Every year, thousands of people buy used cars with hidden faults that dealers knew about but didn't disclose. Here are the most common tricks – and how to catch them before it's too late.
1. Gearbox Problems Masked by Fresh Fluid
The Trick
Dealers know that worn gearboxes often feel smoother with fresh transmission fluid. They'll do a quick fluid change before sale, knowing the problems will return within weeks.
How to Spot It
- Check if the transmission fluid looks unusually new and clean
- Ask for service history – recent fluid change with no other work is suspicious
- Test drive extensively, including multiple gear changes
- Listen for any whining, clunking, or hesitation
2. Engine Warning Lights Reset Before Sale
The Trick
Dashboard warning lights can be cleared with a simple diagnostic tool. Dodgy dealers reset these lights just before you view the car, knowing they'll come back on within a few drive cycles.
How to Spot It
- Ask to see the car "cold" – first start of the day
- Watch all warning lights during startup (they should illuminate then go off)
- Request an OBD diagnostic scan – even cleared codes leave traces
- If a light comes on during your test drive, the fault is live
3. Clocked Mileage
The Trick
Despite being illegal, mileage tampering remains common. Digital odometers can be wound back in minutes, instantly adding thousands to a car's value.
How to Spot It
- Check MOT history online – mileage should increase consistently
- Look for wear that doesn't match the mileage (steering wheel, pedals, seat bolster)
- Service stamps and receipts should show consistent mileage progression
- Ask for a vehicle history check from HPI, Experian or similar
4. Accident Damage Poorly Repaired
The Trick
Cars that have been in accidents can be bought cheaply at auction, given a cosmetic repair, and sold as "great condition". The structural damage remains hidden.
How to Spot It
- Look for inconsistent paint colour or texture between panels
- Check panel gaps – they should be even all around the car
- Look under the bonnet for signs of straightening or welding
- Get a history check for insurance write-off records
- Consider a professional inspection before buying
5. Timing Belt/Chain Due or Overdue
The Trick
Timing belt replacements cost £400-£800+. Dealers often sell cars knowing the belt is due, hoping you won't check. If it snaps, the engine is usually destroyed.
How to Spot It
- Ask specifically about timing belt replacement
- Check service history for belt changes
- Research when your specific model needs it done (usually 60,000-100,000 miles)
- If the dealer doesn't know, assume the worst
6. DPF Problems Temporarily Fixed
The Trick
Diesel Particulate Filter (DPF) replacements cost £1,000-£2,000. Some dealers use additives or forced regeneration to temporarily clear blockages, knowing they'll fail again.
How to Spot It
- Ask if the DPF has been cleaned or regenerated recently
- Check for a DPF warning light during startup
- Extended test drive on varied roads (DPF issues often appear on short journeys)
- Check exhaust emissions during acceleration
7. Flood Damage Cleaned Up
The Trick
Flood-damaged cars are often written off by insurers but then "repaired" and sold. Water damage causes electrical gremlins and corrosion that appears months later.
How to Spot It
- Sniff inside the car – musty smells suggest water damage
- Check under seats and carpets for watermarks or rust
- Look for corrosion in the boot, especially around the spare wheel well
- Examine electrical connections for green corrosion
- Check the vehicle history for insurance claims
What To Do If You've Been Caught Out
If you've bought a car and discovered one of these hidden faults, you likely have strong legal rights:
Within 30 Days
You can reject the car outright for a full refund under the Consumer Rights Act 2015. The dealer cannot insist on attempting repairs first.
Within 6 Months
You can request repair or replacement. If this fails, you can then reject for a refund (potentially with a small deduction for use).
Evidence Is Key
- Keep all paperwork from the sale
- Document the fault with photos and videos
- Get an independent inspection report if possible
- Save all communication with the dealer
The Bottom Line
The best defence is buying from reputable dealers and getting an independent inspection before purchase. But if you do get caught out, knowing your rights means you can fight back.
Dealers who hide faults are breaking the law. The car was not "as described" or of "satisfactory quality" – and that means you have the right to reject it.
Bought a car with hidden faults? Check if you qualify for our rejection service – we've helped thousands get their money back.
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