🏷️ Basic Information

Make:

Mercedes-Benz

Model:

300 SEL

Generation:

W126

Model Years Covered:

1988, 1989, 1990, 1991

Chassis Code:

W126

👋 Introduction

Market Position:

The Mercedes-Benz 300 SEL of this era was positioned as a luxury sedan, emphasizing comfort, build quality, and advanced technology for its time. It competed with other high-end sedans from brands like BMW and Jaguar.

Competitive Analysis:

The W126 generation sedan was a benchmark in luxury car design and engineering. The 300 SEL, with its long wheelbase, offered enhanced rear passenger space and a more stately presence compared to the standard S-Class. Its technological advancements, such as advanced fuel injection and optional features like ABS and ASD, set it apart.

Key Features:

The 300 SEL is known for its robust construction, smooth ride, powerful yet efficient straight-six engine, and sophisticated W126 chassis. Key features include the long-wheelbase body, premium interior materials, and advanced safety systems for the late 1980s and early 1990s.

📋 Manual Details

Coverage Areas:

Engine, Transmission (Manual & Automatic), Fuel System, Cooling System, Exhaust System, Suspension, Steering, Brakes, Electrical System, Body, Climate Control, Drivetrain, Differential, Axles, Chassis

Page Count:

Extensive (Specific number not provided in product info, but comprehensive coverage implies hundreds of pages)

Manual Type:

Service Repair Manual

Language:

English

Format:

PDF / WINRAR

📖 Manual Coverage

Systems Covered:

Engine mechanical and electrical, fuel injection, ignition, cooling, lubrication, intake and exhaust, manual and automatic transmissions, clutch, driveshaft, axles, suspension (front and rear), steering, braking system (including ABS/ASD), electrical components, lighting, bodywork, interior, climate control (HVAC), hydraulic systems (level control, power steering), convertible top operation (if applicable to specific SEL trims of this era).

Procedures Included:

Disassembly, inspection, rebuilding, assembly, troubleshooting, diagnosis, adjustment, replacement, fluid changes, lubrication, filter changes, belt checks, sensor testing, component testing, torque specifications, wiring diagrams (implied for comprehensive coverage).

Technical Depth:

Comprehensive, covering detailed diagnostic procedures, component-level repairs, and factory-recommended service intervals. Suitable for professional mechanics and advanced DIY enthusiasts.

📊 Manual Specifications

File Format:

PDF, WINRAR Archive

Print Quality:

Digital, high resolution (typical for PDF manuals, allowing for clear viewing of diagrams and text)

Binding Type:

N/A (Digital Download)

Paper Type:

N/A (Digital Download)

⚙️ Engine Specifications

Engine Code:

M103

Engine Type:

Inline 6-cylinder, SOHC

Displacement:

2.960 cc (3.0 Liters)

Horsepower:

Approx. 188 hp @ 5700 rpm (US Spec)

Torque:

Approx. 195 lb-ft @ 4400 rpm (US Spec)

Fuel Injection:

Bosch KE-Jetronic (CIS-E)

Fuel Type:

Unleaded Gasoline

Valve Adjustment Interval:

Typically every 30,000-60,000 miles or as needed based on performance. The M103 has adjustable valves.

Spark Plug Replacement:

Refer to manual for specific interval, generally around 30,000-60,000 miles depending on plug type.

V Belt Inspection:

Regular inspection for wear and tension. Poly-V belt is common on later models.

🔧 Transmission

Standard Transmission:

4-speed Automatic Transmission (722.3xx series)

Optional Transmission:

5-speed Manual Transmission (Rare for SEL models in this period, more common on other W126 variants)

Automatic Transmission Fluid Change:

Recommended every 30,000-50,000 miles. Specific fluid (e.g., ATF Dexron III equivalent, consult manual for precise MB spec).

Transfer Case Fluid:

N/A (No transfer case in RWD 300 SEL)

Clutch Fluid Check:

For manual transmission models, check and top off with DOT 4 brake fluid.

📐 Dimensions

Wheelbase:

Approx. 115.9 inches (2944 mm) - Long Wheelbase

Length:

Approx. 201.3 inches (5113 mm) - Long Wheelbase

Curb Weight:

Approx. 3,700 - 3,900 lbs (1680 - 1770 kg)

Gross Vehicle Weight Rating:

Approx. 4,800 - 5,000 lbs (2180 - 2270 kg)

🛡️ Safety Features

Safety Features Era:

Advanced for its time, including crumple zones, padded interior, seat belts, and optional ABS (Anti-lock Braking System) and ASD (Automatic Slip Differential).

Active Safety Features:

ABS (Anti-lock Braking System), ASD (Automatic Slip Differential), power-assisted steering, excellent chassis dynamics.

Passive Safety Features:

Reinforced passenger cell, side-impact protection (post-1986 facelift), driver and passenger airbags (standard from late 1980s), front and rear crumple zones.

💡 Technology Features

Infotainment System:

Basic for the era, typically featuring an analog or early digital radio with cassette player. Speaker systems were usually high quality for the time.

Driver Assistance:

ABS (Anti-lock Braking System), ASD (Automatic Slip Differential), cruise control, power steering. Some models may have had early forms of traction control integrated with ASD.

Connectivity:

Minimal by modern standards. No Bluetooth or USB connectivity. Antenna mast is manual or power-operated.

🔧 Maintenance

Major Service Interval:

Refer to manual for specific intervals, but typically includes spark plug replacement, fluid flushes, belt checks, and comprehensive inspections around 30,000-60,000 miles.

Engine Oil Spec:

API SG or higher, SAE 15W-40 or 10W-30 (check manual for exact MB approval and seasonal recommendations, e.g., MB 229.1 for later approvals)

Coolant Spec:

Mercedes-Benz approved G48 (blue/green) or equivalent long-life coolant (typically 50/50 mix with distilled water)

Brake Fluid Spec:

DOT 4 (for clutch and brake systems)

Power Steering Fluid Spec:

Pentosin CHF 11S or equivalent hydraulic fluid (check manual for specific MB approval)

Known Issues:

Common issues can include aging rubber components (hoses, mounts, bushings), vacuum line leaks, fuel distributor issues (KE-Jetronic), window regulator problems, headliner sagging, and potential rust in certain climates. Electrical issues can arise from aging wiring harnesses and components. Heater blower motor resistor failure. SRS light issues can occur.

📚 Vehicle History

Brand Heritage:

Mercedes-Benz has a long-standing reputation for engineering excellence, luxury, safety, and durability, dating back to the invention of the automobile.

Model Evolution:

The W126 S-Class, introduced in 1979, was a significant advancement over its predecessor. The 300 SEL represented the long-wheelbase variant of the S-Class, offering increased passenger comfort. The 1988-1991 models are part of the facelifted W126 series, featuring updated styling, improved aerodynamics, and enhanced safety features.

Production Period:

W126 production: 1979-1991. Specific 300 SEL (W126) production for these years. Manufacturing primarily in Germany.

🏆 Awards & Recognition

Recognitions:

The W126 S-Class consistently received accolades for its safety, comfort, and engineering prowess from automotive publications worldwide during its production run. Often cited as one of the finest sedans of its generation.