I pulled my hair out looking for a small leak on my 300e. Ended up finding the leak at the very bottom of the condenser. No sniffer found it, and the shroud blocked it from the uv light.

The nitrogen test is simple. just add a bit of freon, and fill the rest with nitrogen. You can charge up to 200 psi. (or more ive heard)

The uv leak detector should show up very well at night with a black light.

Good luck.

__________________
Eugene

10 E63 AMG
93 300te 4matic
07 BMW X3
14 Ford F-150 Fx2