Car servicing: MOT Test Failures 5 Common Examples

Car servicing: 5 common examples of MOT failure

MOT tests are mandatory for almost every private vehicle in the UK on an annual basis. The only exception is when your car is exempt or less than three years old. For many motorists this can be a stressful time as they wait anxiously to find out if their car has passed or failed. In this weeks blog post we are looking to take some of that stress away by looking at the 5 most common MOT test failures and how to avoid them.


MOT test failure: Lighting components

MOT test Flashing indicator

Lighting is an important part of a vehicle, although often over looked. How many times have you seen a car driving with a bulb out? This is among the most common MOT test failures which is unnecessary given how simple it is to avoid. 

Of course there are a variety other lighting related issues that can cause an MOT test failure. These include a misaligned headlight aim, discoloured or miscoloured bulbs, misted lenses and damaged light units.

The best way to avoid this becoming an issue is to check your vehicles lights every so often. Make sure to cycle through each light and have a friend or family member which ones are working. All of your lights should be working correctly and be the correct colour (orange indicator bulbs should not be faded for example).

If you do have any failed bulbs, these are normally relatively easy to change however it can a little more difficult on some cars so don't be afraid to ask you favourite local garage for a bit of help.

For misted Lenses you can use a headlight restoration kit or a machine polishing tool to bring back some clarity. If you suspect that your headlights are misaligned you can also adjust them at home although proper calibration is recommended.

MOT test failure: Number plates

MOT test numberplates

Number plates are another common point of failure for an MOT test. A number plate is one of the fastest and easiest way to identify a vehicle and as such needs to be legible at all times by both human eyes and the dreaded ANPR cameras. 

A number plate will fail an MOT test for any of the following reasons; 

  •  It is obscured, deteriorated or delaminated.
  •  Fixings or features alter the registration number.
  •  The background features overprinting.
  •  The plate is outside of regulations for the vehicles year.

The best way to ensure your vehicle doesn't fail an MOT test on number plate issues is to keep it clean and replace the plate if it is at all damaged or obscured.

You should also ensure that your plate isn't stylised outside of regulations for your cars year and that characters and spacing adhere to British standards.

MOT test failure: tyres

MOT test tyres

Tyres are vital in keeping your car on the road. They come in all shapes and sizes ranging from slimline sports to chunky off road rubber. The one thing they all have in common is that they will deteriorate over time.

When performing an MOT test the technician will be checking your tyres thoroughly for signs of wear or damage. If the tyres are deemed unsafe they will trigger a failure.

Reasons for failure include the tyre showing metal cords, damages to the sidewall in the form of cuts or bulges or if the tyre is below the minimum legal limit of 1.6mm.

MOT test aside, it is important to check your tyres regularly for both pressure and for signs of damage every so often as a matter of safety.

A final note on the minimum legal limit is that it is very low and at a point where a tyres effectiveness is seriously compromised. You should consider changing tyres when the tread depth is below 3mm to maximise safety. 

MOT test failure: brakes

MOT test brake check

Despite their obvious importance, brakes are the cause of 1 in 10 MOT test failures. That equates to 10% of all cars on Britain's roads having inadequate stopping power. Scary.

The most common issue we come across is worn brake pads. Brake pads, for those who don't know, are the small pads that are pushed against the disc when you operate your brake pedal. These pads will wear over time and become thinner and thinner until they are just bare metal.

If your pads are below quarter of an inch thick they will fail the MOT test. This can easily be avoided by checking the pads yourself visually, you simply need to look between the disc and the caliper for an indication on how worn the pads are. 

We also see a number of failures from worn brake discs. Brake discs will fail an MOT test if they are significantly and obviously worn or insecure, fractured or otherwise likely to fail. The best way to keep on top of this is to visually check your discs for any signs or damage or degradation. 


MOT test failure: suspension.

MOT test suspension

If you ask my nan, she will tell you that Britain once had the best roads in the world. If you ask me, they are in an absolute state. The roads today are not too friendly on our suspension, which is especially true for more sport orientated cars. This means that suspension issues are a common problem with many people hitting a large pot hole at least once a year.

Aside from pot holes you also have the natural degradation of suspension components that rust and lose their spring factor over time. Snapped springs, leaking or ineffective shock absorbers and excessive play can all result in an MOT test failure. 

Listen out for any loud knocks and bangs and look for any visual cues as to whether your suspension has failed. This is especially important after hitting a curb or pothole at speed and if you're unsure - get it checked.

You can even take a more hands on approach and try to depress each corner of your vehicle by pushing it down. Does it return to the same level?

The MOT test isn't designed to scare you or rip you off. It is put in place to make sure that your car is checked annually and meets a minimum standard of safety. Some things aren't checked on an MOT which is why we always treat our cars to a rigorous inspection before sale. 

The MOT test should not be relied upon to prove a car is road worthy. A car that passed 6 months ago may have developed a fault during that time which is why we always encourage regular self checks of your vehicle. 

Book your MOT test with us 

Well, here it is. Just what you've been waiting for. It's time for another shameless plug! 

Book your MOT with us and receive a discount if booked with a service.

Book here: MOT Southampton Test Centre | E&J Jarvis (

We also have a very useful MOT reminder service which texts you when your MOT test is due.

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