For a mechanic to assure you that your car is safe, he needs to spend a couple of hours checking it out, taking things apart and inspecting things from one end of the car to the other. You haven't told him anything useful, like where the noise came from, what exactly it sounded like, what you were doing when it occurred. I'm not kidding, someone actually said this to me after her car was towed in with the engine seized tighter than a . . . Men say this a lot, like it is something to be ashamed of not being able to fix their own car. The days when every man could do his own car repairs are gone forever.
Mechanics have two things for sale, diagnostic ability and repairs.
Of the two, diagnostic ability is worth much more. Don't try to scam me into diagnosing your problem for free. Yeah, and you'd probably screw it up too. If you absolutely must have the use of a tool, ask to rent it and offer a security deposit and be sure to get it back as soon as you are finished with it. This should probably be number one.