2004 Mazda B Series — MOT failures & pass rate
The 2004 Mazda B Series passed 70.9% of its 1,376 recorded MOT tests. Against all cars of a similar age (27.7% fail rate), the 2004 B Series comes out 1.4pp worse. Failures cluster in lighting & signalling, body, structure & corrosion and brakes.
What the MOT record shows
Lighting & signalling dominates the failure mix at 19.7% of all tests — 3.7 points clear of body, structure & corrosion, so it is the first thing to check.
At component level the recurring items are joints, rear fog lamp and rigid brake pipes — joints alone was recorded 149 times.
A 150k+ example is materially riskier than a 30-60k one: 29.8% versus 21.6%.
Advisories point at the next bill rather than this one: brakes was flagged on 37.5% of tests without failing them.
The trend is improving — the fail rate fell from 31.4% in 2021 to 27.2% in 2025, as the worst-kept examples leave the fleet.
How it compares
Top failure categories
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Lighting & signalling | 19.7% | 271 |
| 2 | Body, structure & corrosion | 16.0% | 220 |
| 3 | Brakes | 13.1% | 180 |
| 4 | Suspension | 11.5% | 158 |
| 5 | Visibility | 6.8% | 93 |
| 6 | Tyres | 3.6% | 50 |
Most common specific failures
The exact components most often recorded as failures — more specific than the categories above.
| # | Failure item | Times recorded |
|---|---|---|
| 1 | Joints | 149 |
| 2 | Rear fog lamp | 132 |
| 3 | Rigid brake pipes | 107 |
| 4 | Position lamp | 90 |
| 5 | Wipers | 79 |
| 6 | Stop lamp | 69 |
Top advisory categories
Advisories aren't failures, but they flag work likely needed soon — useful when budgeting.
| # | Category | % of tests with advisory | Tests |
|---|---|---|---|
| 1 | Brakes | 37.5% | 516 |
| 2 | Body, structure & corrosion | 32.5% | 447 |
| 3 | Suspension | 29.1% | 400 |
| 4 | Tyres | 22.7% | 312 |
| 5 | Lighting & signalling | 16.7% | 230 |
| 6 | Other defects | 16.1% | 221 |
Failure rate by mileage
Higher-mileage cars tend to fail more — often the most useful guide to real condition.
| Mileage band | Tests | Fail rate |
|---|---|---|
| 30-60k | 102 | 21.6% |
| 60-90k | 259 | 27.4% |
| 90-120k | 362 | 29.8% |
| 120-150k | 338 | 31.1% |
| 150k+ | 302 | 29.8% |
Failure rate by age
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2021 | 379 | 31.4% |
| 2022 | 316 | 27.2% |
| 2023 | 277 | 31.8% |
| 2024 | 220 | 25.9% |
| 2025 | 184 | 27.2% |
What to check before buying a 2004 B Series
On a 2004 B Series, lighting & signalling is what the MOT record says goes wrong most — it appeared in 19.7% of tests. Check these areas before you commit.
- Lighting & signalling (19.7% of tests): Often a cheap bulb, but persistent issues can mean wiring or corrosion in the units. Typical repair: £10–£150.
- Body, structure & corrosion (16.0% of tests): The one to take seriously on older cars — corrosion to structural areas can be costly and is an MOT failure. Typical repair: £200–£1,500+.
- Brakes (13.1% 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
How many 2004 Mazda B Seriess pass their MOT?
70.9% of the 1,376 2004 Mazda B Series MOT tests in this dataset passed — a 29.1% fail rate.
What is the most common MOT failure on a 2004 Mazda B Series?
Lighting & signalling, recorded in 19.7% of tests, followed by body, structure & corrosion (16.0%).
Does the 2004 B Series get worse with mileage?
Its MOT fail rate rises from 21.6% in the 30-60k band to 29.8% in the 150k+ band.
Methodology & source. Based on 1,376 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.