1984 Porsche 911 — MOT failures & pass rate
The 1984 Porsche 911 passed 86.5% of its 1,082 recorded MOT tests. Against coupes & convertibles of a similar age (15.2% fail rate), the 1984 911 comes out 1.8pp better. Failures cluster in lighting & signalling, visibility and brakes.
What the MOT record shows
Lighting & signalling dominates the failure mix at 11.5% of all tests — 6.3 points clear of visibility, so it is the first thing to check.
At component level the recurring items are headlamp aim, rear fog lamp and washers — headlamp aim alone was recorded 59 times.
Condition tracks the odometer closely. Failures run at 12.7% in the 0-30k band and 8.1% in the 150k+ band, a 4.6-point spread.
Advisories point at the next bill rather than this one: suspension was flagged on 10.0% of tests without failing them.
The trend is improving — the fail rate fell from 14.3% in 2021 to 12.6% in 2025, as the worst-kept examples leave the fleet.
How it compares
Top failure categories
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Lighting & signalling | 11.5% | 124 |
| 2 | Visibility | 5.2% | 56 |
| 3 | Brakes | 4.0% | 43 |
| 4 | Emissions & environmental | 2.1% | 23 |
| 5 | Suspension | 1.8% | 20 |
| 6 | Body, structure & corrosion | 1.0% | 11 |
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 | 59 |
| 2 | Rear fog lamp | 57 |
| 3 | Washers | 53 |
| 4 | Service brake performance | 37 |
| 5 | Position lamp | 24 |
| 6 | Headlamp | 20 |
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 | 10.0% | 108 |
| 2 | Brakes | 6.7% | 72 |
| 3 | Emissions & environmental | 6.0% | 65 |
| 4 | Tyres | 6.0% | 65 |
| 5 | Lighting & signalling | 3.1% | 34 |
| 6 | Body, structure & corrosion | 2.4% | 26 |
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 | 79 | 12.7% |
| 30-60k | 115 | 13.9% |
| 60-90k | 292 | 14.7% |
| 90-120k | 341 | 14.7% |
| 120-150k | 191 | 11.0% |
| 150k+ | 62 | 8.1% |
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2021 | 209 | 14.3% |
| 2022 | 252 | 13.1% |
| 2023 | 250 | 13.6% |
| 2024 | 236 | 13.6% |
| 2025 | 135 | 12.6% |
What to check before buying a 1984 911
On a 1984 911, lighting & signalling is what the MOT record says goes wrong most — it appeared in 11.5% of tests. Check these areas before you commit.
- Lighting & signalling (11.5% of tests): Often a cheap bulb, but persistent issues can mean wiring or corrosion in the units. Typical repair: £10–£150.
- Visibility (5.2% of tests): Wipers, washers, mirrors and screen damage — usually inexpensive, but check for chips in the driver's line of sight. Typical repair: £15–£150.
- Brakes (4.0% 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 1984 Porsche 911s pass their MOT?
86.5% of the 1,082 1984 Porsche 911 MOT tests in this dataset passed — a 13.5% fail rate.
What is the most common MOT failure on a 1984 Porsche 911?
Lighting & signalling, recorded in 11.5% of tests, followed by visibility (5.2%).
Does the 1984 911 get worse with mileage?
Its MOT fail rate rises from 12.7% in the 0-30k band to 8.1% in the 150k+ band.
Methodology & source. Based on 1,082 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.