What Are the Most Common Reasons for MOT Failures?
The MOT test is a vital annual check to ensure vehicles are roadworthy and safe. However, many cars fail to pass on their first attempt, often due to predictable issues. The most common MOT failures typically revolve around critical safety and environmental components that wear or degrade over time.
- Brake system faults are the leading cause of MOT failure.
- Tyre condition, including tread depth and damage, is a frequent failing point.
- Lighting and signalling equipment issues are also very common.
- Suspension and steering components often fail safety checks.
Many of these issues stem from regular wear and tear, or simply a lack of routine maintenance. Understanding these common pitfalls allows drivers to proactively inspect their vehicles, potentially saving them the stress and cost of a failed test and subsequent retest.
Tyres: The Foundation of Road Safety
Tyres are one of the most frequently cited reasons for MOT failure. The primary concern is tread depth; it must be a minimum of 1.6mm across the central three-quarters of the tyre's breadth. Beyond depth, inspectors check for cuts, bulges, or any damage that could compromise structural integrity. Uneven wear, often a sign of alignment or suspension issues, can also lead to a fail. It’s not just about the tyre itself; wheel bearings and the condition of the wheels also come under scrutiny.
Brakes: Your Lifeline on the Road
The braking system is paramount for safety, and it's unsurprising that it's a major contributor to MOT failures. Inspectors meticulously check the condition and performance of both the service brake (foot brake) and the parking brake (handbrake). Issues like worn brake pads and discs, leaking brake fluid, corroded or damaged brake pipes, and faulty callipers are all common reasons for failure. The parking brake must hold the vehicle securely on a gradient, so if it's weak or ineffective, it will result in an immediate fail.
Lights and Signalling
For a vehicle to be safe, its lights and signals must be in full working order. This includes headlights (dipped and main beam), taillights, brake lights, indicators, and hazard lights. Common failures here include bulbs that are blown, the wrong wattage, or misaligned. Cracked or missing lenses, and wiring issues that prevent lights from illuminating correctly, are also frequent MOT failure points. The colour of the light emitted must also comply with regulations.
Suspension and Steering
The MOT test places significant emphasis on the steering and suspension systems to ensure the vehicle handles predictably and safely. Components like shock absorbers, springs, wishbones, and anti-roll bars are checked for wear, corrosion, or damage. Loose or seized steering components, as well as excessive play in the steering rack, will lead to failure. A vehicle that drifts significantly or feels unstable when driven is likely to have suspension or steering issues.
Visibility and Windscreen
The driver's ability to see the road clearly is non-negotiable. Windscreen damage, such as large chips or cracks in the driver's line of sight (an area roughly the size of a £1 coin in the centre), will cause the vehicle to fail. Similarly, windscreen wipers that don't clear the screen effectively, or a faulty windscreen washer system that doesn't provide fluid, can lead to a fail. Demisting and defrosting systems are also checked for functionality.
Beyond the Basics: Other Frequent MOT Failure Areas
While tyres, brakes, and lights often top the list, several other critical areas can cause an MOT failure. These include issues that might seem minor but have significant safety or environmental implications, such as exhaust emissions, seatbelts, and body structure. Addressing these can prevent unexpected failures and ensure your vehicle is compliant.
Exhaust Emissions
Modern vehicles are subject to strict emissions tests. The exhaust system is checked for leaks, excessive noise, and its overall condition. More importantly, the vehicle's emissions must fall within the prescribed limits for its age and fuel type. A catalyst that is not working correctly or an engine that is running inefficiently can lead to a failed emissions test. This is particularly relevant for older diesel vehicles, but modern petrol engines are also monitored closely.
Check your exhaust system for rust or damage before your MOT; even minor leaks can impact emissions readings and noise levels.
Seatbelts and Restraints
All fitted seatbelts must be present, correctly marked, and in good working order. This means they should retract smoothly, lock securely when pulled sharply, and show no signs of fraying or damage. The anchor points for the seatbelts must also be secure and free from corrosion. This applies to all seatbelts in the vehicle, including those in the rear.
Body Structure and General Condition
The structural integrity of the vehicle is assessed to ensure it can withstand typical road conditions and provide adequate protection in an accident. This involves checking for excessive corrosion or damage to the chassis, suspension mounts, and other load-bearing parts. Sharp edges or projections that could injure pedestrians are also a cause for failure. The fuel tank and pipes are also inspected for leaks or damage.
Electrical Systems and Battery
Beyond just lights, other electrical components are checked. This includes the horn, which must be functional and audible, and the vehicle's electrics generally. For electric car mot checks, specific battery and charging system components will be scrutinised. While not always a direct failure point unless it impacts safety or emissions, a poorly maintained battery or charging system can lead to other issues.
