Reliability evidence from 2023 official MOT data
Mercedes Benz GLB Class Reliability, Common Problems & MOT Faults
Looking for Mercedes Benz GLB Class common faults or reliability evidence? This guide analyses 2,778 normal initial class 4 MOT tests, showing the problem areas recorded most often and how outcomes change with age and mileage.
Is the Mercedes Benz GLB Class reliable?
In the matched 2023 sample, 89.9% passed as presented. After adjusting for the age mix of vehicles tested, that result was 4.1 percentage points above the age-matched all-model baseline. The tables below show which MOT fault categories recur most often, rather than relying on owner anecdotes or a single headline score.
This is evidence about roadworthiness items inspected at MOT. It does not measure every engine, gearbox, infotainment or intermittent fault, so use it as one part of a used-car reliability check rather than a complete mechanical verdict.
2,778
initial tests
89.9%
passed as presented
91.6%
final pass incl. PRS
+4.1 pts
vs age-matched baseline
What happened at the initial test?
MOT pass rate by vehicle age
Compare each age band with its all-model baseline rather than comparing a three-year-old car with a fifteen-year-old one.
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| Age at test | Tests | Initial pass | Final pass | All-model baseline |
|---|---|---|---|---|
| 3–5 years | 2,555 | 89.4% | 91.2% | 85.8% |
MOT pass rate by recorded mileage
Mileage is the odometer reading recorded at the test. Invalid or implausibly high readings are excluded from this breakdown.
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| Recorded mileage | Tests | Initial pass | Final pass |
|---|---|---|---|
| Under 30,000 | 1,911 | 91.1% | 92.7% |
| 30,000–59,999 | 831 | 87.7% | 89.8% |
Fuel types in the MOT sample
Fuel is recorded for each tested vehicle. The mix helps explain which Mercedes Benz GLB Class variants dominate this MOT sample.
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| Fuel | Initial tests | Share |
|---|---|---|
| Diesel | 2,411 | 86.8% |
| Petrol | 366 | 13.2% |
| Hybrid | 1 | 0% |
Common Mercedes Benz GLB Class faults found at MOT
These are the problem categories most often recorded on tests that initially failed (F or PRS). One test can appear in several categories.
Tyres
57.9%162 tests · of initial failures · 5.8 per 100 initial tests
Lamps and electrical equipment
14.3%40 tests · of initial failures · 1.4 per 100 initial tests
Visibility
13.9%39 tests · of initial failures · 1.4 per 100 initial tests
Seat belts and restraints
8.2%23 tests · of initial failures · 0.8 per 100 initial tests
Brakes
7.5%21 tests · of initial failures · 0.8 per 100 initial tests
Suspension
2.1%6 tests · of initial failures · 0.2 per 100 initial tests
Noise, emissions and leaks
1.8%5 tests · of initial failures · 0.2 per 100 initial tests
Road Wheels
1.8%5 tests · of initial failures · 0.2 per 100 initial tests
Common Mercedes Benz GLB Class advisories and emerging problems
Advisory and minor items can reveal recurring wear before it becomes an MOT failure. Percentages use all matched initial tests.
Tyres
18.4%510 tests · of all tests · 18.4 per 100 initial tests
Brakes
6.6%183 tests · of all tests · 6.6 per 100 initial tests
Visibility
3.2%90 tests · of all tests · 3.2 per 100 initial tests
Seat belts and restraints
0.3%8 tests · of all tests · 0.3 per 100 initial tests
Body, chassis and structure
0.3%7 tests · of all tests · 0.3 per 100 initial tests
Suspension
0.3%7 tests · of all tests · 0.3 per 100 initial tests
Vehicle identification
0.3%7 tests · of all tests · 0.3 per 100 initial tests
Lamps and electrical equipment
0.1%4 tests · of all tests · 0.1 per 100 initial tests
Common Mercedes Benz GLB Class problem areas to check
Start with the fault categories most often recorded for this model. This is a data-led pre-MOT and used-car checklist, not a substitute for a mechanical inspection.
Tyres
Check tread, visible damage, inflation and warning lights. Ask a tyre professional if wear is uneven or close to the legal limit.
Lamps and electrical equipment
Test every exterior lamp, indicator and warning light. Replace failed bulbs and investigate warning lights before the test.
Visibility
Clean the windscreen and mirrors, top up washer fluid, and check the wipers clear the swept area without damage.
Seat belts and restraints
Check every belt latches, retracts and is not visibly damaged, and make sure restraint-system warning lights go out.
Brakes
Treat warning lights, pulling, vibration or unusual pedal feel as reasons for a professional brake inspection.
Suspension
Do not ignore knocks, uneven ride height, steering play or abnormal tyre wear; these need professional diagnosis.
Licensed Mercedes Benz GLB Class vehicles
DfT/DVLA licensing records for Great Britain at 2026 Q1. These are registration-stock figures, separate from the MOT sample.
23,344
licensed
632
SORN
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| Fuel | Licensed vehicles | Share |
|---|---|---|
| Petrol | 9,432 | 40.4% |
| Diesel | 7,492 | 32.1% |
| Hybrid electric (petrol) | 6,420 | 27.5% |
Licensed stock trend
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| Quarter | Licensed vehicles |
|---|---|
| 2026 Q1 | 23,344 |
| 2025 Q4 | 22,230 |
| 2025 Q3 | 21,619 |
| 2025 Q2 | 21,483 |
| 2025 Q1 | 20,823 |
| 2024 Q4 | 19,054 |
| 2024 Q3 | 18,514 |
| 2024 Q2 | 17,784 |
| 2024 Q1 | 16,213 |
Used-car checks that model averages cannot replace
- 1Check the registration's MOT historyLook for mileage changes, repeat advisories and whether defects were fixed at later tests.Open on MOTScout →
- 2Check outstanding safety recallsA model can be affected while an individual car has already had the repair.Open on MOTScout →
- 3Find the exact variant's fuel and CO₂ dataSearch certified VCA Euro 6 records by model, engine and gearbox.Open on MOTScout →
- 4Get an independent inspectionAn MOT certificate only covers testable items at the time of the test and is not a full mechanical inspection.
Plan the next MOT
Calculate the earliest test date
Work out when you can test while keeping the existing renewal date.
Open calculator →Check MOT fees and retest rules
See the current maximum class 4 fee and when a partial retest can be free or reduced.
View cost guide →Find an authorised test centre
Browse MOT stations by town and check the vehicle classes each centre is listed for.
Find a centre →Methodology and limitations
- • Scope: Normal initial class 4 MOT tests in Great Britain matched to a DfT generic car model in 2023.
- • Initial pass = P only. Initial failure = F or PRS. Final pass = P or PRS.
- • Defect percentages count distinct tests with at least one item in a category, so categories do not add to 100%.
- • Detailed trim and engine strings are consolidated using the DfT generic-model field; unmatched records are excluded.
- • The dataset covers Great Britain. Northern Ireland has a separate MOT process.