1984 Ford Sierra — MOT failures & pass rate
The 1984 Ford Sierra passed 89.8% of its 647 recorded MOT tests. That is 1.2 percentage points worse than large family cars of a similar age, which fail at 9.0%. Failures cluster in lighting & signalling, suspension and brakes.
What the MOT record shows
No single area dominates — lighting & signalling (5.3%) and suspension (3.4%) are close, so failures are spread across several systems rather than one weak point.
At component level the recurring items are non catalyst emissions, headlamp aim and washers — non catalyst emissions alone was recorded 18 times.
Mileage is the strongest signal on the record: 12.2% of 0-30k cars fail, rising to 6.9% once past 90-120k.
Advisories point at the next bill rather than this one: suspension was flagged on 9.1% of tests without failing them.
The trend is improving — the fail rate fell from 10.9% in 2021 to 8.9% in 2025, as the worst-kept examples leave the fleet.
How it compares
Top failure categories
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Lighting & signalling | 5.3% | 34 |
| 2 | Suspension | 3.4% | 22 |
| 3 | Brakes | 3.4% | 22 |
| 4 | Emissions & environmental | 3.4% | 22 |
| 5 | Visibility | 3.1% | 20 |
| 6 | Body, structure & corrosion | 2.6% | 17 |
Most common specific failures
The exact components most often recorded as failures — more specific than the categories above.
| # | Failure item | Times recorded |
|---|---|---|
| 1 | Non catalyst emissions | 18 |
| 2 | Headlamp aim | 17 |
| 3 | Washers | 14 |
| 4 | Component mounting prescribed areas | 13 |
| 5 | Position lamp | 13 |
| 6 | Service brake performance | 11 |
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 | 9.1% | 59 |
| 2 | Emissions & environmental | 8.5% | 55 |
| 3 | Tyres | 6.8% | 44 |
| 4 | Body, structure & corrosion | 6.2% | 40 |
| 5 | Brakes | 5.7% | 37 |
| 6 | Other defects | 3.7% | 24 |
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 | 229 | 12.2% |
| 30-60k | 202 | 10.4% |
| 60-90k | 128 | 7.8% |
| 90-120k | 73 | 6.9% |
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2021 | 147 | 10.9% |
| 2022 | 148 | 10.1% |
| 2023 | 159 | 13.8% |
| 2024 | 114 | 5.3% |
| 2025 | 79 | 8.9% |
What to check before buying a 1984 Sierra
On a 1984 Sierra, lighting & signalling is what the MOT record says goes wrong most — it appeared in 5.3% of tests. Check these areas before you commit.
- Lighting & signalling (5.3% of tests): Often a cheap bulb, but persistent issues can mean wiring or corrosion in the units. Typical repair: £10–£150.
- Suspension (3.4% 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.
- Brakes (3.4% 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 Ford Sierras pass their MOT?
89.8% of the 647 1984 Ford Sierra MOT tests in this dataset passed — a 10.2% fail rate.
What is the most common MOT failure on a 1984 Ford Sierra?
Lighting & signalling, recorded in 5.3% of tests, followed by suspension (3.4%).
Does the 1984 Sierra get worse with mileage?
Its MOT fail rate rises from 12.2% in the 0-30k band to 6.9% in the 90-120k band.
Methodology & source. Based on 647 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.