Doors, Mirrors, and Wiper Blades
Small but important details matter. Doors must open and close from both the inside and outside. Mirrors must be present, secure, and in good condition, offering a clear view. Windscreen wiper blades must effectively clear the screen, and the washer fluid system must operate. Any obstructions to the driver's view, such as stickers or damage on the windscreen, can also be a reason for failure.
How to Prepare for Your MOT and Avoid Common Failures
Preventing MOT failures is far more straightforward than dealing with the aftermath. A proactive approach, focusing on regular checks and maintenance, can significantly increase your chances of passing first time. Many common issues are easily spotted and rectified before they become serious problems.
Pre-MOT Checks: What You Can Do
Before taking your vehicle for its MOT test, conduct a thorough visual inspection yourself. Start with the obvious: check all your lights are working, including brake and indicator lights. Walk around the car and examine your tyres for wear, damage, and correct pressure; ensure the tread depth is well above the 1.6mm minimum. Check your windscreen for chips or cracks in your line of sight. Test your horn, windscreen wipers, and washer fluid. Ensure all seatbelts retract and lock properly.
It's also wise to look underneath your car. Check the exhaust system for obvious signs of damage or blowing. While you might not be able to check every suspension component, a quick look for anything obviously loose or damaged can be beneficial.
The Role of Routine Servicing
Regular servicing is perhaps the single most effective way to avoid common MOT failures. A mechanic performing a service will naturally check many of the components that are critical for the MOT test. They can identify wear and tear on brakes, suspension, and steering parts before they reach a dangerous or failing level. They will also check fluid levels, the exhaust system, and other vital areas, often spotting potential MOT issues during routine maintenance.
Understanding MOT Advisories
Sometimes, a vehicle might not fail outright but will receive an MOT advisory notice. This highlights issues that are not serious enough to cause an immediate failure but will likely need attention in the near future. Ignoring these advisories can lead to a failure at a future MOT test or, more importantly, compromise your vehicle's safety. It is always advisable to address advisory items promptly.
When Will a New Car Need its First MOT Test?
For new cars, the first MOT test is typically due three years after the vehicle is first registered. This means that for the first three years of its life, a brand-new car is exempt from the MOT requirement. After this initial period, it will need to undergo the MOT test annually.
Electric Car MOTs
Electric vehicles (EVs) are subject to the same MOT test requirements as conventional vehicles, covering areas like brakes, tyres, lights, and steering. However, the inspection for EVs also includes specific checks related to their high-voltage electrical systems and battery integrity. While the core principles of road safety remain the same, the technical checks for electric car mot failures may differ slightly in detail from those for internal combustion engine vehicles.
What Happens After a Failed MOT?
Receiving a failed MOT certificate can be disheartening, but it's an opportunity to ensure your vehicle is made safe. The process involves identifying the specific reasons for failure and arranging for the necessary repairs. Understanding the steps following a failure can help alleviate stress and get you back on the road quickly and safely.
The Failure Certificate
When your vehicle fails its MOT, you will be issued with a 'Refusal of an MOT Test Certificate' (VT30). This document clearly lists all the reasons for the failure, categorising them as 'Dangerous' or 'Minor' defects. Dangerous defects mean the vehicle must not be driven until repaired, as it poses an immediate risk to road safety. Minor defects are listed as advisories and should be addressed to prevent future failures.
Getting Repairs Done
You can have the necessary repairs carried out by any garage or mechanic of your choice. Some testing centres offer repair services, while others are purely testing stations. It is advisable to get a clear quote for the repairs before authorising any work. Once the repairs are completed, the vehicle will need to undergo a partial or full retest.
Keep your failed MOT certificate safe; it details precisely what needs fixing and can be helpful when discussing repairs with your chosen mechanic.
The MOT Retest
The rules for MOT retests vary depending on when the retest is carried out. If the vehicle is left at the same test centre for a free retest within one working day, only certain items will be checked. If the vehicle is taken away and returned for a retest after one working day, or taken to a different test centre, a full MOT test may be required again. Always clarify the retest procedure with the test centre.
The most common MOT failures highlight the critical importance of regular vehicle maintenance and pre-test checks.
Driving After a Failure
If your vehicle has a 'Dangerous' defect, you must not drive it on public roads until it has been repaired. Driving a vehicle with dangerous defects can result in prosecution and penalty points on your licence, as well as putting yourself and others at risk. You can only drive a vehicle with dangerous defects if you are travelling to a pre-booked appointment for repair or to a pre-booked MOT retest.
MOT Exempt Vehicles
Certain vehicles are exempt from the MOT test requirement, most notably new cars for their first three years. However, this exemption does not mean these vehicles should not be maintained. Regular checks and servicing are still crucial to ensure they remain safe and roadworthy, even if they do not require an annual MOT certificate.