🏷️ Basic Information

Make:

Mercedes-Benz

Model:

W126 SEC

Model Year:

1989

Chassis Code:

W126

Body Style Code:

C126 (Coupé)

👋 Introduction

Vehicle Segment:

Luxury Grand Tourer Coupé

Target Audience:

Discerning individuals seeking a sophisticated and powerful personal luxury vehicle.

Key Competitors:

BMW 6 Series (E24), Jaguar XJ-SC, Aston Martin Virage.

Vehicle Attributes:

Elegant styling, powerful V8 engines, high-quality interior appointments, advanced engineering for its time, comfortable ride.

Benefit For Owner:

Empowers owners to perform maintenance and repairs accurately, reducing reliance on external service providers and preserving vehicle value.

Accuracy Claim:

Exact manual used by dealership technicians, ensuring vehicle-specific accuracy.

📋 Manual Details

Primary Coverage:

1989 Mercedes-Benz W126 SEC Coupé

Model Variants Covered:

All 1989 W126 SEC models, including all engine and trim variations specific to the 1989 model year.

Estimated Page Count:

Likely 800-1200 pages (typical for comprehensive factory service manuals of this era, though exact count not provided).

Type:

Factory Service and Repair Manual

Language:

English

Format:

Digital (PDF)

📖 Manual Coverage

Engine Systems:

Engine mechanical, fuel system, ignition system, lubrication, cooling system, emission control, intake and exhaust.

Transmission Systems:

Automatic transmission (likely 4-speed 722.3/722.4 for SEC models), clutch (where applicable for auxiliary systems), manual transmission (unlikely for SEC, but listed as potential coverage if any variations exist).

Drivetrain Systems:

Transfer case/propeller shaft, drive shafts, differential, axle suspension, wheels and tires.

Brake Systems:

Brake control, hydraulic braking system, parking brake.

Steering Systems:

Steering column, power steering.

Electrical Systems:

Starting and charging system, lighting, instrumentation, power windows, central locking, power seats, power mirrors, cruise control, wipers/washers, horn, multiplex/CAN communication (early forms).

Climate Control Systems:

Air conditioning system, heating.

Body And Interior Systems:

Engine hood/doors, exterior trim, interior trim, seats, windshield/glass/mirrors, instrument panel, supplementary restraint system (SRS - airbags, seatbelt pre-tensioners), seat belts.

Safety And Security Systems:

Engine immobilizer (if equipped), supplementary restraint system (SRS), seat belts, door locks.

Maintenance Procedures:

Scheduled maintenance, fluid level checks, filter replacements, lubrication, tune-ups, pre-delivery inspections (PDI).

Diagnostic Procedures:

Troubleshooting guides, diagnostic flowcharts, identification of common faults, specific component testing procedures.

Repair Procedures:

Step-by-step instructions for component removal, disassembly, repair, reassembly, and installation for all covered systems.

Electrical Repair Procedures:

Wiring schematic interpretation, component testing, troubleshooting electrical circuits, connector diagnosis.

Specification Data:

Torque specifications, clearances, tolerances, fluid capacities, pressure specifications, electrical resistance values.

Depth:

Factory-level, comprehensive A-Z coverage for all repairs and maintenance.

Detail Level:

High detail with step-by-step instructions, diagrams, illustrations, and wiring schematics.

📊 Manual Specifications

File Type:

PDF

Readability:

Searchable text (typical for professional PDFs), allows zooming for detail.

Printability:

Fully printable, allowing users to print specific sections or diagrams as needed.

Binding:

Digital (no physical binding)

Paper Quality Simulated:

Printable on any standard paper; original factory manuals were printed on high-quality paper stock.

⚙️ Engine Specifications

Engine Type:

M117 V8 (SOHC)

Displacement:

5.0 Liters (M117.968)

Horsepower:

Approximately 238 hp (DIN) @ 4750 rpm (for 500 SEC, European spec; US spec may vary slightly due to emissions).

