peter d, I'm not sure I had the same problem but I was told by Chris at Bay Diesel in Red Bay that my hydraulic pump, located on the right side of the engine toward the rear of the coach, 2005 Allegro Bus, was leaking. There is a plate on side of the pump that has several bolts holding the plate on. Several of the bolts had loosened and I had a slow drip. He said that sometimes just tightening the bolts will fix the problem, when it does not the gasket has to be replaced. My needed the gasket replaced.
2011 Tiffin Allegro Bus 43 QGP