The Mercedes-Benz W140, often hailed as the last of the “over-engineered” Mercedes-Benz models, remains a sought-after classic for its imposing presence, luxurious features, and robust build quality. However, like any vehicle of its age, potential owners and enthusiasts need to be aware of common issues, model year variations, and maintenance considerations. This guide delves into the specifics of the Benz W140, providing a detailed overview for those considering purchasing or currently owning this iconic vehicle.
Common Issues and Reliability Concerns of the W140
While celebrated for its durability, the W140 is not without its faults. Certain issues are more prevalent than others, and understanding these can save owners from unexpected headaches and expenses.
Air Conditioning Evaporator Leak
One of the most notorious problems with the W140 is the potential for an A/C evaporator leak. This is a significant issue because rectifying it is labor-intensive, requiring the entire dashboard to be removed. Consequently, repairs can be costly, often reaching around $3,000.
Wiring Harness Degradation
Another well-documented issue, particularly in earlier W140 models, is the degradation of the engine wiring harness. The insulation on the wires can become brittle and crumble over time due to heat and environmental factors. This can lead to a range of electrical malfunctions and requires replacement of the harness.
Suspension Components
Suspension wear is typical in vehicles of this age, and the W140 is no exception. Components like lower control arm bushings are prone to wear and tear, necessitating replacement to maintain ride quality and handling. While not as frequent as A/C or wiring harness issues, suspension work is a standard maintenance item to consider.
Throttle Actuator Problems
Throttle actuators, while less commonly reported than A/C or wiring harness issues, can also present problems in W140 models. These components are crucial for engine management, and their failure can impact performance and drivability.
Head Gasket Leaks
Head gasket leaks are another potential engine issue to be aware of. Over time, the head gasket can fail, leading to coolant and oil mixing, overheating, and other engine problems. It’s important to check for signs of head gasket leaks, especially in higher mileage examples.
The Best Model Years for the Benz W140: 1997-1999
While all W140 models offer a unique blend of luxury and engineering, the 1997 to 1999 model years are generally considered the most desirable. These were the final years of production for the W140, and as such, they benefited from refinements and improvements implemented throughout the model run.
Refinement and “Sorted Out” Issues
By the late 1990s, Mercedes-Benz had addressed many of the initial production issues and incorporated upgrades into the W140. Models from 1997-1999 are often described as being the most “sorted out,” meaning they are likely to have fewer of the early production gremlins.
Software and Build Specifications
The later W140s, particularly the 1999 models, came with the latest software upgrades and build specifications. This can translate to improved performance, reliability, and feature integration compared to earlier models.
The Praised M104 Inline-6 Engine in the S320
For those prioritizing fuel economy without sacrificing smooth performance, the S320 model with the M104 inline-6 engine is an excellent choice. This 3.2-liter engine is widely regarded as one of Mercedes-Benz’s finest engines ever produced.
Robust and Reliable Design
The M104 is a venerable inline-6 engine known for its durability and smooth power delivery. It features variable cam timing and produces a healthy 228 horsepower, providing ample performance for the W140 chassis.
Ease of Maintenance
One of the practical advantages of the M104 in the W140 is its ease of maintenance. The engine bay in the W140 is generously sized, offering excellent access to engine components for servicing and repairs.
The 722.6 Electronic Transmission
The W140 utilizes the 722.6 electronic transmission, a unit that was initially marketed as “sealed for life.” However, Mercedes-Benz later revised this recommendation and now advises fluid and filter changes approximately every 40,000 miles.
Longevity with Proper Maintenance
Regular servicing of the 722.6 transmission is crucial for its longevity. Adhering to the recommended fluid and filter change intervals can help prevent transmission issues and ensure smooth shifting.
Pre-Facelift (1992-1994) vs. Post-Facelift (1995-1999) W140 Models: Key Differences
The W140 underwent a significant facelift in 1995, bringing about a range of changes, both cosmetic and mechanical. Understanding these differences is essential when choosing between pre-facelift and post-facelift models.
Exterior and Interior Styling Updates
Post-1995 changes included:
- New bumpers and plastic side flanks: Designed to make the car appear less bulky.
- New rear lenses: Softer edges and more affordable replacement costs.
- Deletion of rear parking assist antennas: Replaced by the optional “Parktronic” system.
- New A/C electronic center dash panel controls: A cost-saving measure in manufacturing.
- New interior door panel design: Eliminated storage compartments for thicker armrests.
- New headlight lens design: Claimed to be brighter and cheaper to produce, with optional Xenon lights.
- Lowered ride height: Reduced by about 1.5 inches for aesthetics and improved aerodynamics.
