MG B MOT pass rate & common failures
The MG B appears in 2,218 MOT tests spanning model years 1980–2021, and 82.2% of them passed. All cars of a similar age fail at 18.3%, so the B sits squarely on the average. Its most common failure areas are lighting & signalling, emissions & environmental and brakes.
What the MOT record shows
No single area dominates — lighting & signalling (9.1%) and emissions & environmental (7.2%) are close, so failures are spread across several systems rather than one weak point.
At component level the recurring items are non catalyst emissions, washers and service brake performance — non catalyst emissions alone was recorded 184 times.
Mileage matters less than usual here: the B fails 15.2% of the time in the 0-30k band and 17.5% at 90-120k, a spread of only 2.3 points.
Suspension is the most common advisory, noted on 16.3% of tests — work that passed today but is likely due soon.
How it compares
By model year
Every B model year with a usable sample. Years with their own detailed report are linked.
| Year | Tests | Pass rate | Fail rate | Most common failure |
|---|---|---|---|---|
| 1980 | 659 | 81.5% | 18.5% | Lighting & signalling |
| 1981 | 843 | 83.0% | 17.0% | Lighting & signalling |
| 1982 | 156 | 77.6% | 22.4% | Lighting & signalling |
| 1983 | 32 | 75.0% | 25.0% | Emissions & environmental |
| 1991 | 40 | 75.0% | 25.0% | Emissions & environmental |
| 1992 | 32 | 84.4% | 15.6% | Brakes |
| 1996 | 31 | 90.3% | 9.7% | Brakes |
| 1997 | 39 | 84.6% | 15.4% | Brakes |
| 1999 | 30 | 96.7% | 3.3% | Body, structure & corrosion |
Most common failures (all years)
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Lighting & signalling | 9.1% | 201 |
| 2 | Emissions & environmental | 7.2% | 159 |
| 3 | Brakes | 6.6% | 146 |
| 4 | Visibility | 5.9% | 130 |
| 5 | Suspension | 2.8% | 62 |
| 6 | Body, structure & corrosion | 2.7% | 60 |
| 7 | Steering | 2.5% | 56 |
| 8 | Tyres | 0.8% | 17 |
Most common specific failures
The exact components most often recorded as failures — more specific than the categories above.
| # | Failure item | Times recorded |
|---|---|---|
| 1 | Non catalyst emissions | 184 |
| 2 | Washers | 106 |
| 3 | Service brake performance | 82 |
| 4 | Position lamp | 69 |
| 5 | Service brake imbalance | 61 |
| 6 | Headlamp aim | 57 |
| 7 | Rear fog lamp | 46 |
| 8 | Stop lamp | 45 |
Top advisory categories
Advisories aren't failures, but they flag work likely needed soon — useful when budgeting.
| # | Category | % of tests with advisory | Tests |
|---|---|---|---|
| 1 | Suspension | 16.3% | 361 |
| 2 | Emissions & environmental | 16.0% | 354 |
| 3 | Brakes | 8.9% | 197 |
| 4 | Other defects | 4.3% | 96 |
| 5 | Tyres | 4.3% | 96 |
| 6 | Body, structure & corrosion | 4.2% | 93 |
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 | 672 | 15.2% |
| 30-60k | 689 | 20.6% |
| 60-90k | 673 | 17.7% |
| 90-120k | 183 | 17.5% |
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2021 | 679 | 18.3% |
| 2022 | 480 | 18.8% |
| 2023 | 413 | 18.2% |
| 2024 | 328 | 15.8% |
| 2025 | 318 | 17.0% |
What to check before buying a MG B
- Lighting & signalling (9.1% of tests): Often a cheap bulb, but persistent issues can mean wiring or corrosion in the units. Typical repair: £10–£150.
- Emissions & environmental (7.2% of tests): More common on older diesels (DPF/EGR) — can be expensive; check for warning lights and smoke. Typical repair: £100–£600.
- Brakes (6.6% of tests): Pads/discs are routine wear; binding, imbalance or corroded pipes are more serious — test for pulling under braking. Typical repair: £100–£350 per axle.
Repair costs are rough UK ballpark ranges to set expectations, not quotes — actual prices vary widely by car, parts and garage.
Frequently asked questions
What is the MOT pass rate for the MG B?
82.2% of the 2,218 MG B MOT tests in this dataset passed, a 17.8% fail rate, across model years 1980–2021.
What does the MG B most often fail its MOT on?
Lighting & signalling, recorded in 9.1% of tests, then emissions & environmental (7.2%).
How much does mileage affect B MOT results?
Fail rates run at 15.2% for cars in the 0-30k band and 17.5% for 90-120k, a 2.3-point difference.
Methodology & source. Based on 2,218 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.