Most Common MOT Failures in the UK

What an MOT Failure Means

An MOT (Ministry of Transport) test is an annual inspection required for all vehicles over three years old in the UK. It checks that your car meets minimum road safety and environmental standards. When a car fails its MOT, it means one or more components did not meet the required standard and must be repaired before the vehicle can legally be driven on public roads.

An MOT failure does not mean the car is worthless or dangerous beyond repair. Many failures are caused by relatively minor issues — a blown bulb, a worn wiper blade, or a tyre just below the legal tread depth. Others, however, point to more serious and expensive problems like brake disc wear, corroded suspension components, or catalytic converter failure.

Understanding what causes MOT failures helps you make better decisions when buying a used car, because the MOT history reveals exactly how well (or poorly) a vehicle has been maintained.

Why Failure Rates Matter for Buyers

When you are considering buying a used car, the MOT history is one of the most valuable pieces of data available to you — and it is completely free to check on the GOV.UK website.

Here is why MOT failure patterns matter:

• Recurring failures suggest neglect. A car that fails for the same issue year after year (e.g., tyres, brakes) likely has an owner who only fixes things when forced to by the MOT.
• Advisories predict future costs. An advisory note for "brake discs wearing thin" in one year often becomes a failure the next. These are your early warning system.
• High failure rates on certain models are well documented. Some makes and models are statistically more likely to fail in certain areas — knowing this before you buy helps you budget for maintenance.
• Gaps in MOT history can indicate periods off the road. A car with no MOT for 18 months may have been SORN, written off, or simply abandoned. Any gap deserves investigation.

Approximately 37–40% of vehicles fail their MOT each year in the UK. That means the car you are looking at has roughly a one-in-three chance of having failed at some point in its recent history.

Top MOT Failure Reasons

The Driver and Vehicle Standards Agency (DVSA) publishes data on MOT failure reasons. The following are consistently the most common causes, ranked by frequency:

1. Lights and Indicators

Lighting faults are the single most common MOT failure reason, accounting for approximately 18–20% of all failures. This includes:

• Blown bulbs — headlights, tail lights, brake lights, indicators, fog lights, number plate lights
• Incorrect alignment — headlights aimed too high (dazzling oncoming traffic) or too low (insufficient illumination)
• Damaged or discoloured lenses — cracked, fogged, or yellowed headlight lenses that reduce light output
• Faulty indicator operation — incorrect flash rate, non-functioning repeaters, or intermittent connections
• Number plate light failure — one of the most overlooked bulbs on the car

Why it matters for buyers: Lighting failures are cheap to fix (usually under £20), but they indicate how attentive the owner has been. A car that fails for multiple blown bulbs suggests minimal pre-MOT preparation and potentially lax maintenance overall.

2. Tyres and Tread Depth

Tyre-related failures are the second most common MOT issue, covering around 10–12% of failures:

• Tread depth below the legal minimum — the legal limit in the UK is 1.6mm across the central three-quarters of the tyre, around the entire circumference
• Uneven wear patterns — caused by misaligned wheels, worn suspension, or incorrect tyre pressures
• Damage to sidewalls — cuts, bulges, or cracks that compromise the tyre's structural integrity
• Mismatched tyres — different tyre sizes or types on the same axle (not strictly an MOT failure in all cases, but can be flagged)
• Age-related deterioration — perishing, cracking, or hardening of rubber on old tyres (even with adequate tread)

Why it matters for buyers: Tyres cost £50–£200+ each depending on the size. If the car you are viewing has tyres near the legal limit, factor in the cost of replacements. Uneven wear is particularly telling — it often points to underlying suspension or alignment problems that will cost more to fix than the tyres themselves.

3. Brakes

Brake-related failures account for approximately 10% of all MOT failures and are among the most safety-critical:

• Worn brake pads — pads below minimum thickness or worn to the metal backing plate
• Worn or corroded brake discs — discs scored, lipped, or worn below the manufacturer's minimum thickness
• Imbalanced braking — one side braking harder than the other, causing the car to pull under braking
• Binding or seized calipers — brake calipers that do not release properly, causing uneven wear and reduced performance
• Handbrake inefficiency — the handbrake not holding the car on the required gradient
• Corroded or damaged brake lines — especially on older vehicles exposed to road salt

Why it matters for buyers: Brake repairs range from £100 for pads to £400+ for discs and calipers per axle. A car with repeated brake-related MOT failures or advisories likely has a pattern of being run on worn brakes — check the current condition carefully.

