Mercedes-Benz Gl 320 MOT pass rate & common failures
2,746 MOT tests on the Mercedes-Benz Gl 320 (2001–2016) give it a 79.9% pass rate. That is 6.3 percentage points better than all cars of a similar age, which fail at 26.4%. Its most common failure areas are lighting & signalling, brakes and emissions & environmental.
What the MOT record shows
Lighting & signalling dominates the failure mix at 11.7% of all tests — 3.0 points clear of brakes, so it is the first thing to check.
At component level the recurring items are rigid brake pipes, position lamp and tread depth — rigid brake pipes alone was recorded 171 times.
Mileage is the strongest signal on the record: 13.3% of 30-60k cars fail, rising to 19.4% once past 150k.
Advisories point at the next bill rather than this one: brakes was flagged on 37.0% of tests without failing them.
The trend is improving — the fail rate fell from 20.0% in 2021 to 17.7% in 2025, as the worst-kept examples leave the fleet.
How it compares
By model year
Every Gl 320 model year with a usable sample. Years with their own detailed report are linked.
| Year | Tests | Pass rate | Fail rate | Most common failure |
|---|---|---|---|---|
| 2006 | 267 | 83.2% | 16.9% | Lighting & signalling |
| 2007 | 1,465 | 79.7% | 20.3% | Brakes |
| 2008 | 426 | 78.4% | 21.6% | Lighting & signalling |
| 2009 | 506 | 80.0% | 20.0% | Lighting & signalling |
| 2010 | 54 | 83.3% | 16.7% | Brakes |
Most common failures (all years)
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Lighting & signalling | 11.7% | 322 |
| 2 | Brakes | 8.7% | 239 |
| 3 | Emissions & environmental | 5.2% | 142 |
| 4 | Suspension | 4.8% | 133 |
| 5 | Tyres | 4.4% | 122 |
| 6 | Body, structure & corrosion | 2.7% | 74 |
| 7 | Visibility | 2.5% | 68 |
| 8 | Seat belts & restraints | 2.3% | 64 |
Most common specific failures
The exact components most often recorded as failures — more specific than the categories above.
| # | Failure item | Times recorded |
|---|---|---|
| 1 | Rigid brake pipes | 171 |
| 2 | Position lamp | 112 |
| 3 | Tread depth | 99 |
| 4 | Shock absorbers | 86 |
| 5 | Headlamp | 73 |
| 6 | Headlamp aim | 64 |
| 7 | Flexible brake hoses | 61 |
| 8 | Side repeaters | 55 |
Top advisory categories
Advisories aren't failures, but they flag work likely needed soon — useful when budgeting.
| # | Category | % of tests with advisory | Tests |
|---|---|---|---|
| 1 | Brakes | 37.0% | 1,015 |
| 2 | Tyres | 25.6% | 704 |
| 3 | Emissions & environmental | 25.6% | 704 |
| 4 | Suspension | 22.4% | 616 |
| 5 | Lighting & signalling | 10.4% | 285 |
| 6 | Body, structure & corrosion | 8.0% | 220 |
Failure rate by mileage
Higher-mileage cars tend to fail more — often the most useful guide to real condition.
| Mileage band | Tests | Fail rate |
|---|---|---|
| 30-60k | 60 | 13.3% |
| 60-90k | 377 | 20.9% |
| 90-120k | 765 | 20.6% |
| 120-150k | 881 | 20.0% |
| 150k+ | 653 | 19.4% |
Failure rate by age
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2021 | 696 | 20.0% |
| 2022 | 649 | 21.7% |
| 2023 | 534 | 18.5% |
| 2024 | 472 | 21.6% |
| 2025 | 395 | 17.7% |
What to check before buying a Mercedes-Benz Gl 320
- Lighting & signalling (11.7% of tests): Often a cheap bulb, but persistent issues can mean wiring or corrosion in the units. Typical repair: £10–£150.
- Brakes (8.7% 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.
- Emissions & environmental (5.2% of tests): More common on older diesels (DPF/EGR) — can be expensive; check for warning lights and smoke. Typical repair: £100–£600.
Repair costs are rough UK ballpark ranges to set expectations, not quotes — actual prices vary widely by car, parts and garage.
Frequently asked questions
What is the MOT pass rate for the Mercedes-Benz Gl 320?
79.9% of the 2,746 Mercedes-Benz Gl 320 MOT tests in this dataset passed, a 20.1% fail rate, across model years 2001–2016.
What does the Mercedes-Benz Gl 320 most often fail its MOT on?
Lighting & signalling, recorded in 11.7% of tests, then brakes (8.7%).
How much does mileage affect Gl 320 MOT results?
Fail rates run at 13.3% for cars in the 30-60k band and 19.4% for 150k+, a 6.1-point difference.
Methodology & source. Based on 2,746 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.