We have a '93 300TE 4Matic. I had the AC topped up this year and then discovered that I was losing refrigerant. After putting in a dye leak indicator we found that the dust cap over the fill port had been screwed down tight enough to slightly depress the spring loded ball valve. That was the leak. After removing the dust cap there is no leak. Apparently the dimensional tolerances are very close and a slight overtightening hits the valve. I put a small "O" ring in the cap to allow it to seat on the upper surface of the fill port to eliminate the problem.

SRHARVEY

'93 300TE 4Matic 275M
'83 240 D 245M
'82 380 SL 140M