If you have a freon leak, you must fix it before recharging. Check the
area where the AC tubes enter the firewall from the engine bay in front
of the driver. Does the joint that carries the tubes into the firewall,
and into the expansion tank, appear wet and/or oily? This was where my
system was leaking...and is apparently common on these cars. I think you
have had a lot of engine work on your car, including a complete
replacement if I am not mistaken, this could cause the freon to leak out
as well. My dealer found my freon leak, fixed it, and recharged the
system for US$200, and I have had AC for three Summers.
Good Luck,
Mike Savage
Boston, MA