This "might" be the only time I would even consider a stopleak product (like Cryoseal) since I think the "book" time on this is > 25 hrs. for evap. replacement on a 140. There are serious consequences to these type of products, but some have had success (with the right experience, skill and luck). Positive diagnosis, first (but it seems like an evap. leak) then, second, see what a top A/C only shop has to say about alternatives. If you go with the "FULL MONTY" do use a better evaporator than OE as Euro 287 suggested. Cu vs. Al is a real consideration with factory PAG oil, due to even minute amounts of moisture forming HCl. If I went thru the evap. replacement, I'd have it switched to one of the new 134a oils (Texaco Capella HFC, I think
) to minimize future acid formation. (which is probably what got you in this predicament). Good luck and may it be something else that's really simple.