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 dependable, 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. 

So, we run the What Car? Reliability Survey every year to find out which car models are bullet-proof and which should be avoided. As part of the most recent survey, we asked more than 16,000 car owners to give us details of  any faults their cars had suffered in the previous 12 months.

To allow us to drill down into the information, the problems were split 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'. This data was used to compile a chart of the most common car issues, so you know the most important areas to check when you're looking at a potential purchase.

The good news is that only 20% of cars aged up to five years old suffered a fault, and 85% of those issues were fixed free of charge by car makers and dealerships. However, the remaining owners had to pay for repairs, and while 7% paid less than £500, an unlucky 2% shelled out more than £1500 per fault to put things right.

The data in this story only relates to cars up to five years old. To find out about the issues that trouble older cars, read the Best and worst older cars for reliability.    

The most common car fault areas 

14. Steering 

Fault rate 2.5% 

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 95% of affected vehicles were fixed by car makers with no charge, leaving just a handful of owners paying out up to £1000.

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. 

13. Fuel system 

Fault rate 2.8% 

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.

Although 88% of fuel system repairs were carried out for free, 8% of car owners had to pay, and 4% of these motorists were landed with bills ranging from £750 to £1500. Although most cars could still be driven, more than half took more than a week to put right. 

12. Suspension

Fault rate 4.7%

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 three-quarters of vehicles remained drivable and the majority of issues were fixed in a day or less at no cost to the owners. 

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. 

11. Air-con 

Fault rate 5.7%

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 very prone to problems. For that reason, we ask owners about them separately from other electrical components.

On a positive note, 87% of the faulty systems we were told about were fixed under warranty, and most owners who had to pay only had bills totalling a few hundred pounds. Not so good: although a third of cars were fixed in less than a day, another third 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. 

10. Gearbox and clutch

Fault rate 6.7%

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 77% of repairs were carried out under warranty and, worryingly, 10% of drivers paid out more than £1000 per fault. And, although three-quarters of cars could still be driven, just over half were out of action for more than a week. 

Owners told us 11% of cars with manual gearboxes suffered issues, a far higher proportion than those with automatic gearboxes (6%). Of the automatics, cars with continuous variable transmission (CVT) gearboxes appear to be more durable than those with dual-clutch systems (DSGs): 10% of DSG cars had a gearbox problem compared with 4% of CVT cars. 

It's worth checking that it is easy to select all gears, including reverse, on any car you're considering buying, and listening out for clunking noises or reluctance to change up and down on an automatic gearbox. 

9. Exhaust 

Fault rate 8.6%

Niggles with emissions and exhaust systems afflict nearly one in 10 vehicles up to five years old, with many owners telling us their cars' emissions sensors had failed and needed to be replaced.

Although 30% of issues were rectified in a day or less, dealers spent more than a week working on another 27% of broken vehicles. The vast majority (80%) of work was done for free, though, and for those who did pay, most bills didn't top £300. 

8. Interior trim 

Fault rate 8.9%

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 (92%) of problems were sorted out for free and hardly any bills exceeded £300. Even better, 46% of problems were put right the same day, and, although 27% of cars spent more than a week in the garage, just 2% of them were rendered undrivable by the fault. 

7. Brake system

Fault rate 9.4%

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 most cars could still be driven and 47% of brake problems were resolved in a day or less, 22% of cars took more than a week to put right. Cost was an issue for many car owners, with only 66% of bills covered by warranty, although most repairs resulted in bills of less than £300.  

6. Battery 

Fault rate 10.8%

Car batteries have a tough job these days, providing power for the myriad of electrical systems on the latest models. 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 two thirds 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 74% were fixed for free and hardly any repair bills topped £200. 

5. Infotainment and sat-nav

Fault rate 11.3%

Infotainment and sat-nav systems are notorious for going wrong and are costly to repair, so this is an important area to check over thoroughly on any potential purchase. Although car companies often exclude the cost of repairs from their new car warranties, owners told us that 94% of their faulty cars were fixed for free. Those who did pay only had to pay out a few hundred pounds in most cases.  A third of issues were sorted out in a day or less, but 41% of cars spent more than a week in the dealership.

4. Engine 

Fault rate 12.1% 

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 77% of affected cars off the road, and 43% of them spent a week or more in the garage. Only a fifth were repaired in a day or less. Warranty work was carried out on 85% of vehicles, but 7% of owners had to pay up to £750 and another 7% more than £1500 to get their cars fixed.  

3. Engine electrics 

Fault rate 13.4%

The electrical systems that support our car engines are slightly more susceptible to problems than the engines. Although not as detrimental as engine faults, those with the engine electrics still rendered the majority of cars (69%) unable to be driven, but dealers acted quickly in many cases, fixing a quarter of cars in the same day or less and a third in less than a week. Good news for owners is that 91% of issues were addressed at no cost to owners, but an unlucky 5% paid out more than £1000 to get their cars back on the road. 

2. Bodywork 

Fault rate 19.0%

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 highly 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 nine out of 10 cars with bodywork issues could still be driven, and nearly half of repairs were completed in a day or less. Although 90% of work was done for free, 2% of owners paid out £1000 or more for repairs. 

1. Non-engine electrics 

Fault rate 27.1%

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 16% of cars undrivable, they weren't easy to fix; a third took up to a week to repair and a quarter of cars sat in the garage for more than a week. At least most owners weren't stung too sharply with repair bills, with 91% of cars put right under warranty, and repair bills of £200 or less for most of those who had to pay.  

For all the latest reviews, advice and new car deals, sign up to the What Car? newsletter here

Next: The 25 most unreliable cars >>