2004 Mercedes-Benz E320

2004 Mercedes-Benz E320

Overview

The 2004 Mercedes-Benz E320, part of the W211 generation, is generally considered a robust and well-engineered vehicle. It offers a blend of luxury, performance, and comfort, characteristic of the E-Class lineup. While many owners report high satisfaction, like any complex German luxury car of this era, certain components can be prone to issues as they age. This analysis focuses on documented common problems beyond routine maintenance, providing insights into potential areas of concern for prospective buyers or current owners. The E320 was primarily offered with a potent diesel engine and a smooth automatic transmission, both of which have their own reliability profiles.

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Engine

3.2L V6 (M112)

Intake Manifold Gasket Leaks

• Symptoms: Coolant leaks, potential misfires, engine overheating.
• Solution: Replacement of intake manifold gaskets.
• Cost: $300 - $600

Oil Cooler Seals

• Symptoms: Coolant in oil, oil in coolant, potential overheating.
• Solution: Replacement of oil cooler seals.
• Cost: $400 - $700

3.2L V6 Diesel (OM647)

Glow Plug Failure

• Symptoms: Hard starting in cold weather, rough idle.
• Solution: Replacement of faulty glow plugs and potentially the control module.
• Cost: $300 - $700

Injectors

• Symptoms: Rough idle, poor fuel economy, black smoke.
• Solution: Cleaning or replacement of diesel injectors.
• Cost: $600 - $1200

Transmission

5-Speed Automatic (722.6)

Conductor Plate Failure

• Symptoms: Harsh shifting, transmission slipping, ‘limp mode’.
• Solution: Replacement of the conductor plate and transmission fluid service.
• Cost: $700 - $1500

Transmission Control Module (TCM) Issues

• Symptoms: Erratic shifting, no gear engagement.
• Solution: Repair or replacement of the TCM.
• Cost: $500 - $1000

Suspension

Standard Chassis

Air Suspension (Optional)

• Symptoms: Vehicle sagging, uneven ride height, compressor failure.
• Solution: Repair or replacement of air springs, compressor, or lines.
• Cost: $500 - $1500 per corner/component

Control Arm Bushings

• Symptoms: Clunking noises over bumps, vague steering.
• Solution: Replacement of worn control arm bushings.
• Cost: $400 - $800

Electrical

General Electrical System

SAM Unit (Signal Acquisition Module) Corrosion

• Symptoms: Intermittent electrical failures, warning lights, non-functional accessories.
• Solution: Cleaning or replacement of the SAM unit, addressing water ingress.
• Cost: $500 - $1200

Window Regulator Failure

• Symptoms: Power windows not operating, window falling into door.
• Solution: Replacement of the window regulator mechanism.
• Cost: $200 - $400

Xenon Headlight Ballast Failure

• Symptoms: One or both headlights not working, flickering.
• Solution: Replacement of the headlight ballast.
• Cost: $300 - $600

Exterior

Body and Trim

No Major Issues

• Symptoms: No widespread issues reported.
• Solution: No widespread issues reported.
• Cost: N/A

Interior

Cabin Components

Headliner Sagging

• Symptoms: Fabric detaching from the headliner board.
• Solution: Re-gluing or replacement of the headliner.
• Cost: $300 - $700

Climate Control Actuator Failure

• Symptoms: Air not directing correctly, temperature issues.
• Solution: Replacement of faulty HVAC actuators.
• Cost: $200 - $500

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Summary Verdict

The 2004 Mercedes-Benz E320 is a capable luxury sedan, but potential buyers should be aware of common issues that arise with age and mileage. The diesel engine (OM647) can be reliable but may face injector or glow plug problems. The gasoline V6 (M112) is generally robust but can suffer from oil cooler seal and intake manifold gasket leaks. Transmission issues, particularly with the 5-speed automatic’s conductor plate, are a notable concern. Electrical gremlins, especially related to the SAM unit and window regulators, are also frequently reported. While the exterior and interior are generally well-built, minor issues like sagging headliners and climate control actuator failures can occur. Regular maintenance and prompt attention to early symptoms are crucial for maintaining this vehicle’s long-term reliability.