It has prompted a warning to young drivers, who typically buy such vehicles as their first car, to get their prospective purchase checked by an independent engineer before buying.
Nearly 42,000 people complained about second-hand cars in the UK last year.
They were the single biggest source of complaints from consumers received by trading standards officers.
Among the faults unearthed during the probe were a cut brake fluid sensor wire, leaking rear suspension dampers and under-inflated tyres.
A spokesman said the vehicles were unsafe to drive and therefore should have no place on a trader's forecourt.