For 2 years in a row my 98 Lumina has lost AC refrigerant. Eachyear the mechanic used dye, but could not find the leak.Valves were replaced last year, but it appears not to have worked as it is out again.

Would it make sense to have the system charged with dye again, but wait a day or two to go back and checkin order to givethe leak sufficient time to be detected?

Any other suggestions?

Thanks