🏷️ Basic Information

Make:

Mercedes-Benz

Model:

S420

Year:

1997

Chassis Code:

W140

Engine Code:

M119.980

👋 Introduction

Market Position:

The 1997 Mercedes-Benz S420 represented the pinnacle of German luxury and engineering in its era, competing with other flagship luxury sedans like the BMW 7 Series, Lexus LS, and Audi A8. This manual caters to owners and technicians maintaining these high-end vehicles.

Competitive Analysis:

The W140 S-Class was known for its robust build quality, advanced technology for its time, and unparalleled comfort. Servicing these vehicles requires specialized knowledge and access to factory-level information, making this manual an essential tool.

Key Features:

Official factory documentation ensures accuracy and completeness. Digital format allows for quick searching and easy access to specific repair procedures, diagnostic information, and wiring diagrams. Essential for maintaining the complex systems of a 1997 S-Class.

📋 Manual Details

Coverage Areas:

Complete service, repair, diagnostic, troubleshooting, and wiring diagrams for the 1997 Mercedes-Benz S420.

Wiring Diagrams:

Includes comprehensive electrical system wiring diagrams for all major vehicle systems, aiding in troubleshooting and repair of electrical faults.

Page Count:

Estimated 1000+ pages (typical for comprehensive official service manuals of this era).

Manual Type:

Official Factory Service & Repair Manual Software (Digital Format)

Language:

English

Format:

Software (likely executable or specialized viewer format designed for dealership technicians).

📖 Manual Coverage

Systems Covered:

Engine mechanical & electronic systems, fuel & emissions control, cooling system, lubrication system, ignition system, transmission (automatic), drivetrain (rear-wheel drive), suspension (front & rear), steering system, braking system (ABS, ESP), climate control, power accessories (windows, seats, mirrors, sunroof), lighting, body electrical, bodywork & interior, diagnostic trouble codes (DTCs), wiring diagrams.

Procedures Included:

Scheduled maintenance, routine inspections, diagnostic procedures, repair and replacement of all major and minor components, component testing, torque specifications, electrical system troubleshooting, wiring harness repair, body panel alignment, interior trim removal and installation, A/C system servicing.

Component Removal Installation:

Detailed, step-by-step instructions for the removal and installation of virtually every component, from minor trim pieces to major mechanical assemblies.

Technical Depth:

Comprehensive, from basic fluid changes to full engine and transmission overhauls, including detailed diagnostic trees and component-level repair instructions. Suitable for professional technicians and advanced DIY enthusiasts.

Diagnostic Tools:

Procedures may require Mercedes-Benz specific diagnostic tools such as STAR DIAGNOSIS (or earlier equivalents like HHT - Handheld Tester) for accessing ECU data, performing actuator tests, and clearing fault codes. The manual will detail which systems require such tools.

📊 Manual Specifications

File Format:

Proprietary software format, likely requiring a specific application or executable to view. Designed for digital access and searchability.

Print Quality:

N/A (Digital Software). Content is typically rendered digitally with high-resolution diagrams and clear text.

Binding Type:

N/A (Digital Software).

Paper Type:

N/A (Digital Software).

Completeness:

This software is presented as a complete official factory service and repair manual, covering all aspects of vehicle maintenance and repair as intended by the manufacturer.

Searchability:

Software format allows for full-text searching, enabling users to quickly locate specific information or procedures.

⚙️ Engine Specifications

Engine Type:

4.2L V8 SOHC 32-valve

Engine Displacement:

4196 cc (256 cu in)

Engine Bore X Stroke:

88.5 mm x 86.0 mm

Engine Compression Ratio:

10.0:1

Horsepower:

275 hp @ 5700 rpm (approx.)

Torque:

295 lb-ft @ 3900 rpm (approx.)

Fuel Injection:

Bosch Motronic M2.8.3 (Electronic Fuel Injection)

Fuel Type:

Premium Unleaded Gasoline (91 octane or higher recommended)

Engine Management System:

Engine Control Unit (ECU) with integrated diagnostics.

Ignition System:

Distributorless Ignition System (DIS) with coil-on-plug or coil-pack setup (specific configuration may vary).

Emission Controls:

Catalytic converter, oxygen sensors, EGR (Exhaust Gas Recirculation) if applicable to the specific market's emissions standards.

🔧 Transmission

Transmission Type:

4-Speed Automatic Transmission (722.6 Electronic)

Transmission Features:

Electronic control, torque converter lock-up, multiple shift modes (e.g., Comfort, Sport).

Optional Transmission:

N/A for S420 model in 1997, 4-speed automatic was standard.