Mechanical and Feature Changes
Post-1995 also brought mechanical and feature changes:
- Mechanical system changes: Various modifications in the engine compartment and chassis, primarily for cost reduction.
- Infrared remote lock system change: Updated to a more reliable and cheaper system.
- Interior material changes: Standard leather quality was reduced, but more luxurious Nappa leather became an option.
Engine Wiring Harness Issue Resolution
Crucially, the problematic engine wiring harness issue was largely resolved in production from late 1995 onwards. While some early 1996 US models might still have the old harness, later models are generally considered safe from this problem.
Material Quality and Build Philosophy
There is a general consensus that pre-facelift W140 models (1992-1994) boasted superior material quality and overall build quality. This is attributed to the W140 being initially conceived as an “over-engineered” vehicle with less emphasis on cost constraints in its early years.
However, this “over-engineering” also led to complexity and some reliability issues in the initial models. The facelift aimed to address both the car’s perceived bulkiness and production costs, leading to some compromises in material quality but improvements in certain areas of reliability and feature sets.
Pros and Cons: Pre-Facelift (1992-1994) vs. Post-Facelift (1998-1999) W140
To help in the decision-making process, here’s a summary of the pros and cons of pre-facelift and post-facelift W140 models:
Pre-Facelift (1992-1994) PROS:
- Better quality materials: More robust plastics and potentially higher-grade leather as standard.
- More “bulky” and arguably more imposing aesthetics: Appeals to those who prefer the original W140 design intent.
- Powered rear seats: Standard feature, offering enhanced rear passenger comfort.
- Rear seat heating: Often included, sometimes as part of a “comfort package.”
- Parking antennas: A distinctive design feature, standard on pre-facelift models.
- Taller ride height: Maintains a more traditional, stately sedan appearance.
Pre-Facelift (1992-1994) CONS:
- Wiring harness issues: Earlier models are prone to wiring harness degradation.
- Potentially more complex systems: “Over-engineering” could lead to more intricate and potentially less reliable systems in some areas.
Post-Facelift (1998-1999) PROS:
- Resolved wiring harness issue: Later models are free from the degrading wiring harness problem.
- Improved reliability: Benefit from years of refinements and problem-solving.
- More streamlined aesthetics: Modernized appearance with updated styling cues.
- Advanced features: Availability of features like BAS (Brake Assist System), Parktronic, rain-sensing wipers, and Xenon headlights.
- Better keyless alarm system.
- Electrical sunshade on rear windshield (on some models).
Post-Facelift (1998-1999) CONS:
- Cheaper materials in some areas: Cost-cutting measures led to reduced material quality in certain interior and exterior components.
- Less “bulky” appearance: May not appeal to those who prefer the original, more imposing W140 look.
- Powered rear seats became optional.
- Rear seat heating may be optional or less common.
- Parking antennas are absent.
- Lowered ride height: Alters the traditional sedan stance.
Essential Pre-Purchase Inspection for any W140
Regardless of the model year, a thorough pre-purchase inspection (PPI) is absolutely crucial when considering a W140. Due to their age and potential maintenance history, a PPI by a qualified mechanic familiar with Mercedes-Benz vehicles can reveal hidden issues and prevent costly surprises.
Key points to check during a pre-purchase inspection:
- Service records: Review service history for maintenance and repairs performed.
- Coolant condition: Check coolant color (should be orangish/amber, not green).
- Brake fluid condition: Dark fluid indicates it may never have been changed.
- Air filter condition: Inspect for cleanliness.
- Oil filler cap and visible engine areas: Check for cleanliness and sludge.
- Serpentine belt: Inspect for cracks or wear.
- Coolant system: Look for white spots indicating past leaks.
- Head gasket area (passenger side rear): Check for oil leaks.
- Functionality of all systems: Test A/C, heat, turn signals, seat controls (including seat bottom extension and heaters), mirrors (including folding function).
- Wheel vibration during test drive.
- Wind noise during test drive: Should be minimal.
- Exhaust system: Inspect center and rear mufflers for rust and integrity.
Conclusion: Weighing the Pros and Cons for Your Benz W140 Purchase
Choosing a Benz W140 involves weighing the appeal of its classic design, luxurious features, and robust engineering against potential maintenance needs and model year variations. While the 1997-1999 models are often recommended for their refinement and resolved wiring harness issue, pre-facelift models offer a unique charm and potentially higher material quality.
Ultimately, the best W140 for you will depend on your priorities, budget, and willingness to maintain a classic luxury vehicle. Regardless of the model year, a pre-purchase inspection is non-negotiable to ensure you are making an informed decision and enjoying the ownership experience of this iconic Mercedes-Benz.
