Common MOT Failures and How to Avoid Them
Ask any tester what turns up most often and the answer is rarely dramatic. It is a blown bulb, a tyre worn past the limit, a split wiper blade or an empty washer bottle. These are cheap, quick problems that still lead to a fail certificate if they are present on test day.
This guide is aimed at Class 4 vehicles, which means ordinary cars and light vans. Work through it a week or two before your test and you will remove most of the avoidable risk.
Bulbs and lenses: the easiest fail to prevent
Lighting and signalling defects are consistently among the most frequent reasons for failure. The usual suspects are a dead brake light, a failed number plate lamp, an indicator that flashes too fast, and dipped beams that are not working or are pointing the wrong way.
Ask someone to stand behind the car while you press the brake pedal, then switch on each light in turn. Reverse up to a wall or garage door at dusk to see the brake lights without help. Cracked or misted lenses can also be a problem if they let the light spread badly or let water in.
Tyres: tread, condition and pressure
The legal minimum tread depth for cars is 1.6mm across the central three-quarters of the tyre, around the whole circumference. Many drivers prefer to replace tyres well before that point because grip in the wet drops off as the tread wears.
Look at the sidewalls as well as the tread. Cuts, bulges and cracking can fail a tyre that has plenty of tread left. Uneven wear on the inner or outer edge points to a tracking or suspension problem that is worth having looked at, since new tyres will wear out the same way if the cause is not fixed.
Check the spare too if you carry one, and remember that a tyre with a slow puncture will be flat when you turn up.
- Tread depth across the whole width of the tyre
- Cuts, bulges or exposed cord on the sidewalls
- Even wear from edge to edge
- Pressures set to the figure in the handbook
Wipers, washers and the windscreen
A wiper blade that smears or skips rather than clearing the glass is a failure point, and so is a washer system that does not spray onto the screen. Top up the bottle, check the jets are not blocked, and replace tired blades before the test rather than after it.
Look closely at the windscreen too. Damage directly in the driver's line of sight is judged far more strictly than damage near the edge. A chip that looks harmless can spread over a cold night, so deal with it early.
Brakes and suspension: the wear items
Worn pads and discs, seized calipers, corroded brake pipes and a handbrake that will not hold all appear regularly on fail sheets. Warning signs you can notice yourself include a pull to one side when braking, a juddering pedal, grinding noises and a pedal that feels long or soft. If you notice any of these, get the brakes checked and do not wait for the MOT.
Suspension faults are very common on older cars and anywhere with poor road surfaces. Listen for knocking over bumps, look for oil running down a shock absorber, and notice if the car leans or bounces more than it used to. Worn track rod ends and anti-roll bar links often make themselves known with a clunk when you turn.
A ten-minute check before you book
Walk round the car with the engine running and go through the lights, horn, wipers and washers. Check the fluid levels, look at the tyres, and make sure that no warning lights stay on after the engine starts. Clear anything blocking the plates and wash off heavy mud so the tester can see what they need to.
If something looks borderline, a pre-MOT inspection at Banks of the Tyne in Hebburn can identify it, and MOT preparation or MOT repairs can sort it out before the test, so you are not facing a fail on the day.
Key takeaway: Most MOT fails are about bulbs, tyres, wipers and worn brake and suspension parts, all of which show warning signs well in advance. A short check at home and a pre-MOT inspection if you are unsure will remove most of the surprises.
Frequently asked questions
What is the most common reason for an MOT fail?
Lights and signalling faults top the list year after year, followed by suspension, brakes and tyres. Most of the simple ones, like bulbs and wipers, are easy to check yourself.
Will a stone chip in the windscreen fail an MOT?
It depends on the size and where it is. Damage in the area directly in front of the driver is treated much more strictly than damage elsewhere. If you are unsure, have it looked at before the test.
Is it worth getting a pre-MOT check?
For many drivers, yes, particularly on an older car. A pre-MOT inspection gives you a chance to fix small faults on your own timetable instead of dealing with a fail certificate and a retest.
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