Right now checking for leaks is not really an option. Everything was coated in grime from the previous owner so I actually have all the accessories and brackets pulled along with the ac system To get cleaned/painted. I'm replacing all the o rings while I have it apart. The fittings on the compressor it's self, I think they are called manifold fittings. I know they have the 2 o rings between them and the compressor, but what kinda deal is used on the hoses? I don't see where a o ring would go.