How to check for rust and paint damage on a car

In almost all of our buyer's guides, we suggest that the primary thing to check when purchasing a classic car or cherished campervan is the overall condition of the bodywork. Beyond rust holes and obvious accident damage, what are the trickier bits to spot and are they going to cost you a fortune to rectify? Let us explain. 

We know how it is, you have money burning a hole, have travelled a few hours to get there and you don't want to mess the seller about and waste their time. However, you equally don't want to be driving home in a car you're not happy with, purely out of politeness. 

Start by walking around the car, and look for any sign of damage. Make a mental note to come back and inspect each issue individually. You may find. 

• Dents
• Scratches
• Rust scabs
• Flakey paint
• Flat or worn-out paint
• Mis-matched paint
• Signs of a repair

Now, go back around and play detective on each of the items you have found. Ask the seller for the story, but use your own senses to conclude how serious each issue may be, and how much cash it might cost you to fix it!

Dents

Has the paint cracked? Could you, or a paintless dent removal person pop it back out? If the paint has cracked, or access to the rear of the panel is limited, then you'll probably need to book the vehicle into a workshop for repair, and remedial paintwork. 

Scratches 

Can you feel the scratch with your fingertip? Has the paint been taken away, or have you 'got lucky' and collected the paint off another vehicle? If it's the latter, then this can be polished off. If your paintwork has been damaged then it's a touch-up pen, or a trip to the body shop, depending on the size of the issue and how much it will bother you. Visible swirls in the paintwork can often be removed with a comprehensive detailing session. 

Rust Scabs

To preserve the aesthetic of the car it may be best to leave small isolated rust scabs alone. However, below the surface of the paint, they will continue to spread, and eventually, you'll end up with a hole. At some point, you will need to get a professional involved unless you have the skills yourself to fix it. 

Flakey Paint

Vehicles from the 80s and 90s do tend to suffer from lacquer peel, where the clear coat on top of the colour flakes off, leaving an unsightly tide mark on a panel. There's no way to fix this gently. It'll need sanding off and repainting. Should you have body-coloured paint flaking off, that will indicate a poorly completed previous repair, because the paint hasn't adhered to the primer or the metal work below. As above, it will need sanding back and repainting, either at home or by a professional. 

Flat or worn our paint

Particularly common on red vehicles, the paintwork may have faded in the sunshine and lost its gloss finish. This isn't a complete tragedy, but may well indicate how future weekends will be spent trying to maintain the shine should you complete the purchase. Pay particular attention to the corners of panels and swage lines to check that the paint hasn't worn through to the primer in previous attempts to revive the colour. Should that be the case, you'll either have to live with it or consider a respray. Localised fading on one panel may indicate a previous panel re-paint. Before you attack the car with a polisher though, please read on for information about measuring paint depth. 

Mis-matched paint

Matching a paint colour takes particular skill, especially if the paint on the vehicle has already aged considerably. Look at the car from different angles and pay particular attention to panels that are likely to have been impacted, such as the front bumper and bonnet from stone chips, and the rear bumper and tailgate from impact or parking misdemeanours. Likewise easily removed items such as door mirrors and doors themselves, could have been directly swapped with a donor vehicle post-accident, and be sporting different age or shade paintwork. 

Signs of a repair

On top of the paint colour being slightly out, look closely for signs of any overspray in the door shut and inner wings and wheel arches. If the work has been carried out hastily then you may spot slight sanding marks where the filler has been shaped before it was painted. See below for how to check this further.

The magnet test is a simple yet effective way to check for body fillers or worse that may be hiding rust or damage. Check any areas of concern with a fridge magnet, being careful not to scratch the paint with it, of course. The magnet will naturally want to stick to panels made out of steel but will be less attracted to the bodywork should there be filler below the surface. Pay close attention to areas prone to rust, such as lower panels and wheel arches, where a cheap repair is more likely to have occurred in the past. 

As mentioned above, before breaking out the power tools and an aggressive polishing compound, it would be prudent to see what you are actually working with. 

It's very easy to take the paint off... Much trickier and more expensive to put it back!

Using a paint thickness gauge test various sections of the vehicle including the doors, wings, bonnet, roof and any areas of concern where you feel either the vehicle has been repainted, or a previous owner might have been overzealous with the polish.

Significant fluctuations in the reading will indicate either an excess or minimal amount of paint on the panel. From there, you can proceed with any paint correction and polishing and hopefully only make improvements, rather than make the situation worse. 

Paint thickness gauges can be found on Amazon from as little as £20, with prices going into the thousands for a professional quality machine. Read the reviews, and find something you think suits your needs and budget or speak to your local detailer for a recommendation. 

If you have got this far and everything is looking positive then it's time to take a look underneath. Depending on the seller, you may not get the chance to jack the car up, but rolling it onto some wooden blocks, or putting two wheels onto a curb, might just give you the height to inspect things more closely. A decent torch and something blunt to poke with will make this job much easier. Wear protective glasses to avoid years of old underseal falling in your eyes. 

You are looking for two things. Signs of repair, and signs that repairs might be needed. Depending on the vehicle and the asking price will depend on how fussy you are about repairs that have already been made, with regards to how they look. Of course, all welding repairs should be strong and undersealed or painted to prevent rust from attacking it again. 

Any corrosion close to a suspension component, a seatbelt attachment, or an engine or gearbox mount is going to give you immediate cause for concern, especially on a vehicle that requires an MOT. Smaller patches on the floor or sill may not be as structural, but should still be addressed, so take that into account when it comes to price negotiation. 

While rust and paint damage primarily affects the exterior, inspecting the interior for signs of what could be happening out of sight on the floor pans and inner sills would be a good idea.  Damp or stained carpets could indicate previous water ingress issues, and any musty smells should at least be questioned if not traced to the source, before signing on the dotted line. 

If the carpet set is only held in place by a rubber door seal, see if you can slip a hand underneath it to get a feel for what might be happening. You don't really want to find another even soggier carpet (probably an offcut from their bedroom) or polystyrene! Sadly, I've had the 'pleasure' of discovering both on previous vehicles I've bought!

Still not sure? If you don't want to let this car slip away you could always call in a professional and ask them to carry out a pre-purchase inspection for you. Probably not worth the money on a £1500 Polo, but certainly going to offer peace of mind on a £50k Porsche. On top of a full body appraisal, you can expect to find out more about the vehicle's mechanical health, and what kind of bills you could expect to encounter in the coming years. Ask nicely and they'll probably conduct an HPI check to confirm the vehicle isn't stolen, or with outstanding finance to be paid too.  

Best of luck! Do be sure to check out our many model specific buying guides to arm yourself with all you need to know about a particular car or van. 

Andy