The Most Common Causes of Car Breakdowns

Ellie Dyer-Brown, 27 days ago

5 min read

  • Car ownership
Car Breakdown by Side of the Road

WhoCanFixMyCar reveals the top ten reasons that cars break down.

Breaking down is never convenient, but it happens all the time. In 2023 alone, the RAC's roadside patrols attended over 29,000 breakdowns, and pothole-related incidents increased by a third.

They say prevention is the best cure, so this guide will help you avoid ten of the most common causes of car breakdowns next time you go on a trip.

Contents

Faulty or flat battery

Faulty alternator

Tyre damage

Electrical issues

The locking system

Misfuelling

Clutch cable failure

Blocked DPF

Starter motor issues

Overheating


1. Faulty or flat battery

One of the most common causes of breakdowns is a flat or faulty battery, which can happen for several reasons, such as:

  • Too many short journeys

  • Leaving electrical systems on overnight (e.g. interior lights)

  • Old age

  • Corrosion

  • Loose terminal connections

  • A faulty alternator

Batteries last for around five years, so if yours is older than that, it might be that it has naturally come to the end of its usable life. Find out more about why car batteries die.

Technician fitting a car battery.

Before a long or important journey, we recommend inspecting your battery for signs of wear and tear. You could also test it using a multimeter. If it needs replacing, you will likely experience the following symptoms:

Check out our top tips for maintaining your battery. According to our data, the average price of a battery replacement is £217.39.


2. Faulty alternator

The alternator generates power for your car's electrical systems and charges the battery. You can learn more about how it works here. If your battery is flat and you're experiencing the following symptoms, it could be due to the alternator:

A car alternator.

This guide covers five signs of a faulty alternator. You can expect to pay £438.61 on average for an alternator repair.


3. Tyre damage

It'll come as no surprise that damaged tyres are one of the leading causes of breakdowns. Sometimes, punctures are unavoidable from unseen debris or potholes. But your chance of suffering from one is significantly higher if you don't maintain your tyres correctly.

Mechanic checking tyre

Set aside some time before your next journey to inspect your tyres for signs of wear. They should have a tread depth of at least 1.6 mm to be legal (you can use a 20-pence piece to test them), and they should be pumped up to the correct pressure (outlined in your owner's manual or near the driver-side door frame).

This guide provides advice about how to make your tyres last longer.


Did You Know?

There are almost 40 million tyres fitted every year onto cars in the UK.


4. Electrical issues

An auto electrician carrying out wiring repair

Modern car electrical systems are more complex than ever. While this is good news for motorists, who have access to impressive new features in their vehicles, it also leads to more electrical-related breakdowns. Problems often happen due to faulty wiring, burnt-out bulbs and blown fuses.

On average, an electrical fault diagnosis costs £62.34 when you book through WhoCanFixMyCar.


5. The locking system

Car alarms and immobilisers are more sophisticated than they used to be, leading to an increased number of motorists calling their breakdown provider for issues relating to the central locking system, such as the alarm repeatedly going off or a lost key.

Key programming hero image

In this guide, find out what to do if you lose your car keys. The average price of a central locking system repair is £146.53.


6. Misfuelling

Putting the wrong fuel in your car is more common than you might think. This mainly happens when petrol drivers get behind the wheel of a diesel car because the incorrect nozzle still fits into the tank. However, a diesel nozzle will not usually fit into a petrol car.

Fuel pumps at petrol station.

It's easy to get distracted at the pump and fill up on autopilot, but you mustn't turn the engine on. As long as you keep the car switched off, there will be minimal damage - you'll just have to get the fuel pumped out and replaced. On average, a misfuelling repair costs £155.34 when you book through WhoCanFixMyCar.

Here's what to do if you've put the wrong fuel in your car.


Did you know?

According to the RAC, there are about 150,000 incidents of misfuelling in the UK every year.


7. Clutch cable failure

Manual cars are at risk of clutch failure because the cable comes under pressure every time the driver changes gear. As soon as you notice any unusual behaviour from the clutch - such as slipping gears or a sticking pedal - you should get it checked by a mechanic as quickly as possible.

Learn how to tell if you need a new clutch for your car. A clutch replacement costs £624.58 on average, according to our data.


8. Diesel particulate filter (DPF)

Diesel cars are fitted with a particulate filter to reduce the harmful emissions that leave the exhaust. However, DPFs are notoriously problematic when only driven on short journeys. They quickly become blocked, leading to stalling and your car going into limp mode. This guide explains how to avoid DPF problems.

Diesel particulate filter car computer message.

A blocked DPF can sometimes be cleaned using specialist tools and techniques, but if the blockage is severe, the filter may have to be replaced, which can be costly. That's why taking good care of your DPF is important by going on a longer motorway journey every few weeks.

Discover what happens during a professional diesel particulate filter cleaning job.

Getting your DPF cleaned costs £188.29 on average; a replacement costs £445.02.


9. Starter motor issues

The starter motor may be small, but it's an important device that gets your engine going. It experiences a lot of strain - especially in cars with start/stop technology - so eventually, it will wear out. However, many starters last between 100,000 and 150,000 miles before they need replacing.

There are a few tell-tale signs to look for:

  • The dashboard lights up, but the car won’t start

  • Metal-on-metal grinding noise

  • Whirring or clicking sounds when you try to get the engine going

  • A single click with no engine crank when trying to start the car

Starter motor car parts

The average price of a starter motor replacement is £308.85, according to WhoCanFixMyCar's data.


10. Overheating

Overheating often happens due to low coolant or a broken fan. It's essential to check your car's fluid levels regularly - they should be topped up annually during a full service, but it's still worth opening the bonnet every so often to make sure everything is in order. If your coolant is low and you topped it up recently, there is probably a leak somewhere that needs repairing.


Is your car showing signs that it could be about to break down? It’s always best to get it checked by a trained professional – even for something as simple as a loose connection.

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