4. Suspension Components

Suspension failures represent around 8–10% of MOT failures:

• Worn shock absorbers — failing the bounce test or leaking fluid
• Damaged or worn springs — cracked, broken, or corroded coil springs (a very common issue on UK cars due to road salt)
• Worn ball joints and bushings — excessive play in steering and suspension joints
• Damaged anti-roll bar links — worn drop links that cause knocking noises and affect handling
• Corroded suspension components — rust weakening mounting points, especially on vehicles in coastal or heavily salted areas

Why it matters for buyers: Suspension repairs can be expensive, particularly if multiple components need replacing simultaneously. A car with suspension advisories or failures across multiple tests is likely to need ongoing work in this area.

5. Visibility Issues (Wipers, Mirrors, Windscreen)

Visibility-related failures cover around 7–8% of MOT failures:

• Worn wiper blades — not clearing the windscreen effectively
• Windscreen damage — chips or cracks in the driver's line of vision (a crack larger than 10mm in the swept area, or larger than 40mm outside it, is a failure)
• Missing or damaged mirrors — broken, cracked, or missing wing mirrors or interior rear-view mirror
• Windscreen washer not working — empty reservoir, blocked jets, or failed pump

Why it matters for buyers: These are generally inexpensive fixes, but windscreen replacement can cost £100–£500+ depending on the vehicle. A cracked windscreen that has been there for a while suggests the owner has been cutting corners.

6. Emissions Failures

Emissions testing failures have increased significantly in recent years, particularly for diesel vehicles:

• Diesel particulate filter (DPF) issues — blocked, removed, or tampered DPFs are a major failure point for diesel cars
• Catalytic converter failure — deteriorated or stolen catalytic converters causing high emissions readings
• Lambda sensor faults — faulty oxygen sensors causing incorrect fuelling and high emissions
• Engine management faults — the engine management warning light being illuminated is an automatic MOT failure from May 2018 onwards
• Exhaust leaks — holes or damage to the exhaust system allowing unfiltered gases to escape

Why it matters for buyers: Emissions failures on diesel vehicles can be particularly expensive. A new DPF costs £1,000–£3,000+ depending on the vehicle. If a diesel car has had a DPF advisory or failure, investigate thoroughly — DPF removal (which is illegal) is a common bodge that will cause repeated MOT failures.

Failures by Vehicle Age

MOT failure rates vary significantly with age:

Vehicle Age	Approximate Failure Rate
3 years (first MOT)	15–20%
5 years	25–30%
7 years	35–40%
10 years	40–50%
13+ years	50–60%

Older vehicles are more likely to fail because wear-and-tear items like brakes, suspension, tyres, and exhaust components degrade over time. Corrosion also becomes a significant factor on vehicles over 10 years old, particularly in areas where road salt is heavily used.

Common Failures by Mileage Band

Mileage influences which components are most likely to fail:

• Under 30,000 miles — failures tend to be minor (lights, wipers, tyres). Low-mileage cars driven infrequently may have tyre age issues even with adequate tread.
• 30,000–60,000 miles — brake wear becomes more common. First set of pads and discs may be due. Suspension components start showing wear.
• 60,000–100,000 miles — suspension, exhaust, and emissions components become frequent failure points. Second or third set of brakes likely needed.
• Over 100,000 miles — structural corrosion, major suspension work, catalytic converter and DPF issues become increasingly common. Engine and gearbox mounts may need attention.

