Market Position:
The Mercedes-Benz 500 SEC represented the pinnacle of personal luxury coupes in the mid-1980s, offering unparalleled comfort, performance, and sophisticated engineering. Positioned as a grand tourer for the discerning individual, it competed with other high-end luxury coupes of its era.
Competitive Analysis:
Competed directly with models like the BMW 6 Series (E24) and potentially higher-trim Jaguar XJ-S models, emphasizing a blend of performance and refined luxury.
Key Features:
Powerful V8 engine, luxurious interior appointments, advanced safety features for its time (e.g., optional ABS), elegant coupe styling, and the renowned Mercedes-Benz build quality and engineering.
Systems Covered:
Engine Mechanical, Engine Fuel System (Bosch K-Jetronic), Engine Electrical System, Ignition System, Cooling System, Lubrication System, Exhaust System, Transmission (Automatic), Drivetrain, Suspension System (Front & Rear), Steering System, Brake System (Hydraulic & ABS), Electrical Systems (Lighting, Instrumentation, Comfort Features), Climate Control System, Body & Chassis, Interior Trim, Wheels & Tires, Diagnostic Procedures
Procedures Included:
Routine Maintenance, Scheduled Servicing, Component Removal & Installation, Overhaul Procedures, Troubleshooting Guides, Diagnostic Flowcharts, Repair Procedures, Adjustment Specifications, Torque Specifications, Wiring Diagrams, Exploded Views
Technical Depth:
Deep technical detail suitable for professional technicians and advanced DIY enthusiasts, covering from basic adjustments to full engine and transmission rebuilds.
Engine Displacement:
5.0 Liters (4973 cc)
Engine Code Identifier:
M117 E50
Horsepower:
Approx. 230-240 hp (depending on market and specific tuning)
Torque:
Approx. 280-300 lb-ft (depending on market and specific tuning)
Fuel Injection System:
Bosch CIS-E (Continuous Injection System with Electronic Control)
Fuel Type:
Premium Unleaded Gasoline
Bore X Stroke:
92.0 mm x 92.4 mm
Oil Capacity With Filter:
8.0 Liters (8.5 US Quarts)
Recommended Oil Viscosity:
SAE 15W-40 or SAE 20W-50 (refer to manual for specific climate and usage recommendations)
Transmission Type:
4-Speed Automatic (4G-TRONIC)
Optional Transmission:
None offered for this model and year range.
Transmission Features:
Lock-up torque converter for improved fuel efficiency at cruising speeds. Electronic control for shift points.
Transmission Fluid Type:
MB 236.1 (e.g., Dexron II or equivalent)
Transmission Fluid Capacity:
Approx. 2.0 Liters (4.2 US Quarts) for change, 8.0 Liters (8.5 US Quarts) for overhaul.
Length:
Approx. 4,960 mm (195.3 in)
Width:
Approx. 1,820 mm (71.7 in)
Height:
Approx. 1,390 mm (54.7 in)
Wheelbase:
Approx. 2,850 mm (112.2 in)
Curb Weight:
Approx. 1,700 kg (3,748 lbs)
Gross Vehicle Weight Rating:
Approx. 2,200 kg (4,850 lbs)
Safety Ratings:
No formal crash test ratings (like NHTSA/Euro NCAP) existed in the same format as today, but Mercedes-Benz was known for robust construction and advanced passive safety features for its era.
Active Safety Features:
Optional Anti-lock Braking System (ABS) - a significant safety advancement at the time.
Passive Safety Features:
Reinforced passenger cell, energy-absorbing steering column, dual-circuit hydraulic brakes, front and rear crumple zones, safety belts with front pre-tensioners (late models/optional).
Airbag Availability:
Driver's side airbag was introduced in later C126 models, but may not be standard or available on early 1984-1985 units.
Infotainment Features:
Analog radio with cassette player, power antenna, manual climate control with optional automatic climate control. Limited by era.
Driver Assistance Features:
ABS (Anti-lock Braking System) was the primary advanced driver assistance feature available.
Connectivity Options:
N/A (No integrated Bluetooth, USB, or smartphone connectivity).
Comfort Features:
Power-adjustable front seats with memory, power windows, power locks, cruise control, automatic climate control (optional), heated seats (optional), electric sunroof (optional).
Oil Change Interval:
Typically every 7,500 - 10,000 miles or 12 months, whichever comes first (refer to manual for precise intervals based on driving conditions).
Major Service Interval:
Significant checks and component replacements usually scheduled around 30,000, 60,000, and 100,000 miles.
Coolant Type:
Mercedes-Benz Specification 325.0 (Ethylene Glycol based, typically a 50/50 mix with distilled water)
Brake Fluid Type:
DOT 3 or DOT 4 (refer to manual for specific recommendation)
Power Steering Fluid Type:
MB 236.3 (Dexron II or equivalent)
Windshield Washer Fluid:
Water with appropriate washer fluid additive for cleaning and freeze protection.
Common Issues:
Wiring harness degradation (especially insulation), fuel distributor diaphragm leaks (Bosch K-Jetronic), OVP relay failure (if equipped with early electronic systems), head gasket leaks, transmission cooling line leaks, suspension component wear (bushings, ball joints), climate control system leaks (R12 refrigerant), window regulator failures, rust in common areas (wheel arches, sills, sunroof frame).
Bosch Kjetronic Notes:
The K-Jetronic system requires precise adjustment and is susceptible to wear in components like the fuel distributor, warm-up regulator, and injectors, all of which are covered in detail in the manual.
Tune Up Components:
Spark plugs (e.g., Bosch W8AC or equivalent), distributor cap, rotor, spark plug wires, fuel filters, air filter, oil filter.
Belt Replacement Intervals:
V-belts (alternator, power steering, A/C) should be inspected regularly and replaced when cracked, frayed, or excessively worn, typically every 30,000-50,000 miles.
Brand Heritage:
Mercedes-Benz boasts a long and prestigious history dating back to the invention of the automobile, renowned for engineering excellence, luxury, and safety innovation.
Model Evolution:
The C126 SEC coupe was based on the W126 S-Class sedan, introducing a sleeker, more aerodynamic design. It replaced the C107 SLC and was produced from 1981 to 1991. The 500 SEC was a high-performance variant introduced in 1980.
Production Years C126:
1981 - 1991
Production Years 500Sec:
1980 - 1985 (model designation varies by market)
Manufacturing Location:
Germany
Automotive Awards:
While specific awards for the 1984-1985 500 SEC are not widely cited in the same way as modern vehicles, the C126 platform was consistently praised for its build quality, luxury, and driving dynamics by automotive journalists of the period.
Industry Ratings:
Consistently ranked among the top luxury coupes by publications like Road & Track and Car and Driver for its segment.
Certifications:
Not applicable in the modern sense; vehicles of this era were designed to meet the safety and emissions standards of their respective markets.
