Bought a used car privately in NSW and found a defect — what changes?

Private sales are very different from dealer sales. NSW Government guidance says buyers from a private seller are not covered by the Motor Dealers and Repairers Act dealer-guarantee regime or the Australian Consumer Law consumer guarantees that apply to dealer purchases. Before assuming there is no possible route, keep the advertisement, messages, payment record, PPSR result, inspection material and evidence of any representation made about the car. Official source: NSW Government Buying a used vehicle. NSW guide: https://getinstantlaw.com/au/new-south-wales/used-car-problems