hi, I'm new to this so if I didn't post this right I'm sorry.. anyway I'm looking for help. I'm working on a 2009 gillig low floor bus. it has a Cummins isl9 in it. the problem I'm having is the power steering reservoir or hydraulic reservoir (iv heard different people call it different things) keeps over flowing when the bus it turned off. if u fill it up to the fill mark then start it and have it run for awhile nothing happens but as soon as you shut it down it starts over flowing out of the breather on the top. and I can figure out why. the only thing I can think is, the air compressor meets up to the hydro pump and there is a leak somewhere where they meet causing pressure, but I still don't get why it only does it when the bus is turned off. It also takes 15w40 oil if that helps at all. any feed back would be helpful. at least to get me in the right direction.