1997 Chevy Astro air-condition (refrigerant line) gouged

1997 Chevy Astro: the A/C has not been operational for almost one year. I recharged it with 134A, but it won't hold the charge. I am unable to locate the leak. I inspected an a/c line under the vehicle, and notice part of the hard line has a deep gouge against the engine block, close to where it is clamped and secured. I disconnected the line in the rear (fromt he B-nut), and noticed coolant fluid leaking. Isn't this suppose to be a refrigerant line. The a new line is more than $200. I need professional advice on this matter. After careful inspection, the gouged wasn't deep enough to create a pin hole. So I assume the leak is somewhere else in the system.