Back to Mercedes benz
Official AutoWiki Guide

Mercedes Benz Mercedes Benz W140 (S Class)

Find Me One
```html

Mercedes-Benz W140 S-Class: A Comprehensive Guide

The Mercedes-Benz W140, often referred to as simply the W140 or the "Sonderklasse" (special class) in its home market, represents a pivotal and, for many, iconic generation of the S-Class. Produced from 1991 to 1998, it's a full-size luxury sedan that aimed to redefine automotive excellence. Its development was ambitious, resulting in a car that was technologically advanced and exceptionally opulent for its time. While its sheer size and complexity drew some criticism initially, the W140 has since become highly sought after by enthusiasts who appreciate its engineering prowess, ride comfort, and imposing presence.

1. Introduction: A New Era of Luxury

The W140's arrival marked a significant departure from its predecessor, the W126. Mercedes-Benz invested heavily in its development, resulting in features like double-pane windows for superior sound insulation, self-closing doors and trunk, optional rear parking markers (later replaced by parking sensors), and a climate control system capable of operating long after the engine was switched off. The car was conceived as a technological showcase, pushing the boundaries of what a luxury sedan could offer. This commitment to innovation resulted in a larger, heavier, and more expensive car than its predecessor, which, while initially controversial, ultimately contributed to its enduring legacy.

2. Generations & Key Changes

The W140 generation had some minor revisions throughout its production run, but no major generation changes.

  • 1991-1993: Initial Release
    • Early models featured a simpler engine management system in some engines.
    • Less advanced SRS system compared to later years.
    • Generally, these cars are viewed as slightly less reliable than the updated versions due to component maturity.
  • 1994-1996: Facelift and Refinements
    • Minor exterior changes (e.g., updated taillights, clear turn signals).
    • Improved engine management systems for better efficiency and reliability.
    • Addition of some safety features and convenience updates.
    • Dashboard and interior trim updates
  • 1997-1998: Final Years
    • Introduction of the "Electronic Stability Program" (ESP) on some models.
    • Continued refinement of existing systems.
    • Considered the most desirable years for overall reliability and feature set.

3. Reliability & Common Issues

While the W140 was built to a very high standard, its age and complexity mean that certain issues are common. Thorough inspection and preventative maintenance are crucial to owning one of these cars.

  • Engine Issues:
    • M119 V8: Potential for oil leaks from valve cover gaskets, timing chain tensioner, and rear main seal. Also, check the distributor caps and rotors (two of each), as they are a wear item. Early models are known to have issues with the wiring harness insulation degrading over time, leading to short circuits.
    • M120 V12: Similar oil leak issues as the M119. Additionally, these engines are more complex and expensive to maintain due to the sheer number of components. The wiring harness issue is particularly prevalent and problematic on V12 models. Check for error codes related to ignition and fuel systems.
    • M104 Inline-6: Generally considered the most reliable engine option. However, they can still suffer from head gasket failures (especially on early models) and oil leaks. The wiring harness issue also affects these engines.
    • Diesel Engines (OM603, OM606): Very durable and reliable, but can suffer from fuel injection pump issues and turbocharger problems (on turbocharged models).
  • Transmission Issues:
    • The 722.3 and 722.5 transmissions are generally robust, but proper fluid changes are essential. Look for smooth shifting and no slipping. A delayed engagement into drive or reverse can indicate a problem.
  • Suspension Issues:
    • Self-Leveling Suspension (SLS): If equipped with the SLS, check for leaks from the hydraulic accumulators and struts. This system can be expensive to repair.
    • Ball joints and suspension bushings are prone to wear and should be inspected.
  • Electrical Issues:
    • Wiring Harness Degradation: The most significant electrical issue. The engine wiring harness insulation deteriorates, causing short circuits and malfunctions. This affects various systems, including the engine management, ignition, and fuel injection. Replacing the harness is a time-consuming but necessary repair.
    • Self-Closing Doors and Trunk: These systems can fail, requiring repairs or replacement of the vacuum actuators.
    • Climate Control: Check that all functions of the climate control system work correctly. The evaporator can leak, requiring a costly dashboard removal to replace.
    • Instrument Cluster: Pixel loss in the digital displays is common.
  • Rust:
    • Check for rust in typical areas such as the wheel arches, door bottoms, around the windshield, and the trunk. The W140 is generally better protected against rust than some earlier Mercedes models, but rust can still be a problem, especially in regions with harsh winters.

4. Driving Experience

The W140 delivers a driving experience characterized by exceptional comfort, refinement, and a sense of solidity. It's a car designed for long journeys, where its smooth ride and quiet cabin truly shine. However, its large size can make it challenging to maneuver in tight spaces.

Pros:

  • Exceptional Ride Comfort: The suspension soaks up bumps and imperfections in the road, providing a remarkably smooth ride.
  • Quiet Cabin: Double-pane windows and extensive sound insulation create a serene and relaxing atmosphere.
  • Solid Build Quality: The W140 feels incredibly well-built and substantial.
  • Powerful Engines: The V8 and V12 engines offer ample power and effortless acceleration.
  • Status and Presence: The W140 exudes a sense of luxury and prestige.

Cons:

  • Large Size: The W140 is a very large car, making it difficult to park and maneuver in tight spaces.
  • Complexity: Its advanced features and complex systems can be prone to failure and expensive to repair.
  • Fuel Consumption: The V8 and V12 engines are not fuel-efficient.
  • Maintenance Costs: Parts and labor for repairs can be expensive, especially for the V12 models.

5. Buying Advice

Buying a W140 S-Class requires careful consideration and thorough inspection. Here's what to look for:

  • Year: 1997-1998 models are generally considered the most desirable due to the improvements and refinements made in the later years of production. The wiring harness issue is still present, but other systems were more mature.
  • Engine:
    • The M104 inline-6 is the most reliable engine option, but it lacks the power and refinement of the V8 and V12.
    • The M119 V8 offers a good balance of power and reliability, but requires proper maintenance.
    • The M120 V12 is a powerful and impressive engine, but it's the most complex and expensive to maintain. Only consider a V12 if you are prepared for higher maintenance costs.
    • Diesel versions are generally reliable, but finding a well-maintained example can be challenging.
  • Wiring Harness: Check the condition of the engine wiring harness. Look for crumbling insulation and exposed wires. Replacement is a common repair, so factor this into your budget.
  • Rust: Inspect for rust in typical areas.
  • Service History: Look for a car with a complete and well-documented service history. Evidence of regular maintenance is crucial.
  • Test Drive: Thoroughly test drive the car, paying attention to the transmission, suspension, and brakes. Check that all electrical systems are functioning correctly.
  • Pre-Purchase Inspection: Have a qualified mechanic familiar with Mercedes-Benz perform a pre-purchase inspection. This is essential to identify any potential problems before you buy.
  • Budget: Be realistic about the costs of ownership. Factor in potential repairs, maintenance, and fuel consumption. A cheaper initial purchase price can often lead to higher expenses down the road.

The W140 S-Class is a remarkable car that offers a unique blend of luxury, comfort, and engineering. However, its age and complexity mean that it requires careful ownership. By following this guide and conducting thorough research, you can increase your chances of finding a well-maintained example that will provide years of enjoyable driving.

```