Hey guys Ron here. New to the site. I have a 2007 e250 with a sizable ac leak. I have dyed the system twice. First time I dyed it found the low side schrader valve leaking slightly. Not enough for the system to be completely empty in a week but replaced it anyway. Recharged and dyed the system again and ac starting blowing warm again in about 4 days. When I threw a uv light on the engine bay I found no other leaks. It leads me to believe it's the evap core leaking. Wanted to try to get to the drain line but I can't seem to find it. Also I can't seem to find any r&r manuals online that show how to replace the evap core. When fully charged high side and low side pressures are normal so there is no blockage anywhere. Compressor also cycles normally so I know there are no failing components in the system. Just the big leak I can't see. I don't want to start pulling things apart without any info at all so if anyone can lead me in the right direction it would be greatly appreciated. Thanks again!!

 

I had a leak on my E350 that was on the bottom of the compressor and didn't see all the dye until I removed it from the bracket. Not sure how yours sits without knowing the engine.

 

I had a leak after replacing a compressor on my Isuzu Trooper. Like you I attempted to find it with dye. It would leak down in one day and was driving me nuts. I broke down and bought an electronic leak detector. Found out, the rebuilt compressor was leaking at the shaft seal and I couldn't see it because the dye was behind the clutch.

 

That's more common than people realize. I had an 87 Cavalier with the compressor shaft leak.