Common car problems explained: DIY diagnose issues before they get serious

While modern cars are generally pretty reliable, it can be tricky to diagnose an issue when things do go wrong. If you’ve noticed something isn’t quite right with your car – be it an unusual noise, a smell or a dashboard warning light – it’s worth investigating the issue as soon as possible to make sure your car is safe and performing correctly.

If you’re confident to take a look under the bonnet of your car, this guide will help you to get to the bottom of your car’s problem. We’ve covered each issue separately on their individual explainer pages, so you can read about the problem affecting your car in more detail. If you don’t feel confident to check the issue yourself, we recommend letting a professional take a look – read our guide to reporting a fault to make sure you can explain the problem as clearly as possible.

There’s also a chance that the problem with your car is a known issue that the manufacturer can rectify – read more about car recalls to find out how they work. If you’re in the market for a new car and want to minimise maintenance headaches, read our guides to the most reliable cars and the cars with the best warranties. 

A dashboard warning light

If there’s an issue with your car, one of the most obvious giveaways will be an illuminated dashboard warning light. Dashboard warning lights are used to signify various issues, ranging from low tyre pressures to brake problems and incorrect oil pressure. Each symbol represents a different issue, so you’ll often be able to work out what’s wrong with your car by looking up what the symbol means.

One of the more serious dashboard lights to look out for is the engine warning light. This signifies an issue with the engine and will often be accompanied by limp home mode, restricting engine performance. If your engine warning light illuminates, it’s vital to have the issue investigated as soon as possible to prevent further engine damage. 

Something sounds wrong

Sometimes your car will look fine from the outside, with no leaks or smoke to signify an issue, but something won’t sound right. An unusual sound from your car isn’t always a major cause for concern, but it’s still important to investigate, especially if it’s persistent.

The first step is to pinpoint where the sound is coming from. Suspension noises can arise if perishable components like bushes begin to wear out, while a noisy exhaust can be caused by anything from a leak to a loose bracket. Similarly, a rattling noise usually indicates that something is loose and isn’t a major cause for concern.

Unusual engine noises have the potential to be more worrying; it could be something as benign as a loose heat shield under the bonnet, but a knocking or ticking noise should be seen to straight away – ignoring an engine noise could lead to serious and expensive repairs.

Something smells wrong

Yes, even an unusual smell can suggest that something’s not quite right with your car. If a new odour has appeared, you should treat it in the same way that you would if a new smell developed in your house: identify what’s causing it, locate where it’s coming from, and deal with it appropriately.

Our guide to car smells will give you a rundown of the most common odours to be aware of, as well as their severity and how to eradicate them. We’ve covered burning smells in more detail separately – these can be serious so it’s important to stop driving and investigate the cause as soon as possible.

Other issues to be aware of

A common tell-tale sign that your car isn’t performing correctly is smoke from the exhaust. While we all know that smoke isn’t something you want billowing out the back of your car, many drivers are unaware that the colour of the smoke can signify different issues. Black smoke is generally the least concerning, while blue smoke usually means that oil is being burned – something that shouldn’t be happening. 

Steam from the exhaust is often mistaken for white smoke, and isn’t anything to worry about so long as it disappears once your car is up to temperature. If the white cloud persists, then it’s probably smoke, not steam, and will need to be checked as soon as possible – a common cause of white smoke is a faulty head gasket.

Another visual issue that should be easy to spot is a cracked windscreen. Car windscreen repairs are fairly straightforward so long as the crack or chip isn’t too big and is spotted early. A small nick can grow into a large crack if it’s not repaired soon enough, potentially leading to an expensive windscreen replacement. It’s possible to repair small chips with a DIY kit, but we generally recommend taking your car to a professional.

More on car problems

• Causes of an engine management light
• Complete guide to dashboard warning lights
• Reporting a fault on a new car
• Guide to car recalls
• What does smoke from my exhaust mean?
• Car engine noise explained
• Car suspension noise: what does it mean?
• Car windscreen repairs and replacements
• What to do about a noisy car exhaust
• Guide to car smells
• Car burning smells explained