Don’t be pressured into buying a lemon.

Tens of thousands of used-car sellers are hiding potentially serious defects from buyers, flooding the market with lemons and saddling victims with thousands of dollars in repair costs, according to CarHistory.com.au.

The online automotive bureau has analysed more than 154,035 vehicle history checks run through its database in 2015, revealing that 22.2 per cent received a negative report.

The data showed 12.8 per cent of used cars on the market had an encumbrance — money owed on the vehicle — making it the most common problem identified.

Nearly one in 10 (9.3 per cent) had previously been written off, and around four per cent of vehicles had more than one negative issue identified in their history.

The worst region for buying a used car is in Melbourne’s northwest, where 28.3 per cent of reports came back with red flags. Other risky areas were Brisbane South (28.1 per cent), west and northwest Tasmania (27.3 per cent), Shepparton (27.3 per cent) and Melbourne’s west (27 per cent).

A survey of used car buyers, commissioned by CarHistory, has suggested that up to 1.2 million Australians will buy a used car in the next 12 months, yet many won’t do more than basic research.

According to the survey, only 28 per cent of buyers undertook a mechanical check before buying the vehicle, and less than half checked for issues such as past accidents, finance owing or fraudulent incidents such as flood damage, rebirthing and odometer wind-backs.

Many people are unaware that this kind of information can even be tracked, according to CarHistory, which is owned by credit rating and data analytics company Veda.

Naomi Buell.Source:Supplied

Naomi Buell, 32, recently had her own nightmare experience when purchasing a second-hand 2002 Honda Jazz from a used-car lot in Minchinbury in Sydney’s west.

“At one point I suggested doing a third-party inspection. He said, you could, but this vehicle comes with a one-year warranty,” she said.

It was only after paying $4400 for the car and taking it in for a full inspection that she realised she had been duped. All up the car required $2500 worth of work including new brakes, shocks and wheels.

“The mechanic said it should never have been sold to me in that condition in the first place,” Ms Buell said. “I tried to call in the warranty but they said it was regular wear and tear, and none of it was covered.”

She said the experience had made her doubt herself and she felt guilty for not going through the proper due diligence. “I did see some red flags but I didn’t know the questions to ask,” she said.

Izzy Silva, general manager, consumer at Veda, said CarHistory’s research showed many private used car sellers had, at some stage, sold a car they knew had a potentially serious issue.

“No matter how genuine the seller seems, it’s important to know all you can about your car’s past to make an educated decision about whether it’s a smart buy,” he said.

“Australians spend on average $13,000 to $14,000 buying a used car, and an average of 13 hours on the researching, checking and buying process.

“In comparison, the average out of pocket cost of a bad used car purchase is $2000 to $3000. This equates to 20 per cent of the average purchase amount — a high price to pay, and often one that could have been avoided by checking the vehicle’s history.”

frank.chung@news.com.au