1999 Porsche 911 — MOT failures & pass rate
The 1999 Porsche 911 passed 84.8% of its 6,961 recorded MOT tests. That is 6.8 percentage points better than coupes & convertibles of a similar age, which fail at 22.0%. Failures cluster in lighting & signalling, brakes and emissions & environmental.
What the MOT record shows
Lighting & signalling dominates the failure mix at 9.3% of all tests — 4.5 points clear of brakes, so it is the first thing to check.
At component level the recurring items are catalyst emissions, headlamp aim and rigid brake pipes — catalyst emissions alone was recorded 325 times.
Condition tracks the odometer closely. Failures run at 6.4% in the 0-30k band and 20.2% in the 150k+ band, a 13.8-point spread — more than double.
Advisories point at the next bill rather than this one: brakes was flagged on 22.3% of tests without failing them.
How it compares
Top failure categories
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Lighting & signalling | 9.3% | 645 |
| 2 | Brakes | 4.7% | 329 |
| 3 | Emissions & environmental | 3.8% | 267 |
| 4 | Suspension | 2.7% | 191 |
| 5 | Visibility | 2.6% | 178 |
| 6 | Tyres | 2.5% | 176 |
Most common specific failures
The exact components most often recorded as failures — more specific than the categories above.
| # | Failure item | Times recorded |
|---|---|---|
| 1 | Catalyst emissions | 325 |
| 2 | Headlamp aim | 293 |
| 3 | Rigid brake pipes | 290 |
| 4 | Position lamp | 171 |
| 5 | Tread depth | 157 |
| 6 | Headlamp | 140 |
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 | 22.3% | 1,552 |
| 2 | Tyres | 15.5% | 1,082 |
| 3 | Suspension | 15.2% | 1,061 |
| 4 | Emissions & environmental | 9.2% | 642 |
| 5 | Lighting & signalling | 8.3% | 579 |
| 6 | Body, structure & corrosion | 5.6% | 387 |
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 | 173 | 6.4% |
| 30-60k | 871 | 9.9% |
| 60-90k | 2,096 | 13.6% |
| 90-120k | 2,446 | 16.6% |
| 120-150k | 1,057 | 19.4% |
| 150k+ | 307 | 20.2% |
Failure rate by age
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2021 | 1,519 | 16.7% |
| 2022 | 1,442 | 15.0% |
| 2023 | 1,400 | 14.1% |
| 2024 | 1,306 | 14.5% |
| 2025 | 1,294 | 15.4% |
What to check before buying a 1999 911
On a 1999 911, lighting & signalling is what the MOT record says goes wrong most — it appeared in 9.3% of tests. Check these areas before you commit.
- Lighting & signalling (9.3% of tests): Often a cheap bulb, but persistent issues can mean wiring or corrosion in the units. Typical repair: £10–£150.
- Brakes (4.7% 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.
- Emissions & environmental (3.8% of tests): More common on older diesels (DPF/EGR) — can be expensive; check for warning lights and smoke. Typical repair: £100–£600.
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 1999 Porsche 911s pass their MOT?
84.8% of the 6,961 1999 Porsche 911 MOT tests in this dataset passed — a 15.2% fail rate.
What is the most common MOT failure on a 1999 Porsche 911?
Lighting & signalling, recorded in 9.3% of tests, followed by brakes (4.7%).
Does the 1999 911 get worse with mileage?
Its MOT fail rate rises from 6.4% in the 0-30k band to 20.2% in the 150k+ band.
Methodology & source. Based on 6,961 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.