacement, air filter replacement, fuel filter replacement, coolant flush, brake fluid flush, lubrication points.
Diagnostic Procedures:
Troubleshooting charts, fault code interpretation (if applicable), component testing, measurement specifications.
Repair Procedures:
Engine overhaul, transmission overhaul, brake system repair, suspension component replacement, steering system repair, electrical component replacement, body repair.
Component Disassembly Reassembly:
Detailed step-by-step instructions for removing, disassembling, inspecting, repairing, and reassembling all major components.
Special Tools:
Identification and usage of specialized tools required for specific repair and maintenance tasks.
Depth:
Comprehensive factory-level detail suitable for professional mechanics and experienced DIY enthusiasts. Covers everything from basic adjustments to complete engine and transmission rebuilds.
Engine Type:
V8, SOHC (Single Overhead Camshaft)
Displacement:
4.973 Liters (303.5 cubic inches)
Bore X Stroke:
94.5 mm x 85.0 mm
Compression Ratio:
9.2:1 (typical, may vary slightly by market)
Fuel Delivery:
Bosch KE-Jetronic Continuous Injection System (CIS-E)
Horsepower:
Approx. 230-240 hp (DIN) at 4750 rpm (exact figures vary by market and tuning)
Torque:
Approx. 280-288 lb-ft (380-395 Nm) at 2800-3000 rpm
Fuel Type:
Premium Unleaded Gasoline (91+ octane)
Era Specific Ratings:
Considered among the safest sedans of its time due to robust construction and design, though formal crash ratings like NHTSA were less standardized then.
Active Safety:
Four-wheel disc brakes, optional Anti-lock Braking System (ABS), power steering.
Passive Safety:
Reinforced passenger cell, energy-absorbing crumple zones, driver's airbag (introduced on some W126 models during this period, though may not be standard on all '84-'85 500 SEL), seat belts with pre-tensioners, laminated windshield.
Oil Change Interval:
Typically every 5,000-7,500 miles or 12 months, whichever comes first (refer to specific manual for exact recommendation).
Transmission Service:
Fluid and filter change recommended every 30,000-60,000 miles or as per manual.
Coolant Change:
Every 2-3 years or 30,000 miles.
Spark Plug Replacement:
Typically at 30,000-60,000 mile intervals, depending on plug type.
Engine Oil:
API SG/SH, SAE 15W-40 or 10W-40 (check manual for specific viscosity recommendations based on climate).
Coolant:
Mercedes-Benz approved coolant (e.g., G05 or equivalent) with appropriate antifreeze/water mixture.
Transmission Fluid:
MB 236.1 or 236.3 specification ATF (e.g., Dexron II).
Brake Fluid:
DOT 3 or DOT 4 (refer to manual for confirmation).
Common Wear Items:
Ball joints, tie rod ends, control arm bushings, engine mounts, transmission mounts, fuel distributor seals, vacuum lines.
Common Failures:
Fuel distributor issues (KE-Jetronic), vacuum leaks leading to rough idle, blower motor resistor failure, self-leveling suspension components (if equipped), radiator leaks, wiring harness degradation (especially insulation on older models).
Heritage:
Mercedes-Benz has a long-standing reputation for engineering excellence, luxury, and durability since its inception.
W126 Generation:
The W126 S-Class was produced from 1979 to 1991, with significant updates (facelift) in 1985. The 1984-1985 models represent the pre-facelift version of this highly successful generation.
500 Sel Introduction:
The 500 SEL (Long Wheelbase) variant offered increased rear passenger legroom, further emphasizing its luxury positioning.
Production Location:
Germany (primarily Sindelfingen plant)
Production Volume:
The W126 S-Class was a significant volume seller for Mercedes-Benz in the luxury segment, with millions produced globally over its lifespan.
