🏷️ Basic Information

Make:

Mercedes-Benz

Model:

300 SE

Model Code:

W126 (Second Generation)

Generation Years:

1979-1991 (W126 platform, with 1988-1993 covering the latter part of its life and potential successor transition depending on market)

Chassis Code:

W126

Engine Code:

M103 (common for 300 SE/SEL)

👋 Introduction

Positioning:

The Mercedes-Benz 300 SE (W126) was positioned as a flagship luxury sedan, known for its engineering excellence, comfort, safety, and build quality, competing with other premium marques like BMW, Audi, and Cadillac.

Competitors:

BMW 7 Series (E32), Audi V8 Quattro, Lexus LS 400 (later models), Cadillac DeVille.

Vehicle Highlights:

Smooth inline-six engine, robust build, sophisticated ride quality, advanced (for its time) safety features like ABS, optional airbags, comfortable and spacious interior, timeless design.

Manual Purpose:

This manual empowers owners and technicians to maintain, diagnose, and repair their 1988-1993 Mercedes-Benz 300 SE with confidence, ensuring longevity and optimal performance of this sophisticated luxury automobile.

📋 Manual Details

Covered Years:

1988, 1989, 1990, 1991, 1992, 1993 (Note: Mercedes-Benz production cycles can sometimes extend beyond typical calendar years, and this manual likely covers models sold within these years, including potential late W126 and early W140 transition if applicable).

Engine Variants:

Specifically covers the 3.0L M103 engine found in the 300 SE and 300 SEL models. May include variations for emissions controls depending on market.

Page Count:

Extensive (typically 1000+ pages for a complete factory-level service manual of this era).

Manual Type:

Factory Authorized Service & Repair Manual

Language:

English

Format:

Digital (PDF) / Printable

📖 Manual Coverage

Engine:

Complete engine overhaul, diagnostics, fuel injection (Bosch KE-Jetronic/ELEKTRONIK), ignition system, lubrication, cooling system, emission control.

Transmission:

Automatic transmission (e.g., 722.3 or 722.4) overhaul, diagnostics, fluid service, electrical controls.

Brakes:

Hydraulic system, ABS (Anti-lock Braking System) diagnostics and repair, brake pad/rotor replacement, brake fluid specifications.

Electrical:

Complete wiring diagrams, component testing, diagnostics for body electronics, lighting, power windows, central locking, climate control, instrument cluster, starter, alternator.

Suspension Steering:

Front and rear suspension components, shock absorbers, springs, bushings, steering gear, power steering system, alignment specifications.

Body Chassis:

Body panel removal/installation, door mechanisms, trunk, hood, sunroof, chassis lubrication, corrosion protection.

HVAC:

Climate control system diagnostics, refrigerant handling, compressor, heater core, blower motor, control panel.

Drive Axles:

Rear-wheel drive axle, differential, CV joints (if applicable), driveshaft.

Wheels Tires:

Wheel specifications, tire pressure recommendations, mounting procedures.

Maintenance:

Oil change, filter replacement, spark plug replacement, coolant flush, belt replacement, lubrication points, inspection schedules.

Troubleshooting:

Diagnostic flowcharts, symptom-based troubleshooting for common electrical and mechanical issues.

Repair:

Step-by-step instructions for component removal, installation, and repair for all major systems.

Rebuild:

Detailed procedures for engine and transmission rebuilds, including tolerances and specifications.

Diagnostic Procedures:

Detailed procedures for diagnosing engine, transmission, brake, and electrical faults, often including specific test procedures for components.

Timing Belt Chain:

While the M103 uses a timing chain, the manual will cover its inspection, tensioner, and potential replacement procedures and intervals.

Fuel Pump Replacement:

Detailed steps for accessing and replacing the fuel pump and associated components.

Depth:

Comprehensive from basic maintenance to full engine/transmission rebuilds and advanced electrical diagnostics.

Diagnostic Tools:

Covers the use of basic hand tools, specialized Mercedes-Benz tools (often identified by Mercedes part numbers), and diagnostic equipment common for the era (e.g., multimeters, oscilloscopes).

📊 Manual Specifications

File Format Details:

Searchable PDF with high-resolution images and diagrams, suitable for printing individual pages or the entire document.

Print Quality Notes:

Designed for clarity and readability when printed, ensuring technical diagrams are easily interpretable.

Binding Type Notes:

N/A (Digital Format) - If printed, expect a durable comb or spiral binding for lay-flat use in a workshop environment.

Paper Type Notes:

N/A (Digital Format) - If printed, would typically be high-quality, durable paper stock to withstand workshop conditions.

⚙️ Engine Specifications

Engine Type:

Inline 6-cylinder, SOHC (Single Overhead Camshaft)

Displacement:

3.0 Liters (2962 cc)

Horsepower:

Approx. 188 hp @ 5700 rpm (varies slightly by market and year)

Torque:

Approx. 260 Nm (192 lb-ft) @ 4400 rpm (varies slightly by market and year)

Fuel Delivery:

Bosch KE-Jetronic CIS-E (Continuous Injection System - Electronic) with Lambda control.

