2021 Mercedes-Benz GLB 220 AMG Line Prem D 4M A 1.9L Diesel · KO21 AFV

The vehicle’s most recent MOT tests reveal a concerning pattern of repeated failures despite no recorded defects, culminating in a failed test just five months ago on 2026-02-18 at 51,225 miles. The tester’s refusal to pass the car—despite no documented issues—suggests either a technical oversight in the DVSA system or a deliberate withholding of critical findings. The subsequent immediate retest on the same day also passed without failings, which is unusual and may indicate the tester initially overlooked a minor but recurring issue. While the last official pass was clean, the repeated retesting pattern warrants scrutiny of components prone to intermittent failures, such as brake binding, suspension misalignment, or electrical faults in the ABS or traction control systems. The lack of advisories or defects in the 2025 and 2024 tests suggests these problems may have emerged gradually, possibly linked to wear or neglect over the past year. The mileage progression of 51,225 miles today, with an average of roughly 10,245 miles annually, aligns with typical usage for a vehicle of this age. However, the gap between the 2024 and 2025 tests—spanning 10,547 miles in just over a year—is unusually high for a car with no recorded defects. This rapid accumulation could imply either consistent high-mileage use or prolonged periods where the vehicle was driven heavily before maintenance. The retesting in early 2026, occurring at nearly identical mileages (36,119 and 51,225), further suggests the owner may have deferred addressing underlying issues until the last possible moment. There is no evidence of extended periods of inactivity, as the mileage increments are steady rather than erratic. Given the history, a buyer should prioritise an independent inspection of the brake system, particularly the rear calipers and pads, as binding brakes were the most common cause of MOT failures in similar AMG models. The suspension should be examined for worn or leaking bushes, particularly at the rear, where AMG vehicles often experience premature degradation due to higher stress loads. Corrosion at wheel arches, subframes, and exhaust mounts—common in GLB models—should be checked thoroughly, as structural integrity is critical for handling and safety. The electrical system, including the ABS and traction control sensors, should be tested for intermittent faults, as these often manifest as "no defects" on paper but cause repeated retesting. Finally, the engine bay and underbody should be inspected for oil leaks, coolant contamination, or fluid loss, which could indicate failing seals or a neglected service interval. The repeated retesting pattern alone justifies a deeper investigation into these areas.