what are the readings? And what did you use to check for a leak? I use a black light and special glasses to enhance the leak(s) if any. Did you check the evaporator for leaks? You said you replaced the exspansion vavle. Well the exspansion vavle in on the evaportator. Those copper lines bend easliy if you are not careful.

Also did you flush out all the lines when reinstalling a used system? You said your compressor operation is working like it should, did you check the shim adjustment on the clutch assembly. What about resistence to the feild coil?

If everything checks out, maybe a restriction in the condensor? Does the ac fan come on? But then you would have high head pressure. Go through the system and check for restrictions or drastic changes in tempatures using a laser temp pointer. Those work good for check restrictions in the line. I would think though if you had a restriction in the line you would have high head pressure? What you said though doesn't make sense. It should be blowing cold. What are you readings?