MOT failure rate and common problems for the Mercedes 3, and how to check your own car by registration.
Updated 05 September 2026.
Mercedes 3 MOT failure rate
What a Mercedes 3 fails its MOT on, and the part that fixes each.
What it fails on, and why
Suspension failures usually mean a worn or snapped coil spring, a leaking shock absorber, or play in a lower arm ball joint or bush. The tester checks for corrosion, fractures and excessive movement. A broken front spring is one of the most common failures on higher-mileage cars and is a straightforward replacement.
Visibility failures include torn or smearing wiper blades, a washer jet that does not reach the screen, and chips or cracks in the driver's swept area. Blades and washer fluid are quick, cheap fixes.
Brake failures cover worn pads and discs, an imbalance between wheels, corroded or scored discs, or a binding caliper. Braking efficiency is measured on a rolling road, so a spongy or pulling brake shows up as a low reading.
Structural failures are corrosion in load-bearing areas, sharp edges, or insecure panels. These are inspection-and-welding jobs rather than a simple bolt-on part, so weigh them against the value of the car.
Seat-belt failures are frays, cuts, corroded anchorages, or a belt that will not lock under a sharp pull or retract properly.
Tyres fail for tread below the 1.6mm legal limit across the central three-quarters, uneven or exposed-cord wear, or sidewall damage. The tester inspects all four; a single illegal tyre is a fail.
The parts that fix each
If your car has just failed, you have 10 working days to fix the items and get a free partial retest. Confirm the exact fitment against your registration or VIN before buying.
Other models
Questions and answers
What is the MOT failure rate of the Mercedes 3?
It fails 15.3% of its MOT tests across the DVSA record, from 59 tests.
What do these cars fail their MOT on most?
The most common failure area is suspension, at 33.3% of this model's failures.