2009 Mercedes-Benz E 2.1L Diesel · KN59 YAW

The 2009 Mercedes-Benz E presents a mechanical profile defined by a persistent pattern of rear brake system degradation and progressive subframe corrosion that has recurred across multiple test cycles despite intermittent passes. The most recent MOT on 2025-10-13 yielded a passing result, yet the historical record reveals three separate failures spanning 2021 through 2024, with the worst being the 2022 failure where both nearside and offside rear brake pipes were found excessively corroded and one coil spring fractured completely. A subsequent 2024-09-30 test failed again due to severe rear subframe corrosion on both sides and additional front brake pipe corrosion, while the 2024-10-07 pass showed only minor issues such as deteriorated anti-roll bar bushings. This recurring nature of rear-end and suspension-related failures suggests underlying structural weakness rather than isolated incidents, and the 2025-10-13 result appears to have addressed only surface-level concerns without resolving the deeper corrosion and wear problems. The vehicle's mileage of 181,951 miles over 17 years translates to approximately 10,703 miles per annum, which aligns with expected usage for a model of this age but masks important mechanical implications given the failure timeline. Testing gaps between records range from eight months to nearly a full year, with the longest interval occurring between the 2021-09-30 pass and the 2022-09-01 failure, followed by a six-month gap before the next test in September 2022. The acceleration of mileage increase after 2020—evidenced by the clustering of failures in 2022 and 2024—combined with the presence of multiple major advisories involving the subframe and braking system indicates that cumulative wear and environmental exposure have progressively compromised structural integrity. While the current odometer reading may suggest moderate use, the concentration of serious failures concentrated in the rear suspension and drivetrain areas implies that high-mileage components have been subjected to significant stress without adequate intervention. The rear subframe corrosion represents the most critical concern requiring immediate attention during a test drive, as this area has failed repeatedly as a major advisory since 2022 and remains a primary cause of potential safety hazards when the vehicle experiences harsh handling or sudden braking. Listen for any grinding or knocking noises when traversing uneven surfaces, particularly around the rear corners, as corroded subframe bolts can loosen and allow excessive play in the rear axle assembly. The front inner brake pads show consistent thinning across two consecutive passes, and the front brake pipes have suffered corrosive buildup on both sides documented in 2024, which should manifest as pulsating brake pedal feel or reduced braking performance under load. Additionally, the front anti-roll bar ball joints have deteriorated to the point where both bottom boots have perished, meaning the anti-roll bar may develop excessive lateral movement or noise during cornering, potentially affecting stability control responsiveness. Front coil spring failures are another critical area to inspect, as the 2022 failure noted a fractured front coil spring on both sides, indicating a fundamental structural defect in the suspension that compromises ride quality and handling balance. During a test drive, apply moderate torque to each corner and monitor for any abnormal vibrations or clunking sounds that could signal loose coil springs or broken shackles. The rear brake pipe corrosion identified in 2024 and 2025 should produce noticeable heat build-up in the brake system during hard stops, and you should also check for audible hissing or visible exhaust gas escaping from the rear of the vehicle if the exhaust leak mentioned in the 2025 MOT persists. Given the documented history of repeated rear-end failures and the proximity of the last successful MOT to the present date, proceeding with caution and budgeting for comprehensive subframe and brake system restoration is advisable before committing to purchase.