Classic car MOT prep: what fails most (and how to avoid it)

Ah, the MOT. Three letters capable of striking mild dread into the heart of any classic car owner. Not because we don’t look after our cars, of course. Perish the thought. But because a vehicle built sometime between Beatlemania and Britpop occasionally decides to express its personality in… mechanical ways. 

The good news? Most classic car MOT failures are entirely predictable. Even better, many are easy to fix with a bit of preparation. So before you nervously hand your keys to the MOT tester and pretend you’re totally relaxed about the situation, let’s look at the things that most commonly trip up classics, and how to avoid the embarrassment of the dreaded fail sheet. 

If there’s one thing older cars love doing, it’s developing mysterious electrical quirks. 

Indicators that blink like they’re sending Morse code. Brake lights that work perfectly until someone actually checks them. Headlights that illuminate the road with all the intensity of a birthday candle. 

Lighting faults are one of the most common MOT failures full stop, and classics are particularly prone. 

Quick checks worth doing before the test: 

• Test every light. Yes, every single one. 

• Check number plate lights (these are often forgotten). 

• Replace dim bulbs. 

• Clean earth connections if lights are flickering or weak. 

And while you’re there, give the lenses a wipe. A layer of grime accumulated since the Thatcher administration doesn’t help visibility. 

Classic cars often cover low mileage. Sounds great. Unfortunately, tyres don’t care all that much about mileage – they care about age. 

A tyre that looks perfectly fine may actually be well past its best. Cracks in the sidewalls, hardened rubber, or uneven wear can all result in a fail. 

And yes, that spare tyre from 1994 probably counts as “past it”. 

Check for: 

Minimum 1.6mm tread across the central three quarters 

• Cracks or perishing 

• Bulges or damage 

• Incorrect tyre sizes 

• Long past-it date codes 

Tyres can age out even if they still look good, so if they’re approaching a decade old, it might be time for retirement. 

This one probably doesn’t need explaining. 

Classic brakes can be a little… relaxed compared to modern standards. But MOT testers are still looking for proper performance and balance across the axle. 

Common issues include: 

• Sticking calipers 

• Worn pads or shoes 

• Contaminated brake fluid 

• Imbalanced braking between wheels 

If your car pulls to the left like it’s trying to hug the hedge every time you brake, that’s a hint something may need attention. 

A quick pre-MOT drive including a few firm stops can help reveal problems before the tester does. And if your car has been parked up for a while without moving, giving the brakes a good work-out can often be enough to clear any surface rust that has accumulated on the discs. 

Older suspension components tend to wear slowly and quietly. You don’t notice the change until the MOT tester starts poking a pry bar around underneath your pride and joy. 

Typical failure points include: 

• Worn bushes 

• Ball joints 

• Track rod ends 

• Leaking shock absorbers 

If your car has developed a gentle wobble, vague steering, or the ride quality of a trampoline, it may be worth having things inspected before the test. 

A good rule of thumb: if it clunks, creaks, or knocks over bumps, the MOT tester will definitely find it. 

Rust and classic cars go together like tea and biscuits. Or rain and British summers. 

The MOT focuses on structural corrosion, particularly around: 

• sills 

• suspension mounting points 

• seatbelt mounts 

• chassis rails 

A tiny cosmetic bubble isn’t the end of the world. But if corrosion affects structural areas, it can quickly become an MOT failure. 

Before your test, it’s worth giving the underside a proper look. A clean can help, too: years of grime can hide issues or make inspection harder. 

And let’s be honest: a freshly cleaned underside is satisfying for everyone. 

This is the MOT equivalent of failing an exam because you forgot to write your name on the paper. 

Wipers must clear the windscreen properly. Washers must actually wash. 

Common issues include: 

• Perished wiper blades 

• Empty washer bottle 

• Blocked washer jets 

• Dead washer pump 

The fix? Usually about five minutes and a £5 wiper blade. 

Seatbelts on classics can fail for a variety of simple reasons: 

• Fraying belts 

• slow or faulty retractors 

• damaged buckles 

• insecure mounting points 

Give them a quick pull and check they retract properly. If they behave like they’re half-asleep, they may need replacing. 

Most MOT failures aren’t dramatic mechanical disasters. They’re often small, easily avoidable issues that simply went unnoticed. 

A quick half-hour inspection before the test – lights, tyres, fluids, wipers and belts – can save time, money and the mild indignity of explaining to your friends that your cherished classic failed because the number plate bulb packed up. 

And remember: MOT preparation isn’t just about passing a test. It’s about keeping these wonderful machines safe and enjoyable on the road. 

Because classics aren’t just cars. They’re rolling history, cultural icons, and occasionally slightly temperamental old friends.  

Treat them well, give them a quick once-over before MOT day, and there’s every chance you’ll drive away with that lovely little certificate of approval, and a quiet sense of victory. 

Preferably followed by a celebratory pub visit. Your car has earned it. And frankly, so have you.