What goes wrong with cars? The most common car faults revealed

If you've spent thousands of pounds on a new car you'd expect it to be reliable, and most do perform impeccably for some years until parts start to wear or degrade. However, not all cars can be relied on day-in day-out, and if something does go wrong you could be landed with a sizeable repair bill. 

That’s why we run the What Car? Reliability Survey every year to find out which car models are bullet-proof and which should be avoided. For the most recent survey, we asked 21,732 car owners to give us details of any faults their cars had suffered in the previous 24 months.

The good news is that only 21% of cars aged up to five years old suffered a fault, and 83% of those issues were fixed free of charge by car makers and dealerships. However, the remaining owners had to pay for repairs, and while 12% paid less than £500, an unlucky 2% shelled out more than £1500 per fault to put things right.

How the research was carried out

To compile the latest What Car? Reliability Survey we asked our subscribers and readers to give us the lowdown on how dependable their car has been. After finding out if the cars had suffered any problems, we asked how much each one had cost to put right and how long it had kept the car off the road. 

This information was used to create a reliability rating for each model. The survey, conducted in association with MotorEasy, contains data on 178 models aged up to five years old from 32 different car brands.

To drill down further into the most common faults, we split car problems into 15 different areas: air conditioning, battery, bodywork, brakes, clutch and gearbox, engine, engine electrics, exhaust, fuel system, infotainment and sat-nav, interior trim, non-engine electrics, steering, suspension and 'other'. We’ve used this data to compile our rundown of the most common car issues, so you know the most important areas to check when you're looking at a potential purchase.

The most common car fault areas 

1. Non-engine electrics 

Fault rate 24.5%

This fault category covers a huge range of systems from dashboard warning lights to switches for windows and doors. And these are by far the most common complaints, demonstrating just how vital it is to check out all electrical systems on a car before you commit to buying it. 

Although electrical gremlins only rendered 13% of cars undrivable, they weren't easy to fix; 12% took up to a week to repair and 75% of cars sat in the garage for more than a week. At least most owners weren't stung too sharply with repair bills, with 98% of cars put right under warranty, and only 2% of repair bills topping £1500.

2. Infotainment and sat-nav

Fault rate 19.8%

Infotainment and sat-nav systems are used to control more functions than ever on new cars, and it’s worrying that they are going wrong so often. The good news is that 94% of car owners told us their faulty cars were fixed for free. Only 2% of people had to pay £1500 or more to get the problem sorted. It’s a mixed bag when it comes to wait times for cars to be fixed, though: 42% were sorted in a day or less, but 36% were in the workshop for more than a week. 

3. Battery 

Fault rate 13.4%

Car batteries have a tough job these days, providing power for the myriad of electrical systems on the latest models, as well as being responsible for start-stop systems. No wonder then that they have a fairly high failure rate. 

Unsurprisingly, nearly 40% of cars couldn't be driven until they were fixed, but 30% of them were put right in a day or less. The best news if you do have a broken battery on a newer car is that it's not likely to break the bank to put right; some 89% were fixed for free and hardly any repair bills topped £300. Don't forget that carrying a jump starter could make the difference between being stranded at the roadside, or getting to a garage for further inspection.

4. Bodywork 

Fault rate 13.2%

You may not be bothered if a piece of trim falls off a £1000 secondhand car, but if the exterior of your pride and joy starts to develop nasty blemishes or broken bits of plastic, you're likely to be upset. Most new car warranties cover bodywork defects for the first three years at least, but there are caveats in the cover, so you could be left out of pocket. 

The data from our survey shows that 38% of cars with bodywork issues were repaired in a day or less, but another 40% took more than seven days to put right. Although 95% of work was done for free, 2% of owners paid out £1500 or more for repairs. 

5. Engine electrics 

Fault rate 12.9%

The electrical systems that support our car engines are more susceptible to problems than the engines. Although not as detrimental as engine faults, 25% of those with engine electrical issues were rendered undriveable, but dealers acted quickly in many cases, fixing 30% of cars in the same day or less and another 30% in less than a week. The good news for owners is that 95% of issues were addressed at no cost to owners, but an unlucky 2% paid out more than £1500 to get their cars back on the road. 

6. Interior trim 

Fault rate 8.2%

Issues with interior trim are generally not serious, but they will dent the feel-good factor of buying a new car. The good news is that virtually all (98%) of problems were sorted out for free and only 2% of bills cost between £501 and £1000. Even better, 39% of problems were put right the same day, and, although 27% of cars spent more than a week in the garage, just 3% of them were rendered undrivable by the fault.

