Used Volvo S40 saloon 2004 - 2012 reliability

Higher mileage cars are actually more desirable than lower mileage ones if you’re buying a diesel. That’s because the diesel particulate filter can clog up on low-miles cars, and it’s very pricey to rectify.

The 1.8-litre Flexi-Fuel cars are best avoided – they were designed to be able to use E85 bio-ethanol fuel, but they have high CO2 emissions and fuel consumption and are therefore much more expensive to run than a diesel.

The ignition system is the primary cause of concern. The S40 uses a chunky, plastic electronic ignition key that goes into a slot behind the steering wheel, high up on the dashboard (so that the heavy ignition barrel, usually located on the steering column, is kept away from the driver's knees in a crash). But if the key feels loose or wobbly in the slot, that’s a bad sign, because both the key and slot are expensive to replace. The central locking system can also give trouble if the key has become damaged or has been dropped.

Another thing to look for is creaking seats. You'd think that loose runners would be to blame, but in reality it's the internals of the seats that break and the only remedy is replacement, which won't often make sense to do from a financial perspective.

Check the dashboard warning lights closely to make sure they all illuminate when the ignition is turned on and then go out soon after the engine starts. Of particular interest are the diesel particulate filter light in the diesels and another for the anti-lock brakes; the latter's control unit has been known to fail, and it's a very expensive fix.

The 1.6-litre diesel needs a steady diet of high-quality engine oil, or it tends to ‘sludge up’ its head with waste oil. Both the water and diesel pumps on this engine are also weak points. And if there is any slack in the travel of the clutch pedal on manual gearbox cars then the master cylinder will probably need replacing.

Flickering warning lights on the dashboard usually mean that the connection to the engine’s computer, which runs behind the passenger footwell, has become loose.

On cars fitted with a sunroof check the carpets for any dampness as the drainage holes can become blocked, leading to rain water running down the inside of the window pillars.

If the car looks lopsided, or feels as if it’s leaning one way or the other during a test drive, the problem is most likely a cracked suspension spring.