2010 International transtar compresser to power steering pump oil seal

I had problem with engine oil pushing out ps reservoir. I replaced p.s. pump seal . I started truck yesterday without ps pump on and is oil is running out compressor as I expected. Is this normal or is there also a seal in compresser? I would of thought seal in ps pump should prevent ps fluid from pushing out but is it for both? You would think a seal is designed to hold pressure in one direction. I installed the seal with spring/open lip in , flat side towards compresser so not sure how well it will hold engine oil back.

 

It has the maxxforce 13. So it is a side mount BA-921 compressor with power steering pump attached to it. I just took the plate off the compressor the ps pump bolts to and looks like there is no seal that rides on a shaft for compresser. I lost adapter coupler (mystery) . I called Bendix and international dealers but getting information on these bendex compresser is like pulling teeth.

 

You would think the compresser should have been designed to have it's own seal. I imagine seals are designed to hold fluid pressure from one direction as the power steering pump seal is set up to prevent ps fluid from leaking out. Relying on it to hold back the engine oil is unsatisfactory . When I get my new adapter coupler (that I lost) I'm going to see if it's possible to make seal work to ride on it.