7 Common Reasons Why Cars Fail Their MOT Test

Booking an MOT test can feel routine, but that doesn’t mean your car is guaranteed to pass. Every year, plenty of drivers in Sandy get caught off guard by test failures that could have been avoided with some simple checks. Knowing what testers commonly flag during an inspection can help you stay one step ahead and keep your vehicle roadworthy.

This isn’t just about ticking a box. Failing an MOT means you can’t legally drive your car unless it passes a retest. That can disrupt your plans and even cost you more in repairs if small issues are left to develop into larger faults. To help you prepare, we’re breaking down the most common reasons cars don’t pass their MOT and what you can do to avoid them.

Understanding The MOT Test

The MOT test checks whether your vehicle meets the minimum safety and environmental standards for driving on UK roads. It’s required once your car is three years old and every year after that. In Sandy, it plays a big role in keeping daily traffic safe and reliable, especially since many drivers here rely on their cars to get to work, drop the kids off or commute into Bedford.

The test covers areas like lights, brakes, emissions, tyres and more. Failing just one part of the checklist could result in a test failure. That’s why staying on top of maintenance all year matters, not just the week before your MOT appointment.

Tyre And Wheel Issues

Your car’s tyres do more than just roll you along the road. They’re key to handling, stopping and keeping your vehicle safe in all seasons. If your tyres are worn, damaged or under-inflated, you’re more likely to see a red flag on your MOT.

Here are common tyre problems testers often spot:

- Tread depth below the legal limit, which reduces grip and control

- Cracks or bulges in the sidewalls, which can mean structural damage

- Uneven wear patterns, often caused by misalignment or poor suspension

- Tyres that are the wrong type or size for your vehicle

Don’t forget the wheels either. Loose or corroded wheel nuts, damaged rims or missing hubcaps may not seem like a big deal, but they can result in a failed test. A quick visual check now and then, especially before your MOT, can save you a lot of hassle later.

Brakes And Suspension

Brake problems are one of the top reasons vehicles fail their MOT test. It makes sense. If your brakes aren’t fully working, you’re putting yourself and other road users at risk. During the test, inspectors look at how the braking system performs, as well as any visible signs of damage or wear.

Some telltale signs of brake trouble include:

- A soft or spongy brake pedal

- Squeaking or grinding sounds when braking

- Vehicle pulling to one side when stopping

Suspension is another area that sometimes gets overlooked. Potholes, speed bumps and daily wear and tear can cause springs, shock absorbers and linkage components to weaken or break. If your car feels bouncy, drifts during corners or sits unevenly when parked, the suspension might be to blame.

Ignoring signs like these can lead to a failed MOT, but more importantly, it makes your daily driving less safe. Regular inspections and routine servicing are the best way to keep brake and suspension systems working properly.

Lights And Electricals

Lights are one of the easiest things to check on your car, yet they’re among the most common culprits for MOT failures. A single broken headlamp or non-functioning indicator can lead to a fail, even if the rest of your car is in good shape.

Before your MOT, it’s a good idea to do a walk-around. Turn your lights on and check that all of them work, including:

- Headlights

- Brake lights

- Indicators

- Number plate lights

- Reverse lights

It also helps to have someone press the brake pedal while you stand at the back to check the lights respond properly. If any bulbs are out, replace them right away.

Dashboard warning lights can also signal trouble. If there’s an airbag warning, engine management light or another indicator glowing that shouldn’t be, your car could be flagged. Other smaller electrical faults like a broken horn, flickering interior lights or faulty wiper controls may sound unimportant, but they all add up during the test.

Wiring and battery terminals can cause issues too. Corroded battery connections, exposed wires or loose fittings might seem minor but will be noted by the tester. Getting these sorted ahead of time can keep your car on track for a pass.

Exhaust And Emissions

The exhaust system does more than move fumes out of the engine. It helps control emissions, boosts fuel efficiency and keeps engine noise down. If anything in the system is damaged or not working well, it can lead to higher emissions or noise levels, both of which can cause an MOT fail.

Your car might fail the emissions test if:

- There’s too much smoke coming from the exhaust

- The levels of pollutants are too high

- There’s a leak or visible hole in the exhaust system

- The catalytic converter isn’t doing its job

Something as small as a slight leak in the system could make the car sound louder without you realising there’s a deeper issue. Strange rattling noises or roaring from underneath the car often point to loose parts or broken exhaust sections. In one case shared by a Sandy local, their neighbour noticed their car was louder than usual—and MOT failure confirmed a blowing exhaust.

Your sense of smell can also help. If there’s a strong smell of petrol or fumes while your car is idling, it’s time to get the exhaust system inspected.

Keeping Your Car MOT-Ready In Sandy

Staying ahead of your MOT doesn’t start the week before your test. Most of the problems that lead to failure are the result of slow wear and tear. That means they’re easier to spot and fix in advance if you pay attention throughout the year.

Most issues that cause MOT failures are avoidable. You can check your tyres for cracks and low tread, make sure all the lights work and listen out for odd sounds. Brakes that feel different or warning lights that pop up should be addressed early. These signs are your car’s way of telling you something’s not right.

Regular servicing helps you catch these problems before they become costly. It’s especially helpful for drivers in Sandy, where people rely heavily on their cars every day—whether that’s for a morning commute into Bedford or the school run.

The more familiar you are with how your car feels, drives and sounds, the more confident you’ll be when test day comes around. Being MOT-ready means fewer surprises, more confidence, and a smoother driving experience all year long.

If you're in Sandy and want to avoid any surprises at your next MOT test, regular checks and servicing make all the difference. At Krause Autos Ltd, we provide dependable support to keep your car in top working order. Learn how we can help by exploring our services for MOT in Sandy and get your vehicle booked in today.