The same thing happened to me on my 140, the lower condensor fitting/valve was leaking. It is a hairline crack in the thread area of the fitting where the valve screws into the condensor. Replacing the seal will not help, what I did is put two seals in there. One in the normal position, and one just a bit smaller that sealed it at the bottom of the valve where it comes in contact with the inside of the fitting. This fixed the problem and it has been working for 3 years (new owner says working fine, I sold the car). Just go to the parts store and get the r134 seals and it match the size to the bottom of the valve, it has to be the exact size to work. This was much cheaper than replacing the condensor. ($2) Good luck!
Brian

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Brian W. Heitman

www.MBCA.org/northtexas

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