Is it in the shop now? If it's a seal at the box you NEED to try adding the Lucas PS conditioner and leak repair stuff. I had a leak that was hard to find, added about 1/2 a bottle and it stopped completely. It will NOT fix a pressure line leak but it will most likely fix about any seal or gasket leaks that are from aged rubber. It softens the seals and makes them expand back into place.
Just got it back with a new box. Wish I would have known sooner I would have tried that.