[77newell]

Where is the item in the picture? My current best guess is that it is a brake relay valve for the rear brakes; the small black tube is the signal coming from the brake pedal and the large hoses are the one incoming supply hose and two distribution hoses to the brake cans. The vent on the bottom is where air discharges when you release the brake pedal, it should not be venting air on an ongoing basis.

I could be totally wrong in what I just said but hoses that size on the two coaches I've had have always been brake hoses.