MOT test changes – how will they affect you?

From 20 May there will be stricter emissions test for diesel cars and MOT test certificates will be easier to understand...

MOT test changes – how will they affect you?

Stricter emissions checks for diesel cars and new pass and fail categories are being introduced. The changes are being brought in to adhere to a European Union directive called the EU Roadworthiness Package.

Tighter scrutiny of diesel cars’ exhaust emissions and a check of their diesel particulate filters (DPFs) could cause more diesels to fail their MOT tests and land owners with costly repair bills. Other changes include the renaming of the pass and fail categories to make them easier to understand.

How is the MOT test for diesel cars changing?

MOT tester using diagnostic equipment

The most significant area for diesel car owners is stricter rules on the permissible level of emissions of cars fitted with a diesel particulate filter (DPF). If a car’s exhaust emits visible smoke of any colour, it will fail the MOT test.

Testers are also required to check if diesel cars’ DPFs have been tempered with or removed.

If there are visible signs of this, the tester must refuse to test the car unless the owner can provide a legitimate reason for it having been removed, such as for cleaning. It’s already illegal to drive a vehicle that has had its DPF removed.

What else is changing?

MOT test centre sign

Three other areas on cars that have the potential to cause serious accidents will also be scrutinised more closely than before. Testers will check steering systems – a steering box with a heavy leak will now result in a MOT failure. Reversing lights that don’t work or have blown bulbs and brake discs that are “significantly or obviously worn” will also result in an automatic fail.

Faults will now be classed as minor, major or dangerous.

Minor faults are comparable to the current advisory notices written on test certificates for items that aren’t bad enough for the car to fail its test, but that will need to be fixed at some point.

Major faults will need to be repaired for the car to pass the test, but the car can be driven away from the test centre to another garage for the work to be done.

Dangerous faults result in a test failure, and the car cannot be driven on a public road until it's fixed. If you're caught driving a car with a dangerous fault, you could get a fine of up to £2500 and three penalty points on your licence.

How will the changes affect you?

New style MOT certificate

If you own a diesel car with a DPF that has been replaced or repaired, you’ll need to show evidence of this to the MOT tester. You’ll also need to ensure that your car is properly maintained so that there are no visible tailpipe emissions.

Owners of all cars should check for blown reversing light bulbs, as well as regularly checking for leaks. This is easy to do: simply look on the ground under the car for oil or other fluids that may have come out.

Finally, listen out for grinding noises from the brakes, because this is likely to mean the car has worn brake pads, and driving with these will damage the brake discs, resulting in a potential MOT fail.

What should I look out for if I’m buying a diesel?

Mercedes-Benz C-Class diesel with fuel filler flap open

If you're buying a diesel, check if it has a DPF (all post-2010 models will). If it does, ask if it's had any problems and check the dashboard for an orange warning light, often shaped like an exhaust. If this is illuminated, it means the DPF is becoming blocked.

Don't buy a car with this warning light on, because it could indicate the need for a replacement DPF, which will cost several hundred pounds.

What are the most common MOT fail items?

Mercedes-Benz C-Class on ramp in garage

More than 35% of cars failed their MOT test the first time in the 2016-2017 financial year according to data from the Driver and Vehicle Standards Agency. And the majority of cars that failed did so for easily avoidable issues, such as blown headlight or indicator bulbs.

Follow our 10 simple tips to ensure your car passes its MOT at the first attempt.

1. Brake lights

1. Brake lights

With the car’s ignition turned on, press the brake pedal and ask someone to check that the brake lights come on. You can also do this on your own by reversing the car up to a wall and looking over your shoulder.

2. Fuel and fuel cap

2. Fuel and fuel cap

The filler cap needs to close securely and your car needs enough fuel in its tank for the tester to carry out emissions checks, so don’t go for an MOT test with the car running on empty.

3. Headlights and indicators

3. Headlights and indicators

Check all the lights work properly: full and dipped-beam headlights, tail-lights, sidelights, hazard lights and all four indicators.

4. Horn

4. Horn

Beep it to ensure it works properly.

5. Numberplates

5. Numberplates

Ensure that both the front and rear plates are clean and legible and, if applicable, check that the light above the rear plate is working.

6. Suspension

6. Suspension

Press down heavily on each front wing of your car; if the car bounces up and down instead of returning to the right position, the shock absorbers may be worn.

7. Seat and seatbelts

7. Seat and seatbelts

Check that the driver’s seat slides back and forth smoothly. Also look for fraying or damage on the seatbelts and give each one a good tug to ensure that it pings back as it should.

8. Wheels and tyres

8. Wheels and tyres

Check all four wheels and the sidewalls of the tyres for damage; bulges, cracks and gouges out of the tyres are all fail items. Next, check the tyre tread depth is above the legal limit of 1.6mm; if your tyres have tread depth indicators, check that the tread hasn’t worn down to the level of the indicator.

Alternatively, you can put a 20p coin into the area between the tread; if the raised part of the coin is above the tread, the tyre is too worn.

9. Windscreen

9. Windscreen

Check for chips and cracks; any crack larger than 40mm will result in a fail, and any crack or chip covering 10mm or more in the area the windscreen wipers clean is also a fail item.

10. Windscreen wipers

10. Windscreen wipers

Check for splits or perishing on all wipers, and check that they clear the screens properly when they’re used. Also check and top up the screen wash if necessary.


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