7. Air-con 

Fault rate 7.6%

Most mid and high-end versions of new cars come with air-con as standard, and that's great because it enables you to choose the precise temperature you want inside the car. It also helps it demist quicker on cold mornings. However, these systems are prone to problems. For that reason, we ask owners about them separately from other electrical components.

On a positive note, 83% of the faulty systems we were told about were fixed under warranty. Not so good: although a third of cars were fixed in less than a day, another 29% spent more than a week in the garage. 

Air-con systems don't like to be left unused, so, even if you don't feel the need for ultra-chilled air, do turn the air-con on regularly and check that it's working properly. 

8. Engine 

Fault rate 7.3% 

It's surprising that such a major component is one of the most likely to go wrong on cars aged up to five years old. As you'd expect, these faults took two thirds of affected cars off the road, and 55% of them spent a week or more in the garage. Only a quarter were repaired in a day or less. Car makers covered the cost of repairs for 93% of vehicles, and most of those who had to pay were asked for less than £750. 

9. Brake system

Fault rate 7.1%

Your car's brakes are its most critical safety system, so it's vital that they perform properly. The system is likely to include a sophisticated anti-lock braking system and either a mechanical or electronic parking brake, and you're likely to get a dashboard warning light if either of these goes wrong. However, the most common gripe among owners is about brake discs that wear down quicker than expected. 

Although 83% of cars could still be driven and 40% of brake problems were resolved in a day or less, 23% of cars took more than a week to put right. Cost wasn’t an issue for many car owners, with 88% of bills covered by warranty, and no repair bills exceeding £1000.

=10. Exhaust 

Fault rate 5.4%

Niggles with emissions and exhaust systems don’t affect many newer vehicles, although a common complaint is that a car’s emissions sensors have failed and need to be replaced.

Although 41% of issues were rectified in a day or less, dealers spent more than a week working on another 30% of broken vehicles. The vast majority (96%) of work was done for free, though, and only 2% of car owners had to find more than £1500 to get their cars put right. 

=10. Suspension

Fault rate 5.4%

Suspension issues sound like serious problems, but in most cases they didn't keep newer cars off the road for too long. Our data shows that 94% of vehicles remained drivable and nearly half of issues were fixed in a day or less. Most repairs (89%) were put right at no cost to the owners, but 6% were landed with bills in excess of £1500. 

Excessive jarring from hitting a large pothole is a common cause of suspension problems. Signs that something is wrong include the car's ride becoming bumpier than usual or it developing a thudding sound when driven over uneven surfaces. It's worth getting the car checked over straight away because broken suspension components will affect your car's handling. 

12. Gearbox and clutch

Fault rate 5.0%

It's reassuring to know that only a small proportion of newer cars have problems with their gearboxes and clutches. However, the cost of fixing faults isn't covered as comprehensively as other car issues: only 85% of repairs were carried out under warranty. Although three-quarters of cars could still be driven, 37% were out of action for more than a week. 

13. Fuel system 

Fault rate 2.1% 

A range of issues can hamper the operation of the fuel system, from failing fuel pumps and fuel lines to difficulties with the filler flap or fuel tank that made it difficult to refuel the car.

It’s reassuring to know that all issues were resolved at no cost to car owners. Although most cars could still be driven, only 25% were fixed in a day or less and a third were out of action for more than a week. 

14. Steering 

Fault rate 2.0% 

Problems with the steering system are rare on newer cars, and they're something that should be fixed for free, especially if the car is still protected by the manufacturer's warranty. The good news is that owners told us 92% of affected vehicles were fixed by car makers with no charge, leaving just a handful of owners paying out between £501 and £750. Two thirds of problems were sorted out in less than a week. 

Common problems include the steering wheel becoming overly heavy to turn or pulling to one side. These can be caused by the power steering system failing, but worn or incorrectly inflated tyres, misaligned wheels and suspension issues can also affect the steering. 

To read the reliability data for other car classes follow these links:

Most reliable small cars
Most reliable family cars
Most reliable executive cars
Most reliable luxury cars
Most reliable small SUVs
Most reliable family SUVs
Most reliable large SUVs
Most reliable seven-seaters
Most reliable electric cars
Most reliable electric SUVs
Most reliable sports cars
Most reliable car brands
Most reliable diesel cars

About the report author

Claire Evans has been a motoring journalist for more than 30 years, working on consumer issues for a great deal of that time. After a stint as the advice columnist for Carweek magazine in the 1990s, she also spent six years working on motoring content for Which?. It is here she oversaw the running of the charity's annual used car reliability survey.

Claire launched the What Car? Reliability Survey in 2017, and since then has helped thousands of buyers choose the most reliable new cars and SUVs, as well as the most dependable used cars.

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