2004 Porsche 911 — MOT failures & pass rate
13,402 MOT tests on the 2004 Porsche 911 are in this dataset, and 87.1% of them passed. Coupes & convertibles of a similar age fail 22.5% of the time, so this is 9.6pp better than the group it competes with. Failures cluster in lighting & signalling, emissions & environmental and brakes.
What the MOT record shows
Lighting & signalling dominates the failure mix at 6.3% of all tests — 3.1 points clear of emissions & environmental, so it is the first thing to check.
At component level the recurring items are headlamp aim, catalyst emissions and rigid brake pipes — headlamp aim alone was recorded 451 times.
Mileage is the strongest signal on the record: 4.9% of 0-30k cars fail, rising to 21.5% once past 150k — 4.4× the risk.
Advisories point at the next bill rather than this one: brakes was flagged on 20.2% of tests without failing them.
How it compares
Top failure categories
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Lighting & signalling | 6.3% | 849 |
| 2 | Emissions & environmental | 3.3% | 438 |
| 3 | Brakes | 3.0% | 400 |
| 4 | Tyres | 2.7% | 358 |
| 5 | Body, structure & corrosion | 2.3% | 306 |
| 6 | Visibility | 1.8% | 236 |
Most common specific failures
The exact components most often recorded as failures — more specific than the categories above.
| # | Failure item | Times recorded |
|---|---|---|
| 1 | Headlamp aim | 451 |
| 2 | Catalyst emissions | 419 |
| 3 | Rigid brake pipes | 379 |
| 4 | Position lamp | 307 |
| 5 | Headlamp | 197 |
| 6 | Joints | 183 |
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 | 20.2% | 2,709 |
| 2 | Tyres | 14.1% | 1,895 |
| 3 | Lighting & signalling | 7.0% | 937 |
| 4 | Suspension | 6.6% | 881 |
| 5 | Emissions & environmental | 4.8% | 647 |
| 6 | Other defects | 4.5% | 609 |
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 | 870 | 4.9% |
| 30-60k | 3,589 | 8.7% |
| 60-90k | 5,470 | 13.9% |
| 90-120k | 2,647 | 17.1% |
| 120-150k | 646 | 18.6% |
| 150k+ | 172 | 21.5% |
Failure rate by age
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2021 | 2,816 | 12.9% |
| 2022 | 2,715 | 12.8% |
| 2023 | 2,670 | 13.4% |
| 2024 | 2,600 | 13.1% |
| 2025 | 2,601 | 12.0% |
What to check before buying a 2004 911
On a 2004 911, lighting & signalling is what the MOT record says goes wrong most — it appeared in 6.3% of tests. Check these areas before you commit.
- Lighting & signalling (6.3% of tests): Often a cheap bulb, but persistent issues can mean wiring or corrosion in the units. Typical repair: £10–£150.
- Emissions & environmental (3.3% of tests): More common on older diesels (DPF/EGR) — can be expensive; check for warning lights and smoke. Typical repair: £100–£600.
- Brakes (3.0% 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 Porsche 911s pass their MOT?
87.1% of the 13,402 2004 Porsche 911 MOT tests in this dataset passed — a 12.9% fail rate.
What is the most common MOT failure on a 2004 Porsche 911?
Lighting & signalling, recorded in 6.3% of tests, followed by emissions & environmental (3.3%).
Does the 2004 911 get worse with mileage?
Its MOT fail rate rises from 4.9% in the 0-30k band to 21.5% in the 150k+ band.
Methodology & source. Based on 13,402 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.