I had a similar diagnosis for my 240D, it wouldn't hold Freon. A dye test revealed there were leaks at the compressor and the O-rings. I didn't want to spend $1000 + to have it repaired correctly, so I decided on a band-aid approach. With the help of my brother who is a Toyota mechanic, we removed all of the air and what was left of the R 12 from the system with a vacuum device he has. Then we added a new fitting to accept R134. I bought several cans of R134 that has some type of stop leak in it from a local Wal Mart. The whole process was very easy and only took about 30 minutes to do. My AC works better now than it has in years. The best part is it cost less than $40! It's been 4 months since we did this and the AC system is still working perfectly.

__________________
James Duffey
Atlanta, GA
1963 MGB
1972 300SEL
1980 240D
1989 300SEL
1995 E300D
2000 Audi S4