1991 Ford Sierra — MOT failures & pass rate
1,599 MOT tests on the 1991 Ford Sierra are in this dataset, and 87.7% of them passed. That is 3.8 percentage points better than large family cars of a similar age, which fail at 16.1%. Failures cluster in lighting & signalling, suspension and body, structure & corrosion.
What the MOT record shows
No single area dominates — lighting & signalling (6.1%) and suspension (4.2%) are close, so failures are spread across several systems rather than one weak point.
At component level the recurring items are component mounting prescribed areas, headlamp aim and headlamp — component mounting prescribed areas alone was recorded 63 times.
Mileage matters less than usual here: the 1991 Sierra fails 12.0% of the time in the 0-30k band and 8.6% at 90-120k, a spread of only 3.4 points.
Advisories point at the next bill rather than this one: suspension was flagged on 17.2% of tests without failing them.
The trend is improving — the fail rate fell from 13.6% in 2021 to 11.0% in 2025, as the worst-kept examples leave the fleet.
How it compares
Top failure categories
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Lighting & signalling | 6.1% | 98 |
| 2 | Suspension | 4.2% | 67 |
| 3 | Body, structure & corrosion | 3.8% | 60 |
| 4 | Brakes | 3.4% | 55 |
| 5 | Emissions & environmental | 3.3% | 53 |
| 6 | Visibility | 2.6% | 42 |
Most common specific failures
The exact components most often recorded as failures — more specific than the categories above.
| # | Failure item | Times recorded |
|---|---|---|
| 1 | Component mounting prescribed areas | 63 |
| 2 | Headlamp aim | 42 |
| 3 | Headlamp | 38 |
| 4 | Prescribed areas | 36 |
| 5 | Non catalyst emissions | 31 |
| 6 | Integral vehicle structure condition | 29 |
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 | 17.2% | 275 |
| 2 | Brakes | 15.4% | 246 |
| 3 | Emissions & environmental | 12.0% | 192 |
| 4 | Body, structure & corrosion | 11.6% | 186 |
| 5 | Other defects | 8.0% | 128 |
| 6 | Tyres | 7.4% | 118 |
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 | 450 | 12.0% |
| 30-60k | 447 | 13.7% |
| 60-90k | 492 | 13.0% |
| 90-120k | 186 | 8.6% |
By fuel type
| Fuel | Tests | Fail rate |
|---|---|---|
| Petrol | 1,556 | 12.4% |
| Diesel | 43 | 7.0% |
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2021 | 360 | 13.6% |
| 2022 | 335 | 13.1% |
| 2023 | 322 | 11.2% |
| 2024 | 281 | 12.1% |
| 2025 | 301 | 11.0% |
What to check before buying a 1991 Sierra
On a 1991 Sierra, lighting & signalling is what the MOT record says goes wrong most — it appeared in 6.1% of tests. Check these areas before you commit.
- Lighting & signalling (6.1% of tests): Often a cheap bulb, but persistent issues can mean wiring or corrosion in the units. Typical repair: £10–£150.
- Suspension (4.2% of tests): Worn drop links, bushes, springs or shocks — listen for knocks over bumps and check for uneven tyre wear. Typical repair: £150–£450 per corner.
- Body, structure & corrosion (3.8% 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+.
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 1991 Ford Sierras pass their MOT?
87.7% of the 1,599 1991 Ford Sierra MOT tests in this dataset passed — a 12.3% fail rate.
What is the most common MOT failure on a 1991 Ford Sierra?
Lighting & signalling, recorded in 6.1% of tests, followed by suspension (4.2%).
Does the 1991 Sierra get worse with mileage?
Its MOT fail rate rises from 12.0% in the 0-30k band to 8.6% in the 90-120k band.
Methodology & source. Based on 1,599 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.