MOT Failure Points: What to Watch Out For

The annual MOT (Ministry of Transport) test is a crucial legal requirement for most vehicles over three years old in the UK. It ensures your car meets minimum road safety and environmental standards. While it can be a nerve-wracking experience, understanding the common reasons for failure can significantly increase your chances of passing first time, saving you time, money, and the hassle of a re-test. Many failures stem from simple issues that could have been easily rectified with a bit of pre-MOT preparation. Let's delve into the most frequent culprits that lead to an MOT fail and how you can identify them before your test.

Tyres: The Foundation of Safety

Tyres are an extremely common cause of MOT failure, and for good reason – they are your car's only contact with the road. The test will scrutinise their condition, pressure, and legal compliance.

• Tread Depth: The legal minimum tread depth for cars in the UK is 1.6mm across the central three-quarters of the tread around the entire circumference of the tyre. Many motorists fail to check this regularly. You can perform a simple '20p test' by inserting a 20p coin into the main grooves of your tyre. If you can see the outer band of the coin, your tread is likely below the legal limit. Uneven wear, often caused by incorrect wheel alignment or suspension issues, can also lead to failure.
• Condition: Inspectors look for any cuts, bulges, cracks, or perishing of the tyre rubber. Any damage that exposes the cord of the tyre, or a significant bulge indicating internal damage, will result in a fail.
• Pressure: Incorrect tyre pressure, while not a direct fail point itself, can lead to uneven wear and affect braking efficiency, which can then contribute to other failures. Always check your tyre pressures according to your vehicle's manufacturer specifications.
• Spare Tyre: While the spare tyre itself isn't tested unless it's fitted to the vehicle, if your vehicle is equipped with a full-size spare and it's used as one of the road wheels during the test, it must meet all legal requirements. If your vehicle has a tyre pressure monitoring system (TPMS) warning light illuminated, this will also result in a major defect.

Brakes: Stopping Power is Paramount

According to the DVSA (Driver and Vehicle Standards Agency), a significant percentage of MOTs fail on brakes, highlighting their critical role in road safety. The test assesses their efficiency, condition, and operation.

• Brake Pad and Disc Wear: Worn brake pads or excessively thin or corroded brake discs are common issues. Pads have minimum thickness requirements, and discs should be free from deep scoring or warping.
• Brake Fluid: The brake fluid level must be correct, and there should be no leaks from the braking system. Low fluid levels can indicate a leak or severely worn pads.
• Brake Lines and Hoses: These must be free from corrosion, leaks, bulges, or perishing. Any damage here is a serious safety concern.
• Handbrake Effectiveness: The handbrake must be able to hold the vehicle securely, and its mechanism should operate smoothly.
• ABS Warning Light: If your Anti-lock Braking System (ABS) warning light is illuminated on the dashboard, this will result in a major defect.
• Braking Imbalance: The test uses a roller brake tester to check that the brakes apply evenly across the wheels. Significant imbalance can lead to a fail.

Lighting and Signalling: Be Seen, Be Safe

Faulty lights are a surprisingly common and easily avoidable MOT failure. Every light on your vehicle needs to be in perfect working order.

• Bulbs Out: This is the simplest yet most frequent failure. Check all headlights (full beam and dipped), sidelights, brake lights, indicators, fog lights (front and rear), reverse lights, and number plate lights. Even a single bulb out can lead to a fail.
• Correct Colour and Intensity: Lights must emit the correct colour (e.g., white for headlights, amber for indicators, red for brake lights) and be of appropriate intensity.
• Headlight Aim: Headlights must be correctly aimed to avoid dazzling oncoming drivers and to provide adequate illumination of the road. Misaligned headlights are a common fail.
• Lenses: Cracked, missing, or excessively clouded lenses can obscure the light output and lead to a failure.

Visibility: Clear Views are Essential

Your ability to see the road clearly, and for others to see you, is paramount. Several components contribute to this.

• Windscreen Damage: Chips or cracks in the windscreen are common. Any damage larger than 10mm in the 'critical area' (the area directly in front of the driver, roughly the size of an A4 sheet of paper) will result in a fail. Damage larger than 40mm anywhere else on the windscreen will also fail.
• Wipers: Windscreen wipers must clear the screen effectively across their entire sweep. Worn, torn, or split rubber blades are a common cause of failure.
• Washer System: The windscreen washer system must work effectively, delivering fluid to the screen to clear it. Ensure your washer fluid reservoir is topped up.
• Mirrors: All required mirrors must be present, secure, and not excessively damaged.

Exhaust System and Emissions: Breathe Easy

The exhaust system is vital for directing harmful gases away from the vehicle and reducing noise and emissions.

