Plenty of advice exists on buying a classic car, but one tip is worth remembering above the rest: don't be fooled by a shiny exterior. Look past the paint by carefully examining the body and undercarriage for clues about the car's history that could affect your purchase decision.
Uneven panel gaps can hint at previous repairs or poor restoration work. Less visible weld marks can offer clues about structural repairs. Body filler, meanwhile, can conceal anything from minor imperfections to significant damage. Buyers should also watch for corrosion, particularly when it shows up in unexpected places, since it could point to water intrusion or improper storage.
None of these signs are automatic reasons to walk away, but they are indicators that call for closer examination. After decades on the road, a completely untouched classic is unrealistic to find. Given enough time, most classics will have undergone some type of work.
Your job as a buyer often comes down to judging the quality of that work against the vehicle's overall condition. Look at whether the restoration matches the age, condition, and workmanship found throughout the rest of the car. This kind of close inspection, combined with a review of the car's accident history, can also help verify what the seller has told you.
Ultimately, it will help you decide whether the car is worth pursuing or best left alone. Here's what to look for in more detail.
Read the Panel Gaps First
Checking panel gaps is a good starting point. You don’t need any specialized gear (though a panel gap gauge can be handy and is inexpensive), and these body parts are easy to access.
Good lighting is critical, with natural daylight offering the best conditions. Avoid settings that create glare or deep shadows, which can make it difficult to follow body lines and panel gaps from end to end. From about two metres away, walk around the vehicle and survey how the different exterior surfaces come together. Look for inconsistent spacing around the doors, bonnet, boot lid, and other openings. Compare one side with the other, and follow individual gaps from end to end.
Be deliberate and methodical to catch the small details. For example, a door gap may start wide but narrow along its length. Watch for a bonnet that sits higher or lower on one side compared to the adjacent wing. The boot lid could have similar problems alongside an adjoining rear quarter panel.
Next, open and close the doors, bonnet, and boot repeatedly. The action should be reasonably smooth, without obvious binding or interference. A panel that rubs against another surface or that requires extra effort could indicate previous structural work. However, worn or misaligned hinges or locking mechanisms could also cause these issues. Sometimes identifying the root cause requires additional steps or expert help.
Importantly, don’t judge an older car by modern manufacturing standards. Factory tolerances varied considerably between manufacturers and eras, especially with low-volume, hand-built models. Some classics left the factory already with less-than-perfect panel gaps.
Your best approach is to compare what's already there. If the driver's door isn't quite aligned with the surrounding bodywork, check the corresponding door on the other side. For the bonnet and boot, compare the left-side gap to the right. Next, check how the wheels sit within their openings. A significant side-to-side difference can justify investigating the structure beneath the body. A tape measure or ruler can help confirm differences that aren't obvious by eye.
Check Underneath for Weld Marks
Next, go beneath the car and check for weld marks that may indicate previous repair or restoration work. The target areas include accessible floors, sills, chassis or frame members, wheel housings, suspension mounting areas, and inner body panels. While getting underneath the vehicle isn’t always easy, it’s essential. If the undercarriage isn’t safely accessible, have someone better equipped inspect it. Never crawl beneath a car supported only by a jack.
The inspection should look for clues that the metal has been altered. These signs may include fresh weld beads, ground-down seams, patch panels, or metal that differs from the surrounding structure. Patches of newer seam sealer or underbody coating may also conceal evidence of this work.
As with panel gaps, use corresponding areas on the other side of the vehicle to help detect differences. For example, factory spot welds on one side and a continuous, ground-down weld on the other suggest previous work. Differences in the welding don’t necessarily point to poor repair or accident damage. These differences could indicate rust removal or metal replacement. Factory construction methods vary by manufacturer and era. Also, a later repair may not exactly duplicate the factory welding technique. Don’t assume a mismatched weld indicates something suspicious.
If you spot a weld that raises concerns, seek another opinion. Photos posted to a marque-specific online forum may provide more information, or you can contact a specialist familiar with the model.
