The Mercedes-benz W140, often lauded as the last of the “over-engineered” Mercedes, remains a fascinating and desirable classic. However, like any vehicle of its age, particularly one as complex as the W140, potential owners need to be aware of common issues and the nuances between model years. This guide delves into the specifics of the W140, helping you navigate the years and make informed decisions, whether you’re considering a purchase or maintaining an existing model.
W140 Model Years: The Evolution of an Icon
The production run of the W140 spanned from 1991 to 1999, and understanding the timeline is crucial for potential buyers. The general consensus among enthusiasts and mechanics is that the later years, specifically 1997-1999, represent the most refined and sorted versions of the W140. These later models benefited from years of production improvements and addressed some of the initial teething problems found in earlier iterations.
However, the story is more nuanced than simply recommending the latest models. Mercedes-Benz implemented a significant facelift in 1995 (roughly mid-1994 for production). This facelift brought about a series of changes, some aimed at cost reduction, others at improving aesthetics and functionality. This split creates two distinct eras within the W140 lifecycle: pre-facelift (1991-1994/early 1995) and post-facelift (mid-1995-1999).
Pre-Facelift (1991-1994/Early 1995) W140: The Original “Over-Engineered” Marvel
The early W140 models are often praised for their perceived higher build quality and use of premium materials. These were the cars built when Mercedes-Benz was arguably at its peak of engineering ambition, with less concern for cost-cutting.
Key Characteristics of Pre-Facelift W140s:
- Robust Build Quality: Many argue that pre-facelift models boast superior materials, including thicker plastics and higher-grade leather.
- “Bulky” Aesthetics: The pre-facelift design is characterized by a more imposing and substantial appearance, which some enthusiasts find more appealing.
- Standard Features: Features like rear parking assist antennas were standard, reflecting the era’s commitment to luxury and innovation.
- Potential Issues: Early models are more prone to issues like wiring harness degradation and potentially more complex systems that, while advanced for their time, could be less reliable in the long run.
Specific Points to Consider for Pre-Facelift Models:
- Wiring Harness Issues: The engine wiring harness is a known weak point in early W140s, prone to insulation degradation. While many will have been replaced by now, it’s crucial to check for evidence of replacement or factor this potential repair into your budget.
- 722.3 Transmission: Some pre-facelift models used the 722.3 4-speed transmission, which is mechanically robust but lacks the electronic sophistication of later transmissions.
- Complex Systems: While innovative, some early systems might be more challenging and expensive to diagnose and repair compared to later, simplified versions.
Post-Facelift (Mid-1995-1999) W140: Refinement and Cost Optimization
The post-facelift W140 models represent a shift in Mercedes-Benz’s approach. While still luxurious and well-engineered, these models incorporated changes aimed at reducing production costs and addressing some of the initial reliability concerns.
Key Changes in Post-Facelift W140s:
- Aesthetic Updates: New bumpers, side skirts, rear lights, and lower ride height gave the car a less bulky, more modern appearance.
- Interior Modifications: Changes included a redesigned dashboard, door panels (loss of storage compartments), and HVAC controls, often cited as being less luxurious but more user-friendly.
- Simplified Systems: Mercedes-Benz streamlined some electrical and mechanical systems, aiming for improved reliability and reduced manufacturing complexity.
- Engine and Transmission Updates: Later models benefited from engine refinements and the widespread use of the 722.6 5-speed electronic transmission.
Specific Points to Consider for Post-Facelift Models:
- 722.6 Transmission: The 722.6 “sealed for life” electronic transmission, while generally robust, requires fluid changes contrary to its original designation. Regular maintenance is key to longevity.
- Cost-Reduced Materials: While debated, some argue that post-facelift models use slightly cheaper materials in certain areas compared to their predecessors.
- Improved Reliability (Generally): Many of the early W140’s “kinks” were ironed out in later models, potentially leading to better long-term reliability, particularly in areas like wiring harnesses.
