You're leaking 134 from somewhere if you're pressureless. You can either juice up the system and use a sniffer to look for leaks or add dye and use a blacklight to locate the source of the leak. It's possible that you'll be able to see the compressor oil at the source of the leak(s) with the naked eye, but I wouldn't put all your eggs in
that basket. Once you find the leak(s) you'll have to evacuate the system, replace the seals and/or line(s) involved (or possibly the component involved
). If you don't have an a/c machine at your disposal this process will really have to be done at a shop that can fill/evacuate/fill the 134. It may even be the law where you live that a qualified shop work on your a/c system.