Mercedes-Benz 500SEC w126 1984-1985 Factory Workshop Service Repair Manual

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🏷️ Basic Information Identification Make: Mercedes-Benz Model: 500SEC Generation Chassis Code: W126 Generation Years: 1979-1992 (C126 Coupe) Codes Model Code Primary: 500SEC 👋 Introduction Market Position Positioning: The Mercedes-Benz 500SEC...

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Type: Car

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Sku: 357792

Tags: 1984 1985 500SEC Car Cars Mercedes Mercedes-benz W126

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Description

🏷️ Basic Information

Identification

Make:

Mercedes-Benz

Model:

500SEC

Generation

Chassis Code:

Generation Years:

1979-1992 (C126 Coupe)

Codes

Model Code Primary:

500SEC

👋 Introduction

Market Position

Positioning:

The Mercedes-Benz 500SEC W126 represented the pinnacle of luxury coupe engineering and performance in the mid-1980s, a grand tourer competing with high-end offerings from BMW and other European luxury manufacturers.

Competitive Analysis

Competitors:

Primarily competed with the BMW 6 Series (e.g., 633CSi, 635CSi) and other exclusive coupes of the era.

Key Features

Coupe Design:

Elegant and timeless coupe body style, designed for comfort and performance, embodying the 'Sophistication through engineering' philosophy of Mercedes-Benz.

Luxury Appointments:

High-quality interior materials, advanced (for the era) comfort features, and a focus on driver and passenger refinement.

Performance Focus:

Powerful V8 engine delivering smooth and strong acceleration, coupled with sophisticated suspension and braking for confident handling.

Manual Value

Value Proposition:

Provides comprehensive, factory-level repair and maintenance data, crucial for preserving the longevity and performance of a classic luxury vehicle like the 500SEC.

📋 Manual Details

Coverage Areas

Years Covered:

1984-1985

Page Count

Estimated Page Count:

Extensive (likely over 1000 pages, typical for full factory service manuals)

Manual Type

Type:

Factory Workshop Service Repair Manual

Language

Language:

English (presumed based on typical availability, dealer technicians use)

Format

Format Description:

HTML/Flash menu with PDF files

Compatibility:

Win95/98/ME/XP/Vista/win7/linux/MAC

📖 Manual Coverage

Systems Covered

Engine:

Complete engine diagnosis, repair, and overhaul for the M117 V8 engine.

Fuel System:

Fuel injection system (Bosch KE-Jetronic), fuel pump, lines, injectors, pressure regulators.

Ignition System:

Ignition timing, coil, distributor, spark plugs, control modules.

Cooling System:

Radiator, fan, water pump, thermostat, hoses, coolant specifications.

Lubrication System:

Oil pump, oil filter, oil passages, oil specifications.

Exhaust System:

Manifolds, catalytic converter, mufflers, exhaust hangers, emissions components.

Transmission:

Automatic transmission (likely 4-speed 722.3 or 722.4), torque converter, valve body, fluid service, overhaul.

Drivetrain:

Driveshaft, universal joints, rear axle, differential, half-shafts.

Suspension:

Front and rear suspension components, control arms, ball joints, bushings, shock absorbers, springs, alignment procedures.

Steering:

Power steering system, steering gear, steering column, tie rods, hydraulic fluid.

Brakes:

Front and rear disc brakes, ABS (if equipped), brake fluid, master cylinder, calipers, lines, parking brake.

Electrical System:

Battery, alternator, starter, wiring diagrams, fuses, relays, lighting system, power accessories.

Climate Control:

HVAC system, blower motor, heater core, evaporator, A/C compressor, refrigerant, climate control panel.

Bodywork:

Exterior trim, body panels, doors, hood, trunk, bumpers, glass, seals.

Interior:

Seats (adjustment, repair, upholstery), dashboard, door panels, headliner, interior trim, seat belts.

Body Electronics:

Power windows, power locks, central locking system, mirrors, sunroof (if equipped), cruise control.

Procedures Included

Maintenance:

Routine maintenance, oil changes, fluid checks and changes, filter replacements, tune-ups.

Diagnostics:

Troubleshooting guides for common and complex issues, symptom-based diagnostics.

Repair:

Step-by-step repair procedures for all major and minor mechanical and electrical components.

Overhaul:

Complete engine and transmission overhaul procedures.

Installation:

Component installation and replacement procedures.

Adjustment:

Carburetor/fuel injection adjustments, ignition timing, valve adjustments (if applicable).

Technical Depth

Depth:

Comprehensive, covering everything from basic maintenance to complete unit rebuilding, suitable for professional technicians and advanced DIYers.

📊 Manual Specifications

File Format

Format:

HTML/Flash menu with embedded PDF files

Print Quality

Quality:

Digital format; printable PDF pages with clear diagrams and text.

Binding Type

Type:

Digital (no physical binding)

Paper Type

Type:

N/A (Digital)

⚙️ Engine Specifications

Primary Engine

Engine Code:

Engine Type:

V8, SOHC (Single Overhead Camshaft)

Displacement:

4973 cc (5.0 Liters)

Bore X Stroke:

96.7 mm x 85.0 mm

Performance

Horsepower Us Spec:

Approx. 230-240 hp @ 4750 rpm (SAE net)

Torque Us Spec:

Approx. 280-290 lb-ft @ 3250 rpm (SAE net)

Fuel System

Injection System:

Bosch KE-Jetronic (CIS-E) Electronic Fuel Injection

Fuel Type:

Unleaded Gasoline (Premium)

Cooling System

Coolant Type:

Mercedes-Benz Specification Coolant (e.g., G48/G40, a silicate-free OAT coolant, or suitable equivalent)

Lubrication System

Oil Type:

SAE 15W-40 or 10W-40 (API SF or SG specification, or MB 228.1/229.1)

Oil Capacity:

Approx. 7.5 - 8.0 Liters (with filter)

Emissions

System:

Catalytic Converter, Lambda Sensor (O2 sensor), secondary air injection (on some models).

