When it comes to buying a used car, you need to pay particular attention to the body and its condition because fixing a crumbling car can cost a small fortune. Here’s what you need to look out for.

If there’s one thing that can really signal the end of the road for a second-hand car, it’s body condition. Engines, transmissions, suspension and brakes; they’re all relatively easy (and cheap) to repair or replace. But a car with a duff body? Putting that right can easily turn a weekend project into a money-pit. And once the realisation has dawned that the car is financially unviable as a restoration project, the smart money says walk away and find a better car.

Even a car destined to be a humble daily driver can easily fail a roadworthy inspection if the body is rusty or damaged beyond a certain point.

The problem facing buyers, of course, is that crook bodywork can be hidden. And that means the car you thought was a steal and would clean up with a cut and polish and an oil change can, once you’ve scratched the surface (literally, in some cases) turns out to be a complete basket case. At which point, you’re right back at that `walk away’ moment.

Obviously, then, any prospective purchase when it comes to older cars (or any second-hand car for that matter) absolutely hinges on body condition. The good news is that you don’t need to be a panel-and-paint expert to spot the warning signs. Being able to identify the clues and interpreting what you’re seeing can be enough to make an initial yes or no decision on a particular car. So what do you need to look for, and what are the ways sellers hide patchy metalwork?

Dents and scratches are pretty easy to see if they haven’t been messed with, but panel damage that has been poorly or cheaply repaired can be a real hassle once you remove a couple of layers of paint to see what’s what. The problem is that fixing a dent correctly – by using proper metalwork techniques – is neither quick nor cheap. But applying a thick layer of plastic filler, sanding it back and throwing a new coat of paint on it is much quicker, much easier and much, much cheaper. Which is why it happens. Problem is, a properly fixed dent will be fixed forever; a rush job will not. Fact is, a cheap fix-up can cause even more problems down the road as it can allow rust to get a foothold.

Some body filler is often inevitable even in a proper repair, but it shouldn’t be the repair itself. And that’s where a magnet can be your best friend. Fundamentally a car’s bodywork is magnetic (unless it’s a fibreglass car like a Corvette or a stainless-steel DeLorean) plastic body filler is not. So a low-powered magnet (a fridge magnet is ideal) is a great tool to check for thick sections of body filler. And it’s not rocket science: If the magnet sticks to a particular section of the body, there’s metal under there. If it doesn’t there’s plastic filler under there. Sounds simple, but it’s an effective first check. If you want to go pro, there are also electronic sensors that can determine the depth of paint and filler covering a section of metal.

The next thing to do is park the car in direct sunlight, stand back and have a good, long, hard look at the thing. Does it look `right’? Do the panels line up? Are the shut lines even (Don’t forget that some older cars were put together pretty patchily at the factory, so know your target.)? Is the paint all one colour in direct light? Direct, natural light is important as it shows up the smaller imperfections. Artificial light rarely shows up things like clear-coat that has started to go opaque and can even hide smaller dents and bumps.

Don’t be too concerned if the plastic bumpers and metal body panels are slightly different colours; that’s pretty common and it seems that even the makers of quality cars have trouble getting these parts to match, even when they’re still factory-fresh.

One thing that should really sound the alarm bells in your head is an older car with a brand-new coat of fresh paint. It’s not that every car looking freshly painted is a crock, but a quick blow-over by somebody with a few spray-gun skills can hide a whole lot of trouble. We’d much rather buy a car with slightly scruffy original paint and know that we’re not dealing with a car that has been roughly patched up and then resprayed. How do you spot a fresh paint-job? Check for overspray under the wheel-arches, paint haze on the tyres and traces of colour on things like the window rubbers and door handles. If the car has been painted to hide its faults before a quick sale, it’s also probably been done on the cheap and simply masked-up rather than disassembled, painted and then reassembled.

Be wary, too, of a car with, say, a wrapped roof. Sure, a black roof on a white car is a bit of a fashion statement, but it’s also a great way to hide faded or peeling paint on the roof without going to the cost of re-spraying the roof panel.

Rust is, of course, the biggest fear among older car owners, but even newer cars can succumb to the tin-worm, particularly if previous crash-damage has been poorly repaired. Either way, you need to get an idea of the rust hot-spots of a particular make and model and then grab the fine-toothed comb. Typical rust zones include around the front and rear windscreens, around the wheel arches, the sills, and the lower portion of all panels. Any car with a vinyl roof is also a candidate for rot to have taken hold under the vinyl.

It’s also important to check underneath a car to get a proper idea of body condition. Plenty of cars that look good on the surface can be hiding horrible damage underneath. Getting the car on a hoist is a great start if you can organise it, but at the very least, slide under the car with a torch and a screwdriver to give anything suspicious a poke. Floor pans and the area under the boot are prime locations for rust, and make sure you check for bent and damaged suspension arms and cross-members.