I would have to say leaking o-ring. I have had alot of problems lately with mechanical assemblies that seal with an o-ring in motors and auto trans. O-rings are a very simple sealing device that work great when they work or they can cause you to go postal. I have seen slight differences in thickness and quality. Recently experienced same problem you are having and changed the oring and problem solved. Upon observation of the removed oring I noticed a slight parting line on the inside and the outside. I thought maybe it was pinching between the pan and block so I went and got some new ones and noticed these were the same way. I then went to a different parts store and bought more. This time these were completely slick. I greased them up and installed. The oil pressure was now 10 psi higher. My conclusion is the little rubber lip on the cheap china made oring was not letting it properly seal. Not completely sure if this is your problem, but it gives you something to check. Hope this helps and good luck.
__________________
|