If you don't have a vacuum pump you may be able to borrow one from your local parts store (what I did). Pull a vacuum on the system, shut it down and watch the gauges for a while. If no leak then it'll hold vacuum. This should help narrow down the problem if you can eliminate a potential leak. Also make sure you have adequate air flow over the condenser while you're running the system.
-------------------------------------------------------------- ---------------------- Conversation between my sister and my wife (shortly before we got married): Wife: "You know, sometimes I think he loves that Z more than he does me." Sister: "He probably does, and as long as you're okay with that, everything will be fine."