Transmission Fluid Type:

MB 236.10 or MB 236.12 specification automatic transmission fluid (e.g., Shell ATF 134, Mobil ATF 220).

📐 Dimensions

Wheelbase:

3,139 mm (123.6 in)

Length:

5,108 mm (201.1 in)

Width:

1,886 mm (74.3 in)

Height:

1,486 mm (58.5 in)

Curb Weight:

1,960 kg (4,321 lbs) approx.

Gross Vehicle Weight Rating:

Approx. 2,500 kg (5,512 lbs) - consult vehicle's data plate for precise figure.

Wheel Bolt Pattern:

5x112

Standard Wheel Size:

16 x 7.5 inches

Standard Tire Size:

215/60R16

🛡️ Safety Features

Crash Test Ratings:

NHTSA ratings for this generation were not standardized as they are today. However, the W140 was engineered with advanced safety features for its time.

Active Safety Features:

Anti-lock Braking System (ABS), Acceleration Skid Control (ASR - later evolved into ESP), Traction Control System.

Passive Safety Features:

Dual front airbags, front side airbags (optional or standard depending on trim/market), reinforced body structure, crumple zones, seatbelt pre-tensioners, impact-absorbing interior materials.

💡 Technology Features

Infotainment System:

Original system typically featured an AM/FM radio with CD/cassette player, analog climate controls, and a small LCD display. Advanced features included optional navigation systems.

Driver Assistance Features:

Cruise control, parking assist sensors (rear), automatic climate control with dual-zone capability.

Connectivity Features:

Original systems offered limited connectivity. Later aftermarket integrations could include Bluetooth or auxiliary inputs.

Comfort Convenience Features:

Power-adjustable front seats with memory, heated front seats, automatic climate control, power windows, power sunroof, power-adjustable steering column, automatic dimming rearview mirror, rain-sensing wipers (optional).

🔧 Maintenance

Major Service Interval:

Every 10,000 miles or 12 months for oil changes and basic inspections. More comprehensive services typically at 30,000, 60,000, and 100,000-mile intervals, as outlined in the vehicle's owner's manual and detailed in this service manual.

Engine Oil Type:

Mobil 1 Synthetic 0W-40 or equivalent meeting MB-Approval 229.1 specification (check specific vehicle requirements).

Coolant Type:

Mercedes-Benz Approved Antifreeze/Coolant (e.g., G05 or G48 based, typically a blue-green silicate-free HOAT coolant) mixed 50/50 with distilled water.

Brake Fluid Type:

DOT 4 (low viscosity is often recommended for ABS systems).

Power Steering Fluid Type:

Pentosin CHF 11S or MB 236.3 specification hydraulic fluid.

Transmission Fluid Capacity:

Approximately 7.5 liters (7.9 US quarts) for a complete fluid change with torque converter (refer to manual for exact capacity and procedure).

Known Issues:

Ignition coil failures, MAF sensor issues, ABS/ASR system faults (often due to wheel speed sensors or modulator), vacuum leaks, OVP relay failures, window regulator failures, coolant leaks (plastic components), biodegradable wiring insulation degradation, trunk lock actuator problems, climate control system component failures (e.g., blower motor, evaporator).

Oil Filter Part Number:

Example: Mann-Filter HU 718/5 x or Bosch 0 986 452 033 (verify for specific engine variant).

Air Filter Part Number:

Example: Mann-Filter C 30 113/1 or Bosch 1 457 433 916 (verify for specific engine variant).

📚 Vehicle History

Brand Heritage:

Mercedes-Benz has a long-standing reputation for building luxury, quality, and technologically advanced automobiles, dating back to the late 19th century. The S-Class lineage represents the pinnacle of their automotive efforts.

Model Evolution:

The W140 generation, produced from 1991 to 1998, was a significant departure from its predecessor (W126). It was larger, heavier, and featured more advanced technology, earning it the nickname 'The Big S' or 'The Hammer' among enthusiasts due to its imposing presence and robust engineering. It introduced features like dual-pane glass, bi-xenon headlights (optional), and more sophisticated electronic controls.

Design Philosophy:

The W140 was designed to be the ultimate expression of Mercedes-Benz luxury, safety, and engineering, focusing on occupant comfort, structural integrity, and advanced features, even at the expense of weight and sometimes, fuel economy.

Production Years:

1991-1998 (W140 generation)

Manufacturing Location:

Germany (primarily Sindelfingen plant)

🏆 Awards & Recognition

Recognitions:

While specific awards for the 1997 S420 are not as widely publicized as modern vehicles, the W140 generation was consistently recognized for its build quality, safety engineering, and luxury appointments by automotive publications of its time. It set benchmarks in automotive comfort and technological integration for its era.