1986 Mercedes-Benz Sl — MOT failures & pass rate
791 MOT tests on the 1986 Mercedes-Benz Sl are in this dataset, and 84.1% of them passed. Coupes & convertibles of a similar age fail at 16.1%, so the 1986 Sl sits squarely on the average. Failures cluster in lighting & signalling, suspension and brakes.
What the MOT record shows
Lighting & signalling dominates the failure mix at 11.4% of all tests — 5.2 points clear of suspension, so it is the first thing to check.
At component level the recurring items are headlamp aim, ball joint dust cover and washers — headlamp aim alone was recorded 86 times.
A 150k+ example is materially riskier than a 0-30k one: 23.3% versus 16.1%.
Advisories point at the next bill rather than this one: suspension was flagged on 19.9% of tests without failing them.
How it compares
Top failure categories
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Lighting & signalling | 11.4% | 90 |
| 2 | Suspension | 6.2% | 49 |
| 3 | Brakes | 5.8% | 46 |
| 4 | Visibility | 4.4% | 35 |
| 5 | Body, structure & corrosion | 3.5% | 28 |
| 6 | Emissions & environmental | 2.8% | 22 |
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 | 86 |
| 2 | Ball joint dust cover | 44 |
| 3 | Washers | 29 |
| 4 | Service brake performance | 25 |
| 5 | Component mounting prescribed areas | 21 |
| 6 | Wipers | 18 |
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 | 19.9% | 157 |
| 2 | Emissions & environmental | 14.4% | 114 |
| 3 | Brakes | 14.4% | 114 |
| 4 | Body, structure & corrosion | 8.7% | 69 |
| 5 | Tyres | 7.8% | 62 |
| 6 | Steering | 6.1% | 48 |
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 | 31 | 16.1% |
| 30-60k | 104 | 6.7% |
| 60-90k | 197 | 15.7% |
| 90-120k | 283 | 14.5% |
| 120-150k | 116 | 24.1% |
| 150k+ | 60 | 23.3% |
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2021 | 154 | 14.9% |
| 2022 | 165 | 15.2% |
| 2023 | 173 | 18.5% |
| 2024 | 150 | 15.3% |
| 2025 | 149 | 15.4% |
What to check before buying a 1986 Sl
On a 1986 Sl, lighting & signalling is what the MOT record says goes wrong most — it appeared in 11.4% of tests. Check these areas before you commit.
- Lighting & signalling (11.4% of tests): Often a cheap bulb, but persistent issues can mean wiring or corrosion in the units. Typical repair: £10–£150.
- Suspension (6.2% 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.
- Brakes (5.8% 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 1986 Mercedes-Benz Sls pass their MOT?
84.1% of the 791 1986 Mercedes-Benz Sl MOT tests in this dataset passed — a 15.9% fail rate.
What is the most common MOT failure on a 1986 Mercedes-Benz Sl?
Lighting & signalling, recorded in 11.4% of tests, followed by suspension (6.2%).
Does the 1986 Sl get worse with mileage?
Its MOT fail rate rises from 16.1% in the 0-30k band to 23.3% in the 150k+ band.
Methodology & source. Based on 791 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.