I noticed on my 90 sse and 89 sse I had and alot of Bonys and the like at the yard most had seeping power steering fluid on top of fluid box I have been cleaning it off, and only add small bits after time but seems to be leaking either out of cap or the plastic ring that the cap sits on .I have tried a other used cap and still seeps,anyone else have this or knows what the problem is?

Usually too much fluid or the cap is not venting right during the heatup when the fluid expands.
The level should be checked when hot and shouldn't go above the full hot mark on the stick.