A mechanic is liable for damages if you suffer damages as a result of negligent repairs.For example, if the mechanic uses the wrong parts or misplaces a part, and then your engine explodes when you start the car, the mechanic is liable. It does not matter if you already paid the bill and find out about a problem later. The mechanic is still liable. However, if the mechanic offers to correct his negligent repairs at no cost, and you choose not to, you cannot claim that he caused you damage because you failed to have the problem fixed.