Mercedes-Benz 320 common MOT failures and failure rate
What a Mercedes-Benz 320 fails its MOT on, from real DVSA test data, and the part that resolves each item.
Based on 26,442 MOT tests in DVSA data.
About 24.1% of MOT tests recorded on the Mercedes-Benz 320 in DVSA data end in a failure. The same handful of items account for most of them.
Its most common failure is suspension, which makes up 31.2% of the Mercedes-Benz 320's failures, followed by suspension, lamps & electrical, brakes, tyres. Each item below links to the part that resolves it. Confirm the exact fitment against your registration or VIN before buying, and have safety-critical work done by a competent mechanic.
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.
Lighting is the single most common MOT failure and the cheapest to put right. A blown headlight, brake-light or number-plate bulb, a cracked lens, or a headlamp beam that points too high or low will all fail. Most are a two-minute bulb swap.
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.
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.
Exhaust failures cover leaks, insecure mountings and emissions over the limit. A blowing exhaust, a failed lambda reading or a diesel that smokes beyond the limit will fail.
This covers a range of smaller items, from a non-working horn to a warning light left on.
Failure rate by year
How the MOT failure rate varies by the car's year of first registration (older examples generally fail more as wear sets in).
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. These are the usual parts; confirm the exact fitment against your registration or VIN before buying.
Other models
Sources: DVSA MOT History API: MOT test results and defect data · DVSA MOT testing data for Great Britain