Torque:

Approximately 405 Nm (299 lb-ft) @ 2750 rpm (for 500 SEC, European spec).

Fuel Delivery:

Bosch KE-Jetronic (CIS-E) Fuel Injection (K-Jetronic with electronic control).

Fuel Type:

Unleaded Premium Gasoline (91+ octane recommended).

Coolant Type:

Mercedes-Benz specification coolant (e.g., MB 325.0 / G48, typically a glycol-based antifreeze with corrosion inhibitors).

Oil Type:

API SG or higher, SAE 10W-40 or 10W-30 (depending on climate, consult manual for precise W126 specifications).

Oil Change Interval:

Typically 10,000 km or 6,000 miles / 12 months, whichever comes first (consult manual for exact interval).

🔧 Transmission

Type:

4-speed Automatic Transmission

Model Code:

722.3XX or 722.4XX (e.g., 722.364 for 500 SEC).

Control:

Hydraulic control with electronic feedback (KÜMBA system).

Fluid Type:

MB 236.1 specification Automatic Transmission Fluid (ATF), typically Dexron IIE or equivalent approved fluid.

Fluid Change Interval:

Typically 50,000 km or 30,000 miles (consult manual for exact interval).

📐 Dimensions

Length:

Approx. 4960 mm (195.3 in)

Width:

Approx. 1798 mm (70.8 in)

Height:

Approx. 1387 mm (54.6 in)

Curb Weight:

Approx. 1750 - 1850 kg (3858 - 4079 lbs), depending on equipment.

🛡️ Safety Features

Crash Safety Design:

Designed with advanced crumple zones and safety cage for its era.

Brake System:

Anti-lock Braking System (ABS) - standard on SEC models.

Airbags:

Driver-side airbag was becoming standard or optional around this period; manual will detail its presence and servicing.

Seat Belts:

Front and rear seat belts, potentially with pre-tensioners depending on specific US vs. European market configuration for 1989.

💡 Technology Features

Audio System:

Factory fitted premium sound system, potentially with cassette player and external amplifier.

Cruise Control:

Standard feature on the SEC models.

Climate Control:

Automatic Climate Control (Klima-Automatik) with independent temperature and airflow regulation.

Seating:

Power-adjustable front seats with memory function for driver's seat.

🔧 Maintenance

Oil And Filter:

Refer to engine_specs for general interval; manual will provide exact mileage/time intervals.

Transmission Service:

Refer to transmission section for general interval; manual will provide exact mileage/time intervals.

Spark Plugs:

Typical interval for this era V8 might be 50,000-100,000 km (30,000-60,000 miles), manual is crucial for exact spec.

Brake Fluid:

Recommended replacement every 2 years regardless of mileage.

Coolant Capacity:

Approximately 10-12 liters (consult manual for exact capacity).

Brake Fluid Type:

DOT 3 or DOT 4 (confirm with manual).

Common Wear Items:

Rubber hoses, suspension bushings, fuel distributor seals (KE-Jetronic), window regulators, climate control blower motor, various vacuum lines.

Electrical Common Problems:

Wiring harness degradation (especially around engine bay), climate control unit issues, instrument cluster illumination.

📚 Vehicle History

Manufacturer Legacy:

Mercedes-Benz is renowned for its engineering excellence, luxury, and durability.

W126 Generation:

Second generation of Mercedes-Benz S-Class Coupé (C126), building upon the foundation of the W116-based SEC. Known for its refined styling and technological advancements over its predecessor.

Production Period:

W126 SEC models produced from 1981 to 1991. 1989 represents a late-stage model within this generation, benefiting from numerous mid-cycle updates.

Manufacturing Location:

Germany

🏆 Awards & Recognition

Automotive Press Reviews:

Consistently praised by automotive journalists of the era for its blend of performance, luxury, and build quality. Often cited as a benchmark in its class.