Top 10 Reasons UK Cars Fail Their MOT (And How to Avoid Them)

Short answer: The most common MOT failures in the UK are lighting faults, suspension issues, worn brakes, tyre defects, and poor visibility. Together, these five categories account for over 70% of all failures, and nearly every one of them is preventable with a 15-minute pre-MOT check at home.

Here’s the full top 10, what causes each failure, and how to catch them before test day.

Why MOT Failure Rates Keep Climbing

Roughly 1 in 3 UK cars fail their first MOT, and the national pass rate has stayed below 70% for most of the past decade. The reasons are consistent year after year; DVSA data shows the same handful of components causing the vast majority of failures.

The good news is that most of these are small, cheap fixes if caught early. The bad news is that most owners never check until the pass certificate fails to print.

The Top 10 Reasons UK Cars Fail Their MOT

1. Lighting and Signalling Faults

The single biggest cause of MOT failure in the UK. Blown bulbs, cracked lenses, misaligned headlights, and faulty brake lights account for nearly 1 in 5 failures. A full walk-around with the engine running and someone pressing the brake pedal takes two minutes and catches almost all of these.

2. Suspension Problems

Worn springs, failed shock absorbers, perished bushes, and corroded mounts are the second-biggest MOT killer. Signs include bouncing after a bump, uneven tyre wear, or the car sitting lower on one corner. A quick visual check from the front and rear tells you most of what you need to know.

3. Brake Faults

Worn pads, scored discs, soft pedal feel, and leaking brake lines regularly fail cars. A simple test: brake hard from 30mph on an empty road. If the car pulls to one side, the pedal feels spongy, or there’s a grinding noise, book the brakes in before the MOT.

4. Tyre Defects

UK law requires a minimum tread depth of 1.6mm across the central three-quarters of the tyre. Sidewall damage, bulges, cracks, and incorrect pressures all fail instantly. A 20p coin test: if the outer band is visible when you insert the coin into the tread, the tyre is below the legal depth.

5. Visibility Issues

Torn wiper blades, failing wiper motors, washer pumps, cracked windscreens, and obstructed view (dashcams, air fresheners, satnav mounts) all cause MOT failures. Windscreen cracks larger than 10mm in the driver’s line of sight are an automatic fail.

6. Fuel and Exhaust Problems

Rusted fuel filler necks, perforated exhaust pipes, blowing manifolds, and failing emissions all land cars in trouble. Diesel owners should pay particular attention; DPF, EGR, and fuel pipe faults are among the most expensive MOT fails to fix if ignored.

7. Steering Faults

Heavy steering, excessive play in the wheel, worn ball joints, leaking power steering pumps, and damaged racks all fail. Classic early warnings include whining noises when turning and fluid pooling under the front of the car.

8. Seatbelt and Interior Safety

Frayed webbing, jammed reels, and faulty buckles are small issues that fail big. Equally, airbag warning lights that stay on, non-working horns, and missing or faulty mirrors all cause instant failures.

9. Body, Structure and Corrosion

Rust is a quiet MOT killer, particularly on cars 10 years and older. Sills, floor pans, chassis mounts, fuel filler surrounds, and jacking points are the common spots. If you can see daylight through structural metal, the car won’t pass.

10. Registration Plates and VIN

Faded, cracked, or non-standard plates, including novelty fonts and incorrect spacing, are a surprisingly common fail. The VIN plate must also be visible and legible. A new set of plates costs under £30 and takes 10 minutes to fit.

How to Avoid an MOT Failure

Check lights, wipers, and tyres yourself before test day. These three categories alone cause almost half of all UK MOT failures, and all three can be inspected in under 15 minutes.

Listen for new noises. Whining when steering, grinding when braking, rattling over bumps, early mechanical symptoms almost always point to MOT-fail parts.

Fix small issues before they escalate. A failed bulb is a £5 problem. Ignoring it until a brake switch sensor fails too turns it into a £150 problem.

Buy quality replacement parts. Cheap pattern parts fail quickly and often cause repeat MOT failures within a year. OE-spec aftermarket parts cost a fraction of main dealer prices but match them on quality.

Where V6 Auto Parts Comes In

At V6 Auto Parts, we stock brand-new, factory-sourced replacement parts for every one of the top 10 MOT failure categories: bulbs, wiper motors, brake pads, suspension components, fuel filler pipes, power steering parts, exhaust fittings, and more. Every part is OE-spec, backed by a 12-month warranty, and shipped from our UK warehouse with same-day dispatch before 1 pm and free next-day delivery.

Whether you’re a DIY driver sorting your own MOT prep or a workshop fixing a customer’s fail list, we’ve got the parts in stock to get the car back on the road fast, without the main dealer price tag.

Browse the full range at v6autoparts.com.