High-Failure Areas for Certain Makes and Models

Some vehicles are statistically more prone to certain MOT failures. While we will not single out specific models here, these patterns are well documented:

• French and Italian cars tend to have higher rates of electrical and sensor-related failures
• Older German diesels frequently face DPF and emissions issues, particularly after the DPF regeneration cycle has not been maintained (common with short-journey use)
• Japanese vehicles generally have lower failure rates overall, but are not immune to corrosion-related issues
• Budget brands may use lower-quality consumable parts (brake pads, bushings) that wear faster, leading to earlier failures
• Premium SUVs often have complex air suspension systems that are expensive to repair and a common MOT failure point
• Vehicles driven primarily in rural or coastal areas experience accelerated corrosion due to salt spray and untreated roads

When researching a specific make and model, check forums and owner groups for known MOT weak points. This helps you ask the right questions during a viewing and negotiate based on likely upcoming costs.

How Advisories Predict Future Failures

An MOT advisory is not a failure — the car still passes — but it is a formal note that a component is showing wear and may fail in the future. Advisories are arguably more useful than failures for buyers, because they tell you what is going to need attention next.

Common advisory-to-failure progressions:

Advisory Note	Likely Failure Timeframe
"Brake discs worn but not excessively"	Usually fails within 12 months
"Front tyre wearing on inner edge"	Fails at next test unless alignment and tyres are addressed
"Slight play in steering rack"	May fail within 1–2 tests depending on driving conditions
"Exhaust has minor corrosion"	Can progress to a hole and emissions leak within 1–2 years
"Rear shock absorber has light misting"	Full leak and bounce-test failure within 1–2 years
"Spring corroded but not weakened"	Can fracture within 12–24 months, especially in winter

When viewing a used car, always check the most recent MOT advisories. These are the items you will most likely need to budget for in the first year of ownership.

How to Check MOT History

MOT history is publicly available and free to check. Here is how:

GOV.UK MOT History Service

Visit https://www.check-mot.service.gov.uk and enter the vehicle's registration number. You will see:

• Every MOT test result (pass or fail)
• The date and mileage at each test
• All failure reasons and advisory notes
• The current MOT expiry date

Through a Vehicle History Check

A comprehensive vehicle check from Check A Car includes MOT history as part of the report, alongside finance, stolen, write-off, and mileage data. This gives you a single view of the vehicle's full history rather than checking multiple sources separately.

What to Look For

When reviewing MOT history, look for:

• Recurring failures — the same component failing repeatedly suggests ongoing neglect or an underlying issue
• Mileage consistency — mileage should increase steadily between tests. Any decrease or suspicious jump could indicate clocking
• Advisory progression — advisories that appear and then are not mentioned in subsequent tests (suggesting they were fixed) are a good sign. Advisories that persist and worsen are a concern
• Gaps in testing — periods with no MOT record may indicate the car was off the road, possibly due to a write-off or SORN period

How to Avoid Common MOT Failures

If you already own a vehicle and want to minimise the chance of failure, these pre-MOT checks cover the most common failure points:

1. Walk around the car and check every light — headlights (dip and main beam), indicators, brake lights, tail lights, fog lights, reversing lights, and number plate lights. Replace any blown bulbs.
2. Check tyre tread depth and condition — use a tread depth gauge or the 20p test. Look for damage, bulges, or uneven wear. Replace any tyre below 2mm (the legal minimum is 1.6mm, but most garages recommend replacing at 2mm).
3. Test the brakes — listen for grinding or squealing, feel for vibrations, and check if the car pulls to one side. If in doubt, have them inspected.
4. Check wiper blades and washers — replace wiper blades if they streak or miss areas. Top up the washer reservoir and make sure the jets spray correctly.
5. Look at the windscreen — check for chips or cracks in the driver's line of vision.
6. Check the exhaust — listen for blowing or rattling. Look for visible holes or excessive corrosion. On diesels, make sure the engine management light is not on.
7. Inspect the mirrors — ensure both wing mirrors and the interior mirror are intact and securely mounted.
8. Check the horn — a simple press confirms it works.
9. Review the dashboard warning lights — turn the ignition on and check that all warning lights illuminate then go out. A persistent engine management light is an automatic failure.
10. Check the seatbelts — pull each belt out fully and check for fraying, cuts, or damage. Make sure the buckle clicks securely and releases cleanly.

These simple checks can prevent the majority of common MOT failures and take less than 30 minutes.