2014 Mercedes-Benz B-Class — MOT failures & pass rate
Across 49,156 MOT tests, the 2014 Mercedes-Benz B-Class recorded an 83.6% pass rate. MPVs of a similar age fail 19.1% of the time, so this is 2.6pp better than the group it competes with. Failures cluster in lighting & signalling, tyres and suspension.
What the MOT record shows
No single area dominates — lighting & signalling (7.1%) and tyres (6.3%) are close, so failures are spread across several systems rather than one weak point.
At component level the recurring items are registration plate lamp(s), coil spring and headlamp aim — registration plate lamp(s) alone was recorded 1,550 times.
Mileage is the strongest signal on the record: 8.9% of 0-30k cars fail, rising to 22.7% once past 150k — 2.6× the risk.
The petrol cars hold up better: 13.5% fail against 16.8% for diesel, a 3.3-point gap across 49,156 tests.
Tyres is the most common advisory, noted on 26.1% of tests — work that passed today but is likely due soon.
The trend is worsening — 13.5% of tests failed in 2021 against 19.2% in 2025, the usual pattern as a fleet ages.
How it compares
Top failure categories
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Lighting & signalling | 7.1% | 3,505 |
| 2 | Tyres | 6.3% | 3,072 |
| 3 | Suspension | 5.4% | 2,636 |
| 4 | Emissions & environmental | 2.5% | 1,234 |
| 5 | Brakes | 2.5% | 1,234 |
| 6 | Visibility | 2.3% | 1,117 |
Most common specific failures
The exact components most often recorded as failures — more specific than the categories above.
| # | Failure item | Times recorded |
|---|---|---|
| 1 | Registration plate lamp(s) | 1,550 |
| 2 | Coil spring | 1,379 |
| 3 | Headlamp aim | 1,195 |
| 4 | Malfunction indicator lamp | 1,177 |
| 5 | Linkage ball joint dust cover | 1,167 |
| 6 | Tread depth | 937 |
Top advisory categories
Advisories aren't failures, but they flag work likely needed soon — useful when budgeting.
| # | Category | % of tests with advisory | Tests |
|---|---|---|---|
| 1 | Tyres | 26.1% | 12,840 |
| 2 | Brakes | 18.2% | 8,952 |
| 3 | Suspension | 7.2% | 3,528 |
| 4 | Other defects | 7.2% | 3,523 |
| 5 | Visibility | 3.4% | 1,666 |
| 6 | Lighting & signalling | 1.9% | 934 |
Failure rate by mileage
Higher-mileage cars tend to fail more — often the most useful guide to real condition.
| Mileage band | Tests | Fail rate |
|---|---|---|
| 0-30k | 3,465 | 8.9% |
| 30-60k | 19,033 | 13.2% |
| 60-90k | 17,605 | 18.7% |
| 90-120k | 6,807 | 21.5% |
| 120-150k | 1,729 | 22.4% |
| 150k+ | 507 | 22.7% |
Failure rate by age
By fuel type
| Fuel | Tests | Fail rate |
|---|---|---|
| Diesel | 43,480 | 16.8% |
| Petrol | 5,676 | 13.5% |
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2021 | 9,622 | 13.5% |
| 2022 | 9,584 | 14.1% |
| 2023 | 9,988 | 17.2% |
| 2024 | 9,955 | 18.0% |
| 2025 | 10,007 | 19.2% |
What to check before buying a 2014 B-Class
The failure pattern for this year is specific enough to inspect against: lighting & signalling accounted for 7.1% of tests. Start there.
- Lighting & signalling (7.1% of tests): Often a cheap bulb, but persistent issues can mean wiring or corrosion in the units. Typical repair: £10–£150.
- Tyres (6.3% of tests): Usually a quick, known-cost fix, but check tread, age and uneven wear (which can hint at alignment or suspension issues). Typical repair: £50–£120 per tyre.
- Suspension (5.4% of tests): Worn drop links, bushes, springs or shocks — listen for knocks over bumps and check for uneven tyre wear. Typical repair: £150–£450 per corner.
Repair costs are rough UK ballpark ranges to set expectations, not quotes — actual prices vary widely by car, parts and garage.
Frequently asked questions
How many 2014 Mercedes-Benz B-Classs pass their MOT?
83.6% of the 49,156 2014 Mercedes-Benz B-Class MOT tests in this dataset passed — a 16.4% fail rate.
What is the most common MOT failure on a 2014 Mercedes-Benz B-Class?
Lighting & signalling, recorded in 7.1% of tests, followed by tyres (6.3%).
Does the 2014 B-Class get worse with mileage?
Its MOT fail rate rises from 8.9% in the 0-30k band to 22.7% in the 150k+ band.
Methodology & source. Based on 49,156 MOT tests. Dataset: DVSA MOT testing data (2021,2022,2023,2024,2025). Data last updated 2026-07-27. Figures reflect MOT-testable defects only — read the methodology for how these are calculated and what they don't measure.