Answer:
First, realize that you always have the option of suing if there is evidence to suggest a mechanic is at fault. However, if a questionable mechanic job leads to an automobile accident where there is an injury or major damage, then there may be grounds for a lawsuit.
You would have to prove that the mechanic negligently repaired your car, and that the automotive breakdown happened because of the mechanic’s specific act of negligence and not by coincidence.