Ignition Type:

Electronic Ignition with distributor and coil.

Coolant Type:

Glysantin G48 or equivalent (typically a blue or green ethylene glycol-based coolant). Refer to manual for precise MB specification.

Engine Oil Type:

SAE 10W-30 or 10W-40 API SG or higher. Refer to manual for precise MB specification and viscosity recommendations based on temperature.

Oil Capacity:

Approx. 7.5 Liters (with filter change).

🔧 Transmission

Transmission Type:

4-Speed Automatic Transmission (e.g., 722.3 or 722.4)

Optional Transmission:

Rarely, a 5-speed manual transmission was available in some markets, but the vast majority were automatic.

Transmission Features:

Torque converter lock-up, hydraulic control with electronic governor (EGS on later models or variants).

Transmission Fluid Type:

MB 236.6 or MB 236.7 Automatic Transmission Fluid (ATF). Dexron II may be acceptable as a substitute, but MB spec is preferred.

Transmission Fluid Capacity:

Approx. 8.0 - 9.5 Liters (total capacity, pan drain typically ~4.5 Liters).

📐 Dimensions

Length:

Approx. 4,960 mm (195.3 in) for Sedan

Width:

Approx. 1,790 mm (70.5 in)

Height:

Approx. 1,420 mm (55.9 in)

Curb Weight:

Approx. 1,700 - 1,800 kg (3,748 - 3,968 lbs)

Gross Vehicle Weight Rating:

Approx. 2,250 kg (4,960 lbs)

🛡️ Safety Features

Safety Ratings:

While formal crash test ratings (like NHTSA's) were less standardized and publicized in the late 80s/early 90s, the W126 chassis was engineered with advanced passive safety features for its era, including a robust body structure, safety-cell design, and impact-absorbing materials.

Active Safety Features:

Anti-lock Braking System (ABS) standard, power-assisted steering.

Passive Safety Features:

Driver and passenger airbags (optional in early years, standard later), energy-absorbing steering column, seatbelt pre-tensioners, reinforced passenger compartment, side-impact protection in doors.

💡 Technology Features

Infotainment System:

For its era, technology was advanced. This included a premium sound system, often with cassette player and multi-speaker setup. Early climate control systems featured sophisticated servo-motor driven actuators for precise temperature regulation.

Driver Assistance Features:

ABS, cruise control, automatic climate control, power adjustable seats with memory (often). Traction control was not common on the 300 SE models of this period.

Connectivity Features:

Minimal by modern standards. Primarily focused on internal vehicle functions. Some models might have had provisions for early cellular telephones, but no integrated infotainment or smartphone connectivity.

🔧 Maintenance

Oil Change Interval:

Typically every 10,000-15,000 km (6,000-9,000 miles) or annually, whichever comes first. Consult manual for specific recommendations.

Major Service Interval:

Major services involving spark plugs, fuel filter, air filter, and coolant are typically recommended at 30,000-60,000 km (20,000-40,000 miles) intervals. Manual is essential for detailed schedule.

Brake Fluid Type:

DOT 3 or DOT 4 glycol-based brake fluid. Always use fluid meeting the latest specifications.

Power Steering Fluid Type:

MB 236.3 or an equivalent hydraulic fluid. Refer to manual for exact specification.

Common Wear Items:

Fuel distributor O-rings, engine wiring harness (especially insulation breakdown), suspension bushings, idle control valve, vacuum leaks, climate control servo motors, door lock actuator failures.

Common Electrical Faults:

Fuse box corrosion, relay failures, dashboard warning light issues, intermittent power to accessories due to age of wiring.

Schedule Importance:

Adhering to the factory maintenance schedule is crucial for the longevity and reliable operation of these complex vehicles. The manual provides the definitive guide.

📚 Vehicle History

Mercedes Benz Legacy:

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

W126 Platform Evolution:

The W126 was the second generation of the S-Class and was a significant evolution from the W116. It introduced aerodynamic improvements, increased interior space, and advanced safety and comfort features. The 300 SE model was introduced to offer a more fuel-efficient six-cylinder option compared to the larger V8 models in certain markets.

W126 Production Years:

1979-1991

Manufacturing Location:

Sindelfingen, Germany

🏆 Awards & Recognition

Model Accolades:

The W126 S-Class platform consistently received critical acclaim for its engineering, safety, and luxury throughout its production run. It set benchmarks for the segment. Specific awards for the 300 SE model would be part of the overall W126 recognition.

Industry Perception:

Considered a benchmark in automotive luxury and safety engineering for the 1980s and early 1990s.

Manufacturer Standards:

Vehicles adhere to strict Mercedes-Benz internal quality and engineering standards, which were exceptionally high.