Top 10 Most Common Reasons Cars Fail Their MOT

An MOT test is an essential requirement for vehicles in the UK, ensuring they remain safe and roadworthy. Many cars fail their MOT due to minor and preventable issues, causing inconvenience and additional costs for repairs and retesting. Understanding the most common reasons for MOT failures can help vehicle owners take the necessary precautions to improve their chances of passing the test the first time.

Faulty or Non-Working Lights

One of the leading reasons for MOT failures is defective lighting. This includes headlights, brake lights, indicators, reversing lights, and number plate lights. A simple check of all exterior lights before the test can help identify any faulty bulbs that need replacing. Issues with headlamp alignment can also lead to failure if they do not provide adequate road illumination or dazzle oncoming drivers.

Worn or Damaged Tyres

Tyres must meet legal requirements for tread depth and overall condition. The minimum legal tread depth in the UK is 1.6mm, and any tyre below this will result in an MOT failure. Other tyre issues, such as excessive wear, cuts, bulges, or incorrect tyre pressure, can also lead to a fail. Ensuring tyres are in good condition before the test can prevent unnecessary setbacks.

Braking System Issues

Brakes are one of the most critical safety components of a vehicle, and any problems can result in an MOT failure. Worn brake pads, discs, or drums, as well as brake fluid leaks, can compromise braking efficiency. The MOT test includes a rolling road assessment to measure braking performance, and any imbalance or reduced stopping power can result in a fail. Checking the braking system and addressing any concerns before the test is crucial.

Excessive Emissions

A vehicle’s exhaust emissions must comply with environmental standards to pass an MOT. Excessive smoke, high levels of carbon monoxide, or a malfunctioning catalytic converter can all cause failure. Diesel vehicles must also pass a smoke test, and those fitted with a diesel particulate filter (DPF) must ensure it is functioning correctly. Keeping the engine well-maintained and running it at optimal temperature before the test can help reduce emissions.

Obstructed or Damaged Windscreen

Windscreens are assessed for damage that could obstruct the driver’s view. Any chip or crack larger than 10mm in the driver’s direct line of sight, or 40mm anywhere else on the windscreen, will result in failure. Wipers must also be in good working order and effectively clear the windscreen. Ensuring washer fluid is topped up is another simple yet essential step to avoid an MOT fail.

Suspension Defects

Suspension components, including shock absorbers, coil springs, and linkages, are checked for wear and damage during an MOT test. Any leaks, excessive bouncing, or knocking sounds from the suspension system can indicate an issue. A worn or damaged suspension not only affects ride comfort but also compromises vehicle stability and handling.

Steering Problems

The steering system must function correctly, with no excessive play or stiffness. If the steering wheel feels heavy or the car pulls to one side, there may be an issue with the power steering or wheel alignment. The MOT test includes checks for fluid leaks, damaged steering components, and overall responsiveness. Ensuring all elements of the steering system are in good working order can prevent unnecessary failures.

Seatbelt Issues

Seatbelts must be in good condition, securely fastened, and free from cuts, fraying, or damage. The tester will check that they engage properly and lock when pulled sharply. Any warning lights related to the seatbelt system or airbags must not be illuminated, as this can indicate a fault. A quick inspection of all seatbelts before the test can help avoid an MOT failure.

Registration Plate and VIN Issues

The vehicle’s registration plates must be clean, clearly visible, and formatted according to legal requirements. Faded, cracked, or incorrectly spaced plates can lead to an MOT fail. The Vehicle Identification Number (VIN) must also be present and legible, as this is checked to ensure the vehicle’s identity is correct. Cleaning the plates and checking their condition can help prevent unnecessary issues.

Corroded or Damaged Bodywork

Significant rust or structural damage to the vehicle’s body can result in an MOT failure. Areas around the suspension mounts, seatbelt anchor points, and braking components are particularly scrutinised. Any sharp edges or loose panels that could pose a risk to pedestrians or road users will be noted. Addressing bodywork issues before the MOT can improve the chances of passing the test.

Understanding the most common reasons for MOT failures can help vehicle owners take proactive steps to address minor issues before the test. Many of these problems can be identified through simple checks and regular vehicle maintenance, ensuring a smoother and less stressful MOT process.