- Modern Features: Later models incorporated features like Parktronic parking sensors, Xenon headlights, and Brake Assist System (BAS), enhancing safety and convenience.
Common W140 Issues: What to Watch Out For
Regardless of the model year, certain issues are more prevalent in W140s due to their age and complexity. Being aware of these potential problems is vital for both prospective buyers and current owners.
- A/C Evaporator Leak: This is a notorious and expensive W140 problem. Replacing the evaporator requires complete dashboard removal, leading to significant labor costs (around $3000 or more).
- Head Gasket Leak: Head gasket leaks are relatively common on certain W140 engines, particularly the inline-6 M104.
- Lower Control Arm Bushings: Suspension components, especially lower control arm bushings, wear out over time and require replacement.
- Self-Closing Door Pump: The pneumatic system for self-closing doors can develop leaks and failures.
- “Sealed for Life” Transmission (722.6): While robust, neglecting fluid changes in the 722.6 transmission can lead to problems. Regular fluid and filter changes (around every 40,000 miles) are highly recommended.
Engine Choices: S320 and the M104 Inline-6
For those considering a Mercedes-Benz W140 S320, it’s important to understand the engine powering this model. The S320 is equipped with the M104 inline-6 engine, a 3.2-liter powerplant known for its smooth operation, reliability, and respectable performance.
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Key Features of the M104 Engine:
- Inline-6 Configuration: This configuration is inherently balanced, contributing to smooth and refined engine operation.
- Variable Cam Timing: Provides good low-end torque and strong top-end power.
- Robust Design: The M104 is considered one of Mercedes-Benz’s most durable and well-engineered engines.
- Ease of Maintenance: The engine bay in the W140 is spacious, making the M104 relatively accessible for maintenance and repairs.
Pre-Purchase Inspection: An Absolute Necessity
Regardless of the model year or engine, a pre-purchase inspection (PPI) by a qualified Mercedes-Benz mechanic is absolutely essential before buying a W140. Given the age and potential complexity, a PPI can uncover hidden issues and save you significant money and headaches in the long run.
Key Points to Include in a W140 Pre-Purchase Inspection:
- Fluid Checks: Coolant (correct type and color), brake fluid (condition), engine oil (condition and leaks), transmission fluid (condition if possible).
- Visual Inspection: Wiring harness condition (especially on pre-facelift models), coolant system leaks, oil leaks (especially around the head gasket), serpentine belt condition.
- Functional Tests: A/C and heating system, all electrical functions (lights, signals, windows, seats, mirrors), seat heaters, mirror folding, all seat controls including seat bottom extension.
- Test Drive: Check for wheel vibrations, wind noise, transmission smoothness, engine performance.
- Undercarriage Inspection: Rust, exhaust system condition (mufflers), suspension components (bushings, leaks).
- Service Records: Review service history for evidence of maintenance and repairs.
Conclusion: Weighing the Pros and Cons of W140 Model Years
Choosing the “best” W140 year depends on individual priorities.
Pre-Facelift (1992-1994):
Pros:
- Potentially higher build quality and materials.
- Classic “over-engineered” feel.
- Unique aesthetic details (parking antennas, etc.).
Cons:
- Higher risk of wiring harness issues.
- Potentially more complex and older systems.
- May require more maintenance to keep in top condition.
Post-Facelift (1998-1999 – Recommended for Reliability):
Pros:
- Improved reliability and sorted-out issues.
- More modern features (Parktronic, Xenon, BAS).
- Generally easier to live with day-to-day.
- Often more readily available parts and potentially slightly lower prices.
Cons:
- Perceived reduction in material quality (debatable).
- Less “bulky” and arguably less distinctive aesthetics.
- Still requires thorough inspection and maintenance due to age.
Ultimately, a well-maintained Mercedes-Benz W140, regardless of the year, can offer a unique blend of luxury, engineering, and classic Mercedes-Benz character. Focus on condition, service history, and a comprehensive pre-purchase inspection to find the best example for your needs and enjoy the experience of owning this iconic S-Class.