Find the Filler
While body filler has a bad reputation in the classic car world, its presence doesn’t always point to something questionable. A light application of filler can be part of the normal finishing process after metalwork. Excessive filler used to reshape a panel or hide corrosion, however, is more troubling.
An inexpensive body filler detection magnet can help locate filler on steel-bodied cars. Move the tool across the panel and note any changes in how strongly the magnet is attracted to the metal. A noticeably weaker pull may indicate filler beneath the paint, while little or no attraction can point to a thicker application. Pay close attention to areas vulnerable to damage or corrosion, including the front wings, rear quarter panels, wheel openings, and side sills. Keep in mind that a magnet won’t work on aluminium, fibreglass, or other non-magnetic body panels.
A paint-thickness gauge is more expensive but can still be useful. Take readings at several points on the same panel and compare them with surrounding areas. A greater thickness may indicate additional paint or material underneath. Look across a panel from a shallow angle and study how light reflects from the surface. Waves or unusual contours, especially compared to other painted surfaces, may reveal previous work beneath.
Corrosion Where It Shouldn't Be
Dealing with rust goes beyond the obvious spots on the wings or side sills. Classic car buyers should also search for hidden corrosion. Start where moisture can collect, such as the floors, the inside and ends of sills, wheel housings, lower door sections, the boot floor, seams, window surrounds, and suspension mounting points. You may need a torch to examine less visible areas.
Even when you don't see obvious rust, other signs can reveal that moisture has been collecting inside the car. A musty smell may point to damp carpeting, upholstery, or another area where water isn't draining or drying properly. You may also find windows with persistent condensation, a water-line stain on seatbelt webbing (particularly near the base), and rusty seat hardware. If possible, check under the carpet. Moisture is easily trapped here, which encourages corrosion that’s otherwise hard to detect.
On the outside, headlamps with ongoing condensation buildup may indicate a sealing or drainage issue. Also, watch for mismatched, heavily rusted, or newer fasteners. It’s not unusual for a decades-old car to have a few replacement screws or bolts, but a concentration of them in one area can point to previous work. The same rules apply to other undercarriage inspections: exercise caution and seek professional help if you can't do this task safely.
The Questions That Separate Cosmetic From Proper Restoration
You can go further with a physical inspection by asking the seller specific questions that may help address what you find. Here’s a checklist of questions to ask:
- Who performed the restoration? When was the work completed?
- Do you have receipts or other records showing what restoration work was performed?
- Which panels were repaired or replaced?
- Was the body or certain panels stripped to bare metal before repainting?
- Was any structural metal, like the floor, sills, or subframe, replaced or repaired?
- Do you have any photos showing the restoration process?
- Have there been any additional repairs since the restoration?
- Can I have the car independently inspected?
Keep in mind that if you’re buying through a car dealer or motor trader, documentation and restoration details may not be available. This could also be an issue if you're buying from a subsequent owner who didn’t handle the work. For a U.S.-registered car, compare the paperwork and identification numbers with the federal consumer guide to vehicle-history records, which explains what title, odometer, brand, and theft information may be available.
The Real Test Is Getting Underneath the Shine
No matter how modest the price, purchasing a classic car is still an investment. To spend your money wisely, you need to know what you’re buying. Finding replaced body panels or repainted surfaces doesn't necessarily rule out a car. What matters is having that information before you complete the transaction or decide to walk away.
Whether you spot an unusual panel gap, body filler, corrosion, or new metalwork, being an informed buyer means acting on it. An independent inspection from a qualified classic car specialist can double-check your findings and give you the extra reassurance you need before you buy.
Patrick Peterson
Patrick has been with GoodCar for six years, after previously working as a professional vehicle appraiser. He spent years inspecting used vehicles and evaluating post-accident damage. Now, as an Auto expert and team lead at GoodCar, he brings that hands-on experience into creating practical, data-backed content that helps drivers avoid costly mistakes and make smarter car-buying decisions.
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