• Leaks and Security: Any significant leaks in the exhaust system, or if it's insecurely mounted, will result in a fail. Excessive noise from the exhaust can also be a reason for failure.
• Catalytic Converter/DPF: For modern cars, the catalytic converter (petrol) or Diesel Particulate Filter (DPF) must be present and functioning correctly. Removal of these components is illegal and will result in an MOT fail.
• Exhaust Emissions: Your vehicle's emissions (carbon monoxide, hydrocarbons, nitrogen oxides, and particulate matter for diesels) must be within legal limits for its age and fuel type. High emissions often point to underlying engine problems that need addressing.

Steering and Suspension: Smooth and Controlled

These systems are crucial for vehicle control, comfort, and handling. Any significant wear or damage can lead to a dangerous driving experience.

• Steering Play: Excessive play in the steering wheel or any part of the steering system (e.g., steering rack, ball joints) will result in a fail.
• Power Steering: If your vehicle has power steering, it must be functioning correctly and free from leaks. The power steering fluid level should be correct.
• Shock Absorbers: Leaking or ineffective shock absorbers can significantly affect handling and braking. A visual inspection will check for leaks, and a bounce test may be performed.
• Springs: Broken or severely corroded suspension springs are a common fail point.
• Bushes and Ball Joints: Excessive wear or play in suspension bushes, ball joints, or wishbones will lead to a failure as they compromise the integrity and control of the suspension.

Bodywork, Chassis, and Structure: The Vehicle's Integrity

The structural integrity of your vehicle is paramount for occupant safety in the event of a collision.

• Corrosion: Excessive corrosion to the vehicle's structural components (e.g., sills, chassis rails, subframes) that affects its strength will result in a fail. Surface rust is usually fine, but deep, penetrating rust is not.
• Sharp Edges: Any sharp edges or projections on the bodywork that could cause injury to pedestrians or other road users will lead to a fail.
• Security of Panels: All body panels must be securely attached.

Other Common Failure Points

Beyond the major systems, several smaller items can also trip up an MOT test.

• Seatbelts: All fitted seatbelts must be in good condition (no cuts, fraying, or perishing), operate correctly (retract smoothly, buckle securely), and be securely anchored.
• Number Plates: Must be clean, legible, correctly spaced, and free from damage. They must also be securely fitted and illuminated by the number plate lights at the rear. Incorrect font or spacing is also a common fail.
• Horn: The horn must work and emit a continuous, uniform note.
• Warning Lights: Certain illuminated warning lights on your dashboard, such as for the engine management system (MIL), airbag, or ABS, will result in an MOT failure.
• Fuel System: Any leaks from the fuel tank, fuel lines, or filler cap are serious and will cause a fail. The fuel cap must also be present and seal correctly.

Common MOT Failure Points & Quick Checks

Frequently Asked Questions About MOT Failures

Q: What should I do if my car fails its MOT?
A: The MOT test centre will provide you with a 'refusal of MOT test certificate' (VT30) that lists the reasons for failure. You'll need to get the issues rectified and then have a re-test. Some test centres offer a free re-test if the car is repaired and re-tested within a certain timeframe (usually 10 working days) at the same centre.

Q: Can I drive my car after an MOT failure?
A: Generally, no. You can only drive your car if your old MOT certificate is still valid and no 'dangerous' defects were identified. If your car has failed its MOT and your old certificate has expired, or if any 'dangerous' defects were listed, you can only drive it to a pre-booked appointment at a garage for repairs, or to another MOT test station. Driving it for any other purpose is illegal and could lead to fines, points, and invalidate your insurance.

Q: What is the difference between 'Major' and 'Dangerous' defects?
A: The MOT test now categorises defects: 'Minor', 'Major', and 'Dangerous'. Minor defects are advisories and won't fail the test but should be addressed. 'Major' defects will result in a fail and must be repaired. 'Dangerous' defects also result in a fail, but additionally, your vehicle is deemed unsafe to drive and should not be driven on the road until repaired, even if your old MOT is still valid.

Q: How can I prepare my car for an MOT to avoid failure?
A: Many failures are preventable. A few simple checks can make a big difference: check all your lights, test your horn, check tyre tread and pressure, top up screen wash, ensure wipers are effective, check seatbelts, and look for obvious signs of fluid leaks. If you're unsure, consider a pre-MOT check at a trusted garage.

Q: How much does an MOT re-test cost?
A: The cost of a re-test can vary. If your vehicle is repaired and re-tested at the same test centre within 10 working days, it's often free, or only a partial re-test fee is charged. If you take it to a different centre or exceed the timeframe, you'll likely pay the full MOT test fee again.

Understanding these common failure points and performing regular, simple checks on your vehicle can significantly improve your chances of passing your MOT first time. Not only does it save you hassle and money, but more importantly, it ensures your vehicle is safe and roadworthy, protecting yourself, your passengers, and other road users.

If you want to read more articles similar to MOT Failure Points: What to Watch Out For, you can visit the Maintenance category.