I have no engine experience on 737's to speak of, but the talk of pad seals and so on above sounds reminiscent of the cement mixer technology found in the JT9 accessory gearbox.
Whenever we had a problem like this on one of those engines we'd perform a breather pressure check to find which of the carbon seals or mount pad seals was the culprit. It usually turned out to be more than one. Is such a thing as a breather pressure check possible on 737s?
That said, the only time a JT9 wasn't leaking was when the oil tank was empty.