Common MOT Failures and How to Avoid Them

Summary

• Lights are the top failure reason: A blown bulb is the easiest and cheapest fix.
• Tyres are second: Check tread depth and condition before your test.
• Many failures are preventable: A quick home check can save you time and money.

Nobody wants to fail their MOT. It means more expense, more time off work, and more hassle.

The good news? Many MOT failures are easy to prevent. A 15-minute check at home can catch the most common problems before the tester does.

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Top 10 MOT Failure Reasons

According to DVSA data, these are the most common reasons cars fail the MOT:

1. Lighting and signalling (30%) — Blown bulbs, dim headlights, faulty indicators.
2. Suspension (13%) — Worn shocks, broken springs, play in joints.
3. Brakes (10%) — Worn pads, discs, or binding callipers.
4. Tyres (8%) — Below legal tread depth, damage, or wrong size.
5. Driver's view (7%) — Cracked windscreen, faulty wipers, damaged mirrors.
6. Exhaust and emissions (7%) — High emissions, catalytic converter faults, exhaust leaks.
7. Steering (5%) — Excessive play, worn track rod ends.
8. Bodywork and structure (4%) — Sharp edges, excessive corrosion.
9. Registration plates (3%) — Faded, damaged, or illegal spacing.
10. Fuel system (2%) — Leaks or damaged fuel lines.

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Home Checks Before Your MOT

You don't need to be a mechanic to catch these problems. Here's what to check:

Lights

Turn on your headlights, brake lights, indicators, fog lights, and number plate light. Walk around the car and check every bulb. Replace any that are blown — most cost under £5.

Tyres

The legal minimum tread depth is 1.6mm across the central three-quarters of the tyre. Use a 20p coin — if the outer band of the coin is visible, the tyre is too worn.

Also check for cuts, bulges, or uneven wear. These will all fail the MOT.

Windscreen

A chip larger than 10mm in the driver's line of sight will fail. A chip larger than 40mm anywhere in the swept area will also fail.

Get chips repaired before they spread into cracks. Most chips can be fixed for £30-£50.

Wipers and Washers

Worn wiper blades that leave streaks will fail. New blades cost under £15 and take minutes to fit. Also check the washer fluid is topped up and the jets spray properly.

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Emissions Tips

High emissions are a common failure, especially for diesels. Here are some tips:

• Take a motorway drive first: A 20-30 minute run at speed clears out the exhaust system and burns off soot in the DPF.
• Use quality fuel: Premium fuel can help reduce emissions temporarily.
• Check the engine light: If the engine management light is on, fix the issue before the MOT. It's an automatic fail.

Pro tip: Book your MOT for the afternoon. Drive the car for at least 30 minutes before the test to get the engine and exhaust up to temperature.

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What Happens If You Fail?

If your car fails the MOT, you have a few options:

• Get repairs done at the same garage: Many garages offer a free retest if you get the repairs done with them within 10 working days.
• Get repairs elsewhere: You can take the car to another garage for repairs and then bring it back for a partial retest.
• Appeal: If you think the fail was wrong, you can appeal to DVSA within 14 days.

Check your MOT history to see previous results and advisories. This helps you prepare for what might come up next time.

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Understanding MOT Advisories

An advisory is a warning, not a fail. It means something is starting to wear but hasn't reached the fail point yet.

Common advisories include "brake pads wearing thin" or "slight corrosion on subframe." These are heads-up items that may fail next year.

Smart drivers fix advisories before the next MOT. It's cheaper to deal with them on your schedule than as an emergency.

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When to Book Your MOT

You can book your MOT up to one month before it expires without losing any days from the new certificate. The new expiry date will be 12 months from the old one.

Don't leave it until the last day. If your car fails, you'll need time to get repairs done. Booking early gives you a buffer.

Read our full MOT guide for everything you need to know about the MOT test.

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A little preparation goes a long way. Spend 15 minutes checking your car before the MOT and you'll avoid the most common failures. It's the smartest £30 worth of bulbs and wiper blades you'll ever spend.

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