Mercedes-Benz GLS400d — MOT pass rate & failures
2,614 MOT tests on the Mercedes-Benz GLS400d (2019–2023) give an 89.0% pass rate. That is 0.8 percentage points worse than the 10.2% fail rate across all Mercedes-Benz GLS versions, so the GLS400d is a weaker pick within the range. Failures concentrate in tyres, lighting & signalling and brakes.
What the MOT record shows
At component level the recurring items are tread depth, registration plates and brake pads — tread depth alone was recorded 99 times.
Mileage is the strongest signal on the record: 9.4% of 0-30k cars fail, rising to 19.1% once past 90-120k — 2.0× the risk.
Tyres is the most common advisory, noted on 18.4% of tests — work that passed today but is likely due soon.
How it compares
By model year
| Year | Tests | Pass rate | Fail rate |
|---|---|---|---|
| 2019 | 204 | 92.7% | 7.3% |
| 2020 | 1,341 | 89.0% | 11.0% |
| 2021 | 630 | 88.3% | 11.8% |
| 2022 | 403 | 88.1% | 11.9% |
| 2023 | 36 | 94.4% | 5.6% |
Top failure categories
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Tyres | 7.8% | 205 |
| 2 | Lighting & signalling | 1.5% | 38 |
| 3 | Brakes | 1.2% | 31 |
| 4 | Suspension | 1.1% | 28 |
| 5 | Other defects | 0.8% | 20 |
| 6 | Seat belts & restraints | 0.7% | 19 |
| 7 | Visibility | 0.7% | 17 |
| 8 | Road wheels | 0.3% | 8 |
Most common specific failures
The exact components most often recorded as failures — more specific than the categories above.
| # | Failure item | Times recorded |
|---|---|---|
| 1 | Tread depth | 99 |
| 2 | Registration plates | 34 |
| 3 | Brake pads | 33 |
| 4 | Headlamp aim | 30 |
| 5 | Ball joint | 30 |
| 6 | Wipers | 12 |
Top advisory categories
Advisories aren't failures, but they flag work likely needed soon — useful when budgeting.
| # | Category | % of tests with advisory | Tests |
|---|---|---|---|
| 1 | Tyres | 18.4% | 482 |
| 2 | Brakes | 9.1% | 239 |
| 3 | Other defects | 6.4% | 168 |
| 4 | Suspension | 3.3% | 86 |
| 5 | Visibility | 3.1% | 82 |
| 6 | Lighting & signalling | 0.9% | 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 | 989 | 9.4% |
| 30-60k | 1,255 | 10.5% |
| 60-90k | 316 | 16.5% |
| 90-120k | 47 | 19.1% |
Failure rate by age
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2022 | 69 | 10.1% |
| 2023 | 487 | 8.0% |
| 2024 | 836 | 12.3% |
| 2025 | 1,222 | 11.3% |
What to check before buying a Mercedes-Benz GLS400d
Focus on the areas it most often fails on — and remember MOT data covers testable defects only, not engine or gearbox health.
- Tyres (7.8% of tests): Usually a quick, known-cost fix, but check tread, age and uneven wear (which can hint at alignment or suspension issues). Typical repair: £50–£120 per tyre.
- Lighting & signalling (1.5% of tests): Often a cheap bulb, but persistent issues can mean wiring or corrosion in the units. Typical repair: £10–£150.
- Brakes (1.2% 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 reliable is the Mercedes-Benz GLS400d at MOT time?
89.0% of the 2,614 Mercedes-Benz GLS400d MOT tests in this dataset passed — a 11.0% fail rate, in line with the 10.2% average across all GLS versions.
What is the most common MOT failure on a Mercedes-Benz GLS400d?
Tyres, recorded in 7.8% of tests, followed by lighting & signalling (1.5%).
Does the GLS400d get worse with mileage?
Its MOT fail rate rises from 9.4% in the 0-30k band to 19.1% in the 90-120k band.
Methodology & source. Based on 2,614 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.