🔧 Transmission

Standard

Type:

4-Speed Automatic Transmission

Transmission Model:

722.3 or 722.4 (depending on specific production date)

Optional

Type:

Manual transmission was not typically offered on the SEC models.

Features

Control:

Hydraulic control with electronic kickdown and possibly a "sport" mode selection.

Fluid Specifications

Fluid Type:

Dexron III (or equivalent MB specification for 722.3/722.4 transmissions, e.g., MB 236.1)

Fluid Capacity

Capacity:

Approx. 7.5 Liters (for torque converter refill, total capacity higher)

📐 Dimensions

Exterior

Length:

Approx. 4960 mm (195.3 in)

Width:

Approx. 1810 mm (71.3 in)

Height:

Approx. 1420 mm (55.9 in)

Wheelbase:

Approx. 2850 mm (112.2 in)

Weights

Curb Weight:

Approx. 1750 - 1850 kg (3858 - 4079 lbs)

Gross Vehicle Weight Rating:

Typically around 2300 kg

🛡️ Safety Features

Ratings

Crash Test Era:

While formal NHTSA or Euro NCAP ratings as we know them today were less standardized, the W126 chassis was engineered with advanced safety features for its time, including a robust structure and crumple zones.

Active Features

Anti-lock Braking System (ABS) was available and increasingly common in this period.

Traction Control:

Traction control (ASR - Automatic Slip Regulation) became available on later W126 models, but might not be standard or widely equipped on 84-85 SEC.

Passive Features

Airbags:

Driver-side airbag was introduced as an option on W126 models in the mid-80s and became standard later. Passenger airbag was typically not available on this generation.

Seatbelts:

Three-point inertia-reel seatbelts for all occupants.

Structural Design:

Reinforced passenger cell, energy-absorbing steering column, side-impact protection (door beams).

💡 Technology Features

Infotainment

Audio System:

Factory premium sound systems, often with cassette player and AM/FM radio. Upgrades to modern head units are common.

Driver Assistance

Cruise Control:

Standard cruise control system.

Climate Control:

Automatic climate control (often referred to as THERMATIC) was a significant technological feature, maintaining set temperatures automatically.

Connectivity

Features:

Limited connectivity by modern standards. Features focus on comfort and convenience within the vehicle itself.

🔧 Maintenance

Service Intervals

Oil Change:

Every 7,500 to 15,000 miles (12,000 to 25,000 km) or annually, depending on driving conditions and oil used. Consult manual for exact intervals.

Transmission Service:

Every 30,000 to 50,000 miles (50,000 to 80,000 km) for fluid and filter change. Crucial for longevity of the 722.3/722.4 transmission.

Coolant Flush:

Every 2-4 years or specified mileage.

Spark Plugs:

Typically replaced every 30,000 miles for platinum plugs, or earlier for standard plugs. Consult manual for specific plug type and interval.

Fluid Specifications

Brake Fluid:

DOT 3 or DOT 4 (Low Viscosity, typically MB Spec 331.0 or 332.0)

Power Steering Fluid:

MB Specification 236.3 hydraulic fluid (typically a Dexron-II equivalent at the time, but modern equivalents may vary; check manual).

Known Issues

Fuel System Leaks:

Aging fuel lines and seals can lead to leaks, particularly from the fuel distributor or accumulator on the KE-Jetronic system.

Wiring Harness Degradation:

The original wiring harnesses, especially in engine bay and under dash, can degrade due to heat and age, leading to intermittent electrical faults.

Suspension Bushings:

Rubber suspension bushings (control arms, sway bars) are common wear items and can crack or collapse, affecting ride and handling.

Automatic Transmission Clutches:

The 722.3/722.4 transmissions are robust, but wear on clutch packs and valve body issues can occur with high mileage or poor maintenance.

Climate Control Actuators:

Vacuum-operated or electric actuators for the climate control flaps can fail, leading to poor airflow or temperature control.

Headliner Sagging:

The adhesive holding the headliner fabric to its backing can fail, causing the fabric to sag over time.

Window Regulators:

Power window regulators can become weak or fail, especially the anti-pinch mechanisms.

📚 Vehicle History

Brand Heritage

Heritage:

Mercedes-Benz has a long-standing reputation for building robust, luxurious, and technologically advanced vehicles, with a particular focus on safety and engineering excellence.

Model Evolution

W126 Introduction:

The W126 S-Class platform was introduced in 1979 as the successor to the W116. The C126 coupe variant, including the 500SEC, debuted in 1981.

500Sec Positioning:

The 500SEC was the flagship model of the C126 coupe range for its model years, featuring the potent 5.0-liter V8 engine and high levels of standard equipment.

Production

Production Period:

1981-1991 (C126 Coupe)

Assembly Location:

Sindelfingen, West Germany

🏆 Awards & Recognition

Recognitions

Design:

The W126 generation, including the C126 coupe, is widely regarded as a benchmark in automotive design for its era, praised for its clean lines and aerodynamic efficiency. Often featured in 'best design' lists for the 1980s.

Ratings

Automotive Journalism:

Consistently received high marks from automotive journalists for its comfort, build quality, and performance upon release.

Certifications

Manufactured under ISO 9001 quality management standards.