The Most Common MOT Failures – And How to Avoid Them
Nearly 40% of all cars fail their first MOT. Don’t be one of them. By learning which checks to do in advance, you’ll save yourself time, money, and hassle.
Lights and Indicators
Burnt-out bulbs and cracked lenses are among the top reasons cars fail their MOT:
- Burnt-out headlamps, brake lights, or indicators
- Broken or cracked lenses letting in moisture
- Misaligned headlamp beams
Pre-MOT Check: Walk around your car a few days before the test. Enlist a friend to click the indicators, brake the car, and switch on the headlights. Replace any faulty bulbs and adjust aim if needed.
Tyre Condition and Tread Depth
MOT inspectors check tyre tread depth—and it must be at least 1.6 mm across the central three-quarters of the tyre’s breadth. They also look for:
- Sidewall damage (cuts, bulges)
- Uneven wear patterns
Pre-MOT Check: Use the “20p test”: insert a 20p coin into the main tread groove. If you see the outer band, it’s time for new tyres. Inspect sidewalls for bulges or cuts, and ensure all four tyres are inflated to the correct pressure.
Brake Performance
Worn brake pads, corroded discs, and low brake fluid frequently cause MOT failures:
- Thin or uneven brake pads
- Rusty or seized calipers reducing efficiency
- Low or contaminated brake fluid
Pre-MOT Check: Press the brake pedal to check for sponginess. If the pedal feels soft or the car pulls to one side under braking, book in for a quick brake inspection. Replacing pads and topping up fluid now can prevent a fail later.
Suspension and Steering
Worn suspension bushes, leaking shock absorbers, and excessive free play in steering components are common fails:
- Shock absorbers leaking fluid
- Worn or split suspension bushes
- Loose steering joints
Pre-MOT Check: Drive slowly over a speed bump and listen for clunks. If your car bounces excessively or makes knocking noises, book a suspension check with Car Friend. Replacing shocks or bushes early means a smoother ride and a higher chance of passing.
Exhaust Emissions
High CO or HC readings and exhaust leaks can cause MOT failures:
- Corroded exhaust sections leading to leaks
- Emission readings above legal limits
- Loose or broken exhaust hangers
Pre-MOT Check: If your “check engine” light is on, or you notice black smoke from the exhaust, book an emissions check. Fixing a minor exhaust leak or replacing the oxygen sensor can bring emission readings back into the acceptable range.
Seat Belts and Safety Restraints
Inspectors look for:
- Belts that don’t retract properly
- Frayed or damaged webbing
- Missing or damaged buckles
Pre-MOT Check: Sit in every seat position and pull each belt out fully. If it doesn’t retract smoothly or shows fraying, replace it. A £30-£40 belt replacement is far cheaper than a failed MOT.
Windscreen and Wipers
Chips or cracks larger than 10 mm in the driver’s line of sight, and wiper blades that streak or don’t clear water effectively, can lead to a fail:
- Large chips or cracks on the driver’s side
- Worn wiper blades that don’t clear water properly
Pre-MOT Check: Replace wiper blades if you notice streaking. Inspect your windscreen for any stone chips—if a chip is in the driver’s primary field of vision, get it repaired or replaced in advance.
When to Book a Pre-MOT Health Check
If you’ve covered high mileage this year, or if warning lights have popped up on your dash, a quick pre-MOT health check at Car Friend (around £30–£40) can identify fail points before your test date. Catching issues early gives you time to fix them, rather than paying for a re-test and emergency repairs.
Real-Life Examples & Costs
- Clare’s Brake Warning: Our pre-MOT check revealed brake pads at the minimum thickness. She booked a replacement for £75 and sailed through her MOT.
- John’s Headlamp Bulb: Simply replacing a blown headlamp bulb took 10 minutes and avoided a re-test fee.
Your 2-Week Pre-MOT Checklist
- Lights & Indicators: Check every bulb and adjust headlamp aim.
- Tyre Tread & Pressure: Use the 20p test and inflate to correct PSI.
- Fluids: Top up oil, brake fluid, screenwash, and coolant.
- Windshield & Wipers: Look for chips in the driver’s view and replace wiper blades if they streak.
- Under-Bonnet Inspection: Look for oil or coolant leaks—address these before the MOT.
A quick walk-around now can prevent a costly MOT fail later.
If you’d like us to carry out a pre-MOT health check or need friendly advice on any of these items, just book in at Car Friend. We’re always happy to help you pass first time and keep your car safe.