If you already paid for the brake line, it will be hard for you to recover the money for it, since by paying, it will appear you agreed to the cost, as opposed to if you had refused to pay and legal action had resulted (him suing you for the money, or you suing him to get the car back and other compensation). Having paid the amount complicates the case. You would have to convince a court that despite having paid, you did not authorize or agree to the work.You may be able to sue him for causing the damage to your car in the first place, if it was due to his negligence or careleness in how he conducted the test that the brake line blew. However, to do this, you'd have to have another mechanic inspect the car and the damaged brake line (which might not be around any more, if he disposed of it) and offer an opinion as to how/why it blew in court--which would also mean (presumably) having to pay that mechanic for his work, testimony, and time.There might not be a good, cost effective, and practical option for you in this case.