Mercedes Benz Mercedes Benz W251 (R Class) | History, Reliability & Buying Guide

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Mercedes-Benz R-Class (W251): A Comprehensive Guide

The Mercedes-Benz R-Class (W251 chassis code) is a unique vehicle, a "Sports Tourer" that attempted to blend the practicality of an SUV, the space of a minivan, and the luxury of a Mercedes-Benz sedan. Introduced in 2005 for the 2006 model year, it was originally conceived as a grand tourer for families seeking comfort and ample room for passengers and cargo, without sacrificing a premium driving experience. The R-Class was produced in the United States at the Vance, Alabama plant.

Generations

First Generation (W251; 2006-2017)

Years: 2006-2017 (North America: 2006-2012)

Key Features:

Available in both standard and long wheelbase versions ("L" designation). The long-wheelbase variant provided even more rear legroom and cargo capacity.

Seating configurations for five, six, or seven passengers.

Standard all-wheel drive (4MATIC) in many markets. Rear-wheel drive was also available in some variants and markets.

A range of gasoline and diesel engines, including V6 and V8 options.

Air suspension (AIRMATIC) available as an option, providing adjustable ride height and damping.

Luxurious interior appointments, consistent with the Mercedes-Benz brand.

Facelifts:

2008: Minor interior trim updates.

2011: Significant facelift with redesigned front and rear fascias, new headlights and taillights, and updated interior materials. Aimed at giving the R-Class a more modern and appealing look.

Reliability & Common Issues

The W251 R-Class, while offering luxury and space, can be prone to certain reliability issues, especially as models age. Regular maintenance is crucial for ensuring longevity.

Engine-Related Issues:

M272 and M273 Engines (V6 and V8 Gasoline): These engines, used in many Mercedes-Benz models of this era, are known for balance shaft sprocket wear. This issue typically manifests as a check engine light and can lead to serious engine damage if left unaddressed. Listen for rattling noises upon start-up. A pre-purchase inspection is crucial. The issue was largely addressed in later production years of these engines (typically after 2008-2009).

Diesel Injector Issues (OM642 V6 Diesel): Diesel injectors can fail, leading to rough running, poor fuel economy, and excessive smoke. Have the injectors tested if you suspect a problem. Replacing injectors can be expensive.

Oil Leaks: Like many Mercedes-Benz engines, oil leaks are common, particularly from valve cover gaskets, oil cooler seals, and the rear main seal. Regularly check oil levels and address leaks promptly to prevent further damage.

Cooling System Problems: Thermostats, water pumps, and radiators can fail, leading to overheating. Ensure the cooling system is properly maintained and that the coolant is regularly flushed.

Transmission & Drivetrain:

7G-Tronic Transmission (722.9): This transmission, while generally reliable, can experience valve body issues, leading to harsh shifting or delayed engagement. Regular transmission fluid changes are essential.

Transfer Case (4MATIC): The transfer case, used in all-wheel-drive models, can be prone to wear and leaks, especially in high-mileage vehicles. Listen for unusual noises or vibrations from the drivetrain.

Driveshaft Flex Discs (Guibo): These flexible couplings in the driveshaft can crack and fail, causing vibrations. Inspect them regularly, especially if you notice a clunking noise when accelerating or decelerating.

Suspension & Brakes:

AIRMATIC Air Suspension: While providing a comfortable ride, the AIRMATIC system is notorious for its complexity and potential for failure. Air struts can leak, air compressors can fail, and the system's control module can malfunction. Repairing or replacing AIRMATIC components can be costly. Listen for the air compressor running excessively or sagging suspension. A full system diagnostic is recommended during a pre-purchase inspection.

Brake System: Ensure the brakes are in good condition. Rotors can warp, and brake pads wear relatively quickly due to the vehicle's weight. Check the condition of brake lines for corrosion, especially in areas with road salt.

Electrical & Electronic Issues:

SAM (Signal Acquisition Module) Units: These modules control various electrical functions and can fail, leading to issues with lights, wipers, and other systems.

Electronic Control Units (ECUs): Various ECUs can malfunction, causing a range of problems. Diagnostic scans are essential for identifying the source of the issue.

Battery Drain: Electrical gremlins can cause excessive battery drain, especially if aftermarket electronics are installed improperly.

Other Common Issues:

Rust: Check for rust, especially in areas prone to corrosion, such as wheel arches, door bottoms, and undercarriage.

Interior Wear: Inspect the interior for wear and tear, particularly on seats, carpets, and trim.

Driving Experience

Pros:

Spacious and Comfortable: The R-Class offers generous legroom and headroom for passengers in all three rows (depending on configuration), making it ideal for long trips.

Smooth Ride: The standard or optional AIRMATIC suspension provides a comfortable and refined ride.

Powerful Engines: The available V6 and V8 engines offer ample power for acceleration and cruising.

All-Wheel Drive (4MATIC): Provides excellent traction and stability in various weather conditions.

Luxurious Interior: The interior is well-appointed with high-quality materials and features.

Cons:

Large Size: The R-Class can be difficult to maneuver in tight spaces and park in urban environments.

Poor Fuel Economy: Fuel economy is relatively poor, especially with the V8 engine.

Complex Systems: The R-Class has many complex systems that can be expensive to repair.

Depreciation: The R-Class has depreciated significantly, which can be a pro or con depending if you are buying or selling.

Unconventional Styling: The styling of the R-Class is not universally appealing.

Buying Advice

Years to Look For:

2011-2012 (Facelifted Models): The facelifted models offer a more modern appearance and updated features. By these years, many of the early production engine problems had been addressed.

Later Production Years (Generally): Models from 2009 onwards are generally more reliable, as many of the initial production issues were resolved.

Years to Avoid (Potentially):

Early Production Years (2006-2007): These models are more likely to have balance shaft issues in the M272 and M273 engines. Thoroughly inspect any model from these years.

What to Look For:

Maintenance Records: Look for a vehicle with a complete and well-documented service history. Regular maintenance is crucial for the R-Class.

Pre-Purchase Inspection: Have a qualified mechanic perform a thorough pre-purchase inspection, focusing on the engine, transmission, suspension, and electrical systems. Pay particular attention to the AIRMATIC system.

Test Drive: Test drive the vehicle thoroughly, paying attention to engine performance, transmission shifting, suspension behavior, and any unusual noises or vibrations.

4MATIC Functionality: If buying an all-wheel-drive model, ensure the 4MATIC system is functioning correctly. Test its performance in various conditions.

AIRMATIC Condition: If the vehicle is equipped with AIRMATIC, carefully inspect the system for leaks, sagging, and compressor function. Budget accordingly for potential repairs.

Rust Inspection: Check carefully for rust, particularly in areas prone to corrosion.

Clean Title and Accident History: Verify the vehicle's title and accident history to avoid potential problems.

Specific Recommendations:

Consider a Diesel Model (OM642): If fuel economy is a concern, the diesel models offer better fuel efficiency than the gasoline versions. However, be aware of potential diesel-related maintenance costs.

Don't Overlook the R350 BlueTEC: This diesel version provided a cleaner burning alternative to the older diesel options.

Be Prepared for Maintenance Costs: The R-Class can be an expensive vehicle to maintain, so be prepared to budget accordingly.

In conclusion, the Mercedes-Benz R-Class is a unique and versatile vehicle that offers a blend of luxury, space, and performance. However, it's essential to be aware of the potential reliability issues and maintenance costs before making a purchase. With careful research and a thorough inspection, you can find a well-maintained R-Class that provides years of comfortable and